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

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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

pragma solidity >=0.6.2 <0.8.0;

/**
 * @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 on 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"
        );
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) =
            target.call{value: value}(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        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: @openzeppelin/contracts/token/ERC20/SafeERC20.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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/interface/IERC20Usdt.sol

pragma solidity ^0.6.0;

interface IERC20Usdt {
    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external;

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external;

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external;

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

// File: contracts/Config.sol

pragma solidity ^0.6.0;

contract Config {
    // function signature of "postProcess()"
    bytes4 public constant POSTPROCESS_SIG = 0xc2722916;

    // The base amount of percentage function
    uint256 public constant PERCENTAGE_BASE = 1 ether;

    // Handler post-process type. Others should not happen now.
    enum HandlerType {Token, Custom, Others}
}

// File: contracts/lib/LibCache.sol

pragma solidity ^0.6.0;

library LibCache {
    function set(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        bytes32 _value
    ) internal {
        _cache[_key] = _value;
    }

    function setAddress(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        address _value
    ) internal {
        _cache[_key] = bytes32(uint256(uint160(_value)));
    }

    function setUint256(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        uint256 _value
    ) internal {
        _cache[_key] = bytes32(_value);
    }

    function getAddress(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key
    ) internal view returns (address ret) {
        ret = address(uint160(uint256(_cache[_key])));
    }

    function getUint256(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key
    ) internal view returns (uint256 ret) {
        ret = uint256(_cache[_key]);
    }

    function get(mapping(bytes32 => bytes32) storage _cache, bytes32 _key)
        internal
        view
        returns (bytes32 ret)
    {
        ret = _cache[_key];
    }
}

// File: contracts/lib/LibStack.sol

pragma solidity ^0.6.0;

library LibStack {
    function setAddress(bytes32[] storage _stack, address _input) internal {
        _stack.push(bytes32(uint256(uint160(_input))));
    }

    function set(bytes32[] storage _stack, bytes32 _input) internal {
        _stack.push(_input);
    }

    function setHandlerType(bytes32[] storage _stack, Config.HandlerType _input)
        internal
    {
        _stack.push(bytes12(uint96(_input)));
    }

    function getAddress(bytes32[] storage _stack)
        internal
        returns (address ret)
    {
        ret = address(uint160(uint256(peek(_stack))));
        _stack.pop();
    }

    function getSig(bytes32[] storage _stack) internal returns (bytes4 ret) {
        ret = bytes4(peek(_stack));
        _stack.pop();
    }

    function get(bytes32[] storage _stack) internal returns (bytes32 ret) {
        ret = peek(_stack);
        _stack.pop();
    }

    function peek(bytes32[] storage _stack)
        internal
        view
        returns (bytes32 ret)
    {
        require(_stack.length > 0, "stack empty");
        ret = _stack[_stack.length - 1];
    }
}

// File: contracts/Storage.sol

pragma solidity ^0.6.0;

/// @notice A cache structure composed by a bytes32 array
contract Storage {
    using LibCache for mapping(bytes32 => bytes32);
    using LibStack for bytes32[];

    bytes32[] public stack;
    mapping(bytes32 => bytes32) public cache;

    // keccak256 hash of "msg.sender"
    // prettier-ignore
    bytes32 public constant MSG_SENDER_KEY = 0xb2f2618cecbbb6e7468cc0f2aa43858ad8d153e0280b22285e28e853bb9d453a;

    // keccak256 hash of "cube.counter"
    // prettier-ignore
    bytes32 public constant CUBE_COUNTER_KEY = 0xf9543f11459ccccd21306c8881aaab675ff49d988c1162fd1dd9bbcdbe4446be;

    modifier isStackEmpty() {
        require(stack.length == 0, "Stack not empty");
        _;
    }

    modifier isCubeCounterZero() {
        require(_getCubeCounter() == 0, "Cube counter not zero");
        _;
    }

    modifier isInitialized() {
        require(_getSender() != address(0), "Sender is not initialized");
        _;
    }

    modifier isNotInitialized() {
        require(_getSender() == address(0), "Sender is initialized");
        _;
    }

    function _setSender() internal isNotInitialized {
        cache.setAddress(MSG_SENDER_KEY, msg.sender);
    }

    function _resetSender() internal {
        cache.setAddress(MSG_SENDER_KEY, address(0));
    }

    function _getSender() internal view returns (address) {
        return cache.getAddress(MSG_SENDER_KEY);
    }

    function _addCubeCounter() internal {
        cache.setUint256(CUBE_COUNTER_KEY, _getCubeCounter() + 1);
    }

    function _resetCubeCounter() internal {
        cache.setUint256(CUBE_COUNTER_KEY, 0);
    }

    function _getCubeCounter() internal view returns (uint256) {
        return cache.getUint256(CUBE_COUNTER_KEY);
    }
}

