// File: contracts/interfaces/IERC20.sol

// SPDX-License-Identifier: GPL-2.0

pragma solidity ^0.6.8;


/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
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:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * 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);
}

// File: contracts/interfaces/IModule.sol

pragma solidity ^0.6.8;




interface IModule {
    /// @notice receive ETH
    receive() external payable;

    /**
     * @notice Executes an order
     * @param _inputToken - Address of the input token
     * @param _inputAmount - uint256 of the input token amount (order amount)
     * @param _owner - Address of the order's owner
     * @param _data - Bytes of the order's data
     * @param _auxData - Bytes of the auxiliar data used for the handlers to execute the order
     * @return bought - amount of output token bought
     */
    function execute(
        IERC20 _inputToken,
        uint256 _inputAmount,
        address payable _owner,
        bytes calldata _data,
        bytes calldata _auxData
    ) external returns (uint256 bought);

    /**
     * @notice Check whether an order can be executed or not
     * @param _inputToken - Address of the input token
     * @param _inputAmount - uint256 of the input token amount (order amount)
     * @param _data - Bytes of the order's data
     * @param _auxData - Bytes of the auxiliar data used for the handlers to execute the order
     * @return bool - whether the order can be executed or not
     */
    function canExecute(
        IERC20 _inputToken,
        uint256 _inputAmount,
        bytes calldata _data,
        bytes calldata _auxData
    ) external view returns (bool);
}

// File: contracts/interfaces/IHandler.sol

pragma solidity ^0.6.8;


interface IHandler {
    /// @notice receive ETH
    receive() external payable;

    /**
     * @notice Handle an order execution
     * @param _inputToken - Address of the input token
     * @param _outputToken - Address of the output token
     * @param _inputAmount - uint256 of the input token amount
     * @param _minReturn - uint256 of the min return amount of output token
     * @param _data - Bytes of arbitrary data
     * @return bought - Amount of output token bought
     */
    function handle(
        IERC20 _inputToken,
        IERC20 _outputToken,
        uint256 _inputAmount,
        uint256 _minReturn,
        bytes calldata _data
    ) external payable returns (uint256 bought);

    /**
     * @notice Check whether can handle an order execution
     * @param _inputToken - Address of the input token
     * @param _outputToken - Address of the output token
     * @param _inputAmount - uint256 of the input token amount
     * @param _minReturn - uint256 of the min return amount of output token
     * @param _data - Bytes of arbitrary data
     * @return bool - Whether the execution can be handled or not
     */
    function canHandle(
        IERC20 _inputToken,
        IERC20 _outputToken,
        uint256 _inputAmount,
        uint256 _minReturn,
        bytes calldata _data
    ) external view returns (bool);
}

// File: contracts/commons/Order.sol


pragma solidity ^0.6.8;


contract Order {
    address public constant ETH_ADDRESS = address(0x00eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee);
}

// File: contracts/libs/SafeMath.sol


pragma solidity ^0.6.8;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
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.
     */
    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.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        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.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        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.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: contracts/modules/LimitOrders.sol


pragma solidity ^0.6.8;






/// @notice Module used to execute limit orders create in the core contract
contract LimitOrders is IModule, Order {
    using SafeMath for uint256;

    /// @notice receive ETH
    receive() external override payable { }

    /**
     * @notice Executes an order
     * @param _inputToken - Address of the input token
     * @param _inputAmount - uint256 of the input token amount (order amount)
     * @param _owner - Address of the order's owner
     * @param _data - Bytes of the order's data
     * @param _auxData - Bytes of the auxiliar data used for the handlers to execute the order
     * @return bought - amount of output token bought
     */
    function execute(
        IERC20 _inputToken,
        uint256 _inputAmount,
        address payable _owner,
        bytes calldata _data,
        bytes calldata _auxData
    ) external override returns (uint256 bought) {
        (
            IERC20 outputToken,
            uint256 minReturn
        ) = abi.decode(
            _data,
            (
                IERC20,
                uint256
            )
        );

        (IHandler handler) = abi.decode(_auxData, (IHandler));

        _transferAmount(_inputToken, address(handler), _inputAmount);

        handler.handle(
            _inputToken,
            outputToken,
            _inputAmount,
            minReturn,
            _auxData
        );

        bought = _getBalance(outputToken);
        require(bought >= minReturn, "LimitOrders#execute: ISSUFICIENT_BOUGHT_TOKENS");

        _transferAmount(outputToken, _owner, bought);

        return bought;
    }

    /**
     * @notice Check whether an order can be executed or not
     * @param _inputToken - Address of the input token
     * @param _inputAmount - uint256 of the input token amount (order amount)
     * @param _data - Bytes of the order's data
     * @param _auxData - Bytes of the auxiliar data used for the handlers to execute the order
     * @return bool - whether the order can be executed or not
     */
    function canExecute(
        IERC20 _inputToken,
        uint256 _inputAmount,
        bytes calldata _data,
        bytes calldata _auxData
    ) external override view returns (bool) {
         (
            IERC20 outputToken,
            uint256 minReturn
        ) = abi.decode(
            _data,
            (
                IERC20,
                uint256
            )
        );
        (IHandler handler) = abi.decode(_auxData, (IHandler));

        return handler.canHandle(
            _inputToken,
            outputToken,
            _inputAmount,
            minReturn,
            _auxData
        );
    }

    /**
     * @notice Get this contract's balance of token or Ether
     * @param _token - Address of the input token
     * @return uint256 - this contract's balance of _token
     */
    function _getBalance(IERC20 _token) internal view returns (uint256) {
        if (address(_token) == ETH_ADDRESS) {
            return address(this).balance;
        } else {
            return _token.balanceOf(address(this));
        }
    }

    /**
     * @notice Transfer token or Ether amount to a recipient
     * @param _token - Address of the token
     * @param _to - Address of the recipient
     * @param _amount - uint256 of the amount to be transferred
     */
    function _transferAmount(
        IERC20 _token,
        address payable _to,
        uint256 _amount
    ) internal {
        if (address(_token) == ETH_ADDRESS) {
            (bool success,) = _to.call{value: _amount}("");
            require(success, "LimitOrders#_transferAmount: ETH_TRANSFER_FAILED");
        } else {
            _token.transfer(_to, _amount);
        }
    }
}