// 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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * 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);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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/math/Math.sol


pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: @openzeppelin/contracts/utils/ReentrancyGuard.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol

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/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);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(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: @openzeppelin/contracts/utils/Context.sol

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: @uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router01.sol

pragma solidity >=0.6.2;

interface IUniswapV2Router01 {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETHWithPermit(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountToken, uint amountETH);
    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 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: @uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol

pragma solidity >=0.6.2;


interface IUniswapV2Router02 is IUniswapV2Router01 {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountETH);
    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountETH);

    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;
}

// File: @uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol

pragma solidity >=0.5.0;

interface IUniswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint 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 (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint 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 (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    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 (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}

// File: contracts/interfaces/IDMMLiquidityRouter.sol
pragma solidity 0.6.12;


/// @dev an simple interface for integration dApp to contribute liquidity
interface IDMMLiquidityRouter {
    /**
     * @param tokenA address of token in the pool
     * @param tokenB address of token in the pool
     * @param pool the address of the pool
     * @param amountADesired the amount of tokenA users want to add to the pool
     * @param amountBDesired the amount of tokenB users want to add to the pool
     * @param amountAMin bounds to the extents to which amountB/amountA can go up
     * @param amountBMin bounds to the extents to which amountB/amountA can go down
     * @param vReserveRatioBounds bounds to the extents to which vReserveB/vReserveA can go (precision: 2 ** 112)
     * @param to Recipient of the liquidity tokens.
     * @param deadline Unix timestamp after which the transaction will revert.
     */
    function addLiquidity(
        IERC20 tokenA,
        IERC20 tokenB,
        address pool,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256[2] calldata vReserveRatioBounds,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityNewPool(
        IERC20 tokenA,
        IERC20 tokenB,
        uint32 ampBps,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityNewPoolETH(
        IERC20 token,
        uint32 ampBps,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    /**
     * @param token address of token in the pool
     * @param pool the address of the pool
     * @param amountTokenDesired the amount of token users want to add to the pool
     * @dev   msg.value equals to amountEthDesired
     * @param amountTokenMin bounds to the extents to which WETH/token can go up
     * @param amountETHMin bounds to the extents to which WETH/token can go down
     * @param vReserveRatioBounds bounds to the extents to which vReserveB/vReserveA can go (precision: 2 ** 112)
     * @param to Recipient of the liquidity tokens.
     * @param deadline Unix timestamp after which the transaction will revert.
     */
    function addLiquidityETH(
        IERC20 token,
        address pool,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        uint256[2] calldata vReserveRatioBounds,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    /**
     * @param tokenA address of token in the pool
     * @param tokenB address of token in the pool
     * @param pool the address of the pool
     * @param liquidity the amount of lp token users want to burn
     * @param amountAMin the minimum token retuned after burning
     * @param amountBMin the minimum token retuned after burning
     * @param to Recipient of the returned tokens.
     * @param deadline Unix timestamp after which the transaction will revert.
     */
    function removeLiquidity(
        IERC20 tokenA,
        IERC20 tokenB,
        address pool,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountA, uint256 amountB);

    /**
     * @param tokenA address of token in the pool
     * @param tokenB address of token in the pool
     * @param pool the address of the pool
     * @param liquidity the amount of lp token users want to burn
     * @param amountAMin the minimum token retuned after burning
     * @param amountBMin the minimum token retuned after burning
     * @param to Recipient of the returned tokens.
     * @param deadline Unix timestamp after which the transaction will revert.
     * @param approveMax whether users permit the router spending max lp token or not.
     * @param r s v Signature of user to permit the router spending lp token
     */
    function removeLiquidityWithPermit(
        IERC20 tokenA,
        IERC20 tokenB,
        address pool,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountA, uint256 amountB);

    /**
     * @param token address of token in the pool
     * @param pool the address of the pool
     * @param liquidity the amount of lp token users want to burn
     * @param amountTokenMin the minimum token retuned after burning
     * @param amountETHMin the minimum eth in wei retuned after burning
     * @param to Recipient of the returned tokens.
     * @param deadline Unix timestamp after which the transaction will revert
     */
    function removeLiquidityETH(
        IERC20 token,
        address pool,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountToken, uint256 amountETH);

    /**
     * @param token address of token in the pool
     * @param pool the address of the pool
     * @param liquidity the amount of lp token users want to burn
     * @param amountTokenMin the minimum token retuned after burning
     * @param amountETHMin the minimum eth in wei retuned after burning
     * @param to Recipient of the returned tokens.
     * @param deadline Unix timestamp after which the transaction will revert
     * @param approveMax whether users permit the router spending max lp token
     * @param r s v signatures of user to permit the router spending lp token.
     */
    function removeLiquidityETHWithPermit(
        IERC20 token,
        address pool,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountToken, uint256 amountETH);