// File: contracts/handlers/HandlerBase.sol

pragma solidity ^0.6.0;

abstract contract HandlerBase is Storage, Config {
    using SafeERC20 for IERC20;

    function postProcess() external payable virtual {
        revert("Invalid post process");
        /* Implementation template
        bytes4 sig = stack.getSig();
        if (sig == bytes4(keccak256(bytes("handlerFunction_1()")))) {
            // Do something
        } else if (sig == bytes4(keccak256(bytes("handlerFunction_2()")))) {
            bytes32 temp = stack.get();
            // Do something
        } else revert("Invalid post process");
        */
    }

    function _updateToken(address token) internal {
        stack.setAddress(token);
        // Ignore token type to fit old handlers
        // stack.setHandlerType(uint256(HandlerType.Token));
    }

    function _updatePostProcess(bytes32[] memory params) internal {
        for (uint256 i = params.length; i > 0; i--) {
            stack.set(params[i - 1]);
        }
        stack.set(msg.sig);
        stack.setHandlerType(HandlerType.Custom);
    }

    function getContractName() public pure virtual returns (string memory);

    function _revertMsg(string memory functionName, string memory reason)
        internal
        view
    {
        revert(
            string(
                abi.encodePacked(
                    _uint2String(_getCubeCounter()),
                    "_",
                    getContractName(),
                    "_",
                    functionName,
                    ": ",
                    reason
                )
            )
        );
    }

    function _revertMsg(string memory functionName) internal view {
        _revertMsg(functionName, "Unspecified");
    }

    function _uint2String(uint256 n) internal pure returns (string memory) {
        if (n == 0) {
            return "0";
        } else {
            uint256 len = 0;
            for (uint256 temp = n; temp > 0; temp /= 10) {
                len++;
            }
            bytes memory str = new bytes(len);
            for (uint256 i = len; i > 0; i--) {
                str[i - 1] = bytes1(uint8(48 + (n % 10)));
                n /= 10;
            }
            return string(str);
        }
    }

    function _getBalance(address token, uint256 amount)
        internal
        view
        returns (uint256)
    {
        if (amount != uint256(-1)) {
            return amount;
        }

        // ETH case
        if (
            token == address(0) ||
            token == address(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE)
        ) {
            return address(this).balance;
        }
        // ERC20 token case
        return IERC20(token).balanceOf(address(this));
    }

    function _tokenApprove(
        address token,
        address spender,
        uint256 amount
    ) internal {
        try IERC20Usdt(token).approve(spender, amount) {} catch {
            IERC20(token).safeApprove(spender, 0);
            IERC20(token).safeApprove(spender, amount);
        }
    }
}

// File: contracts/handlers/uniswapv2/IUniswapV2Pair.sol

pragma solidity >=0.6.0;

interface IUniswapV2Pair {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

    function name() external pure returns (string memory);

    function symbol() external pure returns (string memory);

    function decimals() external pure returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);

    function PERMIT_TYPEHASH() external pure returns (bytes32);

    function nonces(address owner) external view returns (uint256);

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
    event Burn(
        address indexed sender,
        uint256 amount0,
        uint256 amount1,
        address indexed to
    );
    event Swap(
        address indexed sender,
        uint256 amount0In,
        uint256 amount1In,
        uint256 amount0Out,
        uint256 amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint256);

    function factory() external view returns (address);

    function token0() external view returns (address);

    function token1() external view returns (address);

    function getReserves()
        external
        view
        returns (
            uint112 reserve0,
            uint112 reserve1,
            uint32 blockTimestampLast
        );

    function price0CumulativeLast() external view returns (uint256);

    function price1CumulativeLast() external view returns (uint256);

    function kLast() external view returns (uint256);

    function mint(address to) external returns (uint256 liquidity);

    function burn(address to)
        external
        returns (uint256 amount0, uint256 amount1);

