Contract Source Code:

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

import "@api3/contracts/v0.8/interfaces/IProxy.sol";

contract Api3AggregatorAdaptor {
    // Updating the proxy address is a security-critical action which is why
    // we have made it immutable.
    address public immutable proxy;

    constructor(address _proxy) {
        proxy = _proxy;
    }

    function latestAnswer() external view returns (int256 value) {
        (value, ) = readDataFeed();
    }   

    function latestTimestamp() external view returns (uint256 timestamp) {
        (, timestamp) = readDataFeed();
    }

    function decimals() external view returns (uint8) {
        return 18;
    }

    function readDataFeed()
        internal
        view
        returns (int224 value, uint256 timestamp)
    {
        (value, timestamp) = IProxy(proxy).read();
        // If you have any assumptions about `value` and `timestamp`, make sure
        // to validate them right after reading from the proxy. For example,
        // if the value you are reading is the spot price of an asset, you may
        // want to reject non-positive values...
        // require(value > 0, "Value not positive");
        // ...and if the data feed is being updated with a one day-heartbeat
        // interval, you may want to check for that.
        // require(
        //     timestamp + 1 days > block.timestamp,
        //     "Timestamp older than one day"
        // );
        // Try to be strict about validations, but be wary of:
        // (1) Overly strict validation that may invalidate valid values
        // (2) Mutable validation parameters that are controlled by a trusted
        // party (eliminates the trust-minimization guarantees of first-party
        // oracles)
        // (3) Validation parameters that need to be tuned according to
        // external conditions (if these are forgotten to be handled, it will
        // result in (1), look up the Venus Protocol exploit related to LUNA)

        // After validation, you can implement your contract logic here.
    }

    function getTokenType() external pure returns (uint256) {
        return 1;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@api3/airnode-protocol-v1/contracts/api3-server-v1/proxies/interfaces/IProxy.sol";

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/// @dev See DapiProxy.sol for comments about usage
interface IProxy {
    function read() external view returns (int224 value, uint32 timestamp);

    function api3ServerV1() external view returns (address);
}