    /**
     * @param amountA amount of 1 side token added to the pool
     * @param reserveA current reserve of the pool
     * @param reserveB current reserve of the pool
     * @return amountB amount of the other token added to the pool
     */
    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure returns (uint256 amountB);
}

// File: contracts/interfaces/IERC20Permit.sol
pragma solidity 0.6.12;


interface IERC20Permit is IERC20 {
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

// File: contracts/wrapper/LiquidityMigrator.sol

// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;











interface ILiquidityMigrator {
    struct PermitData {
        bool approveMax;
        uint8 v;
        bytes32 r;
        bytes32 s;
    }

    struct PoolInfo {
        address poolAddress;
        uint32 poolAmp;
        uint256[2] dmmVReserveRatioBounds;
    }

    event RemoveLiquidity(
        address indexed tokenA,
        address indexed tokenB,
        address indexed uniPair,
        uint256 liquidity,
        uint256 amountA,
        uint256 amountB
    );

    event Migrated(
        address indexed tokenA,
        address indexed tokenB,
        uint256 dmmAmountA,
        uint256 dmmAmountB,
        uint256 dmmLiquidity,
        PoolInfo info
    );

    /**
     * @dev Migrate tokens from a pair to a Kyber Dmm Pool
     *   Supporting both normal tokens and tokens with fee on transfer
     *   Support create new pool with received tokens from removing, or
     *       add tokens to a given pool address
     * @param uniPair pair for token that user wants to migrate from
     *   it should be compatible with UniswapPair's interface
     * @param tokenA first token of the pool
     * @param tokenB second token of the pool
     * @param liquidity amount of LP tokens to migrate
     * @param amountAMin min amount for tokenA when removing
     * @param amountBMin min amount for tokenB when removing
     * @param dmmAmountAMin min amount for tokenA when adding
     * @param dmmAmountBMin min amount for tokenB when adding
     * @param poolInfo info the the Kyber DMM Pool - (poolAddress, poolAmp)
     *   if poolAddress is 0x0 -> create new pool with amp factor of poolAmp
     *   otherwise add liquidity to poolAddress
     * @param deadline only allow transaction to be executed before the deadline
     */
    function migrateLpToDmmPool(
        address uniPair,
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256 dmmAmountAMin,
        uint256 dmmAmountBMin,
        PoolInfo calldata poolInfo,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 addedLiquidity
        );

    /**
     * @dev Migrate tokens from a pair to a Kyber Dmm Pool with permit
     *   User doesn't have to make an approve allowance transaction, just need to sign the data
     *   Supporting both normal tokens and tokens with fee on transfer
     *   Support create new pool with received tokens from removing, or
     *       add tokens to a given pool address
     * @param uniPair pair for token that user wants to migrate from
     *   it should be compatible with UniswapPair's interface
     * @param tokenA first token of the pool
     * @param tokenB second token of the pool
     * @param liquidity amount of LP tokens to migrate
     * @param amountAMin min amount for tokenA when removing
     * @param amountBMin min amount for tokenB when removing
     * @param dmmAmountAMin min amount for tokenA when adding
     * @param dmmAmountBMin min amount for tokenB when adding
     * @param poolInfo info the the Kyber DMM Pool - (poolAddress, poolAmp)
     *   if poolAddress is 0x0 -> create new pool with amp factor of poolAmp
     *   otherwise add liquidity to poolAddress
     * @param deadline only allow transaction to be executed before the deadline
     * @param permitData data of approve allowance
     */
    function migrateLpToDmmPoolWithPermit(
        address uniPair,
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256 dmmAmountAMin,
        uint256 dmmAmountBMin,
        PoolInfo calldata poolInfo,
        uint256 deadline,
        PermitData calldata permitData
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 addedLiquidity
        );
}

/**
 * @dev Liquidity Migrator contract to help migrating liquidity
 *       from other sources to Kyber DMM Pool
 */
contract LiquidityMigrator2 is ILiquidityMigrator, Ownable {
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    address public immutable dmmRouter;

    constructor(address _dmmRouter) public {
        require(_dmmRouter != address(0), "Migrator: INVALID_ROUTER");
        dmmRouter = _dmmRouter;
    }

    /**
     * @dev Use only for some special tokens
     */
    function manualApproveAllowance(
        IERC20[] calldata tokens,
        address[] calldata spenders,
        uint256 allowance
    ) external onlyOwner {
        for (uint256 i = 0; i < tokens.length; i++) {
            for (uint256 j = 0; j < spenders.length; j++) {
                tokens[i].safeApprove(spenders[j], allowance);
            }
        }
    }

