Rename 'kohana' to 'system' to conform to the Kohana filesystem layout. I'm comfortable with us not clearly drawing the distinction about the fact that it's Kohana.

system/core/Event.php

@@ -0,0 +1,232 @@
+<?php defined('SYSPATH') OR die('No direct access allowed.');
+/**
+ * Process queuing/execution class. Allows an unlimited number of callbacks
+ * to be added to 'events'. Events can be run multiple times, and can also
+ * process event-specific data. By default, Kohana has several system events.
+ *
+ * $Id: Event.php 3993 2009-02-17 18:42:50Z jheathco $
+ *
+ * @package    Core
+ * @author     Kohana Team
+ * @copyright  (c) 2007 Kohana Team
+ * @license    http://kohanaphp.com/license.html
+ * @link       http://docs.kohanaphp.com/general/events
+ */
+final class Event {
+
+	// Event callbacks
+	private static $events = array();
+
+	// Cache of events that have been run
+	private static $has_run = array();
+
+	// Data that can be processed during events
+	public static $data;
+
+	/**
+	 * Add a callback to an event queue.
+	 *
+	 * @param   string   event name
+	 * @param   array    http://php.net/callback
+	 * @return  boolean
+	 */
+	public static function add($name, $callback)
+	{
+		if ( ! isset(self::$events[$name]))
+		{
+			// Create an empty event if it is not yet defined
+			self::$events[$name] = array();
+		}
+		elseif (in_array($callback, self::$events[$name], TRUE))
+		{
+			// The event already exists
+			return FALSE;
+		}
+
+		// Add the event
+		self::$events[$name][] = $callback;
+
+		return TRUE;
+	}
+
+	/**
+	 * Add a callback to an event queue, before a given event.
+	 *
+	 * @param   string   event name
+	 * @param   array    existing event callback
+	 * @param   array    event callback
+	 * @return  boolean
+	 */
+	public static function add_before($name, $existing, $callback)
+	{
+		if (empty(self::$events[$name]) OR ($key = array_search($existing, self::$events[$name])) === FALSE)
+		{
+			// Just add the event if there are no events
+			return self::add($name, $callback);
+		}
+		else
+		{
+			// Insert the event immediately before the existing event
+			return self::insert_event($name, $key, $callback);
+		}
+	}
+
+	/**
+	 * Add a callback to an event queue, after a given event.
+	 *
+	 * @param   string   event name
+	 * @param   array    existing event callback
+	 * @param   array    event callback
+	 * @return  boolean
+	 */
+	public static function add_after($name, $existing, $callback)
+	{
+		if (empty(self::$events[$name]) OR ($key = array_search($existing, self::$events[$name])) === FALSE)
+		{
+			// Just add the event if there are no events
+			return self::add($name, $callback);
+		}
+		else
+		{
+			// Insert the event immediately after the existing event
+			return self::insert_event($name, $key + 1, $callback);
+		}
+	}
+
+	/**
+	 * Inserts a new event at a specfic key location.
+	 *
+	 * @param   string   event name
+	 * @param   integer  key to insert new event at
+	 * @param   array    event callback
+	 * @return  void
+	 */
+	private static function insert_event($name, $key, $callback)
+	{
+		if (in_array($callback, self::$events[$name], TRUE))
+			return FALSE;
+
+		// Add the new event at the given key location
+		self::$events[$name] = array_merge
+		(
+			// Events before the key
+			array_slice(self::$events[$name], 0, $key),
+			// New event callback
+			array($callback),
+			// Events after the key
+			array_slice(self::$events[$name], $key)
+		);
+
+		return TRUE;
+	}
+
+	/**
+	 * Replaces an event with another event.
+	 *
+	 * @param   string   event name
+	 * @param   array    event to replace
+	 * @param   array    new callback
+	 * @return  boolean
+	 */
+	public static function replace($name, $existing, $callback)
+	{
+		if (empty(self::$events[$name]) OR ($key = array_search($existing, self::$events[$name], TRUE)) === FALSE)
+			return FALSE;
+
+		if ( ! in_array($callback, self::$events[$name], TRUE))
+		{
+			// Replace the exisiting event with the new event
+			self::$events[$name][$key] = $callback;
+		}
+		else
+		{
+			// Remove the existing event from the queue
+			unset(self::$events[$name][$key]);
+
+			// Reset the array so the keys are ordered properly
+			self::$events[$name] = array_values(self::$events[$name]);
+		}
+
+		return TRUE;
+	}
+
+	/**
+	 * Get all callbacks for an event.
+	 *
+	 * @param   string  event name
+	 * @return  array
+	 */
+	public static function get($name)
+	{
+		return empty(self::$events[$name]) ? array() : self::$events[$name];
+	}
+
+	/**
+	 * Clear some or all callbacks from an event.
+	 *
+	 * @param   string  event name
+	 * @param   array   specific callback to remove, FALSE for all callbacks
+	 * @return  void
+	 */
+	public static function clear($name, $callback = FALSE)
+	{
+		if ($callback === FALSE)
+		{
+			self::$events[$name] = array();
+		}
+		elseif (isset(self::$events[$name]))
+		{
+			// Loop through each of the event callbacks and compare it to the
+			// callback requested for removal. The callback is removed if it
+			// matches.
+			foreach (self::$events[$name] as $i => $event_callback)
+			{
+				if ($callback === $event_callback)
+				{
+					unset(self::$events[$name][$i]);
+				}
+			}
+		}
+	}
+
+	/**
+	 * Execute all of the callbacks attached to an event.
+	 *
+	 * @param   string   event name
+	 * @param   array    data can be processed as Event::$data by the callbacks
+	 * @return  void
+	 */
+	public static function run($name, & $data = NULL)
+	{
+		if ( ! empty(self::$events[$name]))
+		{
+			// So callbacks can access Event::$data
+			self::$data =& $data;
+			$callbacks  =  self::get($name);
+
+			foreach ($callbacks as $callback)
+			{
+				call_user_func($callback);
+			}
+
+			// Do this to prevent data from getting 'stuck'
+			$clear_data = '';
+			self::$data =& $clear_data;
+		}
+
+		// The event has been run!
+		self::$has_run[$name] = $name;
+	}
+
+	/**
+	 * Check if a given event has been run.
+	 *
+	 * @param   string   event name
+	 * @return  boolean
+	 */
+	public static function has_run($name)
+	{
+		return isset(self::$has_run[$name]);
+	}
+
+} // End Event