    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external;

    function skim(address to) external;

    function sync() external;

    function initialize(address, address) external;
}

// File: contracts/handlers/uniswapv2/libraries/UniswapV2Library.sol

pragma solidity >=0.6.0;

library UniswapV2Library {
    using SafeMath for uint256;

    // returns sorted token addresses, used to handle return values from pairs sorted in this order
    function sortTokens(address tokenA, address tokenB)
        internal
        pure
        returns (address token0, address token1)
    {
        require(tokenA != tokenB, "UniswapV2Library: IDENTICAL_ADDRESSES");
        (token0, token1) = tokenA < tokenB
            ? (tokenA, tokenB)
            : (tokenB, tokenA);
        require(token0 != address(0), "UniswapV2Library: ZERO_ADDRESS");
    }

    // calculates the CREATE2 address for a pair without making any external calls
    function pairFor(
        address factory,
        address tokenA,
        address tokenB
    ) internal pure returns (address pair) {
        (address token0, address token1) = sortTokens(tokenA, tokenB);

        pair = address(
            uint256(
                keccak256(
                    abi.encodePacked(
                        hex"ff",
                        factory,
                        keccak256(abi.encodePacked(token0, token1)),
                        hex"96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f" // init code hash
                    )
                )
            )
        );
    }

    // fetches and sorts the reserves for a pair
    function getReserves(
        address factory,
        address tokenA,
        address tokenB
    ) internal view returns (uint256 reserveA, uint256 reserveB) {
        (address token0, ) = sortTokens(tokenA, tokenB);
        (uint256 reserve0, uint256 reserve1, ) =
            IUniswapV2Pair(pairFor(factory, tokenA, tokenB)).getReserves();
        (reserveA, reserveB) = tokenA == token0
            ? (reserve0, reserve1)
            : (reserve1, reserve0);
    }

    // given some amount of an asset and pair reserves, returns an equivalent amount of the other asset
    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) internal pure returns (uint256 amountB) {
        require(amountA > 0, "UniswapV2Library: INSUFFICIENT_AMOUNT");
        require(
            reserveA > 0 && reserveB > 0,
            "UniswapV2Library: INSUFFICIENT_LIQUIDITY"
        );
        amountB = amountA.mul(reserveB) / reserveA;
    }

    // given an input amount of an asset and pair reserves, returns the maximum output amount of the other asset
    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) internal pure returns (uint256 amountOut) {
        require(amountIn > 0, "UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
        require(
            reserveIn > 0 && reserveOut > 0,
            "UniswapV2Library: INSUFFICIENT_LIQUIDITY"
        );
        uint256 amountInWithFee = amountIn.mul(997);
        uint256 numerator = amountInWithFee.mul(reserveOut);
        uint256 denominator = reserveIn.mul(1000).add(amountInWithFee);
        amountOut = numerator / denominator;
    }

    // given an output amount of an asset and pair reserves, returns a required input amount of the other asset
    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) internal pure returns (uint256 amountIn) {
        require(amountOut > 0, "UniswapV2Library: INSUFFICIENT_OUTPUT_AMOUNT");
        require(
            reserveIn > 0 && reserveOut > 0,
            "UniswapV2Library: INSUFFICIENT_LIQUIDITY"
        );
        uint256 numerator = reserveIn.mul(amountOut).mul(1000);
        uint256 denominator = reserveOut.sub(amountOut).mul(997);
        amountIn = (numerator / denominator).add(1);
    }

    // performs chained getAmountOut calculations on any number of pairs
    function getAmountsOut(
        address factory,
        uint256 amountIn,
        address[] memory path
    ) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, "UniswapV2Library: INVALID_PATH");
        amounts = new uint256[](path.length);
        amounts[0] = amountIn;
        for (uint256 i; i < path.length - 1; i++) {
            (uint256 reserveIn, uint256 reserveOut) =
                getReserves(factory, path[i], path[i + 1]);
            amounts[i + 1] = getAmountOut(amounts[i], reserveIn, reserveOut);
        }
    }

    // performs chained getAmountIn calculations on any number of pairs
    function getAmountsIn(
        address factory,
        uint256 amountOut,
        address[] memory path
    ) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, "UniswapV2Library: INVALID_PATH");
        amounts = new uint256[](path.length);
        amounts[amounts.length - 1] = amountOut;
        for (uint256 i = path.length - 1; i > 0; i--) {
            (uint256 reserveIn, uint256 reserveOut) =
                getReserves(factory, path[i - 1], path[i]);
            amounts[i - 1] = getAmountIn(amounts[i], reserveIn, reserveOut);
        }
    }
}

