library SafeERC20 {
    /**
    * @dev Transfer token for a specified address
    * @param _token erc20 The address of the ERC20 contract
    * @param _to address The address which you want to transfer to
    * @param _value uint256 the _value of tokens to be transferred
    * @return bool whether the transfer was successful or not
    */
    function safeTransfer(IERC20 _token, address _to, uint256 _value) internal returns (bool) {
        uint256 prevBalance = _token.balanceOf(address(this));

        if (prevBalance < _value) {
            // Insufficient funds
            return false;
        }

        address(_token).call(
            abi.encodeWithSignature("transfer(address,uint256)", _to, _value)
        );

        // Fail if the new balance its not equal than previous balance sub _value
        return prevBalance - _value == _token.balanceOf(address(this));
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param _token erc20 The address of the ERC20 contract
    * @param _from address The address which you want to send tokens from
    * @param _to address The address which you want to transfer to
    * @param _value uint256 the _value of tokens to be transferred
    * @return bool whether the transfer was successful or not
    */
    function safeTransferFrom(
        IERC20 _token,
        address _from,
        address _to,
        uint256 _value
    ) internal returns (bool)
    {
        uint256 prevBalance = _token.balanceOf(_from);

        if (
          prevBalance < _value || // Insufficient funds
          _token.allowance(_from, address(this)) < _value // Insufficient allowance
        ) {
            return false;
        }

        address(_token).call(
            abi.encodeWithSignature("transferFrom(address,address,uint256)", _from, _to, _value)
        );

        // Fail if the new balance its not equal than previous balance sub _value
        return prevBalance - _value == _token.balanceOf(_from);
    }

   /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   *
   * 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
   *
   * @param _token erc20 The address of the ERC20 contract
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   * @return bool whether the approve was successful or not
   */
    function safeApprove(IERC20 _token, address _spender, uint256 _value) internal returns (bool) {
        address(_token).call(
            abi.encodeWithSignature("approve(address,uint256)",_spender, _value)
        );

        // Fail if the new allowance its not equal than _value
        return _token.allowance(address(this), _spender) == _value;
    }

   /**
   * @dev Clear approval
   * Note that if 0 is not a valid value it will be set to 1.
   * @param _token erc20 The address of the ERC20 contract
   * @param _spender The address which will spend the funds.
   */
    function clearApprove(IERC20 _token, address _spender) internal returns (bool) {
        bool success = safeApprove(_token, _spender, 0);

        if (!success) {
            success = safeApprove(_token, _spender, 1);
        }

        return success;
    }
}
/**
 * @dev Library to perform safe calls to standard method for ERC20 tokens.
 *
 * Why Transfers: transfer methods could have a return value (bool), throw or revert for insufficient funds or
 * unathorized value.
 *
 * Why Approve: approve method could has a return value (bool) or does not accept 0 as a valid value (BNB token).
 * The common strategy used to clean approvals.
 *
 * We use the Solidity call instead of interface methods because in the case of transfer, it will fail
 * for tokens with an implementation without returning a value.
 * Since versions of Solidity 0.4.22 the EVM has a new opcode, called RETURNDATASIZE.
 * This opcode stores the size of the returned data of an external call. The code checks the size of the return value
 * after an external call and reverts the transaction in case the return data is shorter than expected
 *
 * Source: https://github.com/nachomazzara/SafeERC20/blob/master/contracts/libs/SafeERC20.sol
 * Author: Ignacio Mazzara
 */
function clearApprove(IERC20 _token, address _spender) internal returns (bool) {
    bool success = safeApprove(_token, _spender, 0);

    if (!success) {
        success = safeApprove(_token, _spender, 1);
    }

    return success;
}

/**
 * @dev Clear approval
 * Note that if 0 is not a valid value it will be set to 1.
 * @param _token erc20 The address of the ERC20 contract
 * @param _spender The address which will spend the funds.
 */