75 lines
2.6 KiB
Solidity
75 lines
2.6 KiB
Solidity
pragma solidity 0.5.12;
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import "../interfaces/IUniswapV2.sol";
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contract Oracle {
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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 Time {
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uint64 blockNumber;
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uint64 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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TokenData private reservesCumulative;
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Time 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 _updateCurrentPrice(TokenData memory averages, uint128 timestampDelta) private {
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TokenData memory nextPrice;
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if (timestampDelta >= period || (currentPrice.token0 == 0 && currentPrice.token1 == 0)) {
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nextPrice = averages;
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} else {
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nextPrice = TokenData({
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token0: (currentPrice.token0 * (period - timestampDelta) + averages.token0 * timestampDelta) / period,
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token1: (currentPrice.token1 * (period - timestampDelta) + averages.token1 * timestampDelta) / period
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});
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}
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currentPrice = nextPrice;
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}
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function updateCurrentPrice() external {
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IUniswapV2 uniswapV2 = IUniswapV2(exchange);
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// TODO handle the case where time has passed (basically, always use the most up-to-date data)
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(uint128 reserveCumulativeToken0, uint128 reserveCumulativeToken1) = uniswapV2.getReservesCumulative();
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(uint64 blockNumber, uint64 blockTimestamp) = uniswapV2.getLastUpdate();
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if (blockNumber > lastUpdate.blockNumber) {
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uint128 blocksElapsed = blockNumber - lastUpdate.blockNumber;
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if (lastUpdate.blockNumber != 0) {
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TokenData memory deltas = TokenData({
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token0: reserveCumulativeToken0 - reservesCumulative.token0,
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token1: reserveCumulativeToken1 - reservesCumulative.token1
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});
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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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uint128 timeElapsed = blockTimestamp - lastUpdate.blockTimestamp;
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_updateCurrentPrice(averages, timeElapsed);
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}
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reservesCumulative.token0 = reserveCumulativeToken0;
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reservesCumulative.token1 = reserveCumulativeToken1;
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lastUpdate.blockNumber = blockNumber;
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lastUpdate.blockTimestamp = blockTimestamp;
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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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