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HistoricalPriceConsumer.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/evm-contracts/src/v0.6/interfaces/AggregatorInterface.sol";

/**
 * Consumer contract which retrieves the latest and historical
 * price data from the ETH/USD price feed on the Ropsten network.
 */
contract HistoricalPriceConsumer {
    
  AggregatorInterface internal priceFeed;
  
  /**
   * Network: Ropsten
   * Aggregator: ETH/USD
   * Address: 0x8468b2bDCE073A157E560AA4D9CcF6dB1DB98507
   */
  constructor() public {
    priceFeed = AggregatorInterface(0x8468b2bDCE073A157E560AA4D9CcF6dB1DB98507);
  }

  /**
   * Returns historical data from previous update rounds
   */
  function getPreviousPrice(uint256 _back) public view returns (int256) {
    uint256 latest = priceFeed.latestRound();
    require(_back <= latest, "Not enough history");
    return priceFeed.getAnswer(latest - _back);
  }

  /**
   * Returns historical data from previous update rounds
   */
  function getPreviousPriceTimestamp(uint256 _back) public view returns (uint256) {
    uint256 latest = priceFeed.latestRound();
    require(_back <= latest, "Not enough history");
    return priceFeed.getTimestamp(latest - _back);
  }
}