Redirect docs.openzeppelin.org to docs root (#2057)

docs.openzeppelin.org was redirecting to the contracts documentation, instead of the documentation landing

.codecov.yml

@@ -1,11 +0,0 @@
-comment: off
-github_checks:
-  annotations: false
-coverage:
-  status:
-    patch:
-      default:
-        target: 95%
-    project:
-      default:
-        threshold: 1%

.editorconfig

@@ -6,16 +6,7 @@ root = true
 [*]
 charset = utf-8
 end_of_line = lf
+indent_size = 2
 indent_style = space
 insert_final_newline = true
-trim_trailing_whitespace = false
-max_line_length = 120
-
-[*.sol]
-indent_size = 4
-
-[*.js]
-indent_size = 2
-
-[*.adoc]
-max_line_length = 0
+trim_trailing_whitespace = true

.eslintrc

@@ -18,8 +18,6 @@
     "contract": false,
     "assert": false,
     "web3": false,
-    "usePlugin": false,
-    "extendEnvironment": false,
   },
   "rules": {
 
@@ -27,7 +25,6 @@
     "strict": ["error", "global"],
 
     // Code style
-    "array-bracket-spacing": ["off"],
     "camelcase": ["error", {"properties": "always"}],
     "comma-dangle": ["error", "always-multiline"],
     "comma-spacing": ["error", {"before": false, "after": true}],
@@ -57,8 +54,5 @@
 
     "promise/always-return": "off",
     "promise/avoid-new": "off",
-  },
-  "parserOptions": {
-    "ecmaVersion": 2018
   }
 }

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,16 +1,16 @@
 ---
 name: Bug report
-about: Report a bug in OpenZeppelin Contracts
+about: Report a bug in OpenZeppelin
 
 ---
 
 <!-- Briefly describe the issue you're experiencing. Tell us what you were trying to do and what happened instead. -->
 
-<!-- Remember, this is not a place to ask for help debugging code. For that, we welcome you in the OpenZeppelin Community Forum: https://forum.openzeppelin.com/. -->
+<!-- Remember, this is not a place to ask for help debugging code. For that, we welcome you in the Zeppelin Forum: https://forum.zeppelin.solutions/. -->
 
 **💻 Environment**
 
-<!-- Tell us what version of OpenZeppelin Contracts you're using, and how you're using it: Truffle, Remix, etc. -->
+<!-- Tell us what version of OpenZeppelin you're using, and how you're using it: Truffle, Remix, etc. -->
 
 **📝 Details**
 

.github/ISSUE_TEMPLATE/config.yml

@@ -1,4 +0,0 @@
-contact_links:
-  - name: Support request
-    url: https://forum.openzeppelin.com/c/support/contracts/18
-    about: Ask the community in the Community Forum

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,6 +1,6 @@
 ---
 name: Feature request
-about: Suggest an idea for OpenZeppelin Contracts
+about: Suggest an idea for OpenZeppelin
 
 ---
 
@@ -11,4 +11,4 @@ about: Suggest an idea for OpenZeppelin Contracts
 <!-- Please describe your feature request in detail. -->
 
 <!-- Make sure that you have reviewed the OpenZeppelin Contributor Guidelines. -->
-<!-- https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/CONTRIBUTING.md -->
+<!-- https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CONTRIBUTING.md -->

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,20 +1,22 @@
-<!-- Thank you for your interest in contributing to OpenZeppelin! -->
+<!-- 0. 🎉 Thank you for submitting a PR! -->
 
-<!-- Consider opening an issue for discussion prior to submitting a PR. -->
-<!-- New features will be merged faster if they were first discussed and designed with the team. -->
+<!-- 1. Does this close any open issues? Please list them below. -->
 
-Fixes #???? <!-- Fill in with issue number -->
+<!-- Keep in mind that new features have a better chance of being merged fast if
+they were first discussed and designed with the maintainers. If there is no
+corresponding issue, please consider opening one for discussion first! -->
 
-<!-- Describe the changes introduced in this pull request. -->
-<!-- Include any context necessary for understanding the PR's purpose. -->
+Fixes #
 
+<!-- 2. Describe the changes introduced in this pull request. -->
+<!--    Include any context necessary for understanding the PR's purpose. -->
 
-#### PR Checklist
-
-<!-- Before merging the pull request all of the following must be complete. -->
-<!-- Feel free to submit a PR or Draft PR even if some items are pending. -->
-<!-- Some of the items may not apply. -->
-
-- [ ] Tests
-- [ ] Documentation
-- [ ] Changelog entry
+<!-- 3. Before submitting, please make sure that you have:
+  - reviewed the OpenZeppelin Contributor Guidelines
+    (https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CONTRIBUTING.md),
+  - added tests where applicable to test new functionality,
+  - made sure that your contracts are well-documented,
+  - run the Solidity linter (`npm run lint:sol`) and fixed any issues,
+  - run the JS linter and fixed any issues (`npm run lint:fix`), and
+  - updated the changelog, if applicable.
+-->

.github/stale.yml

@@ -0,0 +1,66 @@
+# Configuration for probot-stale - https://github.com/probot/stale
+
+# Number of days of inactivity before an Issue or Pull Request becomes stale
+daysUntilStale: 15
+
+# Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
+# Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
+daysUntilClose: 15
+
+# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
+exemptLabels:
+  - on hold
+
+# Set to true to ignore issues in a project (defaults to false)
+exemptProjects: false
+
+# Set to true to ignore issues in a milestone (defaults to false)
+exemptMilestones: false
+
+# Set to true to ignore issues with an assignee (defaults to false)
+exemptAssignees: false
+
+# Label to use when marking as stale
+staleLabel: stale
+
+# Comment to post when marking as stale. Set to `false` to disable
+markComment: >
+  Hi all!
+
+  This Pull Request has not had any recent activity, is it still relevant? If so, what is blocking it?
+  Is there anything we can do to help move it forward?
+
+  Thanks!
+
+
+# Comment to post when removing the stale label.
+# unmarkComment: >
+#   Your comment here.
+
+# Comment to post when closing a stale Issue or Pull Request.
+closeComment: >
+  Hi folks!
+
+  This Pull Request is being closed as there was no response to the previous prompt.
+  However, please leave a comment whenever you're ready to resume, so it can be reopened.
+
+  Thanks again!
+
+
+# Limit the number of actions per hour, from 1-30. Default is 30
+limitPerRun: 30
+
+# Limit to only `issues` or `pulls`
+only: pulls
+
+# Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
+# pulls:
+#   daysUntilStale: 30
+#   markComment: >
+#     This pull request has been automatically marked as stale because it has not had
+#     recent activity. It will be closed if no further activity occurs. Thank you
+#     for your contributions.
+
+# issues:
+#   exemptLabels:
+#     - confirmed

.github/workflows/test.yml

@@ -1,55 +0,0 @@
-name: Test
-
-on:
-  push:
-    branches:
-      - master
-      - release-v*
-  pull_request: {}
-  workflow_dispatch: {}
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
-        with:
-          node-version: 10.x
-      - uses: actions/cache@v2
-        id: cache
-        with:
-          path: '**/node_modules'
-          key: npm-v2-${{ hashFiles('**/package-lock.json') }}
-          restore-keys: npm-v2-
-      - run: npm ci
-        if: steps.cache.outputs.cache-hit != 'true'
-      - run: npm run lint
-      - run: npm run test
-        env:
-          FORCE_COLOR: 1
-          ENABLE_GAS_REPORT: true
-      - name: Print gas report
-        run: cat gas-report.txt
-
-  coverage:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          fetch-depth: 2
-      - uses: actions/setup-node@v2
-        with:
-          node-version: 10.x
-      - uses: actions/cache@v2
-        id: cache
-        with:
-          path: '**/node_modules'
-          key: npm-v2-${{ hashFiles('**/package-lock.json') }}
-          restore-keys: npm-v2-
-      - run: npm ci
-        if: steps.cache.outputs.cache-hit != 'true'
-      - run: npm run coverage
-        env:
-          NODE_OPTIONS: --max_old_space_size=4096
-      - uses: codecov/codecov-action@v1

.gitignore

@@ -41,19 +41,6 @@ build/
 # IntelliJ IDE
 .idea
 
-# docs artifacts
-docs/modules/api
-
-# only used to package @openzeppelin/contracts
-contracts/build/
-contracts/README.md
-
-# temporary artifact from solidity-coverage
-allFiredEvents
-.coverage_artifacts
-.coverage_cache
-.coverage_contracts
-
-# hardhat
-cache
-artifacts
+# docsite artifacts
+docsite-build
+docs/api

.mocharc.js

@@ -1,3 +0,0 @@
-module.exports = {
-  timeout: 4000,
-};

.solcover.js

@@ -1,15 +1,9 @@
 module.exports = {
     norpc: true,
-    testCommand: 'npm test',
-    compileCommand: 'npm run compile',
+    testCommand: 'node --max-old-space-size=4096 ../node_modules/.bin/truffle test --network coverage',
+    compileCommand: 'node --max-old-space-size=4096 ../node_modules/.bin/truffle compile --network coverage',
     skipFiles: [
-        'mocks',
-    ],
-    providerOptions: {
-        default_balance_ether: '10000000000000000000000000',
-    },
-    mocha: {
-        fgrep: '[skip-on-coverage]',
-        invert: true,
-    },
+        'lifecycle/Migrations.sol',
+        'mocks'
+    ]
 }

.solhint.json

@@ -1,12 +1,12 @@
 {
-  "extends": "solhint:recommended",
+  "extends": "default",
   "rules": {
-    "func-order": "off",
-    "mark-callable-contracts": "off",
-    "no-empty-blocks": "off",
-    "compiler-version": "off",
-    "private-vars-leading-underscore": "error",
-    "reason-string": "off",
-    "func-visibility": ["error", { "ignoreConstructors": true }]
+    "indent": ["error", 4],
+    "func-order": false,
+    "bracket-align": false,
+    "compiler-fixed": false,
+    "no-simple-event-func-name": false,
+    "separate-by-one-line-in-contract": false,
+    "two-lines-top-level-separator": false
   }
 }

.travis.yml

@@ -0,0 +1,44 @@
+dist: trusty
+sudo: false
+group: beta
+language: node_js
+node_js:
+  - "8"
+
+cache:
+  directories:
+    - node_modules
+
+jobs:
+  # XXX fast_finish doesn't work with stages yet. See
+  # https://github.com/travis-ci/travis-ci/issues/8425
+  # --elopio - 20180531
+  fast_finish: true
+  allow_failures:
+    - env: SOLC_NIGHTLY=true
+  include:
+    - stage: tests
+      name: "Linter"
+      script: npm run lint
+
+    - stage: tests
+      name: "Unit tests"
+      script: npm run test
+
+    - stage: tests
+      name: "Unit tests with coverage report"
+      script: npm run test
+      env: SOLIDITY_COVERAGE=true
+
+    - stage: tests
+      name: "Unit tests using solc nightly"
+      script: npm run test
+      env: SOLC_NIGHTLY=true
+
+notifications:
+  slack:
+    rooms:
+      - secure: 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
+    on_success: change
+    on_failure: always
+    on_pull_requests: false

CHANGELOG.md

@@ -1,294 +1,38 @@
 # Changelog
 
-## 4.1.0 (2021-04-29)
-
- * `IERC20Metadata`: add a new extended interface that includes the optional `name()`, `symbol()` and `decimals()` functions. ([#2561](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2561))
- * `ERC777`: make reception acquirement optional in `_mint`. ([#2552](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2552))
- * `ERC20Permit`: add a `_useNonce` to enable further usage of ERC712 signatures. ([#2565](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2565))
- * `ERC20FlashMint`: add an implementation of the ERC3156 extension for flash-minting ERC20 tokens. ([#2543](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2543))
- * `SignatureChecker`: add a signature verification library that supports both EOA and ERC1271 compliant contracts as signers. ([#2532](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2532))
- * `Multicall`: add abstract contract with `multicall(bytes[] calldata data)` function to bundle multiple calls together ([#2608](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2608))
- * `ECDSA`: add support for ERC2098 short-signatures. ([#2582](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2582))
- * `AccessControl`: add a `onlyRole` modifier to restrict specific function to callers bearing a specific role. ([#2609](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2609))
- * `StorageSlot`: add a library for reading and writing primitive types to specific storage slots. ([#2542](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2542))
- * UUPS Proxies: add `UUPSUpgradeable` to implement the UUPS proxy pattern together with `EIP1967Proxy`. ([#2542](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2542))
-
-### Breaking changes
-
-This release includes two small breaking changes in `TimelockController`.
-
-1. The `onlyRole` modifier in this contract was designed to let anyone through if the role was granted to `address(0)`,
-   allowing the possibility to to make a role "open", which can be used for `EXECUTOR_ROLE`. This modifier is now
-   replaced by `AccessControl.onlyRole`, which does not have this ability. The previous behavior was moved to the
-   modifier `TimelockController.onlyRoleOrOpenRole`.
-2. It was possible to make `PROPOSER_ROLE` an open role (as described in the previous item) if it was granted to
-   `address(0)`. This would affect the `schedule`, `scheduleBatch`, and `cancel` operations in `TimelockController`.
-   This ability was removed as it does not make sense to open up the `PROPOSER_ROLE` in the same way that it does for
-   `EXECUTOR_ROLE`.
-
-## 4.0.0 (2021-03-23)
-
- * Now targeting the 0.8.x line of Solidity compilers. For 0.6.x (resp 0.7.x) support, use version 3.4.0 (resp 3.4.0-solc-0.7) of OpenZeppelin.
- * `Context`: making `_msgData` return `bytes calldata` instead of `bytes memory` ([#2492](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2492))
- * `ERC20`: removed the `_setDecimals` function and the storage slot associated to decimals. ([#2502](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2502))
- * `Strings`: addition of a `toHexString` function.  ([#2504](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2504))
- * `EnumerableMap`: change implementation to optimize for `key → value` lookups instead of enumeration. ([#2518](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2518))
- * `GSN`: deprecate GSNv1 support in favor of upcoming support for GSNv2. ([#2521](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2521))
- * `ERC165`: remove uses of storage in the base ERC165 implementation. ERC165 based contracts now use storage-less virtual functions. Old behavior remains available in the `ERC165Storage` extension. ([#2505](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2505))
- * `Initializable`: make initializer check stricter during construction. ([#2531](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2531))
- * `ERC721`: remove enumerability of tokens from the base implementation. This feature is now provided separately through the `ERC721Enumerable` extension. ([#2511](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2511))
- * `AccessControl`: removed enumerability by default for a more lightweight contract. It is now opt-in through `AccessControlEnumerable`. ([#2512](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2512))
- * Meta Transactions: add `ERC2771Context` and a `MinimalForwarder` for meta-transactions. ([#2508](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2508))
- * Overall reorganization of the contract folder to improve clarity and discoverability. ([#2503](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2503))
- * `ERC20Capped`: optimize gas usage by enforcing the check directly in `_mint`. ([#2524](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2524))
- * Rename `UpgradeableProxy` to `ERC1967Proxy`. ([#2547](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2547))
- * `ERC777`: optimize the gas costs of the constructor. ([#2551](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2551))
- * `ERC721URIStorage`: add a new extension that implements the `_setTokenURI` behavior as it was available in 3.4.0. ([#2555](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2555))
- * `AccessControl`: added ERC165 interface detection. ([#2562](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2562))
- * `ERC1155`: make `uri` public so overloading function can call it using super. ([#2576](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2576))
-
-### Bug fixes for beta releases
-
- * `AccessControlEnumerable`: Fixed `renounceRole` not updating enumerable set of addresses for a role. ([#2572](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2572))
-
-### How to upgrade from 3.x
-
-Since this version has moved a few contracts to different directories, users upgrading from a previous version will need to adjust their import statements. To make this easier, the package includes a script that will migrate import statements automatically. After upgrading to the latest version of the package, run:
-
-```
-npx openzeppelin-contracts-migrate-imports
-```
-
-Make sure you're using git or another version control system to be able to recover from any potential error in our script.
-
-### How to upgrade from 4.0-beta.x
-
-Some further changes have been done between the different beta iterations. Transitions made during this period are configured in the `migrate-imports` script. Consequently, you can upgrade from any previous 4.0-beta.x version using the same script as described in the *How to upgrade from 3.x* section.
-
-## 3.4.0 (2021-02-02)
-
- * `BeaconProxy`: added new kind of proxy that allows simultaneous atomic upgrades. ([#2411](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2411))
- * `EIP712`: added helpers to verify EIP712 typed data signatures on chain. ([#2418](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2418))
- * `ERC20Permit`: added an implementation of the ERC20 permit extension for gasless token approvals. ([#2237](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237))
- * Presets: added token presets with preminted fixed supply `ERC20PresetFixedSupply` and `ERC777PresetFixedSupply`. ([#2399](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2399))
- * `Address`: added `functionDelegateCall`, similar to the existing `functionCall`. ([#2333](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2333))
- * `Clones`: added a library for deploying EIP 1167 minimal proxies. ([#2449](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2449))
- * `Context`: moved from `contracts/GSN` to `contracts/utils`. ([#2453](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2453))
- * `PaymentSplitter`: replace usage of `.transfer()` with `Address.sendValue` for improved compatibility with smart wallets. ([#2455](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2455))
- * `UpgradeableProxy`: bubble revert reasons from initialization calls. ([#2454](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2454))
- * `SafeMath`: fix a memory allocation issue by adding new `SafeMath.tryOp(uint,uint)→(bool,uint)` functions. `SafeMath.op(uint,uint,string)→uint` are now deprecated. ([#2462](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2462))
- * `EnumerableMap`: fix a memory allocation issue by adding new `EnumerableMap.tryGet(uint)→(bool,address)` functions. `EnumerableMap.get(uint)→string` is now deprecated. ([#2462](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2462))
- * `ERC165Checker`: added batch `getSupportedInterfaces`. ([#2469](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2469))
- * `RefundEscrow`: `beneficiaryWithdraw` will forward all available gas to the beneficiary. ([#2480](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2480))
- * Many view and pure functions have been made virtual to customize them via overrides. In many cases this will not imply that other functions in the contract will automatically adapt to the overridden definitions. People who wish to override should consult the source code to understand the impact and if they need to override any additional functions to achieve the desired behavior.
-
-### Security Fixes
-
- * `ERC777`: fix potential reentrancy issues for custom extensions to `ERC777`. ([#2483](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2483))
-
-If you're using our implementation of ERC777 from version 3.3.0 or earlier, and you define a custom `_beforeTokenTransfer` function that writes to a storage variable, you may be vulnerable to a reentrancy attack. If you're affected and would like assistance please write to security@openzeppelin.com. [Read more in the pull request.](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2483)
-
-## 3.3.0 (2020-11-26)
-
- * Now supports both Solidity 0.6 and 0.7. Compiling with solc 0.7 will result in warnings. Install the `solc-0.7` tag to compile without warnings.
- * `Address`: added `functionStaticCall`, similar to the existing `functionCall`. ([#2333](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2333))
- * `TimelockController`: added a contract to augment access control schemes with a delay. ([#2354](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2354))
- * `EnumerableSet`: added `Bytes32Set`, for sets of `bytes32`. ([#2395](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2395))
-
-## 3.2.2-solc-0.7 (2020-10-28)
- * Resolve warnings introduced by Solidity 0.7.4. ([#2396](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2396))
-
-## 3.2.1-solc-0.7 (2020-09-15)
- * `ERC777`: Remove a warning about function state visibility in Solidity 0.7. ([#2327](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2327))
-
-## 3.2.0 (2020-09-10)
-
-### New features
- * Proxies: added the proxy contracts from OpenZeppelin SDK. ([#2335](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2335))
-
-#### Proxy changes with respect to OpenZeppelin SDK
-
-Aside from upgrading them from Solidity 0.5 to 0.6, we've changed a few minor things from the proxy contracts as they were found in OpenZeppelin SDK.
-
-- `UpgradeabilityProxy` was renamed to `UpgradeableProxy`.
-- `AdminUpgradeabilityProxy` was renamed to `TransparentUpgradeableProxy`.
-- `Proxy._willFallback` was renamed to `Proxy._beforeFallback`.
-- `UpgradeabilityProxy._setImplementation` and `AdminUpgradeabilityProxy._setAdmin` were made private.
-
-### Improvements
- * `Address.isContract`: switched from `extcodehash` to `extcodesize` for less gas usage. ([#2311](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2311))
-
-### Breaking changes
- * `ERC20Snapshot`: switched to using `_beforeTokenTransfer` hook instead of overriding ERC20 operations. ([#2312](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2312))
-
-This small change in the way we implemented `ERC20Snapshot` may affect users who are combining this contract with
-other ERC20 flavors, since it no longer overrides `_transfer`, `_mint`, and `_burn`. This can result in having to remove Solidity `override(...)` specifiers in derived contracts for these functions, and to instead have to add it for `_beforeTokenTransfer`. See [Using Hooks](https://docs.openzeppelin.com/contracts/3.x/extending-contracts#using-hooks) in the documentation.
-
-## 3.1.0 (2020-06-23)
-
-### New features
- * `SafeCast`: added functions to downcast signed integers (e.g. `toInt32`), improving usability of `SignedSafeMath`. ([#2243](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2243))
- * `functionCall`: new helpers that replicate Solidity's function call semantics, reducing the need to rely on `call`. ([#2264](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2264))
- * `ERC1155`: added support for a base implementation, non-standard extensions and a preset contract. ([#2014](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2014), [#2230](https://github.com/OpenZeppelin/openzeppelin-contracts/issues/2230))
-
-### Improvements
- * `ReentrancyGuard`: reduced overhead of using the `nonReentrant` modifier. ([#2171](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2171))
- * `AccessControl`: added a `RoleAdminChanged` event to `_setAdminRole`. ([#2214](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2214))
- * Made all `public` functions in the token preset contracts `virtual`. ([#2257](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2257))
-
-### Deprecations
- * `SafeERC20`: deprecated `safeApprove`. ([#2268](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2268))
-
-## 3.0.2 (2020-06-08)
-
-### Improvements
- * Added SPX license identifier to all contracts. ([#2235](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2235))
-
-## 3.0.1 (2020-04-27)
-
-### Bugfixes
- * `ERC777`: fixed the `_approve` internal function not validating some of their arguments for non-zero addresses. ([#2213](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2213))
-
-## 3.0.0 (2020-04-20)
-
-### New features
- * `AccessControl`: new contract for managing permissions in a system, replacement for `Ownable` and `Roles`. ([#2112](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2112))
- * `SafeCast`: new functions to convert to and from signed and unsigned values: `toUint256` and `toInt256`. ([#2123](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2123))
- * `EnumerableMap`: a new data structure for key-value pairs (like `mapping`) that can be iterated over. ([#2160](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2160))
-
-### Breaking changes
- * `ERC721`: `burn(owner, tokenId)` was removed, use `burn(tokenId)` instead. ([#2125](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2125))
- * `ERC721`: `_checkOnERC721Received` was removed. ([#2125](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2125))
- * `ERC721`: `_transferFrom` and `_safeTransferFrom` were renamed to `_transfer` and `_safeTransfer`. ([#2162](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2162))
- * `Ownable`: removed `_transferOwnership`. ([#2162](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2162))
- * `PullPayment`, `Escrow`: `withdrawWithGas` was removed. The old `withdraw` function now forwards all gas. ([#2125](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2125))
- * `Roles` was removed, use `AccessControl` as a replacement. ([#2112](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2112))
- * `ECDSA`: when receiving an invalid signature, `recover` now reverts instead of returning the zero address. ([#2114](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2114))
- * `Create2`: added an `amount` argument to `deploy` for contracts with `payable` constructors. ([#2117](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2117))
- * `Pausable`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
- * `Strings`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
- * `Counters`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
- * `SignedSafeMath`: moved to the `math` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
- * `ERC20Snapshot`: moved to the `token/ERC20` directory. `snapshot` was changed into an `internal` function. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
- * `Ownable`: moved to the `access` directory. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
- * `Ownable`: removed `isOwner`. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
- * `Secondary`: removed from the library, use `Ownable` instead. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
- * `Escrow`, `ConditionalEscrow`, `RefundEscrow`: these now use `Ownable` instead of `Secondary`, their external API changed accordingly. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
- * `ERC20`: removed `_burnFrom`. ([#2119](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2119))
- * `Address`: removed `toPayable`, use `payable(address)` instead. ([#2133](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2133))
- * `ERC777`: `_send`, `_mint` and `_burn` now use the caller as the operator. ([#2134](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2134))
- * `ERC777`: removed `_callsTokensToSend` and `_callTokensReceived`. ([#2134](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2134))
- * `EnumerableSet`: renamed `get` to `at`. ([#2151](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2151))
- * `ERC165Checker`: functions no longer have a leading underscore. ([#2150](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2150))
- * `ERC721Metadata`, `ERC721Enumerable`: these contracts were removed, and their functionality merged into `ERC721`. ([#2160](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2160))
- * `ERC721`: added a constructor for `name` and `symbol`. ([#2160](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2160))
- * `ERC20Detailed`: this contract was removed and its functionality merged into `ERC20`. ([#2161](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2161))
- * `ERC20`: added a constructor for `name` and `symbol`. `decimals` now defaults to 18. ([#2161](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2161))
- * `Strings`: renamed `fromUint256` to `toString` ([#2188](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2188))
-
-## 2.5.1 (2020-04-24)
-
-### Bugfixes
- * `ERC777`: fixed the `_send` and `_approve` internal functions not validating some of their arguments for non-zero addresses. ([#2212](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2212))
-
-## 2.5.0 (2020-02-04)
-
-### New features
- * `SafeCast.toUintXX`: new library for integer downcasting, which allows for safe operation on smaller types (e.g. `uint32`) when combined with `SafeMath`. ([#1926](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1926))
- * `ERC721Metadata`: added `baseURI`, which can be used for dramatic gas savings when all token URIs share a prefix (e.g. `http://api.myapp.com/tokens/<id>`). ([#1970](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1970))
- * `EnumerableSet`: new library for storing enumerable sets of values. Only `AddressSet` is supported in this release. ([#2061](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/2061))
- * `Create2`: simple library to make usage of the `CREATE2` opcode easier. ([#1744](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1744))
-
-### Improvements
- * `ERC777`: `_burn` is now internal, providing more flexibility and making it easier to create tokens that deflate. ([#1908](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1908))
- * `ReentrancyGuard`: greatly improved gas efficiency by using the net gas metering mechanism introduced in the Istanbul hardfork. ([#1992](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1992), [#1996](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1996))
- * `ERC777`: improve extensibility by making `_send` and related functions `internal`. ([#2027](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2027))
- * `ERC721`: improved revert reason when transferring tokens to a non-recipient contract. ([#2018](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2018))
-
-### Breaking changes
- * `ERC165Checker` now requires a minimum Solidity compiler version of 0.5.10. ([#1829](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1829))
-
-## 2.4.0 (2019-10-29)
-
-### New features
- * `Address.toPayable`: added a helper to convert between address types without having to resort to low-level casting. ([#1773](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1773))
- * Facilities to make metatransaction-enabled contracts through the Gas Station Network. ([#1844](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1844))
- * `Address.sendValue`: added a replacement to Solidity's `transfer`, removing the fixed gas stipend. ([#1962](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1962))
- * Added replacement for functions that don't forward all gas (which have been deprecated): ([#1976](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1976))
-   * `PullPayment.withdrawPaymentsWithGas(address payable payee)`
-   * `Escrow.withdrawWithGas(address payable payee)`
- * `SafeMath`: added support for custom error messages to `sub`, `div` and `mod` functions. ([#1828](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1828))
-
-### Improvements
- * `Address.isContract`: switched from `extcodesize` to `extcodehash` for less gas usage. ([#1802](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1802))
- * `ERC20` and `ERC777` updated to throw custom errors on subtraction overflows. ([#1828](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1828))
-
-### Deprecations
- * Deprecated functions that don't forward all gas: ([#1976](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1976))
-   * `PullPayment.withdrawPayments(address payable payee)`
-   * `Escrow.withdraw(address payable payee)`
-
-### Breaking changes
- * `Address` now requires a minimum Solidity compiler version of 0.5.5. ([#1802](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1802))
- * `SignatureBouncer` has been removed from drafts, both to avoid confusions with the GSN and `GSNRecipientSignature` (previously called `GSNBouncerSignature`) and because the API was not very clear. ([#1879](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1879))
-
-### How to upgrade from 2.4.0-beta
-
-The final 2.4.0 release includes a refactor of the GSN contracts that will be a breaking change for 2.4.0-beta users.
-
- * The default empty implementations of `_preRelayedCall` and `_postRelayedCall` were removed and must now be explicitly implemented always in custom recipients. If your custom recipient didn't include an implementation, you can provide an empty one.
- * `GSNRecipient`, `GSNBouncerBase`, and `GSNContext` were all merged into `GSNRecipient`.
- * `GSNBouncerSignature` and `GSNBouncerERC20Fee` were renamed to `GSNRecipientSignature` and `GSNRecipientERC20Fee`.
- * It is no longer necessary to inherit from `GSNRecipient` when using `GSNRecipientSignature` and `GSNRecipientERC20Fee`.
-
-For example, a contract using `GSNBouncerSignature` would have to be changed in the following way.
-
-```diff
--contract MyDapp is GSNRecipient, GSNBouncerSignature {
-+contract MyDapp is GSNRecipientSignature {
-```
-
-Refer to the table below to adjust your inheritance list.
-
-| 2.4.0-beta                         | 2.4.0                        |
-| ---------------------------------- | ---------------------------- |
-| `GSNRecipient, GSNBouncerSignature`| `GSNRecipientSignature`      |
-| `GSNRecipient, GSNBouncerERC20Fee` | `GSNRecipientERC20Fee`       |
-| `GSNBouncerBase`                   | `GSNRecipient`               |
-
 ## 2.3.0 (2019-05-27)
 
