pragma solidity ^0.6.0; library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}


interface IFlashLoanReceiver {

    function executeOperation(address _reserve, uint256 _amount, uint256 _fee, bytes calldata _params) external;
}

abstract contract ILendingPoolAddressesProvider {

    function getLendingPool() public view virtual returns (address);
    function setLendingPoolImpl(address _pool) public virtual;

    function getLendingPoolCore() public virtual view returns (address payable);
    function setLendingPoolCoreImpl(address _lendingPoolCore) public virtual;

    function getLendingPoolConfigurator() public virtual view returns (address);
    function setLendingPoolConfiguratorImpl(address _configurator) public virtual;

    function getLendingPoolDataProvider() public virtual view returns (address);
    function setLendingPoolDataProviderImpl(address _provider) public virtual;

    function getLendingPoolParametersProvider() public virtual view returns (address);
    function setLendingPoolParametersProviderImpl(address _parametersProvider) public virtual;

    function getTokenDistributor() public virtual view returns (address);
    function setTokenDistributor(address _tokenDistributor) public virtual;


    function getFeeProvider() public virtual view returns (address);
    function setFeeProviderImpl(address _feeProvider) public virtual;

    function getLendingPoolLiquidationManager() public virtual view returns (address);
    function setLendingPoolLiquidationManager(address _manager) public virtual;

    function getLendingPoolManager() public virtual view returns (address);
    function setLendingPoolManager(address _lendingPoolManager) public virtual;

    function getPriceOracle() public virtual view returns (address);
    function setPriceOracle(address _priceOracle) public virtual;

    function getLendingRateOracle() public view virtual returns (address);
    function setLendingRateOracle(address _lendingRateOracle) public virtual;
}

library EthAddressLib {

    function ethAddress() internal pure returns(address) {
        return 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
    }
}

abstract contract FlashLoanReceiverBase is IFlashLoanReceiver {

    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    ILendingPoolAddressesProvider public addressesProvider;

    constructor(ILendingPoolAddressesProvider _provider) public {
        addressesProvider = _provider;
    }

    receive () external virtual payable {}

    function transferFundsBackToPoolInternal(address _reserve, uint256 _amount) internal {

        address payable core = addressesProvider.getLendingPoolCore();

        transferInternal(core,_reserve, _amount);
    }

    function transferInternal(address payable _destination, address _reserve, uint256  _amount) internal {
        if(_reserve == EthAddressLib.ethAddress()) {
            //solium-disable-next-line
            _destination.call{value: _amount}("");
            return;
        }

        IERC20(_reserve).safeTransfer(_destination, _amount);


    }

    function getBalanceInternal(address _target, address _reserve) internal view returns(uint256) {
        if(_reserve == EthAddressLib.ethAddress()) {

            return _target.balance;
        }

        return IERC20(_reserve).balanceOf(_target);

    }
} abstract contract DSProxyInterface {

    /// Truffle wont compile if this isn't commented
    // function execute(bytes memory _code, bytes memory _data)
    //     public virtual
    //     payable
    //     returns (address, bytes32);

    function execute(address _target, bytes memory _data) public virtual payable returns (bytes32);

    function setCache(address _cacheAddr) public virtual payable returns (bool);

    function owner() public virtual returns (address);
} interface ERC20 {
    function totalSupply() external view returns (uint256 supply);

    function balanceOf(address _owner) external view returns (uint256 balance);

    function transfer(address _to, uint256 _value) external returns (bool success);

    function transferFrom(address _from, address _to, uint256 _value)
        external
        returns (bool success);

    function approve(address _spender, uint256 _value) external returns (bool success);

    function allowance(address _owner, address _spender) external view returns (uint256 remaining);

    function decimals() external view returns (uint256 digits);

    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
} /// @title Contract that receives the FL from Aave for Repays/Boost
contract CompoundSaverFlashLoan is FlashLoanReceiverBase {
    ILendingPoolAddressesProvider public LENDING_POOL_ADDRESS_PROVIDER = ILendingPoolAddressesProvider(0x24a42fD28C976A61Df5D00D0599C34c4f90748c8);

    address payable public COMPOUND_SAVER_FLASH_PROXY;
    address public constant ETH_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;

    address public owner;

    constructor()
        FlashLoanReceiverBase(LENDING_POOL_ADDRESS_PROVIDER)
        public {
            owner = msg.sender;
    }

    /// @notice Called by Aave when sending back the FL amount
    /// @param _reserve The address of the borrowed token
    /// @param _amount Amount of FL tokens received
    /// @param _fee FL Aave fee
    /// @param _params The params that are sent from the original FL caller contract
   function executeOperation(
        address _reserve,
        uint256 _amount,
        uint256 _fee,
        bytes calldata _params)
    external override {
        // Format the call data for DSProxy
        (bytes memory proxyData, address payable proxyAddr) = packFunctionCall(_amount, _fee, _params);

        // Send Flash loan amount to DSProxy
        sendLoanToProxy(proxyAddr, _reserve, _amount);

        // Execute the DSProxy call
        DSProxyInterface(proxyAddr).execute(COMPOUND_SAVER_FLASH_PROXY, proxyData);

        // Repay the loan with the money DSProxy sent back
        transferFundsBackToPoolInternal(_reserve, _amount.add(_fee));

        // if there is some eth left (0x fee), return it to user
        if (address(this).balance > 0) {
            tx.origin.transfer(address(this).balance);
        }
    }

    /// @notice Formats function data call so we can call it through DSProxy
    /// @param _amount Amount of FL
    /// @param _fee Fee of the FL
    /// @param _params Saver proxy params
    /// @return proxyData Formated function call data
    function packFunctionCall(uint _amount, uint _fee, bytes memory _params) internal returns (bytes memory proxyData, address payable) {
        (
            uint[5] memory data, // amount, minPrice, exchangeType, gasCost, 0xPrice
            address[3] memory addrData, // cCollAddress, cBorrowAddress, exchangeAddress
            bytes memory callData,
            bool isRepay,
            address payable proxyAddr
        )
        = abi.decode(_params, (uint256[5],address[3],bytes,bool,address));

        uint[2] memory flashLoanData = [_amount, _fee];

        if (isRepay) {
            proxyData = abi.encodeWithSignature("flashRepay(uint256[5],address[3],bytes,uint256[2])", data, addrData, callData, flashLoanData);
        } else {
            proxyData = abi.encodeWithSignature("flashBoost(uint256[5],address[3],bytes,uint256[2])", data, addrData, callData, flashLoanData);
        }

        return (proxyData, proxyAddr);
    }

    /// @notice Send the FL funds received to DSProxy
    /// @param _proxy DSProxy address
    /// @param _reserve Token address
    /// @param _amount Amount of tokens
    function sendLoanToProxy(address payable _proxy, address _reserve, uint _amount) internal {
        if (_reserve != ETH_ADDRESS) {
            ERC20(_reserve).transfer(_proxy, _amount);
        }

        _proxy.transfer(address(this).balance);
    }

    /// @notice Sets the Saver flash proxy address
    /// @dev Only callable once by the owner
    /// @param _saverFlashProxy The flash proxy address
    function setSaverFlashProxy(address payable _saverFlashProxy) public {
        require(msg.sender == owner);

        COMPOUND_SAVER_FLASH_PROXY = _saverFlashProxy;
    }

    receive() external override payable {}
}