// File: contracts/dex-handlers/DexHandlerAbstract.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.8;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";

import "../../interfaces/IDexHandler.sol";
/*
 * DexHandlerAbstract 
 */

abstract
contract DexHandler is IDexHandler {
    using SafeMath for uint256;
    using Address for address;

    address public dex;

    constructor(address _dex) public {
        require(_dex.isContract(), 'dex-handler::constructor:dex-is-not-a-contract');
        dex = _dex;
    }

    function isDexHandler() external override view returns (bool) {
        return true;
    }
    
    function swap(bytes memory _data, uint256 _amount) public virtual override returns (uint256 _amountOut) {}
    function getAmountOut(bytes memory _data, uint256 _amount) public virtual override view returns (uint256 _amountOut) {}
    function swapData() external virtual override pure returns (bytes memory) {}
    function decodeData(bytes memory _data) public virtual pure;
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @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: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
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) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * 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.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    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");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: interfaces/IDexHandler.sol



// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.6.8;

interface IDexHandler {
    function isDexHandler() external view returns(bool);
    function swap(bytes calldata _data, uint256 _amount) external returns(uint256 _amountOut);
    function swapData() external pure returns(bytes memory);
    function getAmountOut(bytes calldata _data, uint256 _amount) external view returns(uint256 _amountOut);
}
// File: contracts/dex-handlers/UniswapV2DexHandler.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.8;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";

import "./DexHandlerAbstract.sol";
import "../../interfaces/dex/IUniswapV2Router.sol";
/*
 * UniswapV2 Handler 
 */

contract UniswapV2DexHandler is DexHandler { // TODO Add dust collection
    using SafeMath for uint256;

    IUniswapV2Router public uniswapV2Router;

    constructor(address _uniswapV2Router) DexHandler(_uniswapV2Router) public {
        uniswapV2Router = IUniswapV2Router(_uniswapV2Router);
    }


    function swap(bytes memory _data) public returns (uint256 _amountOut) {
        return swap(_data, 0);
    }

    function swap(bytes memory _data, uint256 _amount) public override returns (uint256 _amountOut) {
        return customSwap(_data, _amount);
    }

    function customSwap(bytes memory _data, uint256 _amount) public returns (uint256 _amountOut) {
        (, uint256 _min, address[] memory _path,,) = customDecodeData(_data);
        // Transfer _in tokens to self
        require(IERC20(_path[0]).transferFrom(msg.sender, address(this), _amount), 'uniswapv2-dex-handler::custom-swap:transfer-from-failed');

        IERC20(_path[0]).approve(address(uniswapV2Router), _amount);

        uint[] memory _amounts = uniswapV2Router.swapExactTokensForTokens(
            _amount,
            _min,
            _path,
            msg.sender,
            now.add(1 hours)
        );

        return _amounts[_amounts.length.sub(1)];
    }

    function getAmountOut(bytes memory _data, uint256 _amount) public override view returns (uint256 _amountOut) {
        (,, address[] memory _path,,) = customDecodeData(_data);

        uint256[] memory _amounts = uniswapV2Router.getAmountsOut(_amount, _path);

        return _amounts[_amounts.length.sub(1)];
    }
 
    function decodeData(bytes memory _data) public override pure {
        _data; // silence warning
        require(false, 'use customDecodeData(bytes memory _data) returns (uint256 _amount, uint256 _min, address[] memory _path, address _to, uint256 _expire)');
    }
    function customDecodeData(bytes memory _data) public pure returns (uint256 _amount, uint256 _min, address[] memory _path, address _to, uint256 _expire) {
        return abi.decode(_data, (uint256, uint256, address[], address, uint256));
    }

    function swapData() external override pure returns (bytes memory) {
        require(false, 'use customSwapData(uint256 _amount, uint256 _min, address[] memory _path, address _to, uint256 _expire) returns (bytes memory)');
    }
    function customSwapData(
        uint256 _amount,
        uint256 _min,
        address[] memory _path,
        address _to,
        uint256 _expire
    ) public pure returns (bytes memory) {
        return abi.encode(
            _amount,
            _min,
            _path,
            _to,
            _expire
        );
    }
}
// File: interfaces/dex/IUniswapV2Router.sol



// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.6.0 <0.7.0;

interface IUniswapV2Router {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);
    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);
    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;

    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}
// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
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));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    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. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "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");
        }
    }
}

