124 lines
4.5 KiB
Solidity
124 lines
4.5 KiB
Solidity
pragma solidity 0.5.12;
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import "../interfaces/IUniswapV2.sol";
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import "../libraries/SafeMath256.sol";
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contract Oracle {
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using SafeMath256 for uint256;
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enum OracleStates { NeedsInitialization, NeedsActivation, Active }
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struct TokenData {
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uint128 token0;
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uint128 token1;
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}
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struct TimeData {
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uint128 blockNumber;
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uint128 blockTimestamp;
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}
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address public exchange;
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uint128 constant period = 1 days;
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OracleStates private state = OracleStates.NeedsInitialization;
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TokenData private reservesCumulative;
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TimeData private lastUpdate;
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TokenData private currentPrice;
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constructor(address _exchange) public {
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exchange = _exchange;
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}
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function getReservesCumulative() private view returns (TokenData memory) {
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IUniswapV2 uniswapV2 = IUniswapV2(exchange);
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(uint128 reservesCumulativeToken0, uint128 reservesCumulativeToken1,,) = uniswapV2.getReservesCumulativeAndOverflows();
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return TokenData({
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token0: reservesCumulativeToken0,
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token1: reservesCumulativeToken1
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});
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}
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function getTimeData() private view returns (TimeData memory) {
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return TimeData({
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blockNumber: block.number.downcast128(),
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blockTimestamp: block.timestamp.downcast128()
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});
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}
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function initialize() external {
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require(state == OracleStates.NeedsInitialization, "Oracle: DOES_NOT_NEED_INITIALIZATION");
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reservesCumulative = getReservesCumulative();
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lastUpdate = getTimeData();
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state = OracleStates.NeedsActivation;
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}
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function activate() external {
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require(state == OracleStates.NeedsActivation, "Oracle: DOES_NOT_NEED_ACTIVATION");
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// get the current time, ensure it's been >=1 blocks since last update, and record the update
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TimeData memory currentTime = getTimeData();
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uint128 blocksElapsed = currentTime.blockNumber - lastUpdate.blockNumber;
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require(blocksElapsed > 0, "Oracle: INSUFFICIENT_BLOCKS_PASSED");
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lastUpdate = currentTime;
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// get the current cumulative reserves, calculate the deltas, and record the new values
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TokenData memory reservesCumulativeNext = getReservesCumulative();
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TokenData memory deltas = TokenData({
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token0: reservesCumulativeNext.token0 - reservesCumulative.token0,
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token1: reservesCumulativeNext.token1 - reservesCumulative.token1
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});
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reservesCumulative = reservesCumulativeNext;
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// get the average price over the period and set it to the current price
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currentPrice = TokenData({
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token0: deltas.token0 / blocksElapsed,
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token1: deltas.token1 / blocksElapsed
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});
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state = OracleStates.Active;
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}
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function update() external {
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require(state == OracleStates.Active, "Oracle: INACTIVE");
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// get the current time, ensure it's been >=1 blocks since last update, and record the update
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TimeData memory currentTime = getTimeData();
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uint128 blocksElapsed = currentTime.blockNumber - lastUpdate.blockNumber;
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require(blocksElapsed > 0, "Oracle: INSUFFICIENT_BLOCKS_PASSED");
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uint128 timeElapsed = currentTime.blockTimestamp - lastUpdate.blockTimestamp;
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lastUpdate = currentTime;
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// get the current cumulative reserves, calculate the deltas, and record the new values
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TokenData memory reservesCumulativeNext = getReservesCumulative();
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TokenData memory deltas = TokenData({
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token0: reservesCumulativeNext.token0 - reservesCumulative.token0,
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token1: reservesCumulativeNext.token1 - reservesCumulative.token1
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});
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reservesCumulative = reservesCumulativeNext;
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// get the average price over the period
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TokenData memory averages = TokenData({
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token0: deltas.token0 / blocksElapsed,
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token1: deltas.token1 / blocksElapsed
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});
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// update the current price with this information
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if (timeElapsed < period) {
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currentPrice = TokenData({
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token0: (currentPrice.token0 * (period - timeElapsed) + averages.token0 * timeElapsed) / period,
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token1: (currentPrice.token1 * (period - timeElapsed) + averages.token1 * timeElapsed) / period
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});
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} else {
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currentPrice = averages;
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}
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}
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function getCurrentPrice() external view returns (uint128, uint128) {
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return (currentPrice.token0, currentPrice.token1);
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}
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}
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