/**
 * Source Code first verified at https://etherscan.io on Thursday, May 2, 2019
 (UTC) */

pragma solidity 0.5.8;
//import "https://raw.githubusercontent.com/KevK0/solidity-type-casting/master/contracts/stringCasting.sol";
//import "https://raw.githubusercontent.com/Arachnid/solidity-stringutils/master/src/strings.sol";

library SafeMath {
    /**
    * @dev Multiplies two numbers, reverts on 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-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
    * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
    * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
    * @dev Adds two numbers, reverts on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
    * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
    * reverts when dividing by zero.
    */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

contract Ownable {
  address public owner;

  event transferOwner(address indexed existingOwner, address indexed newOwner);

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  function transferOwnership(address newOwner) onlyOwner public {
    if (newOwner != address(0)) {
      owner = newOwner;
      emit transferOwner(msg.sender, owner);
    }
  }
}

contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  uint256 totalSupply_;

  /**
  * @dev total number of tokens in existence
  */
  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  /**
  * @dev transfer token for a specified address
  * @param _to The address to transfer to.
  * @param _value The amount to be transferred.
  */
  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @dev Gets the balance of the specified address.
  * @param _owner The address to query the the balance of.
  * @return An uint256 representing the amount owned by the passed address.
  */
  function balanceOf(address _owner) public view returns (uint256) {
    return balances[_owner];
  }

}

contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;


  /**
   * @dev Transfer tokens from one address to another
   * @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 amount of tokens to be transferred
   */
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);

    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    emit Transfer(_from, _to, _value);
    return true;
  }

  /**
   * @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 _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens that an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }

  /**
   * @dev Increase the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To increment
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _addedValue The amount of tokens to increase the allowance by.
   */
  function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
    allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  /**
   * @dev Decrease the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To decrement
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _subtractedValue The amount of tokens to decrease the allowance by.
   */
  function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
    uint oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue > oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

}

contract ERC865 {

    function transferPreSigned(
        bytes memory _signature,
        address _to,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool);

    function approvePreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool);

    function increaseApprovalPreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _addedValue,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool);

    function decreaseApprovalPreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _subtractedValue,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool);
}

contract ERC865Token is ERC865, StandardToken, Ownable {

    /* Nonces of transfers performed */
    mapping(bytes => bool) signatures;
    /* mapping of nonces of each user */
    mapping (address => uint256) nonces;

    event TransferPreSigned(address indexed from, address indexed to, address indexed delegate, uint256 amount, uint256 fee);
    event ApprovalPreSigned(address indexed from, address indexed to, address indexed delegate, uint256 amount, uint256 fee);

    bytes4 internal constant transferSig = 0x48664c16;
    bytes4 internal constant approvalSig = 0xf7ac9c2e;
    bytes4 internal constant increaseApprovalSig = 0xa45f71ff;
    bytes4 internal constant decreaseApprovalSig = 0x59388d78;
    //bytes memory vvv=0x1d915567e2b192cd7a09915020b24a7980e1705003e97b8774af4aa53d9886176fe4e09916f4d865cfbec913a36030534d9e04c9b0293346743bdcdc0020408f1b;

    //return nonce using function
    function getNonce(address _owner) public view returns (uint256 nonce){
      return nonces[_owner];
    }


    /**
     * @notice Submit a presigned transfer
     * @param _signature bytes The signature, issued by the owner.
     * @param _to address The address which you want to transfer to.
     * @param _value uint256 The amount of tokens to be transferred.
     * @param _fee uint256 The amount of tokens paid to msg.sender, by the owner.
     * @param _nonce uint256 Presigned transaction number.
     */
    function transferPreSigned(
        bytes memory _signature,
        address _to,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool)
    {
        require(_to != address(0));
        require(signatures[_signature] == false);

        bytes32 hashedTx = recoverPreSignedHash(address(this), transferSig, _to, _value, _fee, _nonce);
        address from = recover(hashedTx, _signature);
        require(from != address(0));
        require(_nonce == nonces[from].add(1));
        require(_value.add(_fee) <= balances[from]);

        nonces[from] = _nonce;
        signatures[_signature] = true;
        balances[from] = balances[from].sub(_value).sub(_fee);
        balances[_to] = balances[_to].add(_value);
        balances[msg.sender] = balances[msg.sender].add(_fee);

        emit Transfer(from, _to, _value);
        emit Transfer(from, msg.sender, _fee);
        emit TransferPreSigned(from, _to, msg.sender, _value, _fee);
        return true;
    }

