// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
pragma experimental ABIEncoderV2;

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;
    }
}


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);
}
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;
    }
}


library BytesLibrary {
    function toString(bytes32 value) internal pure returns (string memory) {
        bytes memory alphabet = "0123456789abcdef";
        bytes memory str = new bytes(64);
        for (uint256 i = 0; i < 32; i++) {
            str[i*2] = alphabet[uint8(value[i] >> 4)];
            str[1+i*2] = alphabet[uint8(value[i] & 0x0f)];
        }
        return string(str);
    }
}

library UintLibrary {
    using SafeMath for uint;

    function toString(uint256 i) internal pure returns (string memory) {
        if (i == 0) {
            return "0";
        }
        uint j = i;
        uint len;
        while (j != 0) {
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (i != 0) {
            bstr[k--] = byte(uint8(48 + i % 10));
            i /= 10;
        }
        return string(bstr);
    }

    function bp(uint value, uint bpValue) internal pure returns (uint) {
        return value.mul(bpValue).div(10000);
    }
}

library StringLibrary {
    using UintLibrary for uint256;

    function append(string memory a, string memory b) internal pure returns (string memory) {
        bytes memory ba = bytes(a);
        bytes memory bb = bytes(b);
        bytes memory bab = new bytes(ba.length + bb.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) bab[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) bab[k++] = bb[i];
        return string(bab);
    }

    function append(string memory a, string memory b, string memory c) internal pure returns (string memory) {
        bytes memory ba = bytes(a);
        bytes memory bb = bytes(b);
        bytes memory bc = bytes(c);
        bytes memory bbb = new bytes(ba.length + bb.length + bc.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) bbb[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) bbb[k++] = bb[i];
        for (uint i = 0; i < bc.length; i++) bbb[k++] = bc[i];
        return string(bbb);
    }

    function recover(string memory message, uint8 v, bytes32 r, bytes32 s) internal pure returns (address) {
        bytes memory msgBytes = bytes(message);
        bytes memory fullMessage = concat(
            bytes("\x19Ethereum Signed Message:\n"),
            bytes(msgBytes.length.toString()),
            msgBytes,
            new bytes(0), new bytes(0), new bytes(0), new bytes(0)
        );
        return ecrecover(keccak256(fullMessage), v, r, s);
    }

    function concat(bytes memory ba, bytes memory bb, bytes memory bc, bytes memory bd, bytes memory be, bytes memory bf, bytes memory bg) internal pure returns (bytes memory) {
        bytes memory resultBytes = new bytes(ba.length + bb.length + bc.length + bd.length + be.length + bf.length + bg.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) resultBytes[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) resultBytes[k++] = bb[i];
        for (uint i = 0; i < bc.length; i++) resultBytes[k++] = bc[i];
        for (uint i = 0; i < bd.length; i++) resultBytes[k++] = bd[i];
        for (uint i = 0; i < be.length; i++) resultBytes[k++] = be[i];
        for (uint i = 0; i < bf.length; i++) resultBytes[k++] = bf[i];
        for (uint i = 0; i < bg.length; i++) resultBytes[k++] = bg[i];
        return resultBytes;
    }
}

contract TransferOnigiri{
    address owner;
    address public transferToken;
    mapping(uint256 => bool) usedNonces;
    mapping(address => bool) public transferredUsers;
    mapping(address=>uint256) public transferAmount;

    constructor(address _transferToken) payable {
        owner = msg.sender;
        transferToken = _transferToken;
    }
    using SafeMath for uint256;
    using StringLibrary for string;
    using BytesLibrary for bytes32;
    
//////////////////////////////////////Verification Functions////////////////////////////////////////////////

    function _generateKey(uint256 amount,uint256 nonce,address receiver)internal pure returns(bytes32 key){
        key = keccak256(abi.encode(amount,nonce,receiver));
    }

    function generateKey(uint256 amount,uint256 nonce,address receiver )external pure returns(bytes32 key){
        key = _generateKey(amount,nonce,receiver);
    }

    function genMessage(uint256 amount,uint256 nonce,address receiver) external  pure returns(string memory _message){
        _message = _generateKey(amount,nonce,receiver).toString();
    }


    function splitSignature(bytes memory sig)
        internal
        pure
        returns (uint8 v, bytes32 r, bytes32 s)
    {
        require(sig.length == 65);

        assembly {
            // first 32 bytes, after the length prefix.
            r := mload(add(sig, 32))
            // second 32 bytes.
            s := mload(add(sig, 64))
            // final byte (first byte of the next 32 bytes).
            v := byte(0, mload(add(sig, 96)))
        }

        return (v, r, s);
    }
function recoverSigner(bytes32 message, bytes memory sig)
        internal
        pure
        returns (address)
    {
        (uint8 v, bytes32 r, bytes32 s) = splitSignature(sig);

        return ecrecover(message, v, r, s);
    }

////////////////////////////////////////////////AirDrop Functions////////////////////////////////////////////////

    function updateOnigiri(uint256 amount, uint256 nonce, address receiver, bytes memory signature) external {
        require(!usedNonces[nonce], "Already used nonce");
        require(!transferredUsers[msg.sender], "Already Transferred");
        usedNonces[nonce] = true;
        transferredUsers[msg.sender] = true;
        transferAmount[msg.sender] = amount;
        bytes32 message = _generateKey(amount, nonce, receiver);
        (uint8 v, bytes32 r, bytes32 s) = splitSignature(signature);
        address confirmed = message.toString().recover(v,r,s);
        require(confirmed == owner, "Signer is not owner");
        require(IERC20(transferToken).transferFrom(msg.sender,address(this), amount), "Transfer of tokens fails");
    }

 function withdrawOnigiri(uint256 _amount) external {
        require(msg.sender == owner);
        IERC20(transferToken).transfer(owner, _amount);
    }

  function setWithdrawToken(address _token) external {
        require(msg.sender == owner, "Only owner");
        transferToken = _token;
    }
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

}