// File: contracts/handlers/uniswapv2/IUniswapV2Router02.sol

pragma solidity ^0.6.0;

interface IUniswapV2Router02 {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountA, uint256 amountB);

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountToken, uint256 amountETH);

    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountA, uint256 amountB);

    function removeLiquidityETHWithPermit(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountToken, uint256 amountETH);

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function swapETHForExactTokens(
        uint256 amountOut,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);

    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure returns (uint256 amountB);

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountOut);

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountIn);

    function getAmountsOut(uint256 amountIn, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);

    function getAmountsIn(uint256 amountOut, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);

    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountETH);

    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountETH);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable;

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;
}

// File: contracts/handlers/uniswapv2/HUniswapV2.sol

pragma solidity ^0.6.0;

contract HUniswapV2 is HandlerBase {
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    // prettier-ignore
    address public constant UNISWAPV2_ROUTER = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;

    function getContractName() public pure override returns (string memory) {
        return "HUniswapV2";
    }

    function addLiquidityETH(
        uint256 value,
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        )
    {
        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // Approve token
        value = _getBalance(address(0), value);
        amountTokenDesired = _getBalance(token, amountTokenDesired);
        _tokenApprove(token, UNISWAPV2_ROUTER, amountTokenDesired);

        // Add liquidity ETH
        try
            router.addLiquidityETH{value: value}(
                token,
                amountTokenDesired,
                amountTokenMin,
                amountETHMin,
                address(this),
                now + 1
            )
        returns (uint256 ret1, uint256 ret2, uint256 ret3) {
            amountToken = ret1;
            amountETH = ret2;
            liquidity = ret3;
        } catch Error(string memory reason) {
            _revertMsg("addLiquidityETH", reason);
        } catch {
            _revertMsg("addLiquidityETH");
        }

        // Update involved token
        address pair =
            UniswapV2Library.pairFor(router.factory(), token, router.WETH());
        _updateToken(pair);
    }

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin
    )
        external
        payable
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // Approve token
        amountADesired = _getBalance(tokenA, amountADesired);
        amountBDesired = _getBalance(tokenB, amountBDesired);
        _tokenApprove(tokenA, UNISWAPV2_ROUTER, amountADesired);
        _tokenApprove(tokenB, UNISWAPV2_ROUTER, amountBDesired);

        // Add liquidity
        try
            router.addLiquidity(
                tokenA,
                tokenB,
                amountADesired,
                amountBDesired,
                amountAMin,
                amountBMin,
                address(this),
                now + 1
            )
        returns (uint256 ret1, uint256 ret2, uint256 ret3) {
            amountA = ret1;
            amountB = ret2;
            liquidity = ret3;
        } catch Error(string memory reason) {
            _revertMsg("addLiquidity", reason);
        } catch {
            _revertMsg("addLiquidity");
        }

        // Update involved token
        address pair =
            UniswapV2Library.pairFor(router.factory(), tokenA, tokenB);
        _updateToken(pair);
    }

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin
    ) external payable returns (uint256 amountToken, uint256 amountETH) {
        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);
        address pair =
            UniswapV2Library.pairFor(router.factory(), token, router.WETH());

        // Approve token
        liquidity = _getBalance(pair, liquidity);
        _tokenApprove(pair, UNISWAPV2_ROUTER, liquidity);

        // remove liquidityETH
        try
            router.removeLiquidityETH(
                token,
                liquidity,
                amountTokenMin,
                amountETHMin,
                address(this),
                now + 1
            )
        returns (uint256 ret1, uint256 ret2) {
            amountToken = ret1;
            amountETH = ret2;
        } catch Error(string memory reason) {
            _revertMsg("removeLiquidityETH", reason);
        } catch {
            _revertMsg("removeLiquidityETH");
        }

        // Update involved token
        _updateToken(token);
    }

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin
    ) external payable returns (uint256 amountA, uint256 amountB) {
        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);
        address pair =
            UniswapV2Library.pairFor(router.factory(), tokenA, tokenB);

        // Approve token
        liquidity = _getBalance(pair, liquidity);
        _tokenApprove(pair, UNISWAPV2_ROUTER, liquidity);

