// SPDX-License-Identifier: MIT
pragma solidity >=0.5.4 <0.9.0;


library SafeMath {
    function sub(uint256 a, uint256 b) internal pure returns(uint256) {
        require(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns(uint256) {
        uint256 c = a + b;
        require(c >= a);
        return c;
    }
}

contract SatoshifyToken {
    
    string public constant name = "Satoshify";

    string public constant symbol = "SFT";

    uint256 public constant decimals = 8;
    
    uint256 public constant totalSupply = 1000000000000000;

    mapping(address => uint256) public balanceOf;

    mapping(address => mapping(address => uint256)) public allowance;

    event Transfer(
        address indexed _from,
        address indexed _to,
        uint256 _value
    );
    
    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _value
    );

    using SafeMath for uint256;

    constructor() {
        balanceOf[msg.sender] = totalSupply;
    }

    function transfer(address _to, uint256 _value) public returns(bool success) {
        require(_value > 0);
        require(balanceOf[msg.sender] >= _value);
        
        balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);
        balanceOf[_to] = balanceOf[_to].add(_value);
        
        emit Transfer(msg.sender, _to, _value);
        
        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns(bool success) {
        require(_value <= balanceOf[_from]);
        require(_value <= allowance[_from][msg.sender]);

        balanceOf[_from] = balanceOf[_from].sub(_value);
        balanceOf[_to] = balanceOf[_to].add(_value);

        allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);

        emit Transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) public returns(bool success) {
        allowance[msg.sender][_spender] = _value;
        
        emit Approval(msg.sender, _spender, _value);
        
        return true;
    }

}