observable

class Observable implements IObservable
{
    protected $_events = Array();

    function __construct()
    {

    }

    /**
     * registerEvents('fooEvent');
     * registerEvents(Array('fooEvent','barEvent'));
     */
    function registerEvents($events)
    {
        if ( !is_array($events) ) $events = Array($events);
        foreach ( $events as $eventId ){
            if ( isset($this->_events[$eventId]) )
            throw new Exception("Event already registered: $eventId");
            $this->_events[$eventId] = Array();
        }
    }

    function isRegistered($eventId)
    {
        return isset($this->_events[$eventId]);
    }

    /**
     * on('click','myFunction');
     * on('click','myFunction',$this);
     * on('click','myFunction',$this,$customArguments);
     */
    function on($eventId,$callback,$context=null,$addArg=null)
    {
        if ( !isset($this->_events[$eventId]) )
        throw new Exception("Event not registered: $eventId");

        $handler = $this->_makeHandler($callback,$context,$addArg);
        $this->_events[$eventId][] = $handler;
    }

    function un($eventId,$callback,$context=null,$addArg=null)
    {
        if ( !isset($this->_events[$eventId]) )
        throw new Exception("Event not exists: $eventId");

        $handler = $this->_makeHandler($callback,$context,$addArg);
        foreach ( $this->_events[$eventId] as $index => $h )
        {
            if ( $h === $handler )
            {
                unset($this->_events[$eventId][$index]);
            }
        }
    }

    /**
     * fireEvent($eventId)
     * fireEvent($eventId,$arg1,$arg2,...,$argX)
     */
    function fireEvent($eventId)
    {
        if ( func_num_args() < 1 )
        throw new Exception('At least one argument required');
        $args = func_get_args();
        $eventId = $args[0];
        array_shift($args);

        if ( !isset($this->_events[$eventId]) )
        throw new Exception("Event not registered: $eventId");

        foreach ( $this->_events[$eventId] as $handler )
        {
            $callback = $handler[0];
            $resultArgs = $args;
            if ( $handler[1] === null )
            {
                $resultArgs = $args;
            }else
            if ( is_array($handler[1]) )
            {
                $resultArgs = array_merge($args,$handler[1]);
            }else
            {
                $resultArgs = $args;
                $resultArgs[] = $handler[1];
            }
            $result = call_user_func_array($callback,$resultArgs);
            if ( $result === false ) return false;
        }
        return true;
    }

    function _makeHandler($callback,$context=null,$void=null)
    {
        if ( !is_string($callback) )
        throw new Exception('Callback must be a string value');
        if ( $context ) $callback = Array($context,$callback);
        return Array($callback,$void);
    }

}