Add ERC6909 Implementation along with extensions (#5394)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Ernesto García <ernestognw@gmail.com>

contracts/token/ERC6909/README.adoc

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+= ERC-6909
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/token/erc6909
+
+This set of interfaces and contracts are all related to the https://eips.ethereum.org/EIPS/eip-6909[ERC-6909 Minimal Multi-Token Interface].
+
+The ERC consists of four interfaces which fulfill different roles--the interfaces are as follows:
+
+. {IERC6909}: Base interface for a vanilla ERC6909 token.
+. {IERC6909ContentURI}: Extends the base interface and adds content URI (contract and token level) functionality.
+. {IERC6909Metadata}: Extends the base interface and adds metadata functionality, which exposes a name, symbol, and decimals for each token id.
+. {IERC6909TokenSupply}: Extends the base interface and adds total supply functionality for each token id.
+
+Implementations are provided for each of the 4 interfaces defined in the ERC.
+
+== Core
+
+{{ERC6909}}
+
+== Extensions
+
+{{ERC6909ContentURI}}
+
+{{ERC6909Metadata}}
+
+{{ERC6909TokenSupply}}

contracts/token/ERC6909/draft-ERC6909.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {IERC6909} from "../../interfaces/draft-IERC6909.sol";
+import {Context} from "../../utils/Context.sol";
+import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
+
+/**
+ * @dev Implementation of ERC-6909.
+ * See https://eips.ethereum.org/EIPS/eip-6909
+ */
+contract ERC6909 is Context, ERC165, IERC6909 {
+    mapping(address owner => mapping(uint256 id => uint256)) private _balances;
+
+    mapping(address owner => mapping(address operator => bool)) private _operatorApprovals;
+
+    mapping(address owner => mapping(address spender => mapping(uint256 id => uint256))) private _allowances;
+
+    error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
+    error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
+    error ERC6909InvalidApprover(address approver);
+    error ERC6909InvalidReceiver(address receiver);
+    error ERC6909InvalidSender(address sender);
+    error ERC6909InvalidSpender(address spender);
+
+    /// @inheritdoc IERC165
+    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
+        return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    /// @inheritdoc IERC6909
+    function balanceOf(address owner, uint256 id) public view virtual override returns (uint256) {
+        return _balances[owner][id];
+    }
+
+    /// @inheritdoc IERC6909
+    function allowance(address owner, address spender, uint256 id) public view virtual override returns (uint256) {
+        return _allowances[owner][spender][id];
+    }
+
+    /// @inheritdoc IERC6909
+    function isOperator(address owner, address spender) public view virtual override returns (bool) {
+        return _operatorApprovals[owner][spender];
+    }
+
+    /// @inheritdoc IERC6909
+    function approve(address spender, uint256 id, uint256 amount) public virtual override returns (bool) {
+        _approve(_msgSender(), spender, id, amount);
+        return true;
+    }
+
+    /// @inheritdoc IERC6909
+    function setOperator(address spender, bool approved) public virtual override returns (bool) {
+        _setOperator(_msgSender(), spender, approved);
+        return true;
+    }
+
+    /// @inheritdoc IERC6909
+    function transfer(address receiver, uint256 id, uint256 amount) public virtual override returns (bool) {
+        _transfer(_msgSender(), receiver, id, amount);
+        return true;
+    }
+
+    /// @inheritdoc IERC6909
+    function transferFrom(
+        address sender,
+        address receiver,
+        uint256 id,
+        uint256 amount
+    ) public virtual override returns (bool) {
+        address caller = _msgSender();
+        if (sender != caller && !isOperator(sender, caller)) {
+            _spendAllowance(sender, caller, id, amount);
+        }
+        _transfer(sender, receiver, id, amount);
+        return true;
+    }
+
+    /**
+     * @dev Creates `amount` of token `id` and assigns them to `account`, by transferring it from address(0).
+     * Relies on the `_update` mechanism
+     *
+     * Emits a {Transfer} event with `from` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     */
+    function _mint(address to, uint256 id, uint256 amount) internal {
+        if (to == address(0)) {
+            revert ERC6909InvalidReceiver(address(0));
+        }
+        _update(address(0), to, id, amount);
+    }
+
+    /**