    /**
     * @notice Submit a presigned approval
     * @param _signature bytes The signature, issued by the owner.
     * @param _spender address The address which will spend the funds.
     * @param _value uint256 The amount of tokens to allow.
     * @param _fee uint256 The amount of tokens paid to msg.sender, by the owner.
     * @param _nonce uint256 Presigned transaction number.
     */
    function approvePreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool)
    {
        require(_spender != address(0));
        require(signatures[_signature] == false);

        bytes32 hashedTx = recoverPreSignedHash(address(this), approvalSig, _spender, _value, _fee, _nonce);
        address from = recover(hashedTx, _signature);
        require(from != address(0));
        require(_nonce == nonces[from].add(1));
        require(_value.add(_fee) <= balances[from]);

        nonces[from] = _nonce;
        signatures[_signature] = true;
        allowed[from][_spender] =_value;
        balances[from] = balances[from].sub(_fee);
        balances[msg.sender] = balances[msg.sender].add(_fee);

        emit Approval(from, _spender, _value);
        emit Transfer(from, msg.sender, _fee);
        emit ApprovalPreSigned(from, _spender, msg.sender, _value, _fee);
        return true;
    }

    /**
     * @notice Increase the amount of tokens that an owner allowed to a spender.
     * @param _signature bytes The signature, issued by the owner.
     * @param _spender address The address which will spend the funds.
     * @param _addedValue uint256 The amount of tokens to increase the allowance by.
     * @param _fee uint256 The amount of tokens paid to msg.sender, by the owner.
     * @param _nonce uint256 Presigned transaction number.
     */
    function increaseApprovalPreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _addedValue,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool)
    {
        require(_spender != address(0));
        require(signatures[_signature] == false);

//bytes32 bb=0x59e737eebff4522155b125a11dbd8d225c1a7f047ce93747b103b197e116c224;
//bytes storage nbh=0x7e4362ae61ed93458b1921df843e72570c7f1e11713e6883c0b93ce95e40a1f939daf972b192cff66721f62382c3e3ad423c5d312c2c5c5ac6d00a6d187729861b;
        bytes32 hashedTx = recoverPreSignedHash(address(this), increaseApprovalSig, _spender, _addedValue, _fee, _nonce);
        address from = recover(hashedTx, _signature);
        require(from != address(0));
        require(_nonce == nonces[from].add(1));
        require(allowed[from][_spender].add(_addedValue).add(_fee) <= balances[from]);
        //require(_addedValue <= allowed[from][_spender]);

        nonces[from] = _nonce;
        signatures[_signature] = true;
        allowed[from][_spender] = allowed[from][_spender].add(_addedValue);
        balances[from] = balances[from].sub(_fee);
        balances[msg.sender] = balances[msg.sender].add(_fee);

        emit Approval(from, _spender, allowed[from][_spender]);
        emit Transfer(from, msg.sender, _fee);
        emit ApprovalPreSigned(from, _spender, msg.sender, allowed[from][_spender], _fee);
        return true;
    }

    /**
     * @notice Decrease the amount of tokens that an owner allowed to a spender.
     * @param _signature bytes The signature, issued by the owner
     * @param _spender address The address which will spend the funds.
     * @param _subtractedValue uint256 The amount of tokens to decrease the allowance by.
     * @param _fee uint256 The amount of tokens paid to msg.sender, by the owner.
     * @param _nonce uint256 Presigned transaction number.
     */
    function decreaseApprovalPreSigned(
        bytes memory _signature,
        address _spender,
        uint256 _subtractedValue,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool)
    {
        require(_spender != address(0));
        require(signatures[_signature] == false);

        bytes32 hashedTx = recoverPreSignedHash(address(this), decreaseApprovalSig, _spender, _subtractedValue, _fee, _nonce);
        address from = recover(hashedTx, _signature);
        require(from != address(0));
        require(_nonce == nonces[from].add(1));
        //require(_subtractedValue <= balances[from]);
        //require(_subtractedValue <= allowed[from][_spender]);
        //require(_subtractedValue <= allowed[from][_spender]);
        require(_fee <= balances[from]);

        nonces[from] = _nonce;
        signatures[_signature] = true;
        uint oldValue = allowed[from][_spender];
        if (_subtractedValue > oldValue) {
            allowed[from][_spender] = 0;
        } else {
            allowed[from][_spender] = oldValue.sub(_subtractedValue);
        }
        balances[from] = balances[from].sub(_fee);
        balances[msg.sender] = balances[msg.sender].add(_fee);

        emit Approval(from, _spender, _subtractedValue);
        emit Transfer(from, msg.sender, _fee);
        emit ApprovalPreSigned(from, _spender, msg.sender, allowed[from][_spender], _fee);
        return true;
    }