        // remove liquidity
        try
            router.removeLiquidity(
                tokenA,
                tokenB,
                liquidity,
                amountAMin,
                amountBMin,
                address(this),
                now + 1
            )
        returns (uint256 ret1, uint256 ret2) {
            amountA = ret1;
            amountB = ret2;
        } catch Error(string memory reason) {
            _revertMsg("removeLiquidity", reason);
        } catch {
            _revertMsg("removeLiquidity");
        }

        // Update involved token
        _updateToken(tokenA);
        _updateToken(tokenB);
    }

    function swapExactETHForTokens(
        uint256 value,
        uint256 amountOutMin,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapExactETHForTokens", "invalid path");
        address tokenOut = path[path.length - 1];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);
        value = _getBalance(address(0), value);
        try
            router.swapExactETHForTokens{value: value}(
                amountOutMin,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[amounts.length - 1];
        } catch Error(string memory reason) {
            _revertMsg("swapExactETHForTokens", reason);
        } catch {
            _revertMsg("swapExactETHForTokens");
        }

        _updateToken(tokenOut);
    }

    function swapETHForExactTokens(
        uint256 value,
        uint256 amountOut,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapETHForExactTokens", "invalid path");
        address tokenOut = path[path.length - 1];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // if amount == uint256(-1) return balance of Proxy
        value = _getBalance(address(0), value);

        try
            router.swapETHForExactTokens{value: value}(
                amountOut,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[0];
        } catch Error(string memory reason) {
            _revertMsg("swapETHForExactTokens", reason);
        } catch {
            _revertMsg("swapETHForExactTokens");
        }

        _updateToken(tokenOut);
    }

    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapExactTokensForETH", "invalid path");
        address tokenIn = path[0];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // Approve token
        amountIn = _getBalance(tokenIn, amountIn);
        _tokenApprove(tokenIn, UNISWAPV2_ROUTER, amountIn);

        try
            router.swapExactTokensForETH(
                amountIn,
                amountOutMin,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[amounts.length - 1];
        } catch Error(string memory reason) {
            _revertMsg("swapExactTokensForETH", reason);
        } catch {
            _revertMsg("swapExactTokensForETH");
        }
    }

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapTokensForExactETH", "invalid path");
        address tokenIn = path[0];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // if amount == uint256(-1) return balance of Proxy
        amountInMax = _getBalance(tokenIn, amountInMax);

        // Approve token
        _tokenApprove(tokenIn, UNISWAPV2_ROUTER, amountInMax);

        try
            router.swapTokensForExactETH(
                amountOut,
                amountInMax,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[0];
        } catch Error(string memory reason) {
            _revertMsg("swapTokensForExactETH", reason);
        } catch {
            _revertMsg("swapTokensForExactETH");
        }
    }

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapExactTokensForTokens", "invalid path");
        address tokenIn = path[0];
        address tokenOut = path[path.length - 1];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // Approve token
        amountIn = _getBalance(tokenIn, amountIn);
        _tokenApprove(tokenIn, UNISWAPV2_ROUTER, amountIn);

        try
            router.swapExactTokensForTokens(
                amountIn,
                amountOutMin,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[amounts.length - 1];
        } catch Error(string memory reason) {
            _revertMsg("swapExactTokensForTokens", reason);
        } catch {
            _revertMsg("swapExactTokensForTokens");
        }

        _updateToken(tokenOut);
    }

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path
    ) external payable returns (uint256 amount) {
        if (path.length < 2)
            _revertMsg("swapTokensForExactTokens", "invalid path");
        address tokenIn = path[0];
        address tokenOut = path[path.length - 1];

        // Get uniswapV2 router
        IUniswapV2Router02 router = IUniswapV2Router02(UNISWAPV2_ROUTER);

        // if amount == uint256(-1) return balance of Proxy
        amountInMax = _getBalance(tokenIn, amountInMax);

        // Approve token
        _tokenApprove(tokenIn, UNISWAPV2_ROUTER, amountInMax);

        try
            router.swapTokensForExactTokens(
                amountOut,
                amountInMax,
                path,
                address(this),
                now + 1
            )
        returns (uint256[] memory amounts) {
            amount = amounts[0];
        } catch Error(string memory reason) {
            _revertMsg("swapTokensForExactTokens", reason);
        } catch {
            _revertMsg("swapTokensForExactTokens");
        }

        _updateToken(tokenOut);
    }
}

{
  "compilationTarget": {
    "HUniswapV2.sol": "HUniswapV2"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
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}