    /**
     * @dev Migrate tokens from a pair to a Kyber Dmm Pool
     *   Supporting both normal tokens and tokens with fee on transfer
     *   Support create new pool with received tokens from removing, or
     *       add tokens to a given pool address
     * @param uniPair pair for token that user wants to migrate from
     *   it should be compatible with UniswapPair's interface
     * @param tokenA first token of the pool
     * @param tokenB second token of the pool
     * @param liquidity amount of LP tokens to migrate
     * @param amountAMin min amount for tokenA when removing/adding
     * @param amountBMin min amount for tokenB when removing/adding
     * @param poolInfo info the the Kyber DMM Pool - (poolAddress, poolAmp)
     *   if poolAddress is 0x0 -> create new pool with amp factor of poolAmp
     *   otherwise add liquidity to poolAddress
     * @param deadline only allow transaction to be executed before the deadline
     * @param permitData data of approve allowance
     */
    function migrateLpToDmmPoolWithPermit(
        address uniPair,
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256 dmmAmountAMin,
        uint256 dmmAmountBMin,
        PoolInfo calldata poolInfo,
        uint256 deadline,
        PermitData calldata permitData
    )
        external
        override
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 addedLiquidity
        )
    {
        IERC20Permit(uniPair).permit(
            msg.sender,
            address(this),
            permitData.approveMax ? uint256(-1) : liquidity,
            deadline,
            permitData.v,
            permitData.r,
            permitData.s
        );

        (amountA, amountB, addedLiquidity) = migrateLpToDmmPool(
            uniPair,
            tokenA,
            tokenB,
            liquidity,
            amountAMin,
            amountBMin,
            dmmAmountAMin,
            dmmAmountBMin,
            poolInfo,
            deadline
        );
    }

    /**
     * @dev Migrate tokens from a pair to a Kyber Dmm Pool with permit
     *   User doesn't have to make an approve allowance transaction, just need to sign the data
     *   Supporting both normal tokens and tokens with fee on transfer
     *   Support create new pool with received tokens from removing, or
     *       add tokens to a given pool address
     * @param uniPair pair for token that user wants to migrate from
     *   it should be compatible with UniswapPair's interface
     * @param tokenA first token of the pool
     * @param tokenB second token of the pool
     * @param liquidity amount of LP tokens to migrate
     * @param amountAMin min amount for tokenA when removing/adding
     * @param amountBMin min amount for tokenB when removing/adding
     * @param poolInfo info the the Kyber DMM Pool - (poolAddress, poolAmp)
     *   if poolAddress is 0x0 -> create new pool with amp factor of poolAmp
     *   otherwise add liquidity to poolAddress
     * @param deadline only allow transaction to be executed before the deadline
     */
    function migrateLpToDmmPool(
        address uniPair,
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256 dmmAmountAMin,
        uint256 dmmAmountBMin,
        PoolInfo memory poolInfo,
        uint256 deadline
    )
        public
        override
        returns (
            uint256 dmmAmountA,
            uint256 dmmAmountB,
            uint256 dmmLiquidity
        )
    {
        // support for both normal token and token with fee on transfer
        {
            uint256 balanceTokenA = IERC20(tokenA).balanceOf(address(this));
            uint256 balanceTokenB = IERC20(tokenB).balanceOf(address(this));
            _removeUniLiquidity(
                uniPair,
                tokenA,
                tokenB,
                liquidity,
                amountAMin,
                amountBMin,
                deadline
            );
            dmmAmountA = IERC20(tokenA).balanceOf(address(this)).sub(balanceTokenA);
            dmmAmountB = IERC20(tokenB).balanceOf(address(this)).sub(balanceTokenB);
            require(dmmAmountA > 0 && dmmAmountB > 0, "Migrator: INVALID_AMOUNT");

            emit RemoveLiquidity(tokenA, tokenB, uniPair, liquidity, dmmAmountA, dmmAmountB);
        }

        (dmmAmountA, dmmAmountB, dmmLiquidity) = _addLiquidityToDmmPool(
            tokenA,
            tokenB,
            dmmAmountA,
            dmmAmountB,
            dmmAmountAMin,
            dmmAmountBMin,
            poolInfo,
            deadline
        );

        emit Migrated(tokenA, tokenB, dmmAmountA, dmmAmountB, dmmLiquidity, poolInfo);
    }