-### New features
+### New features:
  * `ERC1820`: added support for interacting with the [ERC1820](https://eips.ethereum.org/EIPS/eip-1820) registry contract (`IERC1820Registry`), as well as base contracts that can be registered as implementers there. ([#1677](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1677))
  * `ERC777`: support for the [ERC777 token](https://eips.ethereum.org/EIPS/eip-777), which has multiple improvements over `ERC20` (but is backwards compatible with it) such as built-in burning, a more  straightforward permission system, and optional sender and receiver hooks on transfer (mandatory for contracts!). ([#1684](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1684))
  * All contracts now have revert reason strings, which give insight into error conditions, and help debug failing transactions. ([#1704](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1704))
 
-### Improvements
+### Improvements:
  * Reverted the Solidity version bump done in v2.2.0, setting the minimum compiler version to v0.5.0, to prevent unexpected build breakage. Users are encouraged however to stay on top of new compiler releases, which usually include bugfixes. ([#1729](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1729))
 
-### Bugfixes
+### Bugfixes:
  * `PostDeliveryCrowdsale`: some validations where skipped when paired with other crowdsale flavors, such as `AllowanceCrowdsale`, or `MintableCrowdsale` and `ERC20Capped`, which could cause buyers to not be able to claim their purchased tokens. ([#1721](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1721))
  * `ERC20._transfer`: the `from` argument was allowed to be the zero address, so it was possible to internally trigger a transfer of 0 tokens from the zero address. This address is not a valid destinatary of transfers, nor can it give or receive allowance, so this behavior was inconsistent. It now reverts. ([#1752](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1752))
 
 ## 2.2.0 (2019-03-14)
 
-### New features
+### New features:
  * `ERC20Snapshot`: create snapshots on demand of the token balances and total supply, to later retrieve and e.g. calculate dividends at a past time. ([#1617](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1617))
  * `SafeERC20`: `ERC20` contracts with no return value (i.e. that revert on failure) are now supported. ([#1655](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1655))
  * `ERC20`: added internal `_approve(address owner, address spender, uint256 value)`, allowing derived contracts to set the allowance of arbitrary accounts. ([#1609](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1609))
  * `ERC20Metadata`: added internal `_setTokenURI(string memory tokenURI)`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
  * `TimedCrowdsale`: added internal `_extendTime(uint256 newClosingTime)` as well as `TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime)` event allowing to extend the crowdsale, as long as it hasn't already closed.
 
-### Improvements
+### Improvements:
  * Upgraded the minimum compiler version to v0.5.2: this removes many Solidity warnings that were false positives. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
  * `ECDSA`: `recover` no longer accepts malleable signatures (those using upper-range values for `s`, or 0/1 for `v`). ([#1622](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1622))
- * ``ERC721``'s transfers are now more gas efficient due to removal of unnecessary `SafeMath` calls. ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
+ * `ERC721`'s transfers are now more gas efficient due to removal of unnecessary `SafeMath` calls. ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
  * Fixed variable shadowing issues. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
 
-### Bugfixes
+### Bugfixes:
  * (minor) `SafeERC20`: `safeApprove` wasn't properly checking for a zero allowance when attempting to set a non-zero allowance. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))
 
-### Breaking changes in drafts
+### Breaking changes in drafts:
  * `TokenMetadata` has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
  * The library `Counter` has been renamed to `Counters` and its API has been improved. See an example in `ERC721`, lines [17](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L17) and [204](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L204). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
 
@@ -303,7 +47,7 @@ Refer to the table below to adjust your inheritance list.
 
 ## 2.1.0 (2019-01-04)
 
-### New features
+### New features:
  * Now targeting the 0.5.x line of Solidity compilers. For 0.4.24 support, use version 2.0 of OpenZeppelin.
  * `WhitelistCrowdsale`: a crowdsale where only whitelisted accounts (`WhitelistedRole`) can purchase tokens. Adding or removing accounts from the whitelist is done by whitelist admins (`WhitelistAdminRole`). Similar to the pre-2.0 `WhitelistedCrowdsale`. ([#1525](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1525), [#1589](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1589))
  * `RefundablePostDeliveryCrowdsale`: replacement for `RefundableCrowdsale` (deprecated, see below) where tokens are only granted once the crowdsale ends (if it meets its goal). ([#1543](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1543))
@@ -314,17 +58,17 @@ Refer to the table below to adjust your inheritance list.
  * Crowdsales: all constructors are now `public`, meaning it is not necessary to extend these contracts in order to deploy them. The exception is `FinalizableCrowdsale`, since it is meaningless unless extended. ([#1564](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1564))
  * `SignedSafeMath`: added overflow-safe operations for signed integers (`int256`). ([#1559](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1559), [#1588](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1588))
 
-### Improvements
+### Improvements:
  * The compiler version required by `Array` was behind the rest of the libray so it was updated to `v0.4.24`. ([#1553](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1553))
  * Now conforming to a 4-space indentation code style. ([1508](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1508))
  * `ERC20`: more gas efficient due to removed redundant `require`s. ([#1409](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1409))
  * `ERC721`: fixed a bug that prevented internal data structures from being properly cleaned, missing potential gas refunds. ([#1539](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1539) and [#1549](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1549))
  * `ERC721`: general gas savings on `transferFrom`, `_mint` and `_burn`, due to redudant `require`s and `SSTORE`s. ([#1549](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1549))
 
-### Bugfixes
+### Bugfixes:
 
-### Breaking changes
+### Breaking changes:
 
-### Deprecations
+### Deprecations:
  * `ERC721._burn(address owner, uint256 tokenId)`: due to the `owner` parameter being unnecessary. ([#1550](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1550))
  * `RefundableCrowdsale`: due to trading abuse potential on crowdsales that miss their goal. ([#1543](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1543))

CODE_STYLE.md

@@ -0,0 +1,63 @@
+# Code Style
+
+We value clean code and consistency, and those are prerequisites for us to
+include new code in the repository. Before proposing a change, please read this
+document and take some time to familiarize yourself with the style of the
+existing codebase.
+
+## Solidity code
+
+In order to be consistent with all the other Solidity projects, we follow the
+[official recommendations documented in the Solidity style guide](http://solidity.readthedocs.io/en/latest/style-guide.html).
+
+Any exception or additions specific to our project are documented below.
+
+### Naming
+
+* Try to avoid acronyms and abbreviations.
+
+* All state variables should be private.
+
+* Private state variables should have an underscore prefix.
+
+    ```
+    contract TestContract {
+      uint256 private _privateVar;
+      uint256 internal _internalVar;
+    }
+    ```
+
+* Parameters must not be prefixed with an underscore.
+
+    ```
+    function test(uint256 testParameter1, uint256 testParameter2) {
+    ...
+    }
+    ```
+
+* Internal and private functions should have an underscore prefix.
+
+    ```
+    function _testInternal() internal {
+      ...
+    }
+    ```
+
+    ```
+    function _testPrivate() private {
+      ...
+    }
+    ```
+
+* Events should be emitted immediately after the state change that they
+  represent, and consequently they should be named in past tense.
+
+    ```
+    function _burn(address _who, uint256 _value) internal {
+      super._burn(_who, _value);
+      emit TokensBurned(_who, _value);
+    }
+    ```
+
+  Some standards (e.g. ERC20) use present tense, and in those cases the
+  standard specification prevails.

CONTRIBUTING.md

@@ -1,27 +1,30 @@
-Contributing to OpenZeppelin Contracts
+Contributing to OpenZeppelin
 =======
 
-We really appreciate and value contributions to OpenZeppelin Contracts. Please take 5' to review the items listed below to make sure that your contributions are merged as soon as possible.
+We really appreciate and value contributions to OpenZeppelin. Please take 5' to review the items listed below to make sure that your contributions are merged as soon as possible. 
 
 ## Contribution guidelines
 
-Smart contracts manage value and are highly vulnerable to errors and attacks. We have very strict [guidelines], please make sure to review them!
+Smart contracts manage value and are highly vulnerable to errors and attacks. We have very strict guidelines, please make sure to review them: ["Contribution guidelines wiki entry"](https://github.com/OpenZeppelin/openzeppelin-solidity/wiki/Contribution-guidelines).
 
 ## Creating Pull Requests (PRs)
 
 As a contributor, you are expected to fork this repository, work on your own fork and then submit pull requests. The pull requests will be reviewed and eventually merged into the main repo. See ["Fork-a-Repo"](https://help.github.com/articles/fork-a-repo/) for how this works.
 
+*IMPORTANT* 
+* Please see ["Git flow wiki entry"](https://github.com/OpenZeppelin/openzeppelin-solidity/wiki/Git-flow) for understanding how to use branches in this repository.
+
 ## A typical workflow
 
 1) Make sure your fork is up to date with the main repository:
 
 ```
-cd openzeppelin-contracts
-git remote add upstream https://github.com/OpenZeppelin/openzeppelin-contracts.git
+cd openzeppelin-solidity
+git remote add upstream https://github.com/OpenZeppelin/openzeppelin-solidity.git
 git fetch upstream
 git pull --rebase upstream master
 ```
-NOTE: The directory `openzeppelin-contracts` represents your fork's local copy.
+NOTE: The directory `openzeppelin-solidity` represents your fork's local copy.
 
 2) Branch out from `master` into `fix/some-bug-#123`:
 (Postfixing #123 will associate your PR with the issue #123 and make everyone's life easier =D)
@@ -29,7 +32,7 @@ NOTE: The directory `openzeppelin-contracts` represents your fork's local copy.
 git checkout -b fix/some-bug-#123
 ```
 
-3) Make your changes, add your files, commit, and push to your fork.
+3) Make your changes, add your files, commit and push to your fork.
 
 ```
 git add SomeFile.js
@@ -37,28 +40,19 @@ git commit "Fix some bug #123"
 git push origin fix/some-bug-#123
 ```
 
-4) Run tests, linter, etc. This can be done by running local continuous integration and make sure it passes.
+4) Go to [github.com/OpenZeppelin/openzeppelin-solidity](https://github.com/OpenZeppelin/zeppelin-solidity) in your web browser and issue a new pull request.
 
-```bash
-npm test
-npm run lint
-```
+*IMPORTANT* Read the PR template very carefully and make sure to follow all the instructions. These instructions 
+refer to some very important conditions that your PR must meet in order to be accepted, such as making sure that all tests pass, JS linting tests pass, solidity linting tests pass, etc.
 
-5) Go to [github.com/OpenZeppelin/openzeppelin-contracts](https://github.com/OpenZeppelin/openzeppelin-contracts) in your web browser and issue a new pull request.
-
-*IMPORTANT* Read the PR template very carefully and make sure to follow all the instructions. These instructions
-refer to some very important conditions that your PR must meet in order to be accepted, such as making sure that all tests pass, JS linting tests pass, Solidity linting tests pass, etc.
-
-6) Maintainers will review your code and possibly ask for changes before your code is pulled in to the main repository. We'll check that all tests pass, review the coding style, and check for general code correctness. If everything is OK, we'll merge your pull request and your code will be part of OpenZeppelin.
+5) Maintainers will review your code and possibly ask for changes before your code is pulled in to the main repository. We'll check that all tests pass, review the coding style, and check for general code correctness. If everything is OK, we'll merge your pull request and your code will be part of OpenZeppelin.
 
 *IMPORTANT* Please pay attention to the maintainer's feedback, since its a necessary step to keep up with the standards OpenZeppelin attains to.
 
 ## All set!
 
-If you have any questions, feel free to post them to github.com/OpenZeppelin/openzeppelin-contracts/issues.
+If you have any questions feel free to post them to github.com/OpenZeppelin/openzeppelin-solidity/issues.
 
-Finally, if you're looking to collaborate and want to find easy tasks to start, look at the issues we marked as ["Good first issue"](https://github.com/OpenZeppelin/openzeppelin-contracts/labels/good%20first%20issue).
+Finally, if you're looking to collaborate and want to find easy tasks to start, look at the issues we marked as ["Good first issue"](https://github.com/OpenZeppelin/openzeppelin-solidity/labels/good%20first%20issue).
 
 Thanks for your time and code!
-
-[guidelines]: GUIDELINES.md

DOCUMENTATION.md

@@ -1,16 +1,19 @@
-Documentation is hosted at https://docs.openzeppelin.com/contracts.
+We're building an improved documentation website. It's still in development and
+contributions will be really appreciated.
 
 All of the content for the site is in this repository. The guides are in the
 [docs](/docs) directory, and the API Reference is extracted from comments in
 the source code. If you want to help improve the content, this is the
 repository you should be contributing to.
 
-[`solidity-docgen`](https://github.com/OpenZeppelin/solidity-docgen) is the
+[`solidity-docgen`](https://github.com/OpenZeppelin/solidity-docgen/tree/next) is the
 program that extracts the API Reference from source code.
 
-The [`docs.openzeppelin.com`](https://github.com/OpenZeppelin/docs.openzeppelin.com)
-repository hosts the configuration for the entire site, which includes
-documentation for all of the OpenZeppelin projects.
+The [`openzeppelin-docsite`](https://github.com/OpenZeppelin/openzeppelin-docsite/tree/next)
+repository hosts the configuration for Docusaurus, the static site generator
+that we use.
 
-To run the docs locally you should run `npm run docs:watch` on this
-repository.
+To run the docsite locally you should run `npm run docsite start` on this
+repository. This will live reload as the guides are edited, but not with
+changes to the source code comments, for that you need to restart the server.
+This should be improved eventually (contributions welcome!).

GUIDELINES.md

@@ -1,105 +0,0 @@
-Design Guidelines
-=======
-
-These are some global design goals in OpenZeppelin.
-
-#### D0 - Security in Depth
-We strive to provide secure, tested, audited code. To achieve this, we need to match intention with function. Thus, documentation, code clarity, community review and security discussions are fundamental.
-
-#### D1 - Simple and Modular
-Simpler code means easier audits, and better understanding of what each component does. We look for small files, small contracts, and small functions. If you can separate a contract into two independent functionalities you should probably do it.
-
-#### D2 - Naming Matters
-
-We take our time with picking names. Code is going to be written once, and read hundreds of times. Renaming for clarity is encouraged.
-
-#### D3 - Tests
-
-Write tests for all your code. We encourage Test Driven Development so we know when our code is right. Even though not all code in the repository is tested at the moment, we aim to test every line of code in the future.
-
-#### D4 - Check preconditions and post-conditions
-
-A very important way to prevent vulnerabilities is to catch a contract’s inconsistent state as early as possible. This is why we want functions to check pre- and post-conditions for executing its logic. When writing code, ask yourself what you are expecting to be true before and after the function runs, and express it in code.
-
-#### D5 - Code Consistency
-
-Consistency on the way classes are used is paramount to an easier understanding of the library. The codebase should be as unified as possible. Read existing code and get inspired before you write your own. Follow the style guidelines. Don’t hesitate to ask for help on how to best write a specific piece of code.
-
-#### D6 - Regular Audits
-Following good programming practices is a way to reduce the risk of vulnerabilities, but professional code audits are still needed. We will perform regular code audits on major releases, and hire security professionals to provide independent review.
-
-# Style Guidelines
-
-The design guidelines have quite a high abstraction level. These style guidelines are more concrete and easier to apply, and also more opinionated. We value clean code and consistency, and those are prerequisites for us to include new code in the repository. Before proposing a change, please read these guidelines and take some time to familiarize yourself with the style of the existing codebase.
-
-## Solidity code
-
-In order to be consistent with all the other Solidity projects, we follow the
-[official recommendations documented in the Solidity style guide](http://solidity.readthedocs.io/en/latest/style-guide.html).
-
-Any exception or additions specific to our project are documented below.
-
-* Try to avoid acronyms and abbreviations.
-
-* All state variables should be private.
-
-* Private state variables should have an underscore prefix.
-
-    ```
-    contract TestContract {
-      uint256 private _privateVar;
-      uint256 internal _internalVar;
-    }
-    ```
-
-* Parameters must not be prefixed with an underscore.
-
-    ```
-    function test(uint256 testParameter1, uint256 testParameter2) {
-    ...
-    }
-    ```
-
-* Internal and private functions should have an underscore prefix.
-
-    ```
-    function _testInternal() internal {
-      ...
-    }
-    ```
-
-    ```
-    function _testPrivate() private {
-      ...
-    }
-    ```
-
-* Events should be emitted immediately after the state change that they
-  represent, and consequently they should be named in past tense.
-
-    ```
-    function _burn(address who, uint256 value) internal {
-      super._burn(who, value);
-      emit TokensBurned(who, value);
-    }
-    ```
-
-  Some standards (e.g. ERC20) use present tense, and in those cases the
-  standard specification prevails.
-  
-* Interface names should have a capital I prefix.
-
-    ```
-    interface IERC777 {
-    ```
-
-
-## Tests
-
-* Tests Must be Written Elegantly
-
-    Tests are a good way to show how to use the library, and maintaining them is extremely necessary. Don't write long tests, write helper functions to make them be as short and concise as possible (they should take just a few lines each), and use good variable names.
-
-* Tests Must not be Random
-
-    Inputs for tests should not be generated randomly. Accounts used to create test contracts are an exception, those can be random. Also, the type and structure of outputs should be checked.

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2016-2020 zOS Global Limited
+Copyright (c) 2016-2019 zOS Global Limited
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

README.md

@@ -1,66 +1,42 @@
-# <img src="logo.svg" alt="OpenZeppelin" height="40px">
+# <img src="logo.png" alt="OpenZeppelin" width="400px">
 
-[![Docs](https://img.shields.io/badge/docs-%F0%9F%93%84-blue)](https://docs.openzeppelin.com/contracts)
-[![NPM Package](https://img.shields.io/npm/v/@openzeppelin/contracts.svg)](https://www.npmjs.org/package/@openzeppelin/contracts)
-[![Coverage Status](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts/graph/badge.svg)](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts)
+[![NPM Package](https://img.shields.io/npm/v/openzeppelin-solidity.svg?style=flat-square)](https://www.npmjs.org/package/openzeppelin-solidity)
+[![Build Status](https://travis-ci.com/OpenZeppelin/openzeppelin-solidity.svg?branch=master)](https://travis-ci.com/OpenZeppelin/openzeppelin-solidity)
+[![Coverage Status](https://coveralls.io/repos/github/OpenZeppelin/openzeppelin-solidity/badge.svg?branch=master)](https://coveralls.io/github/OpenZeppelin/openzeppelin-solidity?branch=master)
 
-**A library for secure smart contract development.** Build on a solid foundation of community-vetted code.
+**OpenZeppelin is a library for secure smart contract development.** It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
 
- * Implementations of standards like [ERC20](https://docs.openzeppelin.com/contracts/erc20) and [ERC721](https://docs.openzeppelin.com/contracts/erc721).
- * Flexible [role-based permissioning](https://docs.openzeppelin.com/contracts/access-control) scheme.
- * Reusable [Solidity components](https://docs.openzeppelin.com/contracts/utilities) to build custom contracts and complex decentralized systems.
- * First-class integration with the [Gas Station Network](https://docs.openzeppelin.com/contracts/gsn) for systems with no gas fees!
- * [Audited](https://github.com/OpenZeppelin/openzeppelin-contracts/tree/master/audit) by leading security firms (_last full audit on v2.0.0_).
+## Install
 
-## Overview
-
-### Installation
-
-```console
-$ npm install @openzeppelin/contracts
+```
+npm install openzeppelin-solidity
 ```
 
-OpenZeppelin Contracts features a [stable API](https://docs.openzeppelin.com/contracts/releases-stability#api-stability), which means your contracts won't break unexpectedly when upgrading to a newer minor version.
+OpenZeppelin features a stable API, which means your contracts won't break unexpectedly when upgrading to a newer minor version. You can read ṫhe details in our [API Stability](https://forum.zeppelin.solutions/t/api-stability/138) document.
 
