// SPDX-License-Identifier: MIXED

// File @boringcrypto/boring-solidity/contracts/libraries/BoringMath.sol@v1.2.2
// License-Identifier: MIT
pragma solidity 0.6.12;

/// @notice A library for performing overflow-/underflow-safe math,
/// updated with awesomeness from of DappHub (https://github.com/dapphub/ds-math).
library BoringMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require(b == 0 || (c = a * b) / b == a, "BoringMath: Mul Overflow");
    }

    function to128(uint256 a) internal pure returns (uint128 c) {
        require(a <= uint128(-1), "BoringMath: uint128 Overflow");
        c = uint128(a);
    }

    function to64(uint256 a) internal pure returns (uint64 c) {
        require(a <= uint64(-1), "BoringMath: uint64 Overflow");
        c = uint64(a);
    }

    function to32(uint256 a) internal pure returns (uint32 c) {
        require(a <= uint32(-1), "BoringMath: uint32 Overflow");
        c = uint32(a);
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint128.
library BoringMath128 {
    function add(uint128 a, uint128 b) internal pure returns (uint128 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint128 a, uint128 b) internal pure returns (uint128 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint64.
library BoringMath64 {
    function add(uint64 a, uint64 b) internal pure returns (uint64 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint64 a, uint64 b) internal pure returns (uint64 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint32.
library BoringMath32 {
    function add(uint32 a, uint32 b) internal pure returns (uint32 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint32 a, uint32 b) internal pure returns (uint32 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }
}

// File contracts/interfaces/IOracle.sol
// License-Identifier: MIT
interface IOracle {
    /// @notice Get the latest exchange rate.
    /// @param data Usually abi encoded, implementation specific data that contains information and arguments to & about the oracle.
    /// For example:
    /// (string memory collateralSymbol, string memory assetSymbol, uint256 division) = abi.decode(data, (string, string, uint256));
    /// @return success if no valid (recent) rate is available, return false else true.
    /// @return rate The rate of the requested asset / pair / pool.
    function get(bytes calldata data) external returns (bool success, uint256 rate);

    /// @notice Check the last exchange rate without any state changes.
    /// @param data Usually abi encoded, implementation specific data that contains information and arguments to & about the oracle.
    /// For example:
    /// (string memory collateralSymbol, string memory assetSymbol, uint256 division) = abi.decode(data, (string, string, uint256));
    /// @return success if no valid (recent) rate is available, return false else true.
    /// @return rate The rate of the requested asset / pair / pool.
    function peek(bytes calldata data) external view returns (bool success, uint256 rate);

    /// @notice Check the current spot exchange rate without any state changes. For oracles like TWAP this will be different from peek().
    /// @param data Usually abi encoded, implementation specific data that contains information and arguments to & about the oracle.
    /// For example:
    /// (string memory collateralSymbol, string memory assetSymbol, uint256 division) = abi.decode(data, (string, string, uint256));
    /// @return rate The rate of the requested asset / pair / pool.
    function peekSpot(bytes calldata data) external view returns (uint256 rate);

    /// @notice Returns a human readable (short) name about this oracle.
    /// @param data Usually abi encoded, implementation specific data that contains information and arguments to & about the oracle.
    /// For example:
    /// (string memory collateralSymbol, string memory assetSymbol, uint256 division) = abi.decode(data, (string, string, uint256));
    /// @return (string) A human readable symbol name about this oracle.
    function symbol(bytes calldata data) external view returns (string memory);

    /// @notice Returns a human readable name about this oracle.
    /// @param data Usually abi encoded, implementation specific data that contains information and arguments to & about the oracle.
    /// For example:
    /// (string memory collateralSymbol, string memory assetSymbol, uint256 division) = abi.decode(data, (string, string, uint256));
    /// @return (string) A human readable name about this oracle.
    function name(bytes calldata data) external view returns (string memory);
}

// File contracts/oracles/YearnChainlinkOracle.sol
// License-Identifier: MIT
// Chainlink Aggregator

interface IAggregator {
    function latestAnswer() external view returns (int256 answer);
}

interface IYearnVault {
    function pricePerShare() external view returns (uint256 price);
}

contract YearnChainlinkOracleV2 is IOracle {
    using BoringMath for uint256; // Keep everything in uint256

    // Calculates the lastest exchange rate
    // Uses both divide and multiply only for tokens not supported directly by Chainlink, for example MKR/USD
    function _get(
        address multiply,
        address divide,
        uint256 decimals,
        address yearnVault
    ) internal view returns (uint256) {
        uint256 price = uint256(1e36);
        if (multiply != address(0)) {
            price = price.mul(uint256(IAggregator(multiply).latestAnswer()));
        } else {
            price = price.mul(1e18);
        }

        if (divide != address(0)) {
            price = price / uint256(IAggregator(divide).latestAnswer());
        }

        // @note decimals have to take into account the decimals of the vault asset
        return price / decimals.mul(IYearnVault(yearnVault).pricePerShare());
    }

    function getDataParameter(
        address multiply,
        address divide,
        uint256 decimals,
        address yearnVault
    ) public pure returns (bytes memory) {
        return abi.encode(multiply, divide, decimals, yearnVault);
    }

    // Get the latest exchange rate
    /// @inheritdoc IOracle
    function get(bytes calldata data) public override returns (bool, uint256) {
        (address multiply, address divide, uint256 decimals, address yearnVault) = abi.decode(data, (address, address, uint256, address));
        return (true, _get(multiply, divide, decimals, yearnVault));
    }

    // Check the last exchange rate without any state changes
    /// @inheritdoc IOracle
    function peek(bytes calldata data) public view override returns (bool, uint256) {
        (address multiply, address divide, uint256 decimals, address yearnVault) = abi.decode(data, (address, address, uint256, address));
        return (true, _get(multiply, divide, decimals, yearnVault));
    }

    // Check the current spot exchange rate without any state changes
    /// @inheritdoc IOracle
    function peekSpot(bytes calldata data) external view override returns (uint256 rate) {
        (, rate) = peek(data);
    }

    /// @inheritdoc IOracle
    function name(bytes calldata) public view override returns (string memory) {
        return "Chainlink";
    }

    /// @inheritdoc IOracle
    function symbol(bytes calldata) public view override returns (string memory) {
        return "LINK";
    }
}