    /** @dev Allow the Owner to withdraw any funds that have been 'wrongly'
     *       transferred to the migrator contract
     */
    function withdrawFund(IERC20 token, uint256 amount) external onlyOwner {
        if (token == IERC20(0)) {
            (bool success, ) = owner().call{value: amount}("");
            require(success, "Migrator: TRANSFER_ETH_FAILED");
        } else {
            token.safeTransfer(owner(), amount);
        }
    }

    /**
     * @dev Add liquidity to Kyber dmm pool, support adding to new pool or an existing pool
     */
    function _addLiquidityToDmmPool(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        PoolInfo memory poolInfo,
        uint256 deadline
    )
        internal
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        // safe approve only if needed
        _safeApproveAllowance(IERC20(tokenA), address(dmmRouter));
        _safeApproveAllowance(IERC20(tokenB), address(dmmRouter));
        if (poolInfo.poolAddress == address(0)) {
            // add to new pool
            (amountA, amountB, liquidity) = _addLiquidityNewPool(
                tokenA,
                tokenB,
                amountADesired,
                amountBDesired,
                amountAMin,
                amountBMin,
                poolInfo.poolAmp,
                deadline
            );
        } else {
            (amountA, amountB, liquidity) = _addLiquidityExistingPool(
                tokenA,
                tokenB,
                amountADesired,
                amountBDesired,
                amountAMin,
                amountBMin,
                poolInfo.poolAddress,
                poolInfo.dmmVReserveRatioBounds,
                deadline
            );
        }
    }

    /**
     * @dev Add liquidity to an existing pool, and return back tokens to users if any
     */
    function _addLiquidityExistingPool(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address dmmPool,
        uint256[2] memory vReserveRatioBounds,
        uint256 deadline
    )
        internal
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        (amountA, amountB, liquidity) = IDMMLiquidityRouter(dmmRouter).addLiquidity(
            IERC20(tokenA),
            IERC20(tokenB),
            dmmPool,
            amountADesired,
            amountBDesired,
            amountAMin,
            amountBMin,
            vReserveRatioBounds,
            msg.sender,
            deadline
        );
        // return back token if needed
        if (amountA < amountADesired) {
            IERC20(tokenA).safeTransfer(msg.sender, amountADesired - amountA);
        }
        if (amountB < amountBDesired) {
            IERC20(tokenB).safeTransfer(msg.sender, amountBDesired - amountB);
        }
    }

    /**
     * @dev Add liquidity to a new pool, and return back tokens to users if any
     */
    function _addLiquidityNewPool(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        uint32 amps,
        uint256 deadline
    )
        internal
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        (amountA, amountB, liquidity) = IDMMLiquidityRouter(dmmRouter).addLiquidityNewPool(
            IERC20(tokenA),
            IERC20(tokenB),
            amps,
            amountADesired,
            amountBDesired,
            amountAMin,
            amountBMin,
            msg.sender,
            deadline
        );
        // return back token if needed
        if (amountA < amountADesired) {
            IERC20(tokenA).safeTransfer(msg.sender, amountADesired - amountA);
        }
        if (amountB < amountBDesired) {
            IERC20(tokenB).safeTransfer(msg.sender, amountBDesired - amountB);
        }
    }

    /**
     * @dev Re-write remove liquidity function from Uniswap
     */
    function _removeUniLiquidity(
        address pair,
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        uint256 deadline
    ) internal {
        require(deadline >= block.timestamp, "Migratior: EXPIRED");
        IERC20(pair).safeTransferFrom(msg.sender, pair, liquidity); // send liquidity to pair
        (uint256 amount0, uint256 amount1) = IUniswapV2Pair(pair).burn(address(this));
        (address token0, ) = _sortTokens(tokenA, tokenB);
        (uint256 amountA, uint256 amountB) = tokenA == token0
            ? (amount0, amount1)
            : (amount1, amount0);
        require(amountA >= amountAMin, "Migratior: UNI_INSUFFICIENT_A_AMOUNT");
        require(amountB >= amountBMin, "Migratior: UNI_INSUFFICIENT_B_AMOUNT");
    }

    /**
     * @dev only approve if the current allowance is 0
     */
    function _safeApproveAllowance(IERC20 token, address spender) internal {
        if (token.allowance(address(this), spender) == 0) {
            token.safeApprove(spender, uint256(-1));
        }
    }

    /**
     * @dev Copy logic of sort token from Uniswap lib
     */
    function _sortTokens(address tokenA, address tokenB)
        internal
        pure
        returns (address token0, address token1)
    {
        require(tokenA != tokenB, "Migrator: IDENTICAL_ADDRESSES");
        (token0, token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        require(token0 != address(0), "Migrator: ZERO_ADDRESS");
    }
}