<?php
/**
 * @package     FrameworkOnFramework
 * @subpackage  utils
 * @copyright   Copyright (C) 2010 - 2014 Akeeba Ltd. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

defined('FOF_INCLUDED') or die;

/**
 * Class to handle dispatching of events.
 *
 * This is the Observable part of the Observer design pattern
 * for the event architecture.
 *
 * This class is based on JEventDispatcher as found in Joomla! 3.2.0
 */
class FOFUtilsObservableDispatcher extends FOFUtilsObject
{
    /**
     * An array of Observer objects to notify
     *
     * @var    array
     */
    protected $_observers = array();

    /**
     * The state of the observable object
     *
     * @var    mixed
     */
    protected $_state = null;

    /**
     * A multi dimensional array of [function][] = key for observers
     *
     * @var    array
     */
    protected $_methods = array();

    /**
     * Stores the singleton instance of the dispatcher.
     *
     * @var    FOFUtilsObservableDispatcher
     */
    protected static $instance = null;

    /**
     * Returns the global Event Dispatcher object, only creating it
     * if it doesn't already exist.
     *
     * @return  FOFUtilsObservableDispatcher  The EventDispatcher object.
     */
    public static function getInstance()
    {
        if (self::$instance === null)
        {
            self::$instance = new static;
        }

        return self::$instance;
    }

    /**
     * Get the state of the FOFUtilsObservableDispatcher object
     *
     * @return  mixed    The state of the object.
     */
    public function getState()
    {
        return $this->_state;
    }

    /**
     * Registers an event handler to the event dispatcher
     *
     * @param   string  $event    Name of the event to register handler for
     * @param   string  $handler  Name of the event handler
     *
     * @return  void
     *
     * @throws  InvalidArgumentException
     */
    public function register($event, $handler)
    {
        // Are we dealing with a class or callback type handler?
        if (is_callable($handler))
        {
            // Ok, function type event handler... let's attach it.
            $method = array('event' => $event, 'handler' => $handler);
            $this->attach($method);
        }
        elseif (class_exists($handler))
        {
            // Ok, class type event handler... let's instantiate and attach it.
            $this->attach(new $handler($this));
        }
        else
        {
            throw new InvalidArgumentException('Invalid event handler.');
        }
    }

    /**
     * Triggers an event by dispatching arguments to all observers that handle
     * the event and returning their return values.
     *
     * @param   string  $event  The event to trigger.
     * @param   array   $args   An array of arguments.
     *
     * @return  array  An array of results from each function call.
     */
    public function trigger($event, $args = array())
    {
        $result = array();

        /*
         * If no arguments were passed, we still need to pass an empty array to
         * the call_user_func_array function.
         */
        $args = (array) $args;

        $event = strtolower($event);

        // Check if any plugins are attached to the event.
        if (!isset($this->_methods[$event]) || empty($this->_methods[$event]))
        {
            // No Plugins Associated To Event!
            return $result;
        }

        // Loop through all plugins having a method matching our event
        foreach ($this->_methods[$event] as $key)
        {
            // Check if the plugin is present.
            if (!isset($this->_observers[$key]))
            {
                continue;
            }

            // Fire the event for an object based observer.
            if (is_object($this->_observers[$key]))
            {
                $args['event'] = $event;
                $value = $this->_observers[$key]->update($args);
            }
            // Fire the event for a function based observer.
            elseif (is_array($this->_observers[$key]))
            {
                $value = call_user_func_array($this->_observers[$key]['handler'], $args);
            }

            if (isset($value))
            {
                $result[] = $value;
            }
        }

        return $result;
    }

    /**
     * Attach an observer object
     *
     * @param   object  $observer  An observer object to attach
     *
     * @return  void
     */
    public function attach($observer)
    {
        if (is_array($observer))
        {
            if (!isset($observer['handler']) || !isset($observer['event']) || !is_callable($observer['handler']))
            {
                return;
            }

            // Make sure we haven't already attached this array as an observer
            foreach ($this->_observers as $check)
            {
                if (is_array($check) && $check['event'] == $observer['event'] && $check['handler'] == $observer['handler'])
                {
                    return;
                }
            }

            $this->_observers[] = $observer;
            end($this->_observers);
            $methods = array($observer['event']);
        }
        else
        {
            if (!($observer instanceof FOFUtilsObservableEvent))
            {
                return;
            }

            // Make sure we haven't already attached this object as an observer
            $class = get_class($observer);

            foreach ($this->_observers as $check)
            {
                if ($check instanceof $class)
                {
                    return;
                }
            }

            $this->_observers[] = $observer;
            //$methods = array_diff(get_class_methods($observer), get_class_methods('JPlugin'));
            $methods = get_class_methods($observer);
        }

        $key = key($this->_observers);

        foreach ($methods as $method)
        {
            $method = strtolower($method);

            if (!isset($this->_methods[$method]))
            {
                $this->_methods[$method] = array();
            }

            $this->_methods[$method][] = $key;
        }
    }

    /**
     * Detach an observer object
     *
     * @param   object  $observer  An observer object to detach.
     *
     * @return  boolean  True if the observer object was detached.
     */
    public function detach($observer)
    {
        $retval = false;

        $key = array_search($observer, $this->_observers);

        if ($key !== false)
        {
            unset($this->_observers[$key]);
            $retval = true;

            foreach ($this->_methods as &$method)
            {
                $k = array_search($key, $method);

                if ($k !== false)
                {
                    unset($method[$k]);
                }
            }
        }

        return $retval;
    }
}
