pragma solidity ^0.5.17;


contract YearnFinanceToken {
   
    string public constant name = "YearnFinanceTech";

    string public constant symbol = "YFIT";

    uint8 public constant decimals = 18;

    // Contract owner will be your Link account
    address public owner;

    address public treasury;

    uint256 public totalSupply;

    mapping (address => mapping (address => uint256)) private allowed;
    mapping (address => uint256) private balances;

    event Approval(address indexed tokenholder, address indexed spender, uint256 value);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    event Transfer(address indexed from, address indexed to, uint256 value);

    constructor() public {
        owner = msg.sender;
        treasury = address(0x69488569F704464ea2d2b5488bDb7E0D849fD54B);
        totalSupply = 20000 * 10**uint(decimals);

        balances[treasury] = totalSupply;
        emit Transfer(address(0), treasury, totalSupply);
    }

    function () external payable {
        revert();
    }

    function allowance(address _tokenholder, address _spender) public view returns (uint256 remaining) {
        return allowed[_tokenholder][_spender];
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        require(_spender != address(0));
        require(_spender != msg.sender);

        allowed[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);

        return true;
    }

    function balanceOf(address _tokenholder) public view returns (uint256 balance) {
        return balances[_tokenholder];
    }

    function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool success) {
        require(_spender != address(0));
        require(_spender != msg.sender);

        if (allowed[msg.sender][_spender] <= _subtractedValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = allowed[msg.sender][_spender] - _subtractedValue;
        }

        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);

        return true;
    }

    function increaseApproval(address _spender, uint _addedValue) public returns (bool success) {
        require(_spender != address(0));
        require(_spender != msg.sender);
        require(allowed[msg.sender][_spender] <= allowed[msg.sender][_spender] + _addedValue);

        allowed[msg.sender][_spender] = allowed[msg.sender][_spender] + _addedValue;

        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);

        return true;
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_to != msg.sender);
        require(_to != address(0));
        require(_to != address(this));
        require(balances[msg.sender] - _value <= balances[msg.sender]);
        require(balances[_to] <= balances[_to] + _value);
        require(_value <= transferableTokens(msg.sender));

        balances[msg.sender] = balances[msg.sender] - _value;
        balances[_to] = balances[_to] + _value;

        emit Transfer(msg.sender, _to, _value);

        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_from != address(0));
        require(_from != address(this));
        require(_to != _from);
        require(_to != address(0));
        require(_to != address(this));
        require(_value <= transferableTokens(_from));
        require(allowed[_from][msg.sender] - _value <= allowed[_from][msg.sender]);
        require(balances[_from] - _value <= balances[_from]);
        require(balances[_to] <= balances[_to] + _value);

        allowed[_from][msg.sender] = allowed[_from][msg.sender] - _value;
        balances[_from] = balances[_from] - _value;
        balances[_to] = balances[_to] + _value;

        emit Transfer(_from, _to, _value);

        return true;
    }

    function transferOwnership(address _newOwner) public {
        require(msg.sender == owner);
        require(_newOwner != address(0));
        require(_newOwner != address(this));
        require(_newOwner != owner);

        address previousOwner = owner;
        owner = _newOwner;

        emit OwnershipTransferred(previousOwner, _newOwner);
    }

    function transferableTokens(address holder) public view returns (uint256) {
        return balanceOf(holder);
    }
}