pragma solidity ^0.4.0;
import "./ERC20interface.sol";

contract FixedSupplyToken is ERC20Interface {
    string public constant symbol = "FIXED";
    string public constant name = "EXE token";
    uint8 public constant decimals = 18;
    uint constant MAX_UINT = 2**256 - 1;
    uint256 _totalSupply = MAX_UINT;
    // Owner of this contract
    address public owner;
    // Balances for each account
    mapping(address => uint256) balances;
    // Owner of account approves the transfer of an amount to another account
    mapping(address => mapping (address => uint256)) allowed;
    // Functions with this modifier can only be executed by the owner
    modifier onlyOwner() {
//        if (msg.sender != owner) {
//           revert(); ony available in 4.x version truffle
//        }
        if (msg.sender != owner) throw;
        _;
    }
    // Constructor
    function FixedSupplyToken() public {
        owner = msg.sender;
        balances[owner] = _totalSupply;
    }
    function totalSupply() public constant returns (uint256 totalSupplyReturn) {
        totalSupplyReturn = _totalSupply;
    }
    // What is the balance of a particular account?
    function balanceOf(address _owner) public constant returns (uint256 balance) {
        return balances[_owner];
    }
    // Transfer the balance from owner's account to another account
    function transfer(address _to, uint256 _amount) public returns (bool success) {
        if (balances[msg.sender] >= _amount
        && _amount > 0
        && balances[_to] + _amount > balances[_to]) {
            balances[msg.sender] -= _amount;
            balances[_to] += _amount;
            Transfer(msg.sender, _to, _amount);
            return true;
        } else {
            return false;
        }
    }
    // Send _value amount of tokens from address _from to address _to
    // The transferFrom method is used for a withdraw workflow, allowing contracts to send
    // tokens on your behalf, for example to "deposit" to a contract address and/or to charge
    // fees in sub-currencies; the command should fail unless the _from account has
    // deliberately authorized the sender of the message via some mechanism; we propose
    // these standardized APIs for approval:
    function transferFrom(
    address _from,
    address _to,
    uint256 _amount
    ) public onlyOwner returns (bool success)  { //&& allowed[_from][msg.sender] >= _amount. And without onlyOwner
        if (balances[_from] >= _amount
        && _amount > 0
        && balances[_to] + _amount > balances[_to]) {
            balances[_from] -= _amount;
//            allowed[_from][msg.sender] -= _amount;
            balances[_to] += _amount;
            Transfer(_from, _to, _amount);
            return true;
        } else {
            return false;
        }
    }
    // Allow _spender to withdraw from your account, multiple times, up to the _value amount.
    // If this function is called again it overwrites the current allowance with _value.
    function approve(address _spender, uint256 _amount) public returns (bool success) {
        allowed[msg.sender][_spender] = _amount;
        Approval(msg.sender, _spender, _amount);
        return true;
    }
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
}