pragma solidity ^0.4.24;

/**
* @dev SafeMath
**/
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a * b;
        assert(a == 0 || c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}


/**
* @dev ERC20Basic Interface
**/
contract ERC20Basic {
    //ERC20 interface


    //returns the total token supply
    function totalSupply() public view returns(uint256);
    //returns the account balance of another account with address
    function balanceOf(address _owner) public view returns (uint256);
    //transfer token, must fire Transfer even
    //this function used for widthdraw
    function transfer(address _to, uint256 _value) public returns (bool);
    //transfer token from _from, _to
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool);
    //allows _spender to withdraw from your account up the _value
    function approve(address _spender, uint256 _value) public returns (bool);
    //returns the amount which _spender is still allowed
    function allowance(address owner, address spender) public view returns (uint256);
    uint256 totalSupply_;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);


}

/**
* @dev StandardToken Interface Function Description
**/
contract StandardToken is ERC20Basic {
    using SafeMath for uint256;

    mapping(address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;

    /**
    * @dev return totalSupply
    */
    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) {
        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];
    }

    /**
     * @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 amout of tokens to be transfered
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        uint _allowance = allowed[_from][msg.sender];

        // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
        // require (_value <= _allowance);

        balances[_to] = balances[_to].add(_value);
        balances[_from] = balances[_from].sub(_value);
        allowed[_from][msg.sender] = _allowance.sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * @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) {

        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender, 0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require((_value == 0) || (allowed[msg.sender][_spender] == 0));

        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 specifing the amount of tokens still available for the spender.
     */
    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

}


/**
* @dev Ownable
**/
contract Ownable {
    address public owner;


    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor() public {
        owner = msg.sender;
    }


    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        owner = newOwner;
    }
}

/**
* @dev MintableToken
**/
contract MintableToken is StandardToken, Ownable {
    event Mint(address indexed to, uint256 amount);
    event MintFinished();

    bool public mintingFinished = false;


    modifier canMint() {
        require(!mintingFinished);
        _;
    }

    /**
     * @dev Function to mint tokens
     * @param _to The address that will recieve the minted tokens.
     * @param _amount The amount of tokens to mint.
     * @return A boolean that indicates if the operation was successful.
     */
    function mint(address _to, uint256 _amount) public onlyOwner canMint returns (bool) {
        totalSupply_ = totalSupply_.add(_amount);
        balances[_to] = balances[_to].add(_amount);
        emit Mint(_to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }

    /**
     * @dev Function to stop minting new tokens.
     * @return True if the operation was successful.
     */
    function finishMinting() public onlyOwner returns (bool) {
        mintingFinished = true;
        emit MintFinished();
        return true;
    }
}



/**
 * @title SimpleToken
 * @dev Very simple ERC20 Token example, where all tokens are pre-assigned to the creator.
 * Note they can later distribute these tokens as they wish using `transfer` and other
 * `ERC20` functions.
 */
contract GlobalPayCoin is MintableToken {

    string public constant name = "Global Pay Coin";
    string public constant symbol = "GPC";
    uint8 public constant decimals = 18;

    uint256 public constant INITIAL_SUPPLY = 10000000000 * (10 ** uint256(decimals));

    /**
     * @dev Constructor that gives msg.sender all of existing tokens.
     */
    constructor(address _owner) public {
        mint(_owner, INITIAL_SUPPLY);
        transferOwnership(_owner);
    }

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transferGasByOwner(address _from, address _to, uint256 _value) public onlyOwner returns (bool) {
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }
}