-### Usage
+## Usage
 
-Once installed, you can use the contracts in the library by importing them:
+To write your custom contracts, import ours and extend them through inheritance.
 
 ```solidity
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
-import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
+import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Full.sol';
+import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Mintable.sol';
 
-contract MyCollectible is ERC721 {
-    constructor() ERC721("MyCollectible", "MCO") {
-    }
+contract MyNFT is ERC721Full, ERC721Mintable {
+  constructor() ERC721Full("MyNFT", "MNFT") public {
+  }
 }
 ```
 
-_If you're new to smart contract development, head to [Developing Smart Contracts](https://docs.openzeppelin.com/learn/developing-smart-contracts) to learn about creating a new project and compiling your contracts._
+> You need an ethereum development framework for the above import statements to work! Check out these guides for [Truffle], [Embark] or [Buidler].
 
-To keep your system secure, you should **always** use the installed code as-is, and neither copy-paste it from online sources, nor modify it yourself. The library is designed so that only the contracts and functions you use are deployed, so you don't need to worry about it needlessly increasing gas costs.
-
-## Learn More
-
-The guides in the [docs site](https://docs.openzeppelin.com/contracts) will teach about different concepts, and how to use the related contracts that OpenZeppelin Contracts provides:
-
-* [Access Control](https://docs.openzeppelin.com/contracts/access-control): decide who can perform each of the actions on your system.
-* [Tokens](https://docs.openzeppelin.com/contracts/tokens): create tradeable assets or collectives, and distribute them via [Crowdsales](https://docs.openzeppelin.com/contracts/crowdsales).
-* [Gas Station Network](https://docs.openzeppelin.com/contracts/gsn): let your users interact with your contracts without having to pay for gas themselves.
-* [Utilities](https://docs.openzeppelin.com/contracts/utilities): generic useful tools, including non-overflowing math, signature verification, and trustless paying systems.
-
-The [full API](https://docs.openzeppelin.com/contracts/api/token/ERC20) is also thoroughly documented, and serves as a great reference when developing your smart contract application. You can also ask for help or follow Contracts's development in the [community forum](https://forum.openzeppelin.com).
-
-Finally, you may want to take a look at the [guides on our blog](https://blog.openzeppelin.com/guides), which cover several common use cases and good practices.. The following articles provide great background reading, though please note, some of the referenced tools have changed as the tooling in the ecosystem continues to rapidly evolve.
-
-* [The Hitchhiker’s Guide to Smart Contracts in Ethereum](https://blog.openzeppelin.com/the-hitchhikers-guide-to-smart-contracts-in-ethereum-848f08001f05) will help you get an overview of the various tools available for smart contract development, and help you set up your environment.
-* [A Gentle Introduction to Ethereum Programming, Part 1](https://blog.openzeppelin.com/a-gentle-introduction-to-ethereum-programming-part-1-783cc7796094) provides very useful information on an introductory level, including many basic concepts from the Ethereum platform.
-* For a more in-depth dive, you may read the guide [Designing the Architecture for Your Ethereum Application](https://blog.openzeppelin.com/designing-the-architecture-for-your-ethereum-application-9cec086f8317), which discusses how to better structure your application and its relationship to the real world.
+On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our forum][forum].
 
 ## Security
 
-This project is maintained by [OpenZeppelin](https://openzeppelin.com), and developed following our high standards for code quality and security. OpenZeppelin is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
+OpenZeppelin the project is maintained by [Zeppelin] the company, and developed following our high standards for code quality and security. OpenZeppelin is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
 
 The core development principles and strategies that OpenZeppelin is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.
 
@@ -70,8 +46,18 @@ Please report any security issues you find to security@openzeppelin.org.
 
 ## Contribute
 
-OpenZeppelin exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the [contribution guide](CONTRIBUTING.md)!
+OpenZeppelin exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the [contribution guide]!
 
 ## License
 
 OpenZeppelin is released under the [MIT License](LICENSE).
+
+
+[API docs]: https://openzeppelin.org/api/docs/token_ERC721_ERC721BasicToken.html
+[guides]: https://openzeppelin.org/api/docs/get-started.html
+[forum]: https://forum.zeppelin.solutions
+[Zeppelin]: https://zeppelin.solutions
+[contribution guide]: CONTRIBUTING.md
+[Truffle]: https://truffleframework.com/docs/truffle/quickstart
+[Embark]: https://embark.status.im/docs/quick_start.html
+[Buidler]: https://buidler.dev/guides/#getting-started

RELEASING.md

@@ -1,20 +1,83 @@
 # Releasing
 
-> Visit the documentation for [details about release schedule].
+This document describes our release process, and contains the steps to be followed by an OpenZeppelin maintainer at the several stages of a release.
 
-Start on an up-to-date `master` branch.
+We release a new version of OpenZeppelin monthly. Release cycles are tracked in the [issue milestones](https://github.com/OpenZeppelin/openzeppelin-solidity/milestones).
 
-Create the release branch with `npm run release start minor`.
+Each release has at least one release candidate published first, intended for community review and any critical fixes that may come out of it. At the moment we leave 1 week between the first release candidate and the final release.
 
-Publish a release candidate with `npm run release rc`.
+Before starting make sure to verify the following items.
+* Your local `master` branch is in sync with your `upstream` remote (it may have another name depending on your setup).
+* Your repo is clean, particularly with no untracked files in the contracts and tests directories. Verify with `git clean -n`.
 
-Publish the final release with `npm run release final`.
 
-Follow the general [OpenZeppelin release checklist].
+## Creating the release branch
 
-[details about release schedule]: https://docs.openzeppelin.com/contracts/releases-stability
-[OpenZeppelin release checklist]: https://github.com/OpenZeppelin/code-style/blob/master/RELEASE_CHECKLIST.md
+We'll refer to a release `vX.Y.Z`.
 
+```
+git checkout master
+git checkout -b release-vX.Y.Z
+```
+
+## Creating a release candidate
+
+Once in the release branch, change the version string in `package.json`, `package-lock.json` and `ethpm.json` to `X.Y.Z-rc.R`. (This will be `X.Y.Z-rc.1` for the first release candidate.) Commit these changes and tag the commit as `vX.Y.Z-rc.R`.
+
+```
+git add package.json package-lock.json ethpm.json
+git commit -m "Release candidate vX.Y.Z-rc.R"
+git tag -a vX.Y.Z-rc.R
+git push upstream release-vX.Y.Z
+git push upstream vX.Y.Z-rc.R
+```
+
+Draft the release notes in our [GitHub releases](https://github.com/OpenZeppelin/openzeppelin-solidity/releases). Make sure to mark it as a pre-release! Try to be consistent with our previous release notes in the title and format of the text. Release candidates don't need a detailed changelog, but make sure to include a link to GitHub's compare page.
+
+Once the CI run for the new tag is green, publish on npm under the `next` tag. You should see the contracts compile automatically.
+
+```
+npm publish --tag next
+```
+
+Publish the release notes on GitHub and the forum, and ask our community manager to announce the release candidate on at least Twitter.
+
+## Creating the final release
+
+Make sure to have the latest changes from `upstream` in your local release branch.
+
+```
+git checkout release-vX.Y.Z
+git pull upstream
+```
+
+Before starting the release process, make one final commit to CHANGELOG.md, including the date of the release.
+
+Change the version string in `package.json`, `package-lock.json` and `ethpm.json` removing the "-rc.R" suffix. Commit these changes and tag the commit as `vX.Y.Z`.
+
+```
+git add package.json package-lock.json ethpm.json
+git commit -m "Release vX.Y.Z"
+git tag -a vX.Y.Z
+git push upstream release-vX.Y.Z
+git push upstream vX.Y.Z
+```
+
+Draft the release notes in GitHub releases. Try to be consistent with our previous release notes in the title and format of the text. Make sure to include a detailed changelog.
+
+Once the CI run for the new tag is green, publish on npm. You should see the contracts compile automatically.
+
+```
+npm publish
+```
+
+Publish the release notes on GitHub and ask our community manager to announce the release!
+
+Delete the `next` tag in the npm package as there is no longer a release candidate.
+
+```
+npm dist-tag rm --otp $2FA_CODE openzeppelin-solidity next
+```
 
 ## Merging the release branch
 

contracts/ARCHITECTURE.md

@@ -0,0 +1,27 @@
+## Architecture
+
+The following provides visibility into how OpenZeppelin's contracts are organized:
+
+- **access** - Smart contracts that enable functionality that can be used for selective restrictions and basic authorization control functions.
+- **crowdsale** - A collection of smart contracts used to manage token crowdsales that allow investors to purchase tokens with ETH. Includes a base contract which implements fundamental crowdsale functionality in its simplest form. The base contract can be extended in order to satisfy your crowdsale’s specific requirements.
+	- **distribution** - Includes extensions of the base crowdsale contract which can be used to customize the completion of a crowdsale.
+	- **emission** - Includes extensions of the base crowdsale contract which can be used to mint and manage how tokens are issued to purchasers.
+	- **price** - Includes extensions of the crowdsale contract that can be used to manage changes in token prices.
+	- **validation**  - Includes extensions of the crowdsale contract that can be used to enforce restraints and limit access to token purchases.
+- **examples** - A collection of simple smart contracts that demonstrate how to add new features to base contracts through multiple inheritance.
+- **introspection**  - An interface that can be used to make a contract comply with the ERC-165 standard as well as a contract that implements ERC-165 using a lookup table.
+- **lifecycle** - A collection of base contracts used to manage the existence and behavior of your contracts and their funds.
+- **math** - Libraries with safety checks on operations that throw on errors.
+- **mocks** - A collection of abstract contracts that are primarily used for unit testing. They also serve as good usage examples and demonstrate how to combine contracts with inheritance when developing your own custom applications.
+- **ownership** - A collection of smart contracts that can be used to manage contract and token ownership
+- **payment** - A collection of smart contracts that can be used to manage payments through escrow arrangements, withdrawals, and claims. Includes support for both single payees and multiple payees.
+- **proposals** - A collection of smart contracts that reflect community Ethereum Improvement Proposals (EIPs). These contracts are under development and standardization. They are not recommended for production, but they are useful for experimentation with pending EIP standards. Go [here](https://github.com/OpenZeppelin/openzeppelin-solidity/wiki/ERC-Process) for more information.
+
+- **token** - A collection of approved ERC standard tokens -- their interfaces and implementations.
+	- **ERC20** - A standard interface for fungible tokens:
+		- *Interfaces* - Includes the ERC-20 token standard basic interface. I.e., what the contract’s ABI can represent.
+		- *Implementations* - Includes ERC-20 token implementations that include all required and some optional ERC-20 functionality.
+	- **ERC721** - A standard interface for non-fungible tokens
+		- *Interfaces* - Includes the ERC-721 token standard basic interface. I.e., what the contract’s ABI can represent.
+		- *Implementations* - Includes ERC-721 token implementations that include all required and some optional ERC-721 functionality.
+

contracts/access/AccessControl.sol

@@ -1,243 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/Context.sol";
-import "../utils/Strings.sol";
-import "../utils/introspection/ERC165.sol";
-
-/**
- * @dev External interface of AccessControl declared to support ERC165 detection.
- */
-interface IAccessControl {
-    function hasRole(bytes32 role, address account) external view returns (bool);
-    function getRoleAdmin(bytes32 role) external view returns (bytes32);
-    function grantRole(bytes32 role, address account) external;
-    function revokeRole(bytes32 role, address account) external;
-    function renounceRole(bytes32 role, address account) external;
-}
-
-/**
- * @dev Contract module that allows children to implement role-based access
- * control mechanisms. This is a lightweight version that doesn't allow enumerating role
- * members except through off-chain means by accessing the contract event logs. Some
- * applications may benefit from on-chain enumerability, for those cases see
- * {AccessControlEnumerable}.
- *
- * Roles are referred to by their `bytes32` identifier. These should be exposed
- * in the external API and be unique. The best way to achieve this is by
- * using `public constant` hash digests:
- *
- * ```
- * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
- * ```
- *
- * Roles can be used to represent a set of permissions. To restrict access to a
- * function call, use {hasRole}:
- *
- * ```
- * function foo() public {
- *     require(hasRole(MY_ROLE, msg.sender));
- *     ...
- * }
- * ```
- *
- * Roles can be granted and revoked dynamically via the {grantRole} and
- * {revokeRole} functions. Each role has an associated admin role, and only
- * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
- *
- * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
- * that only accounts with this role will be able to grant or revoke other
- * roles. More complex role relationships can be created by using
- * {_setRoleAdmin}.
- *
- * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
- * grant and revoke this role. Extra precautions should be taken to secure
- * accounts that have been granted it.
- */
-abstract contract AccessControl is Context, IAccessControl, ERC165 {
-    struct RoleData {
-        mapping (address => bool) members;
-        bytes32 adminRole;
-    }
-
-    mapping (bytes32 => RoleData) private _roles;
-
-    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
-
-    /**
-     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
-     *
-     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
-     * {RoleAdminChanged} not being emitted signaling this.
-     *
-     * _Available since v3.1._
-     */
-    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
-
-    /**
-     * @dev Emitted when `account` is granted `role`.
-     *
-     * `sender` is the account that originated the contract call, an admin role
-     * bearer except when using {_setupRole}.
-     */
-    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
-
-    /**
-     * @dev Emitted when `account` is revoked `role`.
-     *
-     * `sender` is the account that originated the contract call:
-     *   - if using `revokeRole`, it is the admin role bearer
-     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
-     */
-    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
-
-    /**
-     * @dev Modifier that checks that an account has a specific role. Reverts
-     * with a standardized message including the required role.
-     *
-     * The format of the revert reason is given by the following regular expression:
-     *
-     *  /^AccessControl: account (0x[0-9a-f]{20}) is missing role (0x[0-9a-f]{32})$/
-     *
-     * _Available since v4.1._
-     */
-    modifier onlyRole(bytes32 role) {
-        _checkRole(role, _msgSender());
-        _;
-    }
-
-    /**
-     * @dev See {IERC165-supportsInterface}.
-     */
-    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
-        return interfaceId == type(IAccessControl).interfaceId
-            || super.supportsInterface(interfaceId);
-    }
-
-    /**
-     * @dev Returns `true` if `account` has been granted `role`.
-     */
-    function hasRole(bytes32 role, address account) public view override returns (bool) {
-        return _roles[role].members[account];
-    }
-
-    /**
-     * @dev Revert with a standard message if `account` is missing `role`.
-     *
-     * The format of the revert reason is given by the following regular expression:
-     *
-     *  /^AccessControl: account (0x[0-9a-f]{20}) is missing role (0x[0-9a-f]{32})$/
-     */
-    function _checkRole(bytes32 role, address account) internal view {
-        if(!hasRole(role, account)) {
-            revert(string(abi.encodePacked(
-                "AccessControl: account ",
-                Strings.toHexString(uint160(account), 20),
-                " is missing role ",
-                Strings.toHexString(uint256(role), 32)
-            )));
-        }
-    }
-
-    /**
-     * @dev Returns the admin role that controls `role`. See {grantRole} and
-     * {revokeRole}.
-     *
-     * To change a role's admin, use {_setRoleAdmin}.
-     */
-    function getRoleAdmin(bytes32 role) public view override returns (bytes32) {
-        return _roles[role].adminRole;
-    }
-
-    /**
-     * @dev Grants `role` to `account`.
-     *
-     * If `account` had not been already granted `role`, emits a {RoleGranted}
-     * event.
-     *
-     * Requirements:
-     *
-     * - the caller must have ``role``'s admin role.
-     */
-    function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
-        _grantRole(role, account);
-    }
-
-    /**
-     * @dev Revokes `role` from `account`.
-     *
-     * If `account` had been granted `role`, emits a {RoleRevoked} event.
-     *
-     * Requirements:
-     *
-     * - the caller must have ``role``'s admin role.
-     */
-    function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
-        _revokeRole(role, account);
-    }
-
-    /**
-     * @dev Revokes `role` from the calling account.
-     *
-     * Roles are often managed via {grantRole} and {revokeRole}: this function's
-     * purpose is to provide a mechanism for accounts to lose their privileges
-     * if they are compromised (such as when a trusted device is misplaced).
-     *
-     * If the calling account had been granted `role`, emits a {RoleRevoked}
-     * event.
-     *
-     * Requirements:
-     *
-     * - the caller must be `account`.
-     */
-    function renounceRole(bytes32 role, address account) public virtual override {
-        require(account == _msgSender(), "AccessControl: can only renounce roles for self");
-
-        _revokeRole(role, account);
-    }
-
-    /**
-     * @dev Grants `role` to `account`.
-     *
-     * If `account` had not been already granted `role`, emits a {RoleGranted}
-     * event. Note that unlike {grantRole}, this function doesn't perform any
-     * checks on the calling account.
-     *
-     * [WARNING]
-     * ====
-     * This function should only be called from the constructor when setting
-     * up the initial roles for the system.
-     *
-     * Using this function in any other way is effectively circumventing the admin
-     * system imposed by {AccessControl}.
-     * ====
-     */
-    function _setupRole(bytes32 role, address account) internal virtual {
-        _grantRole(role, account);
-    }
-
-    /**
-     * @dev Sets `adminRole` as ``role``'s admin role.
-     *
-     * Emits a {RoleAdminChanged} event.
-     */
-    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
-        emit RoleAdminChanged(role, getRoleAdmin(role), adminRole);
-        _roles[role].adminRole = adminRole;
-    }
-
-    function _grantRole(bytes32 role, address account) private {
-        if (!hasRole(role, account)) {
-            _roles[role].members[account] = true;
-            emit RoleGranted(role, account, _msgSender());
-        }
-    }
-
-    function _revokeRole(bytes32 role, address account) private {
-        if (hasRole(role, account)) {
-            _roles[role].members[account] = false;
-            emit RoleRevoked(role, account, _msgSender());
-        }
-    }
-}

contracts/access/AccessControlEnumerable.sol

@@ -1,87 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "./AccessControl.sol";
-import "../utils/structs/EnumerableSet.sol";
-
-/**
- * @dev External interface of AccessControlEnumerable declared to support ERC165 detection.
- */
-interface IAccessControlEnumerable {
-    function getRoleMember(bytes32 role, uint256 index) external view returns (address);
-    function getRoleMemberCount(bytes32 role) external view returns (uint256);
-}
-
-/**
- * @dev Extension of {AccessControl} that allows enumerating the members of each role.
- */
-abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessControl {
-    using EnumerableSet for EnumerableSet.AddressSet;
-
-    mapping (bytes32 => EnumerableSet.AddressSet) private _roleMembers;
-
-    /**
-     * @dev See {IERC165-supportsInterface}.
-     */
-    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
-        return interfaceId == type(IAccessControlEnumerable).interfaceId
-            || super.supportsInterface(interfaceId);
-    }
-
-    /**
-     * @dev Returns one of the accounts that have `role`. `index` must be a
-     * value between 0 and {getRoleMemberCount}, non-inclusive.
-     *
-     * Role bearers are not sorted in any particular way, and their ordering may
-     * change at any point.
-     *
-     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
-     * you perform all queries on the same block. See the following
-     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
-     * for more information.
-     */
-    function getRoleMember(bytes32 role, uint256 index) public view override returns (address) {
-        return _roleMembers[role].at(index);
-    }
-
-    /**
-     * @dev Returns the number of accounts that have `role`. Can be used
-     * together with {getRoleMember} to enumerate all bearers of a role.
-     */
-    function getRoleMemberCount(bytes32 role) public view override returns (uint256) {
-        return _roleMembers[role].length();
-    }
-
-    /**
-     * @dev Overload {grantRole} to track enumerable memberships
-     */
-    function grantRole(bytes32 role, address account) public virtual override {
-        super.grantRole(role, account);
-        _roleMembers[role].add(account);
-    }
-
-    /**
-     * @dev Overload {revokeRole} to track enumerable memberships
-     */
-    function revokeRole(bytes32 role, address account) public virtual override {
-        super.revokeRole(role, account);
-        _roleMembers[role].remove(account);
-    }
-
-    /**
-     * @dev Overload {renounceRole} to track enumerable memberships
-     */
-    function renounceRole(bytes32 role, address account) public virtual override {
-        super.renounceRole(role, account);
-        _roleMembers[role].remove(account);
-    }
-
-    /**
-     * @dev Overload {_setupRole} to track enumerable memberships
-     */
-    function _setupRole(bytes32 role, address account) internal virtual override {
-        super._setupRole(role, account);
-        _roleMembers[role].add(account);
-    }
-}

contracts/access/README.adoc

@@ -1,17 +0,0 @@
-= Access
-
-[.readme-notice]
-NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/access
-
-This directory provides ways to restrict who can access the functions of a contract or when they can do it.
-
-- {AccessControl} provides a general role based access control mechanism. Multiple hierarchical roles can be created and assigned each to multiple accounts.
-- {Ownable} is a simpler mechanism with a single owner "role" that can be assigned to a single account. This simpler mechanism can be useful for quick tests but projects with production concerns are likely to outgrow it.
-
-== Authorization
-
-{{Ownable}}
-
-{{AccessControl}}
-
-{{AccessControlEnumerable}}

contracts/access/README.md

@@ -0,0 +1,9 @@
+---
+sections:
+  - title: Library
+    contracts:
+      - Roles
+  - subdirectory: roles
+---
+
+> This page is incomplete. We're working to improve it for the next release. Stay tuned!