+     * @dev Moves `amount` of token `id` from `from` to `to` without checking for approvals.
+     *
+     * This internal function is equivalent to {transfer}, and can be used to
+     * e.g. implement automatic token fees, slashing mechanisms, etc.
+     *
+     * Emits a {Transfer} event.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     */
+    function _transfer(address from, address to, uint256 id, uint256 amount) internal {
+        if (from == address(0)) {
+            revert ERC6909InvalidSender(address(0));
+        }
+        if (to == address(0)) {
+            revert ERC6909InvalidReceiver(address(0));
+        }
+        _update(from, to, id, amount);
+    }
+
+    /**
+     * @dev Destroys a `amount` of token `id` from `account`.
+     * Relies on the `_update` mechanism.
+     *
+     * Emits a {Transfer} event with `to` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead
+     */
+    function _burn(address from, uint256 id, uint256 amount) internal {
+        if (from == address(0)) {
+            revert ERC6909InvalidSender(address(0));
+        }
+        _update(from, address(0), id, amount);
+    }
+
+    /**
+     * @dev Transfers `amount` of token `id` from `from` to `to`, or alternatively mints (or burns) if `from`
+     * (or `to`) is the zero address. All customizations to transfers, mints, and burns should be done by overriding
+     * this function.
+     *
+     * Emits a {Transfer} event.
+     */
+    function _update(address from, address to, uint256 id, uint256 amount) internal virtual {
+        address caller = _msgSender();
+
+        if (from != address(0)) {
+            uint256 fromBalance = _balances[from][id];
+            if (fromBalance < amount) {
+                revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
+            }
+            unchecked {
+                // Overflow not possible: amount <= fromBalance.
+                _balances[from][id] = fromBalance - amount;
+            }
+        }
+        if (to != address(0)) {
+            _balances[to][id] += amount;
+        }
+
+        emit Transfer(caller, from, to, id, amount);
+    }
+
+    /**
+     * @dev Sets `amount` as the allowance of `spender` over the `owner`'s `id` tokens.
+     *
+     * This internal function is equivalent to `approve`, and can be used to e.g. set automatic allowances for certain
+     * subsystems, etc.
+     *
+     * Emits an {Approval} event.
+     *
+     * Requirements:
+     *
+     * - `owner` cannot be the zero address.
+     * - `spender` cannot be the zero address.
+     */
+    function _approve(address owner, address spender, uint256 id, uint256 amount) internal virtual {
+        if (owner == address(0)) {
+            revert ERC6909InvalidApprover(address(0));
+        }
+        if (spender == address(0)) {
+            revert ERC6909InvalidSpender(address(0));
+        }
+        _allowances[owner][spender][id] = amount;
+        emit Approval(owner, spender, id, amount);
+    }
+
+    /**
+     * @dev Approve `spender` to operate on all of `owner`'s tokens
+     *
+     * This internal function is equivalent to `setOperator`, and can be used to e.g. set automatic allowances for
+     * certain subsystems, etc.
+     *
+     * Emits an {OperatorSet} event.
+     *
+     * Requirements:
+     *
+     * - `owner` cannot be the zero address.
+     * - `spender` cannot be the zero address.
+     */
+    function _setOperator(address owner, address spender, bool approved) internal virtual {
+        if (owner == address(0)) {
+            revert ERC6909InvalidApprover(address(0));
+        }
+        if (spender == address(0)) {
+            revert ERC6909InvalidSpender(address(0));
+        }
+        _operatorApprovals[owner][spender] = approved;
+        emit OperatorSet(owner, spender, approved);
+    }
+
+    /**
+     * @dev Updates `owner`'s allowance for `spender` based on spent `amount`.
+     *
+     * Does not update the allowance value in case of infinite allowance.
+     * Revert if not enough allowance is available.
+     *
+     * Does not emit an {Approval} event.
+     */
+    function _spendAllowance(address owner, address spender, uint256 id, uint256 amount) internal virtual {
+        uint256 currentAllowance = allowance(owner, spender, id);
+        if (currentAllowance < type(uint256).max) {
+            if (currentAllowance < amount) {
+                revert ERC6909InsufficientAllowance(spender, currentAllowance, amount, id);
+            }
+            unchecked {
+                _allowances[owner][spender][id] = currentAllowance - amount;
+            }
+        }
+    }
+}

contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909ContentURI} from "../../../interfaces/draft-IERC6909.sol";
+
+/**
+ * @dev Implementation of the Content URI extension defined in ERC6909.
+ */
+contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
+    string private _contractURI;
+    mapping(uint256 id => string) private _tokenURIs;
+
+    /// @dev Event emitted when the contract URI is changed. See https://eips.ethereum.org/EIPS/eip-7572[ERC-7572] for details.
+    event ContractURIUpdated();
+
+    /// @dev See {IERC1155-URI}
+    event URI(string value, uint256 indexed id);
+
+    /// @inheritdoc IERC6909ContentURI
+    function contractURI() public view virtual override returns (string memory) {
+        return _contractURI;
+    }
+
+    /// @inheritdoc IERC6909ContentURI
+    function tokenURI(uint256 id) public view virtual override returns (string memory) {
+        return _tokenURIs[id];
+    }
+
+    /**
+     * @dev Sets the {contractURI} for the contract.
+     *
+     * Emits a {ContractURIUpdated} event.
+     */
+    function _setContractURI(string memory newContractURI) internal virtual {
+        _contractURI = newContractURI;
+
+        emit ContractURIUpdated();
+    }
+
+    /**
+     * @dev Sets the {tokenURI} for a given token of type `id`.
+     *
+     * Emits a {URI} event.
+     */
+    function _setTokenURI(uint256 id, string memory newTokenURI) internal virtual {
+        _tokenURIs[id] = newTokenURI;
+
+        emit URI(newTokenURI, id);
+    }
+}

contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909Metadata} from "../../../interfaces/draft-IERC6909.sol";
+
+/**
+ * @dev Implementation of the Metadata extension defined in ERC6909. Exposes the name, symbol, and decimals of each token id.
+ */
+contract ERC6909Metadata is ERC6909, IERC6909Metadata {
+    struct TokenMetadata {
+        string name;
+        string symbol;
+        uint8 decimals;
+    }
+
+    mapping(uint256 id => TokenMetadata) private _tokenMetadata;
+
+    /// @dev The name of the token of type `id` was updated to `newName`.
+    event ERC6909NameUpdated(uint256 indexed id, string newName);
+
+    /// @dev The symbol for the token of type `id` was updated to `newSymbol`.
+    event ERC6909SymbolUpdated(uint256 indexed id, string newSymbol);
+
+    /// @dev The decimals value for token of type `id` was updated to `newDecimals`.
+    event ERC6909DecimalsUpdated(uint256 indexed id, uint8 newDecimals);
+
+    /// @inheritdoc IERC6909Metadata
+    function name(uint256 id) public view virtual override returns (string memory) {
+        return _tokenMetadata[id].name;
+    }
+
+    /// @inheritdoc IERC6909Metadata
+    function symbol(uint256 id) public view virtual override returns (string memory) {
+        return _tokenMetadata[id].symbol;
+    }
+
+    /// @inheritdoc IERC6909Metadata
+    function decimals(uint256 id) public view virtual override returns (uint8) {
+        return _tokenMetadata[id].decimals;
+    }
+
+    /**
+     * @dev Sets the `name` for a given token of type `id`.
+     *
+     * Emits an {ERC6909NameUpdated} event.
+     */
+    function _setName(uint256 id, string memory newName) internal virtual {
+        _tokenMetadata[id].name = newName;
+
+        emit ERC6909NameUpdated(id, newName);
+    }
+
+    /**
+     * @dev Sets the `symbol` for a given token of type `id`.
+     *
+     * Emits an {ERC6909SymbolUpdated} event.
+     */
+    function _setSymbol(uint256 id, string memory newSymbol) internal virtual {
+        _tokenMetadata[id].symbol = newSymbol;
+
+        emit ERC6909SymbolUpdated(id, newSymbol);
+    }
+
+    /**
+     * @dev Sets the `decimals` for a given token of type `id`.
+     *
+     * Emits an {ERC6909DecimalsUpdated} event.
+     */
+    function _setDecimals(uint256 id, uint8 newDecimals) internal virtual {
+        _tokenMetadata[id].decimals = newDecimals;
+
+        emit ERC6909DecimalsUpdated(id, newDecimals);
+    }
+}

contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909TokenSupply} from "../../../interfaces/draft-IERC6909.sol";
+
+/**
+ * @dev Implementation of the Token Supply extension defined in ERC6909.
+ * Tracks the total supply of each token id individually.
+ */
+contract ERC6909TokenSupply is ERC6909, IERC6909TokenSupply {
+    mapping(uint256 id => uint256) private _totalSupplies;
+
+    /// @inheritdoc IERC6909TokenSupply
+    function totalSupply(uint256 id) public view virtual override returns (uint256) {
+        return _totalSupplies[id];
+    }
+
+    /// @dev Override the `_update` function to update the total supply of each token id as necessary.
+    function _update(address from, address to, uint256 id, uint256 amount) internal virtual override {
+        super._update(from, to, id, amount);
+
+        if (from == address(0)) {
+            _totalSupplies[id] += amount;
+        }
+        if (to == address(0)) {
+            unchecked {
+                // amount <= _balances[id][from] <= _totalSupplies[id]
+                _totalSupplies[id] -= amount;
+            }
+        }
+    }
+}