New Historical Price Consumer

HistoricalPriceConsumerV3.sol

// This example code is designed to quickly deploy an example contract using Remix.

pragma solidity ^0.6.7;

import "https://github.com/smartcontractkit/chainlink/blob/master/evm-contracts/src/v0.6/interfaces/AggregatorV3Interface.sol";

contract HistoricalPriceConsumerV3 {

    AggregatorV3Interface internal priceFeed;
    
    /**
     * Network: Kovan
     * Aggregator: ETH/USD
     * Address: 0x9326BFA02ADD2366b30bacB125260Af641031331
     */
    constructor() public {
        priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331);
    }

    /**
     * Returns historical price for a round id.
     * roundId is NOT incremental. Not all roundIds are valid.
     * You must know a valid roundId before consuming historical data.
     *
     * ROUNDID VALUES:
     *    InValid:      18446744073709562300
     *    Valid:        18446744073709562301
     *    
     * @dev A timestamp with zero value means the round is not complete and should not be used.
     */
    function getHistoricalPrice(uint80 roundId) public view returns (int256) {
        (
            uint80 id, 
            int price,
            uint startedAt,
            uint timeStamp,
            uint80 answeredInRound
        ) = priceFeed.getRoundData(roundId);
        require(timeStamp > 0, "Round not complete");
        return price;
    }
}