contracts/access/Roles.sol

@@ -0,0 +1,36 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @title Roles
+ * @dev Library for managing addresses assigned to a Role.
+ */
+library Roles {
+    struct Role {
+        mapping (address => bool) bearer;
+    }
+
+    /**
+     * @dev Give an account access to this role.
+     */
+    function add(Role storage role, address account) internal {
+        require(!has(role, account), "Roles: account already has role");
+        role.bearer[account] = true;
+    }
+
+    /**
+     * @dev Remove an account's access to this role.
+     */
+    function remove(Role storage role, address account) internal {
+        require(has(role, account), "Roles: account does not have role");
+        role.bearer[account] = false;
+    }
+
+    /**
+     * @dev Check if an account has this role.
+     * @return bool
+     */
+    function has(Role storage role, address account) internal view returns (bool) {
+        require(account != address(0), "Roles: account is the zero address");
+        return role.bearer[account];
+    }
+}

contracts/access/roles/CapperRole.sol

@@ -0,0 +1,43 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+
+contract CapperRole {
+    using Roles for Roles.Role;
+
+    event CapperAdded(address indexed account);
+    event CapperRemoved(address indexed account);
+
+    Roles.Role private _cappers;
+
+    constructor () internal {
+        _addCapper(msg.sender);
+    }
+
+    modifier onlyCapper() {
+        require(isCapper(msg.sender), "CapperRole: caller does not have the Capper role");
+        _;
+    }
+
+    function isCapper(address account) public view returns (bool) {
+        return _cappers.has(account);
+    }
+
+    function addCapper(address account) public onlyCapper {
+        _addCapper(account);
+    }
+
+    function renounceCapper() public {
+        _removeCapper(msg.sender);
+    }
+
+    function _addCapper(address account) internal {
+        _cappers.add(account);
+        emit CapperAdded(account);
+    }
+
+    function _removeCapper(address account) internal {
+        _cappers.remove(account);
+        emit CapperRemoved(account);
+    }
+}

contracts/access/roles/MinterRole.sol

@@ -0,0 +1,43 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+
+contract MinterRole {
+    using Roles for Roles.Role;
+
+    event MinterAdded(address indexed account);
+    event MinterRemoved(address indexed account);
+
+    Roles.Role private _minters;
+
+    constructor () internal {
+        _addMinter(msg.sender);
+    }
+
+    modifier onlyMinter() {
+        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
+        _;
+    }
+
+    function isMinter(address account) public view returns (bool) {
+        return _minters.has(account);
+    }
+
+    function addMinter(address account) public onlyMinter {
+        _addMinter(account);
+    }
+
+    function renounceMinter() public {
+        _removeMinter(msg.sender);
+    }
+
+    function _addMinter(address account) internal {
+        _minters.add(account);
+        emit MinterAdded(account);
+    }
+
+    function _removeMinter(address account) internal {
+        _minters.remove(account);
+        emit MinterRemoved(account);
+    }
+}

contracts/access/roles/PauserRole.sol

@@ -0,0 +1,43 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+
+contract PauserRole {
+    using Roles for Roles.Role;
+
+    event PauserAdded(address indexed account);
+    event PauserRemoved(address indexed account);
+
+    Roles.Role private _pausers;
+
+    constructor () internal {
+        _addPauser(msg.sender);
+    }
+
+    modifier onlyPauser() {
+        require(isPauser(msg.sender), "PauserRole: caller does not have the Pauser role");
+        _;
+    }
+
+    function isPauser(address account) public view returns (bool) {
+        return _pausers.has(account);
+    }
+
+    function addPauser(address account) public onlyPauser {
+        _addPauser(account);
+    }
+
+    function renouncePauser() public {
+        _removePauser(msg.sender);
+    }
+
+    function _addPauser(address account) internal {
+        _pausers.add(account);
+        emit PauserAdded(account);
+    }
+
+    function _removePauser(address account) internal {
+        _pausers.remove(account);
+        emit PauserRemoved(account);
+    }
+}

contracts/access/roles/SignerRole.sol

@@ -0,0 +1,43 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+
+contract SignerRole {
+    using Roles for Roles.Role;
+
+    event SignerAdded(address indexed account);
+    event SignerRemoved(address indexed account);
+
+    Roles.Role private _signers;
+
+    constructor () internal {
+        _addSigner(msg.sender);
+    }
+
+    modifier onlySigner() {
+        require(isSigner(msg.sender), "SignerRole: caller does not have the Signer role");
+        _;
+    }
+
+    function isSigner(address account) public view returns (bool) {
+        return _signers.has(account);
+    }
+
+    function addSigner(address account) public onlySigner {
+        _addSigner(account);
+    }
+
+    function renounceSigner() public {
+        _removeSigner(msg.sender);
+    }
+
+    function _addSigner(address account) internal {
+        _signers.add(account);
+        emit SignerAdded(account);
+    }
+
+    function _removeSigner(address account) internal {
+        _signers.remove(account);
+        emit SignerRemoved(account);
+    }
+}

contracts/access/roles/WhitelistAdminRole.sol

@@ -0,0 +1,47 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+
+/**
+ * @title WhitelistAdminRole
+ * @dev WhitelistAdmins are responsible for assigning and removing Whitelisted accounts.
+ */
+contract WhitelistAdminRole {
+    using Roles for Roles.Role;
+
+    event WhitelistAdminAdded(address indexed account);
+    event WhitelistAdminRemoved(address indexed account);
+
+    Roles.Role private _whitelistAdmins;
+
+    constructor () internal {
+        _addWhitelistAdmin(msg.sender);
+    }
+
+    modifier onlyWhitelistAdmin() {
+        require(isWhitelistAdmin(msg.sender), "WhitelistAdminRole: caller does not have the WhitelistAdmin role");
+        _;
+    }
+
+    function isWhitelistAdmin(address account) public view returns (bool) {
+        return _whitelistAdmins.has(account);
+    }
+
+    function addWhitelistAdmin(address account) public onlyWhitelistAdmin {
+        _addWhitelistAdmin(account);
+    }
+
+    function renounceWhitelistAdmin() public {
+        _removeWhitelistAdmin(msg.sender);
+    }
+
+    function _addWhitelistAdmin(address account) internal {
+        _whitelistAdmins.add(account);
+        emit WhitelistAdminAdded(account);
+    }
+
+    function _removeWhitelistAdmin(address account) internal {
+        _whitelistAdmins.remove(account);
+        emit WhitelistAdminRemoved(account);
+    }
+}

contracts/access/roles/WhitelistedRole.sol

@@ -0,0 +1,50 @@
+pragma solidity ^0.5.0;
+
+import "../Roles.sol";
+import "./WhitelistAdminRole.sol";
+
+/**
+ * @title WhitelistedRole
+ * @dev Whitelisted accounts have been approved by a WhitelistAdmin to perform certain actions (e.g. participate in a
+ * crowdsale). This role is special in that the only accounts that can add it are WhitelistAdmins (who can also remove
+ * it), and not Whitelisteds themselves.
+ */
+contract WhitelistedRole is WhitelistAdminRole {
+    using Roles for Roles.Role;
+
+    event WhitelistedAdded(address indexed account);
+    event WhitelistedRemoved(address indexed account);
+
+    Roles.Role private _whitelisteds;
+
+    modifier onlyWhitelisted() {
+        require(isWhitelisted(msg.sender), "WhitelistedRole: caller does not have the Whitelisted role");
+        _;
+    }
+
+    function isWhitelisted(address account) public view returns (bool) {
+        return _whitelisteds.has(account);
+    }
+
+    function addWhitelisted(address account) public onlyWhitelistAdmin {
+        _addWhitelisted(account);
+    }
+
+    function removeWhitelisted(address account) public onlyWhitelistAdmin {
+        _removeWhitelisted(account);
+    }
+
+    function renounceWhitelisted() public {
+        _removeWhitelisted(msg.sender);
+    }
+
+    function _addWhitelisted(address account) internal {
+        _whitelisteds.add(account);
+        emit WhitelistedAdded(account);
+    }
+
+    function _removeWhitelisted(address account) internal {
+        _whitelisteds.remove(account);
+        emit WhitelistedRemoved(account);
+    }
+}

contracts/crowdsale/Crowdsale.sol

@@ -0,0 +1,198 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/IERC20.sol";
+import "../math/SafeMath.sol";
+import "../token/ERC20/SafeERC20.sol";
+import "../utils/ReentrancyGuard.sol";
+
+/**
+ * @title Crowdsale
+ * @dev Crowdsale is a base contract for managing a token crowdsale,
+ * allowing investors to purchase tokens with ether. This contract implements
+ * such functionality in its most fundamental form and can be extended to provide additional
+ * functionality and/or custom behavior.
+ * The external interface represents the basic interface for purchasing tokens, and conforms
+ * the base architecture for crowdsales. It is *not* intended to be modified / overridden.
+ * The internal interface conforms the extensible and modifiable surface of crowdsales. Override
+ * the methods to add functionality. Consider using 'super' where appropriate to concatenate
+ * behavior.
+ */
+contract Crowdsale is ReentrancyGuard {
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
+
+    // The token being sold
+    IERC20 private _token;
+
+    // Address where funds are collected
+    address payable private _wallet;
+
+    // How many token units a buyer gets per wei.
+    // The rate is the conversion between wei and the smallest and indivisible token unit.
+    // So, if you are using a rate of 1 with a ERC20Detailed token with 3 decimals called TOK
+    // 1 wei will give you 1 unit, or 0.001 TOK.
+    uint256 private _rate;
+
+    // Amount of wei raised
+    uint256 private _weiRaised;
+
+    /**
+     * Event for token purchase logging
+     * @param purchaser who paid for the tokens
+     * @param beneficiary who got the tokens
+     * @param value weis paid for purchase
+     * @param amount amount of tokens purchased
+     */
+    event TokensPurchased(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
+
+    /**
+     * @param rate Number of token units a buyer gets per wei
+     * @dev The rate is the conversion between wei and the smallest and indivisible
+     * token unit. So, if you are using a rate of 1 with a ERC20Detailed token
+     * with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
+     * @param wallet Address where collected funds will be forwarded to
+     * @param token Address of the token being sold
+     */
+    constructor (uint256 rate, address payable wallet, IERC20 token) public {
+        require(rate > 0, "Crowdsale: rate is 0");
+        require(wallet != address(0), "Crowdsale: wallet is the zero address");
+        require(address(token) != address(0), "Crowdsale: token is the zero address");
+
+        _rate = rate;
+        _wallet = wallet;
+        _token = token;
+    }
+
+    /**
+     * @dev fallback function ***DO NOT OVERRIDE***
+     * Note that other contracts will transfer funds with a base gas stipend
+     * of 2300, which is not enough to call buyTokens. Consider calling
+     * buyTokens directly when purchasing tokens from a contract.
+     */
+    function () external payable {
+        buyTokens(msg.sender);
+    }
+
+    /**
+     * @return the token being sold.
+     */
+    function token() public view returns (IERC20) {
+        return _token;
+    }
+
+    /**
+     * @return the address where funds are collected.
+     */
+    function wallet() public view returns (address payable) {
+        return _wallet;
+    }
+
+    /**
+     * @return the number of token units a buyer gets per wei.
+     */
+    function rate() public view returns (uint256) {
+        return _rate;
+    }
+
+    /**
+     * @return the amount of wei raised.
+     */
+    function weiRaised() public view returns (uint256) {
+        return _weiRaised;
+    }
+
+    /**
+     * @dev low level token purchase ***DO NOT OVERRIDE***
+     * This function has a non-reentrancy guard, so it shouldn't be called by
+     * another `nonReentrant` function.
+     * @param beneficiary Recipient of the token purchase
+     */
+    function buyTokens(address beneficiary) public nonReentrant payable {
+        uint256 weiAmount = msg.value;
+        _preValidatePurchase(beneficiary, weiAmount);
+
+        // calculate token amount to be created
+        uint256 tokens = _getTokenAmount(weiAmount);
+
+        // update state
+        _weiRaised = _weiRaised.add(weiAmount);
+
+        _processPurchase(beneficiary, tokens);
+        emit TokensPurchased(msg.sender, beneficiary, weiAmount, tokens);
+
+        _updatePurchasingState(beneficiary, weiAmount);
+
+        _forwardFunds();
+        _postValidatePurchase(beneficiary, weiAmount);
+    }
+
+    /**
+     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
+     * Use `super` in contracts that inherit from Crowdsale to extend their validations.
+     * Example from CappedCrowdsale.sol's _preValidatePurchase method:
+     *     super._preValidatePurchase(beneficiary, weiAmount);
+     *     require(weiRaised().add(weiAmount) <= cap);
+     * @param beneficiary Address performing the token purchase
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        require(beneficiary != address(0), "Crowdsale: beneficiary is the zero address");
+        require(weiAmount != 0, "Crowdsale: weiAmount is 0");
+    }
+
+    /**
+     * @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid
+     * conditions are not met.
+     * @param beneficiary Address performing the token purchase
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _postValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    /**
+     * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends
+     * its tokens.
+     * @param beneficiary Address performing the token purchase
+     * @param tokenAmount Number of tokens to be emitted
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        _token.safeTransfer(beneficiary, tokenAmount);
+    }
+
+    /**
+     * @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send
+     * tokens.
+     * @param beneficiary Address receiving the tokens
+     * @param tokenAmount Number of tokens to be purchased
+     */
+    function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
+        _deliverTokens(beneficiary, tokenAmount);
+    }
+
+    /**
+     * @dev Override for extensions that require an internal state to check for validity (current user contributions,
+     * etc.)
+     * @param beneficiary Address receiving the tokens
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    /**
+     * @dev Override to extend the way in which ether is converted to tokens.
+     * @param weiAmount Value in wei to be converted into tokens
+     * @return Number of tokens that can be purchased with the specified _weiAmount
+     */
+    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
+        return weiAmount.mul(_rate);
+    }
+
+    /**
+     * @dev Determines how ETH is stored/forwarded on purchases.
+     */
+    function _forwardFunds() internal {
+        _wallet.transfer(msg.value);
+    }
+}

contracts/crowdsale/README.md

@@ -0,0 +1,13 @@
+---
+title: Crowdsales
+sections:
+  - title: Core
+    contracts:
+      - Crowdsale
+  - subdirectory: emission
+  - subdirectory: price
+  - subdirectory: validation
+  - subdirectory: distribution
+---
+
+> This page is incomplete. We're working to improve it for the next release. Stay tuned!

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

@@ -0,0 +1,51 @@
+pragma solidity ^0.5.0;
+
+import "../../math/SafeMath.sol";
+import "../validation/TimedCrowdsale.sol";
+
+/**
+ * @title FinalizableCrowdsale
+ * @dev Extension of TimedCrowdsale with a one-off finalization action, where one
+ * can do extra work after finishing.
+ */
+contract FinalizableCrowdsale is TimedCrowdsale {
+    using SafeMath for uint256;
+
+    bool private _finalized;
+
+    event CrowdsaleFinalized();
+
+    constructor () internal {
+        _finalized = false;
+    }
+
+    /**
+     * @return true if the crowdsale is finalized, false otherwise.
+     */
+    function finalized() public view returns (bool) {
+        return _finalized;
+    }
+
+    /**
+     * @dev Must be called after crowdsale ends, to do some extra finalization
+     * work. Calls the contract's finalization function.
+     */
+    function finalize() public {
+        require(!_finalized, "FinalizableCrowdsale: already finalized");
+        require(hasClosed(), "FinalizableCrowdsale: not closed");
+
+        _finalized = true;
+
+        _finalization();
+        emit CrowdsaleFinalized();
+    }
+
+    /**
+     * @dev Can be overridden to add finalization logic. The overriding function
+     * should call super._finalization() to ensure the chain of finalization is
+     * executed entirely.
+     */
+    function _finalization() internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -0,0 +1,65 @@
+pragma solidity ^0.5.0;
+
+import "../validation/TimedCrowdsale.sol";
+import "../../math/SafeMath.sol";
+import "../../ownership/Secondary.sol";
+import "../../token/ERC20/IERC20.sol";
+
+/**
+ * @title PostDeliveryCrowdsale
+ * @dev Crowdsale that locks tokens from withdrawal until it ends.
+ */
+contract PostDeliveryCrowdsale is TimedCrowdsale {
+    using SafeMath for uint256;
+
+    mapping(address => uint256) private _balances;
+    __unstable__TokenVault private _vault;
+
+    constructor() public {
+        _vault = new __unstable__TokenVault();
+    }
+
+    /**
+     * @dev Withdraw tokens only after crowdsale ends.
+     * @param beneficiary Whose tokens will be withdrawn.
+     */
+    function withdrawTokens(address beneficiary) public {
+        require(hasClosed(), "PostDeliveryCrowdsale: not closed");
+        uint256 amount = _balances[beneficiary];
+        require(amount > 0, "PostDeliveryCrowdsale: beneficiary is not due any tokens");
+
+        _balances[beneficiary] = 0;
+        _vault.transfer(token(), beneficiary, amount);
+    }
+
+    /**
+     * @return the balance of an account.
+     */
+    function balanceOf(address account) public view returns (uint256) {
+        return _balances[account];
+    }
+
+    /**
+     * @dev Overrides parent by storing due balances, and delivering tokens to the vault instead of the end user. This
+     * ensures that the tokens will be available by the time they are withdrawn (which may not be the case if
+     * `_deliverTokens` was called later).
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Amount of tokens purchased
+     */
+    function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
+        _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
+        _deliverTokens(address(_vault), tokenAmount);
+    }
+}
+
+/**
+ * @title __unstable__TokenVault
+ * @dev Similar to an Escrow for tokens, this contract allows its primary account to spend its tokens as it sees fit.
+ * This contract is an internal helper for PostDeliveryCrowdsale, and should not be used outside of this context.
+ */
+// solhint-disable-next-line contract-name-camelcase
+contract __unstable__TokenVault is Secondary {
+    function transfer(IERC20 token, address to, uint256 amount) public onlyPrimary {
+        token.transfer(to, amount);
+    }
+}

contracts/crowdsale/distribution/RefundableCrowdsale.sol

@@ -0,0 +1,82 @@
+pragma solidity ^0.5.0;
+
+import "../../math/SafeMath.sol";
+import "./FinalizableCrowdsale.sol";
+import "../../payment/escrow/RefundEscrow.sol";
+
+/**
+ * @title RefundableCrowdsale
+ * @dev Extension of `FinalizableCrowdsale` contract that adds a funding goal, and the possibility of users
+ * getting a refund if goal is not met.
+ *
+ * Deprecated, use `RefundablePostDeliveryCrowdsale` instead. Note that if you allow tokens to be traded before the goal
+ * is met, then an attack is possible in which the attacker purchases tokens from the crowdsale and when they sees that
+ * the goal is unlikely to be met, they sell their tokens (possibly at a discount). The attacker will be refunded when
+ * the crowdsale is finalized, and the users that purchased from them will be left with worthless tokens.
+ */
+contract RefundableCrowdsale is FinalizableCrowdsale {
+    using SafeMath for uint256;
+
+    // minimum amount of funds to be raised in weis
+    uint256 private _goal;
+
+    // refund escrow used to hold funds while crowdsale is running
+    RefundEscrow private _escrow;
+
+    /**
+     * @dev Constructor, creates RefundEscrow.
+     * @param goal Funding goal
+     */
+    constructor (uint256 goal) public {
+        require(goal > 0, "RefundableCrowdsale: goal is 0");
+        _escrow = new RefundEscrow(wallet());
+        _goal = goal;
+    }
+
+    /**
+     * @return minimum amount of funds to be raised in wei.
+     */
+    function goal() public view returns (uint256) {
+        return _goal;
+    }
+
+    /**
+     * @dev Investors can claim refunds here if crowdsale is unsuccessful.
+     * @param refundee Whose refund will be claimed.
+     */
+    function claimRefund(address payable refundee) public {
+        require(finalized(), "RefundableCrowdsale: not finalized");
+        require(!goalReached(), "RefundableCrowdsale: goal reached");
+
+        _escrow.withdraw(refundee);
+    }
+
+    /**
+     * @dev Checks whether funding goal was reached.
+     * @return Whether funding goal was reached
+     */
+    function goalReached() public view returns (bool) {
+        return weiRaised() >= _goal;
+    }
+
+    /**
+     * @dev Escrow finalization task, called when finalize() is called.
+     */
+    function _finalization() internal {
+        if (goalReached()) {
+            _escrow.close();
+            _escrow.beneficiaryWithdraw();
+        } else {
+            _escrow.enableRefunds();
+        }
+
+        super._finalization();
+    }
+
+    /**
+     * @dev Overrides Crowdsale fund forwarding, sending funds to escrow.
+     */
+    function _forwardFunds() internal {
+        _escrow.deposit.value(msg.value)(msg.sender);
+    }
+}

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

@@ -0,0 +1,20 @@
+pragma solidity ^0.5.0;
+
+import "./RefundableCrowdsale.sol";
+import "./PostDeliveryCrowdsale.sol";
+
+
+/**
+ * @title RefundablePostDeliveryCrowdsale
+ * @dev Extension of RefundableCrowdsale contract that only delivers the tokens
+ * once the crowdsale has closed and the goal met, preventing refunds to be issued
+ * to token holders.
+ */
+contract RefundablePostDeliveryCrowdsale is RefundableCrowdsale, PostDeliveryCrowdsale {
+    function withdrawTokens(address beneficiary) public {
+        require(finalized(), "RefundablePostDeliveryCrowdsale: not finalized");
+        require(goalReached(), "RefundablePostDeliveryCrowdsale: goal not reached");
+
+        super.withdrawTokens(beneficiary);
+    }
+}

contracts/crowdsale/emission/AllowanceCrowdsale.sol

@@ -0,0 +1,51 @@
+pragma solidity ^0.5.0;
+
+import "../Crowdsale.sol";
+import "../../token/ERC20/IERC20.sol";
+import "../../token/ERC20/SafeERC20.sol";
+import "../../math/SafeMath.sol";
+import "../../math/Math.sol";
+
+/**
+ * @title AllowanceCrowdsale
+ * @dev Extension of Crowdsale where tokens are held by a wallet, which approves an allowance to the crowdsale.
+ */
+contract AllowanceCrowdsale is Crowdsale {
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
+
+    address private _tokenWallet;
+
+    /**
+     * @dev Constructor, takes token wallet address.
+     * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale.
+     */
+    constructor (address tokenWallet) public {
+        require(tokenWallet != address(0), "AllowanceCrowdsale: token wallet is the zero address");
+        _tokenWallet = tokenWallet;
+    }
+
+    /**
+     * @return the address of the wallet that will hold the tokens.
+     */
+    function tokenWallet() public view returns (address) {
+        return _tokenWallet;
+    }
+
+    /**
+     * @dev Checks the amount of tokens left in the allowance.
+     * @return Amount of tokens left in the allowance
+     */
+    function remainingTokens() public view returns (uint256) {
+        return Math.min(token().balanceOf(_tokenWallet), token().allowance(_tokenWallet, address(this)));
+    }
+
+    /**
+     * @dev Overrides parent behavior by transferring tokens from wallet.
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Amount of tokens purchased
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        token().safeTransferFrom(_tokenWallet, beneficiary, tokenAmount);
+    }
+}

contracts/crowdsale/emission/MintedCrowdsale.sol

@@ -0,0 +1,24 @@
+pragma solidity ^0.5.0;
+
+import "../Crowdsale.sol";
+import "../../token/ERC20/ERC20Mintable.sol";
+
+/**
+ * @title MintedCrowdsale
+ * @dev Extension of Crowdsale contract whose tokens are minted in each purchase.
+ * Token ownership should be transferred to MintedCrowdsale for minting.
+ */
+contract MintedCrowdsale is Crowdsale {
+    /**
+     * @dev Overrides delivery by minting tokens upon purchase.
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Number of tokens to be minted
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        // Potentially dangerous assumption about the type of the token.
+        require(
+            ERC20Mintable(address(token())).mint(beneficiary, tokenAmount),
+                "MintedCrowdsale: minting failed"
+        );
+    }
+}