// File: contracts/utils/CollectableDust.sol




// SPDX-License-Identifier: MIT

pragma solidity >=0.6.8;

import '@openzeppelin/contracts/utils/Address.sol';
import '@openzeppelin/contracts/utils/EnumerableSet.sol';
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';

import '../../interfaces/utils/ICollectableDust.sol';

abstract
contract CollectableDust is ICollectableDust {
  using EnumerableSet for EnumerableSet.AddressSet;

  address public constant ETH_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
  EnumerableSet.AddressSet internal protocolTokens;

  constructor() public {}

  function _addProtocolToken(address _token) internal {
    require(!protocolTokens.contains(_token), 'collectable-dust::token-is-part-of-the-protocol');
    protocolTokens.add(_token);
  }

  function _removeProtocolToken(address _token) internal {
    require(protocolTokens.contains(_token), 'collectable-dust::token-not-part-of-the-protocol');
    protocolTokens.remove(_token);
  }

  function _sendDust(
    address _to,
    address _token,
    uint256 _amount
  ) internal {
    require(_to != address(0), 'collectable-dust::cant-send-dust-to-zero-address');
    require(!protocolTokens.contains(_token), 'collectable-dust::token-is-part-of-the-protocol');
    if (_token == ETH_ADDRESS) {
      payable(_to).transfer(_amount);
    } else {
      IERC20(_token).transfer(_to, _amount);
    }
    emit DustSent(_to, _token, _amount);
  }
}
// File: @openzeppelin/contracts/utils/EnumerableSet.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: interfaces/utils/ICollectableDust.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.8;

interface ICollectableDust {
  event DustSent(address _to, address token, uint256 amount);

  function sendDust(address _to, address _token, uint256 _amount) external;
}

// File: contracts/swap/SafeSmartSwapAbstract.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.8;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';

import "../../interfaces/IDexHandler.sol";
import "../../interfaces/IGovernanceSwap.sol";

/*
 * SafeSmartSwapAbstract
 */
abstract
contract SafeSmartSwap {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    IGovernanceSwap public governanceSwap;

    constructor(address _governanceSwap) public {
        _setGovernanceSwap(_governanceSwap);
    }

    // Setter
    function _setGovernanceSwap(address _governanceSwap) internal {
        governanceSwap = IGovernanceSwap(_governanceSwap);
        require(governanceSwap.isGovernanceSwap(), 'safe-smart-swap::set-governance-swap:is-not-governance-swap');
    }

    // Governance swap
    function _swap(uint256 _amount, address _in, address _out) internal returns (uint _amountOut) {

        address _handler = governanceSwap.getPairDefaultDexHandler(_in, _out);
        bytes memory _data = governanceSwap.getPairDefaultData(_in, _out);

        _approve(_in, _handler, _amount);
        return IDexHandler(_handler).swap(_data, _amount);

    }

    // Custom swap
    function _swap(uint256 _amount, address _in, address _out, address _dex, bytes memory _data) internal returns (uint _amountOut) {
        // Use default swap if no custom dex and data was used
        if (_dex == address(0) && _data.length == 0) {
            return _swap(_amount, _in, _out);
        }

        uint256 inBalancePreSwap = IERC20(_in).balanceOf(address(this));
        uint256 outBalancePreSwap = IERC20(_out).balanceOf(address(this));

        // Get governanceSwap amount for token pair
        address _defaultHandler = governanceSwap.getPairDefaultDexHandler(_in, _out);
        bytes memory _defaultData = governanceSwap.getPairDefaultData(_in, _out);
        uint256 _governanceAmountOut = IDexHandler(_defaultHandler).getAmountOut(_defaultData, _amount);

        address _handler = governanceSwap.getDexHandler(_dex);
        require(_handler != address(0), 'no-handler-for-dex');
        
        _approve(_in, _handler, _amount);

        _amountOut = IDexHandler(_handler).swap(_data, _amount);

        require(_amountOut >= _governanceAmountOut, 'custom-swap-is-suboptimal');
        // TODO Check gas spendage if _amountOut == _governanceAmountOut to avoid gas mining? (overkill) [need this check for keep3r ]

        uint256 inBalancePostSwap = IERC20(_in).balanceOf(address(this));
        uint256 outBalancePostSwap = IERC20(_out).balanceOf(address(this));

        // Extra checks to avoid custom dex+data exploits
        require(inBalancePostSwap >= inBalancePreSwap.sub(_amount), 'in-balance-mismatch');
        require(outBalancePostSwap >= outBalancePreSwap.add(_governanceAmountOut), 'out-balance-mismatch');
    }

    function _approve(address _in, address _handler, uint256 _amount) internal {
        IERC20(_in).safeApprove(_handler, _amount);
    }

