pragma solidity ^0.4.18;

// https://www.ethereum.org/token
interface tokenRecipient {
  function receiveApproval( address from, uint256 value, bytes data ) public;
}

// ERC223
interface ContractReceiver {
  function tokenFallback( address from, uint value, bytes data ) public;
}

// ERC20 token with added ERC223 and Ethereum-Token support
//
// Blend of multiple interfaces:
// - https://theethereum.wiki/w/index.php/ERC20_Token_Standard
// - https://www.ethereum.org/token (uncontrolled, non-standard)
// - https://github.com/Dexaran/ERC23-tokens/blob/Recommended/ERC223_Token.sol

contract ERC223Token
{
  string  public name;        // ERC20
  string  public symbol;      // ERC20
  uint8   public decimals;    // ERC20
  uint256 public totalSupply; // ERC20

  mapping( address => uint256 ) balances_;
  mapping( address => mapping(address => uint256) ) allowances_;

  // ERC20
  event Approval( address indexed owner,
                  address indexed spender,
                  uint value );

  // ERC223, ERC20-compatible
  event Transfer( address indexed from,
                  address indexed to,
                  uint256 value,
                  bytes    data );

  // Ethereum Token
  event Burn( address indexed from, uint256 value );

  function ERC223Token( uint256 initialSupply,
                        string tokenName,
                        uint8 decimalUnits,
                        string tokenSymbol ) public
  {
    balances_[msg.sender] = initialSupply;
    totalSupply = initialSupply;
    name = tokenName;
    decimals = decimalUnits;
    symbol = tokenSymbol;
  }

  function() public payable { revert(); } // does not accept money

  // ERC20
  function balanceOf( address owner ) public constant returns (uint) {
    return balances_[owner];
  }

  // ERC20
  function approve( address spender, uint256 value ) public
  returns (bool success)
  {
    allowances_[msg.sender][spender] = value;
    Approval( msg.sender, spender, value );
    return true;
  }
 
  // ERC20
  function allowance( address owner, address spender ) public constant
  returns (uint256 remaining)
  {
    return allowances_[owner][spender];
  }

  // ERC20
  function transfer(address to, uint256 value) public
  {
    bytes memory empty; // null
    _transfer( msg.sender, to, value, empty );
  }

  // ERC20
  function transferFrom( address from, address to, uint256 value ) public
  returns (bool success)
  {
    require( value <= allowances_[from][msg.sender] );

    allowances_[from][msg.sender] -= value;
    bytes memory empty;
    _transfer( from, to, value, empty );

    return true;
  }

  // Ethereum Token
  function approveAndCall( address spender,
                           uint256 value,
                           bytes context ) public
  returns (bool success)
  {
    if ( approve(spender, value) )
    {
      tokenRecipient recip = tokenRecipient( spender );
      recip.receiveApproval( msg.sender, value, context );
      return true;
    }
    return false;
  }        

  // Ethereum Token
  function burn( uint256 value ) public
  returns (bool success)
  {
    require( balances_[msg.sender] >= value );
    balances_[msg.sender] -= value;
    totalSupply -= value;

    Burn( msg.sender, value );
    return true;
  }

  // Ethereum Token
  function burnFrom( address from, uint256 value ) public
  returns (bool success)
  {
    require( balances_[from] >= value );
    require( value <= allowances_[from][msg.sender] );

    balances_[from] -= value;
    allowances_[from][msg.sender] -= value;
    totalSupply -= value;

    Burn( from, value );
    return true;
  }

  // ERC223 Transfer and invoke specified callback
  function transfer( address to,
                     uint value,
                     bytes data,
                     string custom_fallback ) public returns (bool success)
  {
    _transfer( msg.sender, to, value, data );

    if ( isContract(to) )
    {
      ContractReceiver rx = ContractReceiver( to );
      require( rx.call.value(0)(bytes4(keccak256(custom_fallback)),
               msg.sender,
               value,
               data) );
    }

    return true;
  }

  // ERC223 Transfer to a contract or externally-owned account
  function transfer( address to, uint value, bytes data ) public
  returns (bool success)
  {
    if (isContract(to)) {
      return transferToContract( to, value, data );
    }

    _transfer( msg.sender, to, value, data );
    return true;
  }

  // ERC223 Transfer to contract and invoke tokenFallback() method
  function transferToContract( address to, uint value, bytes data ) private
  returns (bool success)
  {
    _transfer( msg.sender, to, value, data );

    ContractReceiver rx = ContractReceiver(to);
    rx.tokenFallback( msg.sender, value, data );

    return true;
  }

  // ERC223 fetch contract size (must be nonzero to be a contract)
  function isContract( address _addr ) private constant returns (bool)
  {
    uint length;
    assembly { length := extcodesize(_addr) }
    return (length > 0);
  }

  function _transfer( address from,
                      address to,
                      uint value,
                      bytes data ) internal
  {
    require( to != 0x0 );
    require( balances_[from] >= value );
    require( balances_[to] + value > balances_[to] ); // catch overflow

    balances_[from] -= value;
    balances_[to] += value;

    Transfer( from, to, value, data );
  }
}