YHWHToken.sol

pragma solidity ^0.4.23;

interface tokenRecipient { 
    function receiveApproval(address _from, uint256 _value, bytes _extraData) external;
}

// TODO: MAN6666

contract YHWHcoin
{
    address owner; 
    bool public canBurn;
    bool public canApproveCall;
    uint8 public decimals = 6;
    uint256 public totalSupply = 1000000000000 * (10 ** uint256(decimals));
    string public name = "YHWHcoin";
    string public symbol = "YHWH";

    mapping (address => uint256) balances;
    mapping (address => mapping(address => uint256)) allowed;
    
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    event Burn(address indexed _from, uint256 _value);

    constructor() public {
        owner = msg.sender;
        canBurn = false;
        canApproveCall = false;
        balances[owner] = totalSupply;
    }

    function setCanBurn(bool _val) external {
        require(msg.sender == owner);
        require(_val != canBurn);
        canBurn = _val;
    }

    function setCanApproveCall(bool _val) external {
        require(msg.sender == owner);
        require(_val != canApproveCall);
        canApproveCall = _val;
    }

    function transferOwnership(address _newOwner) external {
        require(msg.sender == owner);
        require(_newOwner != address(0) && _newOwner != owner);
        owner = _newOwner;
    }

    function balanceOf(address _owner) external view returns (uint256) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) external view returns (uint256) {
        return allowed[_owner][_spender];
    }

    function transferFrom(address _from, address _to, uint256 _value) external returns (bool) {
        require(_value <= allowed[_from][msg.sender]);
        allowed[_from][msg.sender] -= _value;
        return _transfer(_from, _to, _value);
    }

    function transfer(address _to, uint256 _value) external returns (bool) {
        return _transfer(msg.sender, _to, _value);     
    }

    function _transfer(address _from, address _to, uint256 _value) internal returns (bool) {
        require(_to != address(0));
        uint256 oldFromVal = balances[_from];
        require(_value > 0 && oldFromVal >= _value);
        uint256 oldToVal = balances[_to];
        uint256 newToVal = oldToVal + _value;
        require(newToVal > oldToVal);
        uint256 newFromVal = oldFromVal - _value;
        balances[_from] = newFromVal;
        balances[_to] = newToVal;

        assert((oldFromVal + oldToVal) == (newFromVal + newToVal));
        emit Transfer(_from, _to, _value);

        return true;
    }

    function burn(uint256 _value) 
        external 
        returns (bool success) 
    {
        require(canBurn == true);
        uint256 oldBalance = balances[msg.sender];
        require(oldBalance >= _value && totalSupply > _value);
        balances[msg.sender] = oldBalance - _value;
        totalSupply = totalSupply - _value;                                
        emit Burn(msg.sender, _value);
        return true;
    }

    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        external
        returns (bool success) 
    {
        require(canApproveCall == true);
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, _extraData);
            return true;
        }
    }
}