}

// File: interfaces/IGovernanceSwap.sol



// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.6.8;

interface IGovernanceSwap {
    function isGovernanceSwap() external pure returns (bool);
    function addDexHandler(address _dex, address _handler) external /*onlyGovernance*/ returns (bool);
    function removeDexHandler(address _dex) external /*onlyGovernance*/ returns (bool);
    function setPairDefaults(address _in, address _out, address _dex, bytes calldata _data) external /*onlyGovernance*/ returns (bool);
    function getPairDefaultDex(address _in, address _out) external returns (address _dex);
    function getPairDefaultDexHandler(address _in, address _out) external returns (address _handler);
    function getDexHandler(address _dex) external returns (address _handler);
    function getPairDefaultData(address _in, address _out) external returns (bytes memory _data);
}
// File: contracts/swap/GovernanceSwap.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.8;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";

import "../../interfaces/IGovernanceSwap.sol";
import "../../interfaces/IDexHandler.sol";

import '../utils/Governable.sol';
import '../utils/CollectableDust.sol';

contract GovernanceSwap is Governable, CollectableDust, IGovernanceSwap {
    using SafeMath for uint256;

    mapping(address => address) internal dexHandlers;

    mapping(address => mapping(address => address)) internal defaultPairDex;
    mapping(address => mapping(address => bytes)) internal defaultPairData;

    constructor() public Governable(msg.sender) CollectableDust() {
    }

    function isGovernanceSwap() external pure override returns (bool) {
        return true;
    }


    function addDexHandler(address _dex, address _handler) external override onlyGovernor returns (bool) {
        require(dexHandlers[_dex] == address(0), 'governance-swap::add-dex:dex-already-exists');
        require(IDexHandler(_handler).isDexHandler(), 'governance-swap::add-dex:contract-is-not-handler');
        dexHandlers[_dex] = _handler;
        return true;
    }

    function removeDexHandler(address _dex) external override onlyGovernor returns (bool) {
        require(dexHandlers[_dex] != address(0), 'governance-swap::add-dex:dex-does-not-exists');
        dexHandlers[_dex] = address(0);
        return true;
    }

    function setPairDefaults(address _in, address _out, address _dex, bytes memory _data) public override onlyGovernor returns (bool) {
        require(dexHandlers[_dex] != address(0), 'governance-swap::set-pair-defaults:dex-does-not-have-handler');
        require(_in != _out, 'governance-swap::set-pair-defaults:in-equals-out');
        defaultPairDex[_in][_out] = _dex;
        defaultPairData[_in][_out] = _data;
        return true;
    }


    function getPairDefaultDex(address _in, address _out) external override returns (address _dex) {
        return defaultPairDex[_in][_out];
    }
    function getPairDefaultDexHandler(address _in, address _out) external override returns (address _handler) {
        return dexHandlers[defaultPairDex[_in][_out]];
    }
    function getDexHandler(address _dex) external override returns (address _handler) {
        return dexHandlers[_dex];
    }
    function getPairDefaultData(address _in, address _out) external override returns (bytes memory _data) {
        return defaultPairData[_in][_out];
    }


    function setPendingGovernor(address _pendingGovernor) external override onlyGovernor {
        _setPendingGovernor(_pendingGovernor);
    }

    function acceptGovernor() external override onlyPendingGovernor {
        _acceptGovernor();
    }

    function sendDust(
        address _to,
        address _token,
        uint256 _amount
    ) external override onlyGovernor {
        _sendDust(_to, _token, _amount);
    }

}

// File: contracts/utils/Governable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.8;

import '../../interfaces/utils/IGovernable.sol';

abstract
contract Governable is IGovernable {
  address public governor;
  address public pendingGovernor;

  constructor(address _governor) public {
    require(_governor != address(0), 'governable::governor-should-not-be-zero-address');
    governor = _governor;
  }

  function _setPendingGovernor(address _pendingGovernor) internal {
    require(_pendingGovernor != address(0), 'governable::pending-governor-should-not-be-zero-addres');
    pendingGovernor = _pendingGovernor;
    emit PendingGovernorSet(_pendingGovernor);
  }

  function _acceptGovernor() internal {
    governor = pendingGovernor;
    pendingGovernor = address(0);
    emit GovernorAccepted();
  }

  modifier onlyGovernor {
    require(msg.sender == governor, 'governable::only-governor');
    _;
  }

  modifier onlyPendingGovernor {
    require(msg.sender == pendingGovernor, 'governable::only-pending-governor');
    _;
  }
}
// File: interfaces/utils/IGovernable.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.8;

interface IGovernable {
  event PendingGovernorSet(address pendingGovernor);
  event GovernorAccepted();

  function setPendingGovernor(address _pendingGovernor) external;
  function acceptGovernor() external;
}