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

@@ -0,0 +1,79 @@
+pragma solidity ^0.5.0;
+
+import "../validation/TimedCrowdsale.sol";
+import "../../math/SafeMath.sol";
+
+/**
+ * @title IncreasingPriceCrowdsale
+ * @dev Extension of Crowdsale contract that increases the price of tokens linearly in time.
+ * Note that what should be provided to the constructor is the initial and final _rates_, that is,
+ * the amount of tokens per wei contributed. Thus, the initial rate must be greater than the final rate.
+ */
+contract IncreasingPriceCrowdsale is TimedCrowdsale {
+    using SafeMath for uint256;
+
+    uint256 private _initialRate;
+    uint256 private _finalRate;
+
+    /**
+     * @dev Constructor, takes initial and final rates of tokens received per wei contributed.
+     * @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
+     * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
+     */
+    constructor (uint256 initialRate, uint256 finalRate) public {
+        require(finalRate > 0, "IncreasingPriceCrowdsale: final rate is 0");
+        // solhint-disable-next-line max-line-length
+        require(initialRate > finalRate, "IncreasingPriceCrowdsale: initial rate is not greater than final rate");
+        _initialRate = initialRate;
+        _finalRate = finalRate;
+    }
+
+    /**
+     * The base rate function is overridden to revert, since this crowdsale doesn't use it, and
+     * all calls to it are a mistake.
+     */
+    function rate() public view returns (uint256) {
+        revert("IncreasingPriceCrowdsale: rate() called");
+    }
+
+    /**
+     * @return the initial rate of the crowdsale.
+     */
+    function initialRate() public view returns (uint256) {
+        return _initialRate;
+    }
+
+    /**
+     * @return the final rate of the crowdsale.
+     */
+    function finalRate() public view returns (uint256) {
+        return _finalRate;
+    }
+
+    /**
+     * @dev Returns the rate of tokens per wei at the present time.
+     * Note that, as price _increases_ with time, the rate _decreases_.
+     * @return The number of tokens a buyer gets per wei at a given time
+     */
+    function getCurrentRate() public view returns (uint256) {
+        if (!isOpen()) {
+            return 0;
+        }
+
+        // solhint-disable-next-line not-rely-on-time
+        uint256 elapsedTime = block.timestamp.sub(openingTime());
+        uint256 timeRange = closingTime().sub(openingTime());
+        uint256 rateRange = _initialRate.sub(_finalRate);
+        return _initialRate.sub(elapsedTime.mul(rateRange).div(timeRange));
+    }
+
+    /**
+     * @dev Overrides parent method taking into account variable rate.
+     * @param weiAmount The value in wei to be converted into tokens
+     * @return The number of tokens _weiAmount wei will buy at present time
+     */
+    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
+        uint256 currentRate = getCurrentRate();
+        return currentRate.mul(weiAmount);
+    }
+}

contracts/crowdsale/validation/CappedCrowdsale.sol

@@ -0,0 +1,48 @@
+pragma solidity ^0.5.0;
+
+import "../../math/SafeMath.sol";
+import "../Crowdsale.sol";
+
+/**
+ * @title CappedCrowdsale
+ * @dev Crowdsale with a limit for total contributions.
+ */
+contract CappedCrowdsale is Crowdsale {
+    using SafeMath for uint256;
+
+    uint256 private _cap;
+
+    /**
+     * @dev Constructor, takes maximum amount of wei accepted in the crowdsale.
+     * @param cap Max amount of wei to be contributed
+     */
+    constructor (uint256 cap) public {
+        require(cap > 0, "CappedCrowdsale: cap is 0");
+        _cap = cap;
+    }
+
+    /**
+     * @return the cap of the crowdsale.
+     */
+    function cap() public view returns (uint256) {
+        return _cap;
+    }
+
+    /**
+     * @dev Checks whether the cap has been reached.
+     * @return Whether the cap was reached
+     */
+    function capReached() public view returns (bool) {
+        return weiRaised() >= _cap;
+    }
+
+    /**
+     * @dev Extend parent behavior requiring purchase to respect the funding cap.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+        require(weiRaised().add(weiAmount) <= _cap, "CappedCrowdsale: cap exceeded");
+    }
+}

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

@@ -0,0 +1,64 @@
+pragma solidity ^0.5.0;
+
+import "../../math/SafeMath.sol";
+import "../Crowdsale.sol";
+import "../../access/roles/CapperRole.sol";
+
+/**
+ * @title IndividuallyCappedCrowdsale
+ * @dev Crowdsale with per-beneficiary caps.
+ */
+contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
+    using SafeMath for uint256;
+
+    mapping(address => uint256) private _contributions;
+    mapping(address => uint256) private _caps;
+
+    /**
+     * @dev Sets a specific beneficiary's maximum contribution.
+     * @param beneficiary Address to be capped
+     * @param cap Wei limit for individual contribution
+     */
+    function setCap(address beneficiary, uint256 cap) external onlyCapper {
+        _caps[beneficiary] = cap;
+    }
+
+    /**
+     * @dev Returns the cap of a specific beneficiary.
+     * @param beneficiary Address whose cap is to be checked
+     * @return Current cap for individual beneficiary
+     */
+    function getCap(address beneficiary) public view returns (uint256) {
+        return _caps[beneficiary];
+    }
+
+    /**
+     * @dev Returns the amount contributed so far by a specific beneficiary.
+     * @param beneficiary Address of contributor
+     * @return Beneficiary contribution so far
+     */
+    function getContribution(address beneficiary) public view returns (uint256) {
+        return _contributions[beneficiary];
+    }
+
+    /**
+     * @dev Extend parent behavior requiring purchase to respect the beneficiary's funding cap.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+        // solhint-disable-next-line max-line-length
+        require(_contributions[beneficiary].add(weiAmount) <= _caps[beneficiary], "IndividuallyCappedCrowdsale: beneficiary's cap exceeded");
+    }
+
+    /**
+     * @dev Extend parent behavior to update beneficiary contributions.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
+        super._updatePurchasingState(beneficiary, weiAmount);
+        _contributions[beneficiary] = _contributions[beneficiary].add(weiAmount);
+    }
+}

contracts/crowdsale/validation/PausableCrowdsale.sol

@@ -0,0 +1,21 @@
+pragma solidity ^0.5.0;
+
+import "../Crowdsale.sol";
+import "../../lifecycle/Pausable.sol";
+
+/**
+ * @title PausableCrowdsale
+ * @dev Extension of Crowdsale contract where purchases can be paused and unpaused by the pauser role.
+ */
+contract PausableCrowdsale is Crowdsale, Pausable {
+    /**
+     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
+     * Use super to concatenate validations.
+     * Adds the validation that the crowdsale must not be paused.
+     * @param _beneficiary Address performing the token purchase
+     * @param _weiAmount Value in wei involved in the purchase
+     */
+    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view whenNotPaused {
+        return super._preValidatePurchase(_beneficiary, _weiAmount);
+    }
+}

contracts/crowdsale/validation/TimedCrowdsale.sol

@@ -0,0 +1,98 @@
+pragma solidity ^0.5.0;
+
+import "../../math/SafeMath.sol";
+import "../Crowdsale.sol";
+
+/**
+ * @title TimedCrowdsale
+ * @dev Crowdsale accepting contributions only within a time frame.
+ */
+contract TimedCrowdsale is Crowdsale {
+    using SafeMath for uint256;
+
+    uint256 private _openingTime;
+    uint256 private _closingTime;
+
+    /**
+     * Event for crowdsale extending
+     * @param newClosingTime new closing time
+     * @param prevClosingTime old closing time
+     */
+    event TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime);
+
+    /**
+     * @dev Reverts if not in crowdsale time range.
+     */
+    modifier onlyWhileOpen {
+        require(isOpen(), "TimedCrowdsale: not open");
+        _;
+    }
+
+    /**
+     * @dev Constructor, takes crowdsale opening and closing times.
+     * @param openingTime Crowdsale opening time
+     * @param closingTime Crowdsale closing time
+     */
+    constructor (uint256 openingTime, uint256 closingTime) public {
+        // solhint-disable-next-line not-rely-on-time
+        require(openingTime >= block.timestamp, "TimedCrowdsale: opening time is before current time");
+        // solhint-disable-next-line max-line-length
+        require(closingTime > openingTime, "TimedCrowdsale: opening time is not before closing time");
+
+        _openingTime = openingTime;
+        _closingTime = closingTime;
+    }
+
+    /**
+     * @return the crowdsale opening time.
+     */
+    function openingTime() public view returns (uint256) {
+        return _openingTime;
+    }
+
+    /**
+     * @return the crowdsale closing time.
+     */
+    function closingTime() public view returns (uint256) {
+        return _closingTime;
+    }
+
+    /**
+     * @return true if the crowdsale is open, false otherwise.
+     */
+    function isOpen() public view returns (bool) {
+        // solhint-disable-next-line not-rely-on-time
+        return block.timestamp >= _openingTime && block.timestamp <= _closingTime;
+    }
+
+    /**
+     * @dev Checks whether the period in which the crowdsale is open has already elapsed.
+     * @return Whether crowdsale period has elapsed
+     */
+    function hasClosed() public view returns (bool) {
+        // solhint-disable-next-line not-rely-on-time
+        return block.timestamp > _closingTime;
+    }
+
+    /**
+     * @dev Extend parent behavior requiring to be within contributing period.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal onlyWhileOpen view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+    }
+
+    /**
+     * @dev Extend crowdsale.
+     * @param newClosingTime Crowdsale closing time
+     */
+    function _extendTime(uint256 newClosingTime) internal {
+        require(!hasClosed(), "TimedCrowdsale: already closed");
+        // solhint-disable-next-line max-line-length
+        require(newClosingTime > _closingTime, "TimedCrowdsale: new closing time is before current closing time");
+
+        emit TimedCrowdsaleExtended(_closingTime, newClosingTime);
+        _closingTime = newClosingTime;
+    }
+}

contracts/crowdsale/validation/WhitelistCrowdsale.sol

@@ -0,0 +1,21 @@
+pragma solidity ^0.5.0;
+import "../Crowdsale.sol";
+import "../../access/roles/WhitelistedRole.sol";
+
+
+/**
+ * @title WhitelistCrowdsale
+ * @dev Crowdsale in which only whitelisted users can contribute.
+ */
+contract WhitelistCrowdsale is WhitelistedRole, Crowdsale {
+    /**
+     * @dev Extend parent behavior requiring beneficiary to be whitelisted. Note that no
+     * restriction is imposed on the account sending the transaction.
+     * @param _beneficiary Token beneficiary
+     * @param _weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view {
+        require(isWhitelisted(_beneficiary), "WhitelistCrowdsale: beneficiary doesn't have the Whitelisted role");
+        super._preValidatePurchase(_beneficiary, _weiAmount);
+    }
+}

contracts/cryptography/ECDSA.sol

@@ -0,0 +1,82 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
+ *
+ * These functions can be used to verify that a message was signed by the holder
+ * of the private keys of a given address.
+ */
+library ECDSA {
+    /**
+     * @dev Returns the address that signed a hashed message (`hash`) with
+     * `signature`. This address can then be used for verification purposes.
+     *
+     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
+     * this function rejects them by requiring the `s` value to be in the lower
+     * half order, and the `v` value to be either 27 or 28.
+     *
+     * (.note) This call _does not revert_ if the signature is invalid, or
+     * if the signer is otherwise unable to be retrieved. In those scenarios,
+     * the zero address is returned.
+     *
+     * (.warning) `hash` _must_ be the result of a hash operation for the
+     * verification to be secure: it is possible to craft signatures that
+     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
+     * this is by receiving a hash of the original message (which may otherwise)
+     * be too long), and then calling `toEthSignedMessageHash` on it.
+     */
+    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
+        // Check the signature length
+        if (signature.length != 65) {
+            return (address(0));
+        }
+
+        // Divide the signature in r, s and v variables
+        bytes32 r;
+        bytes32 s;
+        uint8 v;
+
+        // ecrecover takes the signature parameters, and the only way to get them
+        // currently is to use assembly.
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            r := mload(add(signature, 0x20))
+            s := mload(add(signature, 0x40))
+            v := byte(0, mload(add(signature, 0x60)))
+        }
+
+        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
+        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
+        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
+        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
+        //
+        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
+        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
+        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
+        // these malleable signatures as well.
+        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
+            return address(0);
+        }
+
+        if (v != 27 && v != 28) {
+            return address(0);
+        }
+
+        // If the signature is valid (and not malleable), return the signer address
+        return ecrecover(hash, v, r, s);
+    }
+
+    /**
+     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
+     * replicates the behavior of the
+     * [`eth_sign`](https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign)
+     * JSON-RPC method.
+     *
+     * See `recover`.
+     */
+    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
+        // 32 is the length in bytes of hash,
+        // enforced by the type signature above
+        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
+    }
+}

contracts/cryptography/MerkleProof.sol

@@ -1,15 +1,7 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 /**
- * @dev These functions deal with verification of Merkle Trees proofs.
- *
- * The proofs can be generated using the JavaScript library
- * https://github.com/miguelmota/merkletreejs[merkletreejs].
- * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
- *
- * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
+ * @dev These functions deal with verification of Merkle trees (hash trees),
  */
 library MerkleProof {
     /**
@@ -24,7 +16,7 @@ library MerkleProof {
         for (uint256 i = 0; i < proof.length; i++) {
             bytes32 proofElement = proof[i];
 
-            if (computedHash <= proofElement) {
+            if (computedHash < proofElement) {
                 // Hash(current computed hash + current element of the proof)
                 computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
             } else {

contracts/cryptography/README.md

@@ -0,0 +1,9 @@
+---
+sections:
+  - title: Libraries
+    contracts:
+      - ECDSA
+      - MerkleProof
+---
+
+This collection of libraries provides simple and safe ways to use different cryptographic primitives.

contracts/drafts/Counters.sol

@@ -1,6 +1,6 @@
-// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.0;
 
-pragma solidity ^0.8.0;
+import "../math/SafeMath.sol";
 
 /**
  * @title Counters
@@ -9,8 +9,13 @@ pragma solidity ^0.8.0;
  * of elements in a mapping, issuing ERC721 ids, or counting request ids.
  *
  * Include with `using Counters for Counters.Counter;`
+ * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the SafeMath
+ * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
+ * directly accessed.
  */
 library Counters {
+    using SafeMath for uint256;
+
     struct Counter {
         // This variable should never be directly accessed by users of the library: interactions must be restricted to
         // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
@@ -23,16 +28,10 @@ library Counters {
     }
 
     function increment(Counter storage counter) internal {
-        unchecked {
-            counter._value += 1;
-        }
+        counter._value += 1;
     }
 
     function decrement(Counter storage counter) internal {
-        uint256 value = counter._value;
-        require(value > 0, "Counter: decrement overflow");
-        unchecked {
-            counter._value = value - 1;
-        }
+        counter._value = counter._value.sub(1);
     }
 }

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -0,0 +1,24 @@
+pragma solidity ^0.5.0;
+
+import "../../token/ERC20/IERC20.sol";
+
+/**
+ * @title ERC-1047 Token Metadata
+ * @dev See https://eips.ethereum.org/EIPS/eip-1046
+ * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
+ */
+contract ERC20Metadata {
+    string private _tokenURI;
+
+    constructor (string memory tokenURI_) public {
+        _setTokenURI(tokenURI_);
+    }
+
+    function tokenURI() external view returns (string memory) {
+        return _tokenURI;
+    }
+
+    function _setTokenURI(string memory tokenURI_) internal {
+        _tokenURI = tokenURI_;
+    }
+}

contracts/drafts/ERC20Migrator.sol

@@ -0,0 +1,102 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/IERC20.sol";
+import "../token/ERC20/ERC20Mintable.sol";
+import "../token/ERC20/SafeERC20.sol";
+import "../math/Math.sol";
+
+/**
+ * @title ERC20Migrator
+ * @dev This contract can be used to migrate an ERC20 token from one
+ * contract to another, where each token holder has to opt-in to the migration.
+ * To opt-in, users must approve for this contract the number of tokens they
+ * want to migrate. Once the allowance is set up, anyone can trigger the
+ * migration to the new token contract. In this way, token holders "turn in"
+ * their old balance and will be minted an equal amount in the new token.
+ * The new token contract must be mintable. For the precise interface refer to
+ * OpenZeppelin's ERC20Mintable, but the only functions that are needed are
+ * `isMinter(address)` and `mint(address, amount)`. The migrator will check
+ * that it is a minter for the token.
+ * The balance from the legacy token will be transferred to the migrator, as it
+ * is migrated, and remain there forever.
+ * Although this contract can be used in many different scenarios, the main
+ * motivation was to provide a way to migrate ERC20 tokens into an upgradeable
+ * version of it using ZeppelinOS. To read more about how this can be done
+ * using this implementation, please follow the official documentation site of
+ * ZeppelinOS: https://docs.zeppelinos.org/docs/erc20_onboarding.html
+ * Example of usage:
+ * ```
+ * const migrator = await ERC20Migrator.new(legacyToken.address);
+ * await newToken.addMinter(migrator.address);
+ * await migrator.beginMigration(newToken.address);
+ * ```
+ */
+contract ERC20Migrator {
+    using SafeERC20 for IERC20;
+
+    /// Address of the old token contract
+    IERC20 private _legacyToken;
+
+    /// Address of the new token contract
+    ERC20Mintable private _newToken;
+
+    /**
+     * @param legacyToken address of the old token contract
+     */
+    constructor (IERC20 legacyToken) public {
+        require(address(legacyToken) != address(0), "ERC20Migrator: legacy token is the zero address");
+        _legacyToken = legacyToken;
+    }
+
+    /**
+     * @dev Returns the legacy token that is being migrated.
+     */
+    function legacyToken() public view returns (IERC20) {
+        return _legacyToken;
+    }
+
+    /**
+     * @dev Returns the new token to which we are migrating.
+     */
+    function newToken() public view returns (IERC20) {
+        return _newToken;
+    }
+
+    /**
+     * @dev Begins the migration by setting which is the new token that will be
+     * minted. This contract must be a minter for the new token.
+     * @param newToken_ the token that will be minted
+     */
+    function beginMigration(ERC20Mintable newToken_) public {
+        require(address(_newToken) == address(0), "ERC20Migrator: migration already started");
+        require(address(newToken_) != address(0), "ERC20Migrator: new token is the zero address");
+        //solhint-disable-next-line max-line-length
+        require(newToken_.isMinter(address(this)), "ERC20Migrator: not a minter for new token");
+
+        _newToken = newToken_;
+    }
+
+    /**
+     * @dev Transfers part of an account's balance in the old token to this
+     * contract, and mints the same amount of new tokens for that account.
+     * @param account whose tokens will be migrated
+     * @param amount amount of tokens to be migrated
+     */
+    function migrate(address account, uint256 amount) public {
+        require(address(_newToken) != address(0), "ERC20Migrator: migration not started");
+        _legacyToken.safeTransferFrom(account, address(this), amount);
+        _newToken.mint(account, amount);
+    }
+
+    /**
+     * @dev Transfers all of an account's allowed balance in the old token to
+     * this contract, and mints the same amount of new tokens for that account.
+     * @param account whose tokens will be migrated
+     */
+    function migrateAll(address account) public {
+        uint256 balance = _legacyToken.balanceOf(account);
+        uint256 allowance = _legacyToken.allowance(account, address(this));
+        uint256 amount = Math.min(balance, allowance);
+        migrate(account, amount);
+    }
+}

contracts/drafts/ERC20Snapshot.sol

@@ -0,0 +1,140 @@
+pragma solidity ^0.5.0;
+
+import "../math/SafeMath.sol";
+import "../utils/Arrays.sol";
+import "../drafts/Counters.sol";
+import "../token/ERC20/ERC20.sol";
+
+/**
+ * @title ERC20 token with snapshots.
+ * @dev Inspired by Jordi Baylina's MiniMeToken to record historical balances:
+ * https://github.com/Giveth/minime/blob/ea04d950eea153a04c51fa510b068b9dded390cb/contracts/MiniMeToken.sol
+ * When a snapshot is made, the balances and totalSupply at the time of the snapshot are recorded for later
+ * access.
+ *
+ * To make a snapshot, call the `snapshot` function, which will emit the `Snapshot` event and return a snapshot id.
+ * To get the total supply from a snapshot, call the function `totalSupplyAt` with the snapshot id.
+ * To get the balance of an account from a snapshot, call the `balanceOfAt` function with the snapshot id and the
+ * account address.
+ * @author Validity Labs AG <info@validitylabs.org>
+ */
+contract ERC20Snapshot is ERC20 {
+    using SafeMath for uint256;
+    using Arrays for uint256[];
+    using Counters for Counters.Counter;
+
+    // Snapshotted values have arrays of ids and the value corresponding to that id. These could be an array of a
+    // Snapshot struct, but that would impede usage of functions that work on an array.
+    struct Snapshots {
+        uint256[] ids;
+        uint256[] values;
+    }
+
+    mapping (address => Snapshots) private _accountBalanceSnapshots;
+    Snapshots private _totalSupplySnapshots;
+
+    // Snapshot ids increase monotonically, with the first value being 1. An id of 0 is invalid.
+    Counters.Counter private _currentSnapshotId;
+
+    event Snapshot(uint256 id);
+
+    // Creates a new snapshot id. Balances are only stored in snapshots on demand: unless a snapshot was taken, a
+    // balance change will not be recorded. This means the extra added cost of storing snapshotted balances is only paid
+    // when required, but is also flexible enough that it allows for e.g. daily snapshots.
+    function snapshot() public returns (uint256) {
+        _currentSnapshotId.increment();
+
+        uint256 currentId = _currentSnapshotId.current();
+        emit Snapshot(currentId);
+        return currentId;
+    }
+
+    function balanceOfAt(address account, uint256 snapshotId) public view returns (uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _accountBalanceSnapshots[account]);
+
+        return snapshotted ? value : balanceOf(account);
+    }
+
+    function totalSupplyAt(uint256 snapshotId) public view returns(uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnapshots);
+
+        return snapshotted ? value : totalSupply();
+    }
+
+    // _transfer, _mint and _burn are the only functions where the balances are modified, so it is there that the
+    // snapshots are updated. Note that the update happens _before_ the balance change, with the pre-modified value.
+    // The same is true for the total supply and _mint and _burn.
+    function _transfer(address from, address to, uint256 value) internal {
+        _updateAccountSnapshot(from);
+        _updateAccountSnapshot(to);
+
+        super._transfer(from, to, value);
+    }
+
+    function _mint(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._mint(account, value);
+    }
+
+    function _burn(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._burn(account, value);
+    }
+
+    // When a valid snapshot is queried, there are three possibilities:
+    //  a) The queried value was not modified after the snapshot was taken. Therefore, a snapshot entry was never
+    //  created for this id, and all stored snapshot ids are smaller than the requested one. The value that corresponds
+    //  to this id is the current one.
+    //  b) The queried value was modified after the snapshot was taken. Therefore, there will be an entry with the
+    //  requested id, and its value is the one to return.
+    //  c) More snapshots were created after the requested one, and the queried value was later modified. There will be
+    //  no entry for the requested id: the value that corresponds to it is that of the smallest snapshot id that is
+    //  larger than the requested one.
+    //
+    // In summary, we need to find an element in an array, returning the index of the smallest value that is larger if
+    // it is not found, unless said value doesn't exist (e.g. when all values are smaller). Arrays.findUpperBound does
+    // exactly this.
+    function _valueAt(uint256 snapshotId, Snapshots storage snapshots)
+        private view returns (bool, uint256)
+    {
+        require(snapshotId > 0, "ERC20Snapshot: id is 0");
+        // solhint-disable-next-line max-line-length
+        require(snapshotId <= _currentSnapshotId.current(), "ERC20Snapshot: nonexistent id");
+
+        uint256 index = snapshots.ids.findUpperBound(snapshotId);
+
+        if (index == snapshots.ids.length) {
+            return (false, 0);
+        } else {
+            return (true, snapshots.values[index]);
+        }
+    }
+
+    function _updateAccountSnapshot(address account) private {
+        _updateSnapshot(_accountBalanceSnapshots[account], balanceOf(account));
+    }
+
+    function _updateTotalSupplySnapshot() private {
+        _updateSnapshot(_totalSupplySnapshots, totalSupply());
+    }
+
+    function _updateSnapshot(Snapshots storage snapshots, uint256 currentValue) private {
+        uint256 currentId = _currentSnapshotId.current();
+        if (_lastSnapshotId(snapshots.ids) < currentId) {
+            snapshots.ids.push(currentId);
+            snapshots.values.push(currentValue);
+        }
+    }
+
+    function _lastSnapshotId(uint256[] storage ids) private view returns (uint256) {
+        if (ids.length == 0) {
+            return 0;
+        } else {
+            return ids[ids.length - 1];
+        }
+    }
+}

contracts/drafts/README.md

@@ -0,0 +1,16 @@
+---
+sections:
+  - title: ERC 20
+    contracts:
+    - ERC20Migrator
+    - ERC20Snapshot
+    - TokenVesting
+  - title: Miscellenous
+    contracts:
+    - Counters
+    - SignatureBouncer
+    - SignedSafeMath
+  - subdirectory: ERC1046
+---
+
+> This page is incomplete. We're working to improve it for the next release. Stay tuned!

