pragma solidity ^0.4.18;

// EIP20 - ERC20 Token standard
contract ERC20TokenInterface {

    /// @return The total amount of tokens
    function totalSupply() constant returns (uint256 supply);

    /// @param _owner The address from which the balance will be retrieved
    /// @return The balance
    function balanceOf(address _owner) constant public returns (uint256 balance);

    /// @notice send `_value` token to `_to` from `msg.sender`
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transfer(address _to, uint256 _value) public returns (bool success);

    /// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
    /// @param _from The address of the sender
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);

    /// @notice `msg.sender` approves `_spender` to spend `_value` tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _value The amount of tokens to be approved for transfer
    /// @return Whether the approval was successful or not
    function approve(address _spender, uint256 _value) public returns (bool success);

    /// @param _owner The address of the account owning tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens allowed to spent
    function allowance(address _owner, address _spender) constant public returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

}

// DDToken contract
contract DDToken is ERC20TokenInterface {

    string public constant name = "DDToken";
    string public constant symbol = "DDT";
    uint256 public constant decimals = 6;
    uint256 public constant totalTokens = 50000000 * (10 ** decimals);

    mapping (address => uint256) public balances;
    mapping (address => mapping (address => uint256)) public allowed;

    function DDToken() {
        balances[msg.sender] = totalTokens;
    }

    function totalSupply() constant returns (uint256) {
        return totalTokens;
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        if (balances[msg.sender] >= _value) {
            balances[msg.sender] -= _value;
            balances[_to] += _value;
            Transfer(msg.sender, _to, _value);
            return true;
        }
        return false;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value) {
            balances[_from] -= _value;
            allowed[_from][msg.sender] -= _value;
            balances[_to] += _value;
            Transfer(_from, _to, _value);
            return true;
        }
        return false;
    }

    function balanceOf(address _owner) constant public returns (uint256) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) constant public returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

}