    /**
     * @notice Transfer tokens from one address to another
     * @param _signature bytes The signature, issued by the spender.
     * @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 amount of tokens to be transferred.
     * @param _fee uint256 The amount of tokens paid to msg.sender, by the spender.
     * @param _nonce uint256 Presigned transaction number.
     */
    /*function transferFromPreSigned(
        bytes _signature,
        address _from,
        address _to,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
    )
        public
        returns (bool)
    {
        require(_to != address(0));
        require(signatures[_signature] == false);
        signatures[_signature] = true;

        bytes32 hashedTx = transferFromPreSignedHashing(address(this), _from, _to, _value, _fee, _nonce);

        address spender = recover(hashedTx, _signature);
        require(spender != address(0));
        require(_value.add(_fee) <= balances[_from])?;

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][spender] = allowed[_from][spender].sub(_value);

        balances[spender] = balances[spender].sub(_fee);
        balances[msg.sender] = balances[msg.sender].add(_fee);

        emit Transfer(_from, _to, _value);
        emit Transfer(spender, msg.sender, _fee);
        return true;
    }*/

     /**
      * @notice Hash (keccak256) of the payload used by recoverPreSignedHash
      * @param _token address The address of the token
      * @param _spender address The address which will spend the funds.
      * @param _value uint256 The amount of tokens.
      * @param _fee uint256 The amount of tokens paid to msg.sender, by the owner.
      * @param _nonce uint256 Presigned transaction number.
      */    
    function recoverPreSignedHash(
        address _token,
        bytes4 _functionSig,
        address _spender,
        uint256 _value,
        uint256 _fee,
        uint256 _nonce
        )
      public pure returns (bytes32)
      {
        //return keccak256(_token, _functionSig, _spender, _value, _fee, _nonce);
        return keccak256(abi.encodePacked(_token, _functionSig, _spender, _value, _fee,_nonce));
    }

    /**
     * @notice Recover signer address from a message by using his signature
     * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
     * @param sig bytes signature, the signature is generated using web3.eth.sign()
     */
    function recover(bytes32 hash, bytes memory sig) public pure returns (address) {
      bytes32 r;
      bytes32 s;
      uint8 v;

      //Check the signature length
      if (sig.length != 65) {
        return (address(0));
      }

      // Divide the signature in r, s and v variables
      assembly {
        r := mload(add(sig, 32))
        s := mload(add(sig, 64))
        v := byte(0, mload(add(sig, 96)))
      }

      // Version of signature should be 27 or 28, but 0 and 1 are also possible versions
      if (v < 27) {
        v += 27;
      }

      // If the version is correct return the signer address
      if (v != 27 && v != 28) {
        return (address(0));
      } else {
        return ecrecover(hash, v, r, s);
      }
    }

}


contract SampleERC865Token is ERC865Token {
  //using strings for *;
  using SafeMath for uint256;

  uint256 public constant _tokenSupply = 42000000;
  string public constant name = "Gravity Cash";
  string public constant symbol = "GVCH";
  uint8 public constant decimals = 18;
  uint256 public constant decimalValue = 10 ** uint256(decimals);
  
  bytes32 internal constant digest = 0x618e860eefb172f655b56aad9bdc5685c037efba70b9c34a8e303b19778efd2c;//=""
  
  uint256 public sellPrice;
  uint256 public buyPrice;
    
  
  constructor() public {
    //require(_tokenSupply > 0);
    totalSupply_ = _tokenSupply.mul(decimalValue);
    balances[msg.sender] = totalSupply_;
    owner = msg.sender;
    emit Transfer(address(this), msg.sender, totalSupply_);
  }
  /*
  function transferMul(address[] froms,
    address[] _toes,
    uint256[] _values,
    uint256[] _fees) public returns (bool[]) {
        require(msg.sender == owner);
        
        bool[] storage isSuccess;
        //uint256 fee=0;
            
        for (uint i=0; i < _toes.length; i++) {
        
            if(_values[i].add(_fees[i]) <= balances[froms[i]]){
                balances[froms[i]] = balances[froms[i]].sub(_values[i]).sub(_fees[i]);
                balances[_toes[i]] = balances[_toes[i]].add(_values[i]);
                
                balances[msg.sender] = balances[msg.sender].add(_fees[i]);
                
                emit Transfer(froms[i], _toes[i], _values[i]);
                if(froms[i] != msg.sender){
                emit Transfer(froms[i], msg.sender, _fees[i]);
                    