contracts/drafts/SignatureBouncer.sol

@@ -0,0 +1,122 @@
+pragma solidity ^0.5.0;
+
+import "../access/roles/SignerRole.sol";
+import "../cryptography/ECDSA.sol";
+
+/**
+ * @title SignatureBouncer
+ * @author PhABC, Shrugs and aflesher
+ * @dev SignatureBouncer allows users to submit a signature as a permission to
+ * do an action.
+ * If the signature is from one of the authorized signer addresses, the
+ * signature is valid.
+ * Note that SignatureBouncer offers no protection against replay attacks, users
+ * must add this themselves!
+ *
+ * Signer addresses can be individual servers signing grants or different
+ * users within a decentralized club that have permission to invite other
+ * members. This technique is useful for whitelists and airdrops; instead of
+ * putting all valid addresses on-chain, simply sign a grant of the form
+ * keccak256(abi.encodePacked(`:contractAddress` + `:granteeAddress`)) using a
+ * valid signer address.
+ * Then restrict access to your crowdsale/whitelist/airdrop using the
+ * `onlyValidSignature` modifier (or implement your own using _isValidSignature).
+ * In addition to `onlyValidSignature`, `onlyValidSignatureAndMethod` and
+ * `onlyValidSignatureAndData` can be used to restrict access to only a given
+ * method or a given method with given parameters respectively.
+ * See the tests in SignatureBouncer.test.js for specific usage examples.
+ *
+ * @notice A method that uses the `onlyValidSignatureAndData` modifier must make
+ * the _signature parameter the "last" parameter. You cannot sign a message that
+ * has its own signature in it so the last 128 bytes of msg.data (which
+ * represents the length of the _signature data and the _signature data itself)
+ * is ignored when validating. Also non fixed sized parameters make constructing
+ * the data in the signature much more complex.
+ * See https://ethereum.stackexchange.com/a/50616 for more details.
+ */
+contract SignatureBouncer is SignerRole {
+    using ECDSA for bytes32;
+
+    // Function selectors are 4 bytes long, as documented in
+    // https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector
+    uint256 private constant _METHOD_ID_SIZE = 4;
+    // Signature size is 65 bytes (tightly packed v + r + s), but gets padded to 96 bytes
+    uint256 private constant _SIGNATURE_SIZE = 96;
+
+    constructor () internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    /**
+     * @dev Requires that a valid signature of a signer was provided.
+     */
+    modifier onlyValidSignature(bytes memory signature) {
+        require(_isValidSignature(msg.sender, signature), "SignatureBouncer: invalid signature for caller");
+        _;
+    }
+
+    /**
+     * @dev Requires that a valid signature with a specified method of a signer was provided.
+     */
+    modifier onlyValidSignatureAndMethod(bytes memory signature) {
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndMethod(msg.sender, signature), "SignatureBouncer: invalid signature for caller and method");
+        _;
+    }
+
+    /**
+     * @dev Requires that a valid signature with a specified method and params of a signer was provided.
+     */
+    modifier onlyValidSignatureAndData(bytes memory signature) {
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndData(msg.sender, signature), "SignatureBouncer: invalid signature for caller and data");
+        _;
+    }
+
+    /**
+     * @dev is the signature of `this + account` from a signer?
+     * @return bool
+     */
+    function _isValidSignature(address account, bytes memory signature) internal view returns (bool) {
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account)), signature);
+    }
+
+    /**
+     * @dev is the signature of `this + account + methodId` from a signer?
+     * @return bool
+     */
+    function _isValidSignatureAndMethod(address account, bytes memory signature) internal view returns (bool) {
+        bytes memory data = new bytes(_METHOD_ID_SIZE);
+        for (uint i = 0; i < data.length; i++) {
+            data[i] = msg.data[i];
+        }
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
+    }
+
+    /**
+     * @dev is the signature of `this + account + methodId + params(s)` from a signer?
+     * @notice the signature parameter of the method being validated must be the "last" parameter
+     * @return bool
+     */
+    function _isValidSignatureAndData(address account, bytes memory signature) internal view returns (bool) {
+        require(msg.data.length > _SIGNATURE_SIZE, "SignatureBouncer: data is too short");
+
+        bytes memory data = new bytes(msg.data.length - _SIGNATURE_SIZE);
+        for (uint i = 0; i < data.length; i++) {
+            data[i] = msg.data[i];
+        }
+
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
+    }
+
+    /**
+     * @dev Internal function to convert a hash to an eth signed message
+     * and then recover the signature and check it against the signer role.
+     * @return bool
+     */
+    function _isValidDataHash(bytes32 hash, bytes memory signature) internal view returns (bool) {
+        address signer = hash.toEthSignedMessageHash().recover(signature);
+
+        return signer != address(0) && isSigner(signer);
+    }
+}

contracts/drafts/SignedSafeMath.sol

@@ -0,0 +1,60 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @title SignedSafeMath
+ * @dev Signed math operations with safety checks that revert on error.
+ */
+library SignedSafeMath {
+    int256 constant private INT256_MIN = -2**255;
+
+    /**
+     * @dev Multiplies two signed integers, reverts on overflow.
+     */
+    function mul(int256 a, int256 b) internal pure returns (int256) {
+        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+        // benefit is lost if 'b' is also tested.
+        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+        if (a == 0) {
+            return 0;
+        }
+
+        require(!(a == -1 && b == INT256_MIN), "SignedSafeMath: multiplication overflow");
+
+        int256 c = a * b;
+        require(c / a == b, "SignedSafeMath: multiplication overflow");
+
+        return c;
+    }
+
+    /**
+     * @dev Integer division of two signed integers truncating the quotient, reverts on division by zero.
+     */
+    function div(int256 a, int256 b) internal pure returns (int256) {
+        require(b != 0, "SignedSafeMath: division by zero");
+        require(!(b == -1 && a == INT256_MIN), "SignedSafeMath: division overflow");
+
+        int256 c = a / b;
+
+        return c;
+    }
+
+    /**
+     * @dev Subtracts two signed integers, reverts on overflow.
+     */
+    function sub(int256 a, int256 b) internal pure returns (int256) {
+        int256 c = a - b;
+        require((b >= 0 && c <= a) || (b < 0 && c > a), "SignedSafeMath: subtraction overflow");
+
+        return c;
+    }
+
+    /**
+     * @dev Adds two signed integers, reverts on overflow.
+     */
+    function add(int256 a, int256 b) internal pure returns (int256) {
+        int256 c = a + b;
+        require((b >= 0 && c >= a) || (b < 0 && c < a), "SignedSafeMath: addition overflow");
+
+        return c;
+    }
+}

contracts/drafts/TokenVesting.sol

@@ -0,0 +1,174 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/SafeERC20.sol";
+import "../ownership/Ownable.sol";
+import "../math/SafeMath.sol";
+
+/**
+ * @title TokenVesting
+ * @dev A token holder contract that can release its token balance gradually like a
+ * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
+ * owner.
+ */
+contract TokenVesting is Ownable {
+    // The vesting schedule is time-based (i.e. using block timestamps as opposed to e.g. block numbers), and is
+    // therefore sensitive to timestamp manipulation (which is something miners can do, to a certain degree). Therefore,
+    // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a
+    // cliff period of a year and a duration of four years, are safe to use.
+    // solhint-disable not-rely-on-time
+
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
+
+    event TokensReleased(address token, uint256 amount);
+    event TokenVestingRevoked(address token);
+
+    // beneficiary of tokens after they are released
+    address private _beneficiary;
+
+    // Durations and timestamps are expressed in UNIX time, the same units as block.timestamp.
+    uint256 private _cliff;
+    uint256 private _start;
+    uint256 private _duration;
+
+    bool private _revocable;
+
+    mapping (address => uint256) private _released;
+    mapping (address => bool) private _revoked;
+
+    /**
+     * @dev Creates a vesting contract that vests its balance of any ERC20 token to the
+     * beneficiary, gradually in a linear fashion until start + duration. By then all
+     * of the balance will have vested.
+     * @param beneficiary address of the beneficiary to whom vested tokens are transferred
+     * @param cliffDuration duration in seconds of the cliff in which tokens will begin to vest
+     * @param start the time (as Unix time) at which point vesting starts
+     * @param duration duration in seconds of the period in which the tokens will vest
+     * @param revocable whether the vesting is revocable or not
+     */
+    constructor (address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable) public {
+        require(beneficiary != address(0), "TokenVesting: beneficiary is the zero address");
+        // solhint-disable-next-line max-line-length
+        require(cliffDuration <= duration, "TokenVesting: cliff is longer than duration");
+        require(duration > 0, "TokenVesting: duration is 0");
+        // solhint-disable-next-line max-line-length
+        require(start.add(duration) > block.timestamp, "TokenVesting: final time is before current time");
+
+        _beneficiary = beneficiary;
+        _revocable = revocable;
+        _duration = duration;
+        _cliff = start.add(cliffDuration);
+        _start = start;
+    }
+
+    /**
+     * @return the beneficiary of the tokens.
+     */
+    function beneficiary() public view returns (address) {
+        return _beneficiary;
+    }
+
+    /**
+     * @return the cliff time of the token vesting.
+     */
+    function cliff() public view returns (uint256) {
+        return _cliff;
+    }
+
+    /**
+     * @return the start time of the token vesting.
+     */
+    function start() public view returns (uint256) {
+        return _start;
+    }
+
+    /**
+     * @return the duration of the token vesting.
+     */
+    function duration() public view returns (uint256) {
+        return _duration;
+    }
+
+    /**
+     * @return true if the vesting is revocable.
+     */
+    function revocable() public view returns (bool) {
+        return _revocable;
+    }
+
+    /**
+     * @return the amount of the token released.
+     */
+    function released(address token) public view returns (uint256) {
+        return _released[token];
+    }
+
+    /**
+     * @return true if the token is revoked.
+     */
+    function revoked(address token) public view returns (bool) {
+        return _revoked[token];
+    }
+
+    /**
+     * @notice Transfers vested tokens to beneficiary.
+     * @param token ERC20 token which is being vested
+     */
+    function release(IERC20 token) public {
+        uint256 unreleased = _releasableAmount(token);
+
+        require(unreleased > 0, "TokenVesting: no tokens are due");
+
+        _released[address(token)] = _released[address(token)].add(unreleased);
+
+        token.safeTransfer(_beneficiary, unreleased);
+
+        emit TokensReleased(address(token), unreleased);
+    }
+
+    /**
+     * @notice Allows the owner to revoke the vesting. Tokens already vested
+     * remain in the contract, the rest are returned to the owner.
+     * @param token ERC20 token which is being vested
+     */
+    function revoke(IERC20 token) public onlyOwner {
+        require(_revocable, "TokenVesting: cannot revoke");
+        require(!_revoked[address(token)], "TokenVesting: token already revoked");
+
+        uint256 balance = token.balanceOf(address(this));
+
+        uint256 unreleased = _releasableAmount(token);
+        uint256 refund = balance.sub(unreleased);
+
+        _revoked[address(token)] = true;
+
+        token.safeTransfer(owner(), refund);
+
+        emit TokenVestingRevoked(address(token));
+    }
+
+    /**
+     * @dev Calculates the amount that has already vested but hasn't been released yet.
+     * @param token ERC20 token which is being vested
+     */
+    function _releasableAmount(IERC20 token) private view returns (uint256) {
+        return _vestedAmount(token).sub(_released[address(token)]);
+    }
+
+    /**
+     * @dev Calculates the amount that has already vested.
+     * @param token ERC20 token which is being vested
+     */
+    function _vestedAmount(IERC20 token) private view returns (uint256) {
+        uint256 currentBalance = token.balanceOf(address(this));
+        uint256 totalBalance = currentBalance.add(_released[address(token)]);
+
+        if (block.timestamp < _cliff) {
+            return 0;
+        } else if (block.timestamp >= _start.add(_duration) || _revoked[address(token)]) {
+            return totalBalance;
+        } else {
+            return totalBalance.mul(block.timestamp.sub(_start)).div(_duration);
+        }
+    }
+}

contracts/examples/SampleCrowdsale.sol

@@ -0,0 +1,53 @@
+pragma solidity ^0.5.0;
+
+import "../crowdsale/validation/CappedCrowdsale.sol";
+import "../crowdsale/distribution/RefundableCrowdsale.sol";
+import "../crowdsale/emission/MintedCrowdsale.sol";
+import "../token/ERC20/ERC20Mintable.sol";
+import "../token/ERC20/ERC20Detailed.sol";
+
+/**
+ * @title SampleCrowdsaleToken
+ * @dev Very simple ERC20 Token that can be minted.
+ * It is meant to be used in a crowdsale contract.
+ */
+contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
+    constructor () public ERC20Detailed("Sample Crowdsale Token", "SCT", 18) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}
+
+/**
+ * @title SampleCrowdsale
+ * @dev This is an example of a fully fledged crowdsale.
+ * The way to add new features to a base crowdsale is by multiple inheritance.
+ * In this example we are providing following extensions:
+ * CappedCrowdsale - sets a max boundary for raised funds
+ * RefundableCrowdsale - set a min goal to be reached and returns funds if it's not met
+ * MintedCrowdsale - assumes the token can be minted by the crowdsale, which does so
+ * when receiving purchases.
+ *
+ * After adding multiple features it's good practice to run integration tests
+ * to ensure that subcontracts works together as intended.
+ */
+contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
+    constructor (
+        uint256 openingTime,
+        uint256 closingTime,
+        uint256 rate,
+        address payable wallet,
+        uint256 cap,
+        ERC20Mintable token,
+        uint256 goal
+    )
+        public
+        Crowdsale(rate, wallet, token)
+        CappedCrowdsale(cap)
+        TimedCrowdsale(openingTime, closingTime)
+        RefundableCrowdsale(goal)
+    {
+        //As goal needs to be met for a successful crowdsale
+        //the value needs to less or equal than a cap which is limit for accepted funds
+        require(goal <= cap, "SampleCrowdSale: goal is greater than cap");
+    }
+}

contracts/examples/SimpleToken.sol

@@ -0,0 +1,22 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/ERC20.sol";
+import "../token/ERC20/ERC20Detailed.sol";
+
+/**
+ * @title SimpleToken
+ * @dev Very simple ERC20 Token example, where all tokens are pre-assigned to the creator.
+ * Note they can later distribute these tokens as they wish using `transfer` and other
+ * `ERC20` functions.
+ */
+contract SimpleToken is ERC20, ERC20Detailed {
+    uint8 public constant DECIMALS = 18;
+    uint256 public constant INITIAL_SUPPLY = 10000 * (10 ** uint256(DECIMALS));
+
+    /**
+     * @dev Constructor that gives msg.sender all of existing tokens.
+     */
+    constructor () public ERC20Detailed("SimpleToken", "SIM", DECIMALS) {
+        _mint(msg.sender, INITIAL_SUPPLY);
+    }
+}

contracts/finance/README.adoc

@@ -1,10 +0,0 @@
-= Finance
-
-[.readme-notice]
-NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/finance
-
-This directory includes primitives for financial systems. We currently only offer the {PaymentSplitter} contract, but we want to grow this directory so we welcome ideas.
-
-== PaymentSplitter
-
-{{PaymentSplitter}}

contracts/governance/README.adoc

@@ -1,91 +0,0 @@
-= Governance
-
-[.readme-notice]
-NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/governance
-
-This directory includes primitives for on-chain governance. We currently only offer the {TimelockController} contract, that can be used as a component in a governance systems to introduce a delay between a proposal and its execution.
-
-== Timelock
-
-{{TimelockController}}
-
-[[timelock-terminology]]
-==== Terminology
-
-* *Operation:* A transaction (or a set of transactions) that is the subject of the timelock. It has to be scheduled by a proposer and executed by an executor. The timelock enforces a minimum delay between the proposition and the execution (see xref:access-control.adoc#operation_lifecycle[operation lifecycle]). If the operation contains multiple transactions (batch mode), they are executed atomically. Operations are identified by the hash of their content.
-* *Operation status:*
-** *Unset:* An operation that is not part of the timelock mechanism.
-** *Pending:* An operation that has been scheduled, before the timer expires.
-** *Ready:* An operation that has been scheduled, after the timer expires.
-** *Done:* An operation that has been executed.
-* *Predecessor*: An (optional) dependency between operations. An operation can depend on another operation (its predecessor), forcing the execution order of these two operations.
-* *Role*:
-** *Proposer:* An address (smart contract or EOA) that is in charge of scheduling (and cancelling) operations.
-** *Executor:* An address (smart contract or EOA) that is in charge of executing operations.
-
-[[timelock-operation]]
-==== Operation structure
-
-Operation executed by the xref:api:governance.adoc#TimelockController[`TimelockControler`] can contain one or multiple subsequent calls. Depending on whether you need to multiple calls to be executed atomically, you can either use simple or batched operations.
-
-Both operations contain:
-
-* *Target*, the address of the smart contract that the timelock should operate on.
-* *Value*, in wei, that should be sent with the transaction. Most of the time this will be 0. Ether can be deposited before-end or passed along when executing the transaction.
-* *Data*, containing the encoded function selector and parameters of the call. This can be produced using a number of tools. For example, a maintenance operation granting role `ROLE` to `ACCOUNT` can be encode using web3js as follows:
-
-```javascript
-const data = timelock.contract.methods.grantRole(ROLE, ACCOUNT).encodeABI()
-```
-
-* *Predecessor*, that specifies a dependency between operations. This dependency is optional. Use `bytes32(0)` if the operation does not have any dependency.
-* *Salt*, used to disambiguate two otherwise identical operations. This can be any random value.
-
-In the case of batched operations, `target`, `value` and `data` are specified as arrays, which must be of the same length.
-
-[[timelock-operation-lifecycle]]
-==== Operation lifecycle
-
-Timelocked operations are identified by a unique id (their hash) and follow a specific lifecycle:
-
-`Unset` -> `Pending` -> `Pending` + `Ready` -> `Done`
-
-* By calling xref:api:governance.adoc#TimelockController-schedule-address-uint256-bytes-bytes32-bytes32-uint256-[`schedule`] (or xref:api:governance.adoc#TimelockController-scheduleBatch-address---uint256---bytes---bytes32-bytes32-uint256-[`scheduleBatch`]), a proposer moves the operation from the `Unset` to the `Pending` state. This starts a timer that must be longer than the minimum delay. The timer expires at a timestamp accessible through the xref:api:governance.adoc#TimelockController-getTimestamp-bytes32-[`getTimestamp`] method.
-* Once the timer expires, the operation automatically gets the `Ready` state. At this point, it can be executed.
-* By calling xref:api:governance.adoc#TimelockController-TimelockController-execute-address-uint256-bytes-bytes32-bytes32-[`execute`] (or xref:api:governance.adoc#TimelockController-executeBatch-address---uint256---bytes---bytes32-bytes32-[`executeBatch`]), an executor triggers the operation's underlying transactions and moves it to the `Done` state. If the operation has a predecessor, it has to be in the `Done` state for this transition to succeed.
-* xref:api:governance.adoc#TimelockController-TimelockController-cancel-bytes32-[`cancel`] allows proposers to cancel any `Pending` operation. This resets the operation to the `Unset` state. It is thus possible for a proposer to re-schedule an operation that has been cancelled. In this case, the timer restarts when the operation is re-scheduled.
-
-Operations status can be queried using the functions:
-
-* xref:api:governance.adoc#TimelockController-isOperationPending-bytes32-[`isOperationPending(bytes32)`]
-* xref:api:governance.adoc#TimelockController-isOperationReady-bytes32-[`isOperationReady(bytes32)`]
-* xref:api:governance.adoc#TimelockController-isOperationDone-bytes32-[`isOperationDone(bytes32)`]
-
-[[timelock-roles]]
-==== Roles
-
-[[timelock-admin]]
-===== Admin
-
-The admins are in charge of managing proposers and executors. For the timelock to be self-governed, this role should only be given to the timelock itself. Upon deployment, both the timelock and the deployer have this role. After further configuration and testing, the deployer can renounce this role such that all further maintenance operations have to go through the timelock process.
-
-This role is identified by the *TIMELOCK_ADMIN_ROLE* value: `0x5f58e3a2316349923ce3780f8d587db2d72378aed66a8261c916544fa6846ca5`
-
-[[timelock-proposer]]
-===== Proposer
-
-The proposers are in charge of scheduling (and cancelling) operations. This is a critical role, that should be given to governing entities. This could be an EOA, a multisig, or a DAO.
-
-WARNING: *Proposer fight:* Having multiple proposers, while providing redundancy in case one becomes unavailable, can be dangerous. As proposer have their say on all operations, they could cancel operations they disagree with, including operations to remove them for the proposers.
-
-This role is identified by the *PROPOSER_ROLE* value: `0xb09aa5aeb3702cfd50b6b62bc4532604938f21248a27a1d5ca736082b6819cc1`
-
-[[timelock-executor]]
-===== Executor
-
-The executors are in charge of executing the operations scheduled by the proposers once the timelock expires. Logic dictates that multisig or DAO that are proposers should also be executors in order to guarantee operations that have been scheduled will eventually be executed. However, having additional executor can reduce the cost (the executing transaction does not require validation by the multisig or DAO that proposed it), while ensuring whoever is in charge of execution cannot trigger actions that have not been scheduled by the proposers.
-
-This role is identified by the *EXECUTOR_ROLE* value: `0xd8aa0f3194971a2a116679f7c2090f6939c8d4e01a2a8d7e41d55e5351469e63`
-
-
-WARNING: A live contract without at least one proposer and one executor is locked. Make sure these roles are filled by reliable entities before the deployer renounces its administrative rights in favour of the timelock contract itself. See the {AccessControl} documentation to learn more about role management.

contracts/governance/TimelockController.sol

@@ -1,298 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../access/AccessControl.sol";
-
-/**
- * @dev Contract module which acts as a timelocked controller. When set as the
- * owner of an `Ownable` smart contract, it enforces a timelock on all
- * `onlyOwner` maintenance operations. This gives time for users of the
- * controlled contract to exit before a potentially dangerous maintenance
- * operation is applied.
- *
- * By default, this contract is self administered, meaning administration tasks
- * have to go through the timelock process. The proposer (resp executor) role
- * is in charge of proposing (resp executing) operations. A common use case is
- * to position this {TimelockController} as the owner of a smart contract, with
- * a multisig or a DAO as the sole proposer.
- *
- * _Available since v3.3._
- */
-contract TimelockController is AccessControl {
-    bytes32 public constant TIMELOCK_ADMIN_ROLE = keccak256("TIMELOCK_ADMIN_ROLE");
-    bytes32 public constant PROPOSER_ROLE = keccak256("PROPOSER_ROLE");
-    bytes32 public constant EXECUTOR_ROLE = keccak256("EXECUTOR_ROLE");
-    uint256 internal constant _DONE_TIMESTAMP = uint256(1);
-
-    mapping(bytes32 => uint256) private _timestamps;
-    uint256 private _minDelay;
-
-    /**
-     * @dev Emitted when a call is scheduled as part of operation `id`.
-     */
-    event CallScheduled(bytes32 indexed id, uint256 indexed index, address target, uint256 value, bytes data, bytes32 predecessor, uint256 delay);
-
-    /**
-     * @dev Emitted when a call is performed as part of operation `id`.
-     */
-    event CallExecuted(bytes32 indexed id, uint256 indexed index, address target, uint256 value, bytes data);
-
-    /**
-     * @dev Emitted when operation `id` is cancelled.
-     */
-    event Cancelled(bytes32 indexed id);
-
-    /**
-     * @dev Emitted when the minimum delay for future operations is modified.
-     */
-    event MinDelayChange(uint256 oldDuration, uint256 newDuration);
-
-    /**
-     * @dev Initializes the contract with a given `minDelay`.
-     */
-    constructor(uint256 minDelay, address[] memory proposers, address[] memory executors) {
-        _setRoleAdmin(TIMELOCK_ADMIN_ROLE, TIMELOCK_ADMIN_ROLE);
-        _setRoleAdmin(PROPOSER_ROLE, TIMELOCK_ADMIN_ROLE);
-        _setRoleAdmin(EXECUTOR_ROLE, TIMELOCK_ADMIN_ROLE);
-
-        // deployer + self administration
-        _setupRole(TIMELOCK_ADMIN_ROLE, _msgSender());
-        _setupRole(TIMELOCK_ADMIN_ROLE, address(this));
-
-        // register proposers
-        for (uint256 i = 0; i < proposers.length; ++i) {
-            _setupRole(PROPOSER_ROLE, proposers[i]);
-        }
-
-        // register executors
-        for (uint256 i = 0; i < executors.length; ++i) {
-            _setupRole(EXECUTOR_ROLE, executors[i]);
-        }
-
-        _minDelay = minDelay;
-        emit MinDelayChange(0, minDelay);
-    }
-
-    /**
-     * @dev Modifier to make a function callable only by a certain role. In
-     * addition to checking the sender's role, `address(0)` 's role is also
-     * considered. Granting a role to `address(0)` is equivalent to enabling
-     * this role for everyone.
-     */
-    modifier onlyRoleOrOpenRole(bytes32 role) {
-        if (!hasRole(role, address(0))) {
-            _checkRole(role, _msgSender());
-        }
-        _;
-    }
-
-    /**
-     * @dev Contract might receive/hold ETH as part of the maintenance process.
-     */
-    receive() external payable {}
-
-    /**
-     * @dev Returns whether an id correspond to a registered operation. This
-     * includes both Pending, Ready and Done operations.
-     */
-    function isOperation(bytes32 id) public view virtual returns (bool pending) {
-        return getTimestamp(id) > 0;
-    }
-
-    /**
-     * @dev Returns whether an operation is pending or not.
-     */
-    function isOperationPending(bytes32 id) public view virtual returns (bool pending) {
-        return getTimestamp(id) > _DONE_TIMESTAMP;
-    }
-
-    /**
-     * @dev Returns whether an operation is ready or not.
-     */
-    function isOperationReady(bytes32 id) public view virtual returns (bool ready) {
-        uint256 timestamp = getTimestamp(id);
-        // solhint-disable-next-line not-rely-on-time
-        return timestamp > _DONE_TIMESTAMP && timestamp <= block.timestamp;
-    }
-
-    /**
-     * @dev Returns whether an operation is done or not.
-     */
-    function isOperationDone(bytes32 id) public view virtual returns (bool done) {
-        return getTimestamp(id) == _DONE_TIMESTAMP;
-    }
-
-    /**
-     * @dev Returns the timestamp at with an operation becomes ready (0 for
-     * unset operations, 1 for done operations).
-     */
-    function getTimestamp(bytes32 id) public view virtual returns (uint256 timestamp) {
-        return _timestamps[id];
-    }
-
-    /**
-     * @dev Returns the minimum delay for an operation to become valid.
-     *
-     * This value can be changed by executing an operation that calls `updateDelay`.
-     */
-    function getMinDelay() public view virtual returns (uint256 duration) {
-        return _minDelay;
-    }
-
-    /**
-     * @dev Returns the identifier of an operation containing a single
-     * transaction.
-     */
-    function hashOperation(address target, uint256 value, bytes calldata data, bytes32 predecessor, bytes32 salt) public pure virtual returns (bytes32 hash) {
-        return keccak256(abi.encode(target, value, data, predecessor, salt));
-    }
-
-    /**
-     * @dev Returns the identifier of an operation containing a batch of
-     * transactions.
-     */
-    function hashOperationBatch(address[] calldata targets, uint256[] calldata values, bytes[] calldata datas, bytes32 predecessor, bytes32 salt) public pure virtual returns (bytes32 hash) {
-        return keccak256(abi.encode(targets, values, datas, predecessor, salt));
-    }
-
-    /**
-     * @dev Schedule an operation containing a single transaction.
-     *
-     * Emits a {CallScheduled} event.
-     *
-     * Requirements:
-     *
-     * - the caller must have the 'proposer' role.
-     */
-    function schedule(address target, uint256 value, bytes calldata data, bytes32 predecessor, bytes32 salt, uint256 delay) public virtual onlyRole(PROPOSER_ROLE) {
-        bytes32 id = hashOperation(target, value, data, predecessor, salt);
-        _schedule(id, delay);
-        emit CallScheduled(id, 0, target, value, data, predecessor, delay);
-    }
-
-    /**
-     * @dev Schedule an operation containing a batch of transactions.
-     *
-     * Emits one {CallScheduled} event per transaction in the batch.
-     *
-     * Requirements:
-     *
-     * - the caller must have the 'proposer' role.
-     */
-    function scheduleBatch(address[] calldata targets, uint256[] calldata values, bytes[] calldata datas, bytes32 predecessor, bytes32 salt, uint256 delay) public virtual onlyRole(PROPOSER_ROLE) {
-        require(targets.length == values.length, "TimelockController: length mismatch");
-        require(targets.length == datas.length, "TimelockController: length mismatch");
-
-        bytes32 id = hashOperationBatch(targets, values, datas, predecessor, salt);
-        _schedule(id, delay);
-        for (uint256 i = 0; i < targets.length; ++i) {
-            emit CallScheduled(id, i, targets[i], values[i], datas[i], predecessor, delay);
-        }
-    }
-
-    /**
-     * @dev Schedule an operation that is to becomes valid after a given delay.
-     */
-    function _schedule(bytes32 id, uint256 delay) private {
-        require(!isOperation(id), "TimelockController: operation already scheduled");
-        require(delay >= getMinDelay(), "TimelockController: insufficient delay");
-        // solhint-disable-next-line not-rely-on-time
-        _timestamps[id] = block.timestamp + delay;
-    }
-
-    /**
-     * @dev Cancel an operation.
-     *
-     * Requirements:
-     *
-     * - the caller must have the 'proposer' role.
-     */
-    function cancel(bytes32 id) public virtual onlyRole(PROPOSER_ROLE) {
-        require(isOperationPending(id), "TimelockController: operation cannot be cancelled");
-        delete _timestamps[id];
-
-        emit Cancelled(id);
-    }
-
-    /**
-     * @dev Execute an (ready) operation containing a single transaction.
-     *
-     * Emits a {CallExecuted} event.
-     *
-     * Requirements:
-     *
-     * - the caller must have the 'executor' role.
-     */
-    function execute(address target, uint256 value, bytes calldata data, bytes32 predecessor, bytes32 salt) public payable virtual onlyRoleOrOpenRole(EXECUTOR_ROLE) {
-        bytes32 id = hashOperation(target, value, data, predecessor, salt);
-        _beforeCall(predecessor);
-        _call(id, 0, target, value, data);
-        _afterCall(id);
-    }
-
-    /**
-     * @dev Execute an (ready) operation containing a batch of transactions.
-     *
-     * Emits one {CallExecuted} event per transaction in the batch.
-     *
-     * Requirements:
-     *
-     * - the caller must have the 'executor' role.
-     */
-    function executeBatch(address[] calldata targets, uint256[] calldata values, bytes[] calldata datas, bytes32 predecessor, bytes32 salt) public payable virtual onlyRoleOrOpenRole(EXECUTOR_ROLE) {
-        require(targets.length == values.length, "TimelockController: length mismatch");
-        require(targets.length == datas.length, "TimelockController: length mismatch");
-
-        bytes32 id = hashOperationBatch(targets, values, datas, predecessor, salt);
-        _beforeCall(predecessor);
-        for (uint256 i = 0; i < targets.length; ++i) {
-            _call(id, i, targets[i], values[i], datas[i]);
-        }
-        _afterCall(id);
-    }
-
-    /**
-     * @dev Checks before execution of an operation's calls.
-     */
-    function _beforeCall(bytes32 predecessor) private view {
-        require(predecessor == bytes32(0) || isOperationDone(predecessor), "TimelockController: missing dependency");
-    }
-
-    /**
-     * @dev Checks after execution of an operation's calls.
-     */
-    function _afterCall(bytes32 id) private {
-        require(isOperationReady(id), "TimelockController: operation is not ready");
-        _timestamps[id] = _DONE_TIMESTAMP;
-    }
-
-    /**
-     * @dev Execute an operation's call.
-     *
-     * Emits a {CallExecuted} event.
-     */
-    function _call(bytes32 id, uint256 index, address target, uint256 value, bytes calldata data) private {
-        // solhint-disable-next-line avoid-low-level-calls
-        (bool success,) = target.call{value: value}(data);
-        require(success, "TimelockController: underlying transaction reverted");
-
-        emit CallExecuted(id, index, target, value, data);
-    }
-
-    /**
-     * @dev Changes the minimum timelock duration for future operations.
-     *
-     * Emits a {MinDelayChange} event.
-     *
-     * Requirements:
-     *
-     * - the caller must be the timelock itself. This can only be achieved by scheduling and later executing
-     * an operation where the timelock is the target and the data is the ABI-encoded call to this function.
-     */
-    function updateDelay(uint256 newDelay) external virtual {
-        require(msg.sender == address(this), "TimelockController: caller must be timelock");
-        emit MinDelayChange(_minDelay, newDelay);
-        _minDelay = newDelay;
-    }
-}

contracts/interfaces/IERC1271.sol

@@ -1,18 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-/**
- * @dev Interface of the ERC1271 standard signature validation method for
- * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
- *
- * _Available since v4.1._
- */
-interface IERC1271 {
-  /**
-   * @dev Should return whether the signature provided is valid for the provided data
-   * @param hash      Hash of the data to be signed
-   * @param signature Signature byte array associated with _data
-   */
-  function isValidSignature(bytes32 hash, bytes memory signature) external view returns (bytes4 magicValue);
-}

contracts/interfaces/IERC3156.sol

@@ -1,68 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-/**
- * @dev Interface of the ERC3156 FlashBorrower, as defined in
- * https://eips.ethereum.org/EIPS/eip-3156[ERC-3156].
- *
- * _Available since v4.1._
- */
-interface IERC3156FlashBorrower {
-    /**
-     * @dev Receive a flash loan.
-     * @param initiator The initiator of the loan.
-     * @param token The loan currency.
-     * @param amount The amount of tokens lent.
-     * @param fee The additional amount of tokens to repay.
-     * @param data Arbitrary data structure, intended to contain user-defined parameters.
-     * @return The keccak256 hash of "ERC3156FlashBorrower.onFlashLoan"
-     */
-    function onFlashLoan(
-        address initiator,
-        address token,
-        uint256 amount,
-        uint256 fee,
-        bytes calldata data
-    ) external returns (bytes32);
-}
-
-/**
- * @dev Interface of the ERC3156 FlashLender, as defined in
- * https://eips.ethereum.org/EIPS/eip-3156[ERC-3156].
- */
-interface IERC3156FlashLender {
-    /**
-     * @dev The amount of currency available to be lended.
-     * @param token The loan currency.
-     * @return The amount of `token` that can be borrowed.
-     */
-    function maxFlashLoan(
-        address token
-    ) external view returns (uint256);
-
-    /**
-     * @dev The fee to be charged for a given loan.
-     * @param token The loan currency.
-     * @param amount The amount of tokens lent.
-     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
-     */
-    function flashFee(
-        address token,
-        uint256 amount
-    ) external view returns (uint256);
-
-    /**
-     * @dev Initiate a flash loan.
-     * @param receiver The receiver of the tokens in the loan, and the receiver of the callback.
-     * @param token The loan currency.
-     * @param amount The amount of tokens lent.
-     * @param data Arbitrary data structure, intended to contain user-defined parameters.
-     */
-    function flashLoan(
-        IERC3156FlashBorrower receiver,
-        address token,
-        uint256 amount,
-        bytes calldata data
-    ) external returns (bool);
- }

contracts/introspection/ERC165.sol

@@ -0,0 +1,52 @@
+pragma solidity ^0.5.0;
+
+import "./IERC165.sol";
+
+/**
+ * @dev Implementation of the `IERC165` interface.
+ *
+ * Contracts may inherit from this and call `_registerInterface` to declare
+ * their support of an interface.
+ */
+contract ERC165 is IERC165 {
+    /*
+     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
+     */
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
+
+    /**
+     * @dev Mapping of interface ids to whether or not it's supported.
+     */
+    mapping(bytes4 => bool) private _supportedInterfaces;
+
+    constructor () internal {
+        // Derived contracts need only register support for their own interfaces,
+        // we register support for ERC165 itself here
+        _registerInterface(_INTERFACE_ID_ERC165);
+    }
+
+    /**
+     * @dev See `IERC165.supportsInterface`.
+     *
+     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
+     */
+    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
+        return _supportedInterfaces[interfaceId];
+    }
+
+    /**
+     * @dev Registers the contract as an implementer of the interface defined by
+     * `interfaceId`. Support of the actual ERC165 interface is automatic and
+     * registering its interface id is not required.
+     *
+     * See `IERC165.supportsInterface`.
+     *
+     * Requirements:
+     *
+     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
+     */
+    function _registerInterface(bytes4 interfaceId) internal {
+        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
+        _supportedInterfaces[interfaceId] = true;
+    }
+}

contracts/introspection/ERC165Checker.sol

@@ -0,0 +1,121 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @dev Library used to query support of an interface declared via `IERC165`.
+ *
+ * Note that these functions return the actual result of the query: they do not
+ * `revert` if an interface is not supported. It is up to the caller to decide
+ * what to do in these cases.
+ */
+library ERC165Checker {
+    // As per the EIP-165 spec, no interface should ever match 0xffffffff
+    bytes4 private constant _INTERFACE_ID_INVALID = 0xffffffff;
+
+    /*
+     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
+     */
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
+
+    /**
+     * @dev Returns true if `account` supports the `IERC165` interface,
+     */
+    function _supportsERC165(address account) internal view returns (bool) {
+        // Any contract that implements ERC165 must explicitly indicate support of
+        // InterfaceId_ERC165 and explicitly indicate non-support of InterfaceId_Invalid
+        return _supportsERC165Interface(account, _INTERFACE_ID_ERC165) &&
+            !_supportsERC165Interface(account, _INTERFACE_ID_INVALID);
+    }
+
+    /**
+     * @dev Returns true if `account` supports the interface defined by
+     * `interfaceId`. Support for `IERC165` itself is queried automatically.
+     *
+     * See `IERC165.supportsInterface`.
+     */
+    function _supportsInterface(address account, bytes4 interfaceId) internal view returns (bool) {
+        // query support of both ERC165 as per the spec and support of _interfaceId
+        return _supportsERC165(account) &&
+            _supportsERC165Interface(account, interfaceId);
+    }
+
+    /**
+     * @dev Returns true if `account` supports all the interfaces defined in
+     * `interfaceIds`. Support for `IERC165` itself is queried automatically.
+     *
+     * Batch-querying can lead to gas savings by skipping repeated checks for
+     * `IERC165` support.
+     *
+     * See `IERC165.supportsInterface`.
+     */
+    function _supportsAllInterfaces(address account, bytes4[] memory interfaceIds) internal view returns (bool) {
+        // query support of ERC165 itself
+        if (!_supportsERC165(account)) {
+            return false;
+        }
+
+        // query support of each interface in _interfaceIds
+        for (uint256 i = 0; i < interfaceIds.length; i++) {
+            if (!_supportsERC165Interface(account, interfaceIds[i])) {
+                return false;
+            }
+        }
+
+        // all interfaces supported
+        return true;
+    }
+
+    /**
+     * @notice Query if a contract implements an interface, does not check ERC165 support
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @return true if the contract at account indicates support of the interface with
+     * identifier interfaceId, false otherwise
+     * @dev Assumes that account contains a contract that supports ERC165, otherwise
+     * the behavior of this method is undefined. This precondition can be checked
+     * with the `supportsERC165` method in this library.
+     * Interface identification is specified in ERC-165.
+     */
+    function _supportsERC165Interface(address account, bytes4 interfaceId) private view returns (bool) {
+        // success determines whether the staticcall succeeded and result determines
+        // whether the contract at account indicates support of _interfaceId
+        (bool success, bool result) = _callERC165SupportsInterface(account, interfaceId);
+
+        return (success && result);
+    }
+
+    /**
+     * @notice Calls the function with selector 0x01ffc9a7 (ERC165) and suppresses throw
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @return success true if the STATICCALL succeeded, false otherwise
+     * @return result true if the STATICCALL succeeded and the contract at account
+     * indicates support of the interface with identifier interfaceId, false otherwise
+     */
+    function _callERC165SupportsInterface(address account, bytes4 interfaceId)
+        private
+        view
+        returns (bool success, bool result)
+    {
+        bytes memory encodedParams = abi.encodeWithSelector(_INTERFACE_ID_ERC165, interfaceId);
+
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            let encodedParams_data := add(0x20, encodedParams)
+            let encodedParams_size := mload(encodedParams)
+
+            let output := mload(0x40)    // Find empty storage location using "free memory pointer"
+            mstore(output, 0x0)
+
+            success := staticcall(
+                30000,                   // 30k gas
+                account,                 // To addr
+                encodedParams_data,
+                encodedParams_size,
+                output,
+                0x20                     // Outputs are 32 bytes long
+            )
+
+            result := mload(output)      // Load the result
+        }
+    }
+}

contracts/introspection/ERC1820Implementer.sol

@@ -0,0 +1,35 @@
+pragma solidity ^0.5.0;
+
+import "./IERC1820Implementer.sol";
+
+/**
+ * @dev Implementation of the `IERC1820Implementer` interface.
+ *
+ * Contracts may inherit from this and call `_registerInterfaceForAddress` to
+ * declare their willingness to be implementers.
+ * `IERC1820Registry.setInterfaceImplementer` should then be called for the
+ * registration to be complete.
+ */
+contract ERC1820Implementer is IERC1820Implementer {
+    bytes32 constant private ERC1820_ACCEPT_MAGIC = keccak256(abi.encodePacked("ERC1820_ACCEPT_MAGIC"));
+
+    mapping(bytes32 => mapping(address => bool)) private _supportedInterfaces;
+
+    /**
+     * See `IERC1820Implementer.canImplementInterfaceForAddress`.
+     */
+    function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view returns (bytes32) {
+        return _supportedInterfaces[interfaceHash][account] ? ERC1820_ACCEPT_MAGIC : bytes32(0x00);
+    }
+
+    /**
+     * @dev Declares the contract as willing to be an implementer of
+     * `interfaceHash` for `account`.
+     *
+     * See `IERC1820Registry.setInterfaceImplementer` and
+     * `IERC1820Registry.interfaceHash`.
+     */
+    function _registerInterfaceForAddress(bytes32 interfaceHash, address account) internal {
+        _supportedInterfaces[interfaceHash][account] = true;
+    }
+}

contracts/introspection/IERC165.sol

@@ -1,21 +1,19 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 /**
  * @dev Interface of the ERC165 standard, as defined in the
- * https://eips.ethereum.org/EIPS/eip-165[EIP].
+ * [EIP](https://eips.ethereum.org/EIPS/eip-165).
  *
  * Implementers can declare support of contract interfaces, which can then be
- * queried by others ({ERC165Checker}).
+ * queried by others (`ERC165Checker`).
  *
- * For an implementation, see {ERC165}.
+ * For an implementation, see `ERC165`.
  */
 interface IERC165 {
     /**
      * @dev Returns true if this contract implements the interface defined by
      * `interfaceId`. See the corresponding
-     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
+     * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
      * to learn more about how these ids are created.
      *
      * This function call must use less than 30 000 gas.

contracts/introspection/IERC1820Implementer.sol

@@ -1,19 +1,17 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 /**
  * @dev Interface for an ERC1820 implementer, as defined in the
- * https://eips.ethereum.org/EIPS/eip-1820#interface-implementation-erc1820implementerinterface[EIP].
+ * [EIP](https://eips.ethereum.org/EIPS/eip-1820#interface-implementation-erc1820implementerinterface).
  * Used by contracts that will be registered as implementers in the
- * {IERC1820Registry}.
+ * `IERC1820Registry`.
  */
 interface IERC1820Implementer {
     /**
      * @dev Returns a special value (`ERC1820_ACCEPT_MAGIC`) if this contract
      * implements `interfaceHash` for `account`.
      *
-     * See {IERC1820Registry-setInterfaceImplementer}.
+     * See `IERC1820Registry.setInterfaceImplementer`.
      */
     function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view returns (bytes32);
 }

contracts/introspection/IERC1820Registry.sol

@@ -1,10 +1,8 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 /**
  * @dev Interface of the global ERC1820 Registry, as defined in the
- * https://eips.ethereum.org/EIPS/eip-1820[EIP]. Accounts may register
+ * [EIP](https://eips.ethereum.org/EIPS/eip-1820). Accounts may register
  * implementers for interfaces in this registry, as well as query support.
  *
  * Implementers may be shared by multiple accounts, and can also implement more
@@ -12,7 +10,7 @@ pragma solidity ^0.8.0;
  * for themselves, but externally-owned accounts (EOA) must delegate this to a
  * contract.
  *
- * {IERC165} interfaces can also be queried via the registry.
+ * `IERC165` interfaces can also be queried via the registry.
  *
  * For an in-depth explanation and source code analysis, see the EIP text.
  */
@@ -24,7 +22,7 @@ interface IERC1820Registry {
      * By default, each account is its own manager. Passing a value of `0x0` in
      * `newManager` will reset the manager to this initial state.
      *
-     * Emits a {ManagerChanged} event.
+     * Emits a `ManagerChanged` event.
      *
      * Requirements:
      *
@@ -35,73 +33,73 @@ interface IERC1820Registry {
     /**
      * @dev Returns the manager for `account`.
      *
-     * See {setManager}.
+     * See `setManager`.
      */
     function getManager(address account) external view returns (address);
 
     /**
-     * @dev Sets the `implementer` contract as ``account``'s implementer for
+     * @dev Sets the `implementer` contract as `account`'s implementer for
      * `interfaceHash`.
      *
      * `account` being the zero address is an alias for the caller's address.
      * The zero address can also be used in `implementer` to remove an old one.
      *
-     * See {interfaceHash} to learn how these are created.
+     * See `interfaceHash` to learn how these are created.
      *
-     * Emits an {InterfaceImplementerSet} event.
+     * Emits an `InterfaceImplementerSet` event.
      *
      * Requirements:
      *
      * - the caller must be the current manager for `account`.
-     * - `interfaceHash` must not be an {IERC165} interface id (i.e. it must not
+     * - `interfaceHash` must not be an `IERC165` interface id (i.e. it must not
      * end in 28 zeroes).
-     * - `implementer` must implement {IERC1820Implementer} and return true when
+     * - `implementer` must implement `IERC1820Implementer` and return true when
      * queried for support, unless `implementer` is the caller. See
-     * {IERC1820Implementer-canImplementInterfaceForAddress}.
+     * `IERC1820Implementer.canImplementInterfaceForAddress`.
      */
-    function setInterfaceImplementer(address account, bytes32 _interfaceHash, address implementer) external;
+    function setInterfaceImplementer(address account, bytes32 interfaceHash, address implementer) external;
 
     /**
      * @dev Returns the implementer of `interfaceHash` for `account`. If no such
      * implementer is registered, returns the zero address.
      *
-     * If `interfaceHash` is an {IERC165} interface id (i.e. it ends with 28
+     * If `interfaceHash` is an `IERC165` interface id (i.e. it ends with 28
      * zeroes), `account` will be queried for support of it.
      *
      * `account` being the zero address is an alias for the caller's address.
      */
-    function getInterfaceImplementer(address account, bytes32 _interfaceHash) external view returns (address);
+    function getInterfaceImplementer(address account, bytes32 interfaceHash) external view returns (address);
 
     /**
      * @dev Returns the interface hash for an `interfaceName`, as defined in the
      * corresponding
-     * https://eips.ethereum.org/EIPS/eip-1820#interface-name[section of the EIP].
+     * [section of the EIP](https://eips.ethereum.org/EIPS/eip-1820#interface-name).
      */
     function interfaceHash(string calldata interfaceName) external pure returns (bytes32);
 
     /**
-     * @notice Updates the cache with whether the contract implements an ERC165 interface or not.
-     * @param account Address of the contract for which to update the cache.
-     * @param interfaceId ERC165 interface for which to update the cache.
+     *  @notice Updates the cache with whether the contract implements an ERC165 interface or not.
+     *  @param account Address of the contract for which to update the cache.
+     *  @param interfaceId ERC165 interface for which to update the cache.
      */
     function updateERC165Cache(address account, bytes4 interfaceId) external;
 
     /**
-     * @notice Checks whether a contract implements an ERC165 interface or not.
-     * If the result is not cached a direct lookup on the contract address is performed.
-     * If the result is not cached or the cached value is out-of-date, the cache MUST be updated manually by calling
-     * {updateERC165Cache} with the contract address.
-     * @param account Address of the contract to check.
-     * @param interfaceId ERC165 interface to check.
-     * @return True if `account` implements `interfaceId`, false otherwise.
+     *  @notice Checks whether a contract implements an ERC165 interface or not.
+     *  If the result is not cached a direct lookup on the contract address is performed.
+     *  If the result is not cached or the cached value is out-of-date, the cache MUST be updated manually by calling
+     *  'updateERC165Cache' with the contract address.
+     *  @param account Address of the contract to check.
+     *  @param interfaceId ERC165 interface to check.
+     *  @return True if `account.address()` implements `interfaceId`, false otherwise.
      */
     function implementsERC165Interface(address account, bytes4 interfaceId) external view returns (bool);
 