                }
                isSuccess.push(true);
            }else{
                isSuccess.push(false);}
        
    }
    //emit Transfer(msg.sender, _to, _value);
    
    return isSuccess;
  }
  */
  /// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
    /// @param newSellPrice Price the users can sell to the contract
    /// @param newBuyPrice Price users can buy from the contract
    function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
        sellPrice = newSellPrice;
        buyPrice = newBuyPrice;
    }

    /// @notice Buy tokens from contract by sending ether
    function buy() payable public {
        uint amount = msg.value / buyPrice;                 // calculates the amount
        emit Transfer(address(this), msg.sender, amount);       // makes the transfers
    }

    /// @notice Sell `amount` tokens to contract
    /// @param amount amount of tokens to be sold
    function sell(uint256 amount) public {
        address myAddress = address(this);
        require(myAddress.balance >= amount * sellPrice);   // checks if the contract has enough ether to buy
        emit Transfer(msg.sender, address(this), amount);       // makes the transfers
        msg.sender.transfer(amount * sellPrice);            // sends ether to the seller. It's important to do this last to avoid recursion attacks
    }
/*
  using stringcast for string;
  function transferArray(string signs,address[] _toes,
        uint256[] _values,
        uint256[] _fees,
        uint256[] _nonces) public returns (bool) {
            require(msg.sender == owner);
         
            var s = signs.toSlice();
            var delim = ".".toSlice();
            var parts = new string[](s.count(delim) + 1);
            for(uint i = 0; i < parts.length; i++) {
                parts[i] = s.split(delim).toString();
                
                bytes32 hashedTx = recoverPreSignedHash(address(this), transferSig, _toes[i], _values[i], _fees[i], _nonces[i]);
                address from = recover(hashedTx,parts[i].toBytes());
                
                if(_values[i].add(_fees[i]) <= balances[from]){
                balances[from] = balances[from].sub(_values[i]).sub(_fees[i]);
                balances[_toes[i]] = balances[_toes[i]].add(_values[i]);
                
                balances[msg.sender] = balances[msg.sender].add(_fees[i]);
                
                emit Transfer(from, _toes[i], _values[i]);
                if(_fees[i] != 0){
                    emit Transfer(from, msg.sender, _fees[i]);
                    
                }
            }
        }
    return true;
  }
  */
  
    
  function transferArray(uint8[] memory v,bytes32[] memory r,bytes32[] memory s,address[] memory _toes,
        uint256[] memory _values,
        uint256[] memory _fees) public returns (bool) {
            require(msg.sender == owner);
            uint totalFee = 0;
         
            for(uint i = 0; i < _toes.length; i++) {
                //bytes32 messageDigest = keccak256(hashes[i]);
                address from = ecrecover(digest, v[i], r[i], s[i]);
                
                uint256 value=_values[i];
                uint256 fee=_fees[i];
                
                uint fromBalance = balances[from];
                
                
                if(value.add(fee) <= fromBalance){
                    address to = _toes[i];
                    uint toBalance = balances[to];
                    
                    balances[from] = fromBalance.sub(value).sub(fee);
                    balances[to] = toBalance.add(value);
                    
                    //balances[msg.sender] = balances[msg.sender].add(_fees[i]);
                    
                    emit Transfer(from, to, value);
                   
                    totalFee=totalFee.add(fee);
                    
                    if(fee != 0){
                        
                        emit Transfer(from, msg.sender, fee);
                    
                    }
                    
                    
                
                }
            
            }
            balances[msg.sender] = balances[msg.sender].add(totalFee);
            
        return true;
  }
  
  
  
  
    function sendBatchCS(address[] calldata _recipients, uint[] calldata _values) external returns (bool) {
            require(_recipients.length == _values.length);
    
            uint senderBalance = balances[msg.sender];
            for (uint i = 0; i < _values.length; i++) {
                uint value = _values[i];
                address to = _recipients[i];
                require(senderBalance >= value);
                if(msg.sender != to){
                    senderBalance = senderBalance - value;
                    balances[to] += value;
                }
    			emit Transfer(msg.sender, to, value);
            }
            balances[msg.sender] = senderBalance;
            return true;
    }
  
}