     /**
-     * @notice Checks whether a contract implements an ERC165 interface or not without using nor updating the cache.
-     * @param account Address of the contract to check.
-     * @param interfaceId ERC165 interface to check.
-     * @return True if `account` implements `interfaceId`, false otherwise.
+     *  @notice Checks whether a contract implements an ERC165 interface or not without using nor updating the cache.
+     *  @param account Address of the contract to check.
+     *  @param interfaceId ERC165 interface to check.
+     *  @return True if `account.address()` implements `interfaceId`, false otherwise.
      */
     function implementsERC165InterfaceNoCache(address account, bytes4 interfaceId) external view returns (bool);
 

contracts/introspection/README.md

@@ -0,0 +1,23 @@
+---
+sections:
+  - title: Local
+    contracts:
+      - IERC165
+      - ERC165
+      - ERC165Checker
+  - title: Global
+    contracts:
+      - IERC1820Registry
+      - IERC1820Implementer
+      - ERC1820Implementer
+---
+
+This set of interfaces and contracts deal with [type introspection](https://en.wikipedia.org/wiki/Type_introspection) of contracts, that is, examining which functions can be called on them. This is usually referred to as a contract's _interface_.
+
+Ethereum contracts have no native concept of an interface, so applications must usually simply trust they are not making an incorrect call. For trusted setups this is a non-issue, but often unknown and untrusted third-party addresses need to be interacted with. There may even not be any direct calls to them! (e.g. `ERC20` tokens may be sent to a contract that lacks a way to transfer them out of it, locking them forever). In these cases, a contract _declaring_ its interface can be very helpful in preventing errors.
+
+There are two main ways to approach this.
+ - Locally, where a contract implements `IERC165` and declares an interface, and a second one queries it directly via `ERC165Checker`.
+ - Globally, where a global and unique registry (`IERC1820Registry`) is used to register implementers of a certain interface (`IERC1820Implementer`). It is then the registry that is queried, which allows for more complex setups, like contracts implementing interfaces for externally-owned accounts.
+
+Note that, in all cases, accounts simply _declare_ their interfaces, but they are not required to actually implement them. This mechanism can therefore be used to both prevent errors and allow for complex interactions (see `ERC777`), but it must not be relied on for security.

contracts/lifecycle/Pausable.sol

@@ -1,8 +1,6 @@
-// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.0;
 
-pragma solidity ^0.8.0;
-
-import "../utils/Context.sol";
+import "../access/roles/PauserRole.sol";
 
 /**
  * @dev Contract module which allows children to implement an emergency stop
@@ -13,78 +11,63 @@ import "../utils/Context.sol";
  * the functions of your contract. Note that they will not be pausable by
  * simply including this module, only once the modifiers are put in place.
  */
-abstract contract Pausable is Context {
+contract Pausable is PauserRole {
     /**
-     * @dev Emitted when the pause is triggered by `account`.
+     * @dev Emitted when the pause is triggered by a pauser (`account`).
      */
     event Paused(address account);
 
     /**
-     * @dev Emitted when the pause is lifted by `account`.
+     * @dev Emitted when the pause is lifted by a pauser (`account`).
      */
     event Unpaused(address account);
 
     bool private _paused;
 
     /**
-     * @dev Initializes the contract in unpaused state.
+     * @dev Initializes the contract in unpaused state. Assigns the Pauser role
+     * to the deployer.
      */
-    constructor () {
+    constructor () internal {
         _paused = false;
     }
 
     /**
      * @dev Returns true if the contract is paused, and false otherwise.
      */
-    function paused() public view virtual returns (bool) {
+    function paused() public view returns (bool) {
         return _paused;
     }
 
     /**
      * @dev Modifier to make a function callable only when the contract is not paused.
-     *
-     * Requirements:
-     *
-     * - The contract must not be paused.
      */
     modifier whenNotPaused() {
-        require(!paused(), "Pausable: paused");
+        require(!_paused, "Pausable: paused");
         _;
     }
 
     /**
      * @dev Modifier to make a function callable only when the contract is paused.
-     *
-     * Requirements:
-     *
-     * - The contract must be paused.
      */
     modifier whenPaused() {
-        require(paused(), "Pausable: not paused");
+        require(_paused, "Pausable: not paused");
         _;
     }
 
     /**
-     * @dev Triggers stopped state.
-     *
-     * Requirements:
-     *
-     * - The contract must not be paused.
+     * @dev Called by a pauser to pause, triggers stopped state.
      */
-    function _pause() internal virtual whenNotPaused {
+    function pause() public onlyPauser whenNotPaused {
         _paused = true;
-        emit Paused(_msgSender());
+        emit Paused(msg.sender);
     }
 
     /**
-     * @dev Returns to normal state.
-     *
-     * Requirements:
-     *
-     * - The contract must be paused.
+     * @dev Called by a pauser to unpause, returns to normal state.
      */
-    function _unpause() internal virtual whenPaused {
+    function unpause() public onlyPauser whenPaused {
         _paused = false;
-        emit Unpaused(_msgSender());
+        emit Unpaused(msg.sender);
     }
 }

contracts/math/Math.sol

@@ -1,6 +1,4 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 /**
  * @dev Standard math utilities missing in the Solidity language.

contracts/math/README.md

@@ -0,0 +1,10 @@
+---
+title: Math
+sections:
+  - title: Libraries
+    contracts:
+      - SafeMath
+      - Math
+---
+
+These are math-related utilities.

contracts/math/SafeMath.sol

@@ -0,0 +1,107 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @dev Wrappers over Solidity's arithmetic operations with added overflow
+ * checks.
+ *
+ * Arithmetic operations in Solidity wrap on overflow. This can easily result
+ * in bugs, because programmers usually assume that an overflow raises an
+ * error, which is the standard behavior in high level programming languages.
+ * `SafeMath` restores this intuition by reverting the transaction when an
+ * operation overflows.
+ *
+ * Using this library instead of the unchecked operations eliminates an entire
+ * class of bugs, so it's recommended to use it always.
+ */
+library SafeMath {
+    /**
+     * @dev Returns the addition of two unsigned integers, reverting on
+     * overflow.
+     *
+     * Counterpart to Solidity's `+` operator.
+     *
+     * Requirements:
+     * - Addition cannot overflow.
+     */
+    function add(uint256 a, uint256 b) internal pure returns (uint256) {
+        uint256 c = a + b;
+        require(c >= a, "SafeMath: addition overflow");
+
+        return c;
+    }
+
+    /**
+     * @dev Returns the subtraction of two unsigned integers, reverting on
+     * overflow (when the result is negative).
+     *
+     * Counterpart to Solidity's `-` operator.
+     *
+     * Requirements:
+     * - Subtraction cannot overflow.
+     */
+    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b <= a, "SafeMath: subtraction overflow");
+        uint256 c = a - b;
+
+        return c;
+    }
+
+    /**
+     * @dev Returns the multiplication of two unsigned integers, reverting on
+     * overflow.
+     *
+     * Counterpart to Solidity's `*` operator.
+     *
+     * Requirements:
+     * - Multiplication cannot overflow.
+     */
+    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+        // benefit is lost if 'b' is also tested.
+        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+        if (a == 0) {
+            return 0;
+        }
+
+        uint256 c = a * b;
+        require(c / a == b, "SafeMath: multiplication overflow");
+
+        return c;
+    }
+
+    /**
+     * @dev Returns the integer division of two unsigned integers. Reverts on
+     * division by zero. The result is rounded towards zero.
+     *
+     * Counterpart to Solidity's `/` operator. Note: this function uses a
+     * `revert` opcode (which leaves remaining gas untouched) while Solidity
+     * uses an invalid opcode to revert (consuming all remaining gas).
+     *
+     * Requirements:
+     * - The divisor cannot be zero.
+     */
+    function div(uint256 a, uint256 b) internal pure returns (uint256) {
+        // Solidity only automatically asserts when dividing by 0
+        require(b > 0, "SafeMath: division by zero");
+        uint256 c = a / b;
+        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+
+        return c;
+    }
+
+    /**
+     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
+     * Reverts when dividing by zero.
+     *
+     * Counterpart to Solidity's `%` operator. This function uses a `revert`
+     * opcode (which leaves remaining gas untouched) while Solidity uses an
+     * invalid opcode to revert (consuming all remaining gas).
+     *
+     * Requirements:
+     * - The divisor cannot be zero.
+     */
+    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b != 0, "SafeMath: modulo by zero");
+        return a % b;
+    }
+}

contracts/metatx/ERC2771Context.sol

@@ -1,37 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/Context.sol";
-
-/*
- * @dev Context variant with ERC2771 support.
- */
-abstract contract ERC2771Context is Context {
-    address immutable _trustedForwarder;
-
-    constructor(address trustedForwarder) {
-        _trustedForwarder = trustedForwarder;
-    }
-
-    function isTrustedForwarder(address forwarder) public view virtual returns(bool) {
-        return forwarder == _trustedForwarder;
-    }
-
-    function _msgSender() internal view virtual override returns (address sender) {
-        if (isTrustedForwarder(msg.sender)) {
-            // The assembly code is more direct than the Solidity version using `abi.decode`.
-            assembly { sender := shr(96, calldataload(sub(calldatasize(), 20))) }
-        } else {
-            return super._msgSender();
-        }
-    }
-
-    function _msgData() internal view virtual override returns (bytes calldata) {
-        if (isTrustedForwarder(msg.sender)) {
-            return msg.data[:msg.data.length-20];
-        } else {
-            return super._msgData();
-        }
-    }
-}

contracts/metatx/MinimalForwarder.sol

@@ -1,58 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/cryptography/ECDSA.sol";
-import "../utils/cryptography/draft-EIP712.sol";
-
-/*
- * @dev Simple minimal forwarder to be used together with an ERC2771 compatible contract. See {ERC2771Context}.
- */
-contract MinimalForwarder is EIP712 {
-    using ECDSA for bytes32;
-
-    struct ForwardRequest {
-        address from;
-        address to;
-        uint256 value;
-        uint256 gas;
-        uint256 nonce;
-        bytes data;
-    }
-
-    bytes32 private constant TYPEHASH = keccak256("ForwardRequest(address from,address to,uint256 value,uint256 gas,uint256 nonce,bytes data)");
-
-    mapping(address => uint256) private _nonces;
-
-    constructor() EIP712("MinimalForwarder", "0.0.1") {}
-
-    function getNonce(address from) public view returns (uint256) {
-        return _nonces[from];
-    }
-
-    function verify(ForwardRequest calldata req, bytes calldata signature) public view returns (bool) {
-        address signer = _hashTypedDataV4(keccak256(abi.encode(
-            TYPEHASH,
-            req.from,
-            req.to,
-            req.value,
-            req.gas,
-            req.nonce,
-            keccak256(req.data)
-        ))).recover(signature);
-        return _nonces[req.from] == req.nonce && signer == req.from;
-    }
-
-    function execute(ForwardRequest calldata req, bytes calldata signature) public payable returns (bool, bytes memory) {
-        require(verify(req, signature), "MinimalForwarder: signature does not match request");
-        _nonces[req.from] = req.nonce + 1;
-
-        // solhint-disable-next-line avoid-low-level-calls
-        (bool success, bytes memory returndata) = req.to.call{gas: req.gas, value: req.value}(abi.encodePacked(req.data, req.from));
-        // Validate that the relayer has sent enough gas for the call.
-        // See https://ronan.eth.link/blog/ethereum-gas-dangers/
-        assert(gasleft() > req.gas / 63);
-
-        return (success, returndata);
-    }
-}

contracts/metatx/README.adoc

@@ -1,12 +0,0 @@
-= Meta Transactions
-
-[.readme-notice]
-NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/metatx
-
-== Core
-
-{{ERC2771Context}}
-
-== Utils
-
-{{MinimalForwarder}}

contracts/mocks/AccessControlEnumerableMock.sol

@@ -1,17 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../access/AccessControlEnumerable.sol";
-
-contract AccessControlEnumerableMock is AccessControlEnumerable {
-    constructor() {
-        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
-    }
-
-    function setRoleAdmin(bytes32 roleId, bytes32 adminRoleId) public {
-        _setRoleAdmin(roleId, adminRoleId);
-    }
-
-    function senderProtected(bytes32 roleId) public onlyRole(roleId) {}
-}

contracts/mocks/AccessControlMock.sol

@@ -1,17 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../access/AccessControl.sol";
-
-contract AccessControlMock is AccessControl {
-    constructor() {
-        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
-    }
-
-    function setRoleAdmin(bytes32 roleId, bytes32 adminRoleId) public {
-        _setRoleAdmin(roleId, adminRoleId);
-    }
-
-    function senderProtected(bytes32 roleId) public onlyRole(roleId) {}
-}

contracts/mocks/AddressImpl.sol

@@ -1,42 +1,9 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 import "../utils/Address.sol";
 
 contract AddressImpl {
-    string public sharedAnswer;
-
-    event CallReturnValue(string data);
-
     function isContract(address account) external view returns (bool) {
         return Address.isContract(account);
     }
-
-    function sendValue(address payable receiver, uint256 amount) external {
-        Address.sendValue(receiver, amount);
-    }
-
-    function functionCall(address target, bytes calldata data) external {
-        bytes memory returnData = Address.functionCall(target, data);
-        emit CallReturnValue(abi.decode(returnData, (string)));
-    }
-
-    function functionCallWithValue(address target, bytes calldata data, uint256 value) external payable {
-        bytes memory returnData = Address.functionCallWithValue(target, data, value);
-        emit CallReturnValue(abi.decode(returnData, (string)));
-    }
-
-    function functionStaticCall(address target, bytes calldata data) external {
-        bytes memory returnData = Address.functionStaticCall(target, data);
-        emit CallReturnValue(abi.decode(returnData, (string)));
-    }
-
-    function functionDelegateCall(address target, bytes calldata data) external {
-        bytes memory returnData = Address.functionDelegateCall(target, data);
-        emit CallReturnValue(abi.decode(returnData, (string)));
-    }
-
-    // sendValue's tests require the contract to hold Ether
-    receive () external payable { }
 }

contracts/mocks/AllowanceCrowdsaleImpl.sol

@@ -0,0 +1,14 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/IERC20.sol";
+import "../crowdsale/emission/AllowanceCrowdsale.sol";
+
+contract AllowanceCrowdsaleImpl is AllowanceCrowdsale {
+    constructor (uint256 rate, address payable wallet, IERC20 token, address tokenWallet)
+        public
+        Crowdsale(rate, wallet, token)
+        AllowanceCrowdsale(tokenWallet)
+    {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}

contracts/mocks/ArraysImpl.sol

@@ -1,19 +1,17 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
+pragma solidity ^0.5.0;
 
 import "../utils/Arrays.sol";
 
 contract ArraysImpl {
     using Arrays for uint256[];
 
-    uint256[] private _array;
+    uint256[] private array;
 
-    constructor (uint256[] memory array) {
-        _array = array;
+    constructor (uint256[] memory _array) public {
+        array = _array;
     }
 
-    function findUpperBound(uint256 element) external view returns (uint256) {
-        return _array.findUpperBound(element);
+    function findUpperBound(uint256 _element) external view returns (uint256) {
+        return array.findUpperBound(_element);
     }
 }

contracts/mocks/BadBeacon.sol

@@ -1,12 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-contract BadBeaconNoImpl {
-}
-
-contract BadBeaconNotContract {
-    function implementation() external pure returns (address) {
-        return address(0x1);
-    }
-}

contracts/mocks/CallReceiverMock.sol

@@ -1,50 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-contract CallReceiverMock {
-    string public sharedAnswer;
-
-    event MockFunctionCalled();
-
-    uint256[] private _array;
-
-    function mockFunction() public payable returns (string memory) {
-        emit MockFunctionCalled();
-
-        return "0x1234";
-    }
-
-    function mockFunctionNonPayable() public returns (string memory) {
-        emit MockFunctionCalled();
-
-        return "0x1234";
-    }
-
-    function mockStaticFunction() public pure returns (string memory) {
-        return "0x1234";
-    }
-
-    function mockFunctionRevertsNoReason() public payable {
-        revert();
-    }
-
-    function mockFunctionRevertsReason() public payable {
-        revert("CallReceiverMock: reverting");
-    }
-
-    function mockFunctionThrows() public payable {
-        assert(false);
-    }
-
-    function mockFunctionOutOfGas() public payable {
-        for (uint256 i = 0; ; ++i) {
-            _array.push(i);
-        }
-    }
-
-    function mockFunctionWritesStorage() public returns (string memory) {
-        sharedAnswer = "42";
-        return "0x1234";
-    }
-}

contracts/mocks/CappedCrowdsaleImpl.sol

@@ -0,0 +1,14 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/IERC20.sol";
+import "../crowdsale/validation/CappedCrowdsale.sol";
+
+contract CappedCrowdsaleImpl is CappedCrowdsale {
+    constructor (uint256 rate, address payable wallet, IERC20 token, uint256 cap)
+        public
+        Crowdsale(rate, wallet, token)
+        CappedCrowdsale(cap)
+    {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}

contracts/mocks/CapperRoleMock.sol

@@ -0,0 +1,18 @@
+pragma solidity ^0.5.0;
+
+import "../access/roles/CapperRole.sol";
+
+contract CapperRoleMock is CapperRole {
+    function removeCapper(address account) public {
+        _removeCapper(account);
+    }
+
+    function onlyCapperMock() public view onlyCapper {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    // Causes a compilation error if super._removeCapper is not internal
+    function _removeCapper(address account) internal {
+        super._removeCapper(account);
+    }
+}

contracts/mocks/ClashingImplementation.sol

@@ -1,20 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-
-/**
- * @dev Implementation contract with an admin() function made to clash with
- * @dev TransparentUpgradeableProxy's to test correct functioning of the
- * @dev Transparent Proxy feature.
- */
-contract ClashingImplementation {
-
-  function admin() external pure returns (address) {
-    return 0x0000000000000000000000000000000011111142;
-  }
-
-  function delegatedFunction() external pure returns (bool) {
-    return true;
-  }
-}

contracts/mocks/ClonesMock.sol

@@ -1,32 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../proxy/Clones.sol";
-import "../utils/Address.sol";
-
-contract ClonesMock {
-    using Address for address;
-    using Clones for address;
-
-    event NewInstance(address instance);
-
-    function clone(address implementation, bytes calldata initdata) public payable {
-        _initAndEmit(implementation.clone(), initdata);
-    }
-
-    function cloneDeterministic(address implementation, bytes32 salt, bytes calldata initdata) public payable {
-        _initAndEmit(implementation.cloneDeterministic(salt), initdata);
-    }
-
-    function predictDeterministicAddress(address implementation, bytes32 salt) public view returns (address predicted) {
-        return implementation.predictDeterministicAddress(salt);
-    }
-
-    function _initAndEmit(address instance, bytes memory initdata) private {
-        if (initdata.length > 0) {
-            instance.functionCallWithValue(initdata, msg.value);
-        }
-        emit NewInstance(instance);
-    }
-}

contracts/mocks/ConditionalEscrowMock.sol

@@ -1,8 +1,6 @@
-// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.0;
 
-pragma solidity ^0.8.0;
-
-import "../utils/escrow/ConditionalEscrow.sol";
+import "../payment/escrow/ConditionalEscrow.sol";
 
 // mock class using ConditionalEscrow
 contract ConditionalEscrowMock is ConditionalEscrow {
@@ -12,7 +10,7 @@ contract ConditionalEscrowMock is ConditionalEscrow {
         _allowed[payee] = allowed;
     }
 
-    function withdrawalAllowed(address payee) public view override returns (bool) {
+    function withdrawalAllowed(address payee) public view returns (bool) {
         return _allowed[payee];
     }
 }

contracts/mocks/ContextMock.sol

@@ -1,29 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/Context.sol";
-
-contract ContextMock is Context {
-    event Sender(address sender);
-
-    function msgSender() public {
-        emit Sender(_msgSender());
-    }
-
-    event Data(bytes data, uint256 integerValue, string stringValue);
-
-    function msgData(uint256 integerValue, string memory stringValue) public {
-        emit Data(_msgData(), integerValue, stringValue);
-    }
-}
-
-contract ContextMockCaller {
-    function callSender(ContextMock context) public {
-        context.msgSender();
-    }
-
-    function callData(ContextMock context, uint256 integerValue, string memory stringValue) public {
-        context.msgData(integerValue, stringValue);
-    }
-}

contracts/mocks/CountersImpl.sol

@@ -1,8 +1,6 @@
-// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.0;
 
-pragma solidity ^0.8.0;
-
-import "../utils/Counters.sol";
+import "../drafts/Counters.sol";
 
 contract CountersImpl {
     using Counters for Counters.Counter;

contracts/mocks/Create2Impl.sol

@@ -1,27 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/Create2.sol";
-import "../utils/introspection/ERC1820Implementer.sol";
-
-contract Create2Impl {
-    function deploy(uint256 value, bytes32 salt, bytes memory code) public {
-        Create2.deploy(value, salt, code);
-    }
-
-    function deployERC1820Implementer(uint256 value, bytes32 salt) public {
-        // solhint-disable-next-line indent
-        Create2.deploy(value, salt, type(ERC1820Implementer).creationCode);
-    }
-
-    function computeAddress(bytes32 salt, bytes32 codeHash) public view returns (address) {
-        return Create2.computeAddress(salt, codeHash);
-    }
-
-    function computeAddressWithDeployer(bytes32 salt, bytes32 codeHash, address deployer) public pure returns (address) {
-        return Create2.computeAddress(salt, codeHash, deployer);
-    }
-
-    receive() external payable {}
-}

contracts/mocks/CrowdsaleMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.0;
+
+import "../crowdsale/Crowdsale.sol";
+
+contract CrowdsaleMock is Crowdsale {
+    constructor (uint256 rate, address payable wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}

contracts/mocks/DummyImplementation.sol

@@ -1,57 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-abstract contract Impl {
-  function version() public pure virtual returns (string memory); 
-}
-
-contract DummyImplementation {
-  uint256 public value;
-  string public text;
-  uint256[] public values;
-
-  function initializeNonPayable() public {
-    value = 10;
-  }
-
-  function initializePayable() public payable {
-    value = 100;
-  }
-
-  function initializeNonPayableWithValue(uint256 _value) public {
-    value = _value;
-  }
-
-  function initializePayableWithValue(uint256 _value) public payable {
-    value = _value;
-  }
-
-  function initialize(uint256 _value, string memory _text, uint256[] memory _values) public {
-    value = _value;
-    text = _text;
-    values = _values;
-  }
-
-  function get() public pure returns (bool) {
-    return true;
-  }
-
-  function version() public pure virtual returns (string memory) {
-    return "V1";
-  }
-
-  function reverts() public pure {
-    require(false, "DummyImplementation reverted");
-  }
-}
-
-contract DummyImplementationV2 is DummyImplementation {
-  function migrate(uint256 newVal) public payable {
-    value = newVal;
-  }
-
-  function version() public pure override returns (string memory) {
-    return "V2";
-  }
-}

contracts/mocks/ECDSAMock.sol

@@ -1,8 +1,6 @@
-// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.0;
 
-pragma solidity ^0.8.0;
-
-import "../utils/cryptography/ECDSA.sol";
+import "../cryptography/ECDSA.sol";
 
 contract ECDSAMock {
     using ECDSA for bytes32;

contracts/mocks/EIP712External.sol

@@ -1,28 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.0;
-
-import "../utils/cryptography/draft-EIP712.sol";
-import "../utils/cryptography/ECDSA.sol";
-
-contract EIP712External is EIP712 {
-    constructor(string memory name, string memory version) EIP712(name, version) {}
-
-    function domainSeparator() external view returns (bytes32) {
-        return _domainSeparatorV4();
-    }
-
-    function verify(bytes memory signature, address signer, address mailTo, string memory mailContents) external view {
-        bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
-            keccak256("Mail(address to,string contents)"),
-            mailTo,
-            keccak256(bytes(mailContents))
-        )));
-        address recoveredSigner = ECDSA.recover(digest, signature);
-        require(recoveredSigner == signer);
-    }
-
-    function getChainId() external view returns (uint256) {
-        return block.chainid;
-    }
-}