J2.5:Creating a System Plugin to augment JRouter

JRouter Modifications

The Joomla! Router can be modified with additional rules by using the attatchBuildRules and attatchParseRules methods. Ideally, this can be done from a system plugin so these rules will apply globally.

Here are 2 examples of modifying JRouter using rules and a System Plugin. One will augment the results returned by JRouter while the other will completely replace the results returned by JRouter

Augmentation

JRouter returns an array of variables which are then used through the API by JInput to override the actual _GET/_POST/_REQUEST variables. If you merely want to augment the variables being returned, then this is straightforward.

class plgSystemMyRouterAugmentor extends JPlugin
{
	/**
	 * @return  void
	 */
	public function onAfterInitialise()
	{
		$app = JFactory::getApplication();

		// Get the router
		$router = $app->getRouter();

		// Add my own rule:

		// Create a callback array to call the augmentRoute method of this object
		$augmentRouteCallback = array($this, 'augmentRoute');

		// Attach the callback to the router
		$router->attachBuildRule($augmentRouteCallback);
	}

	/**
	 * @param   JRouterSite  $router  The Joomla site Router
	 * @param   JURI         $uri     The URI to parse
	 *
	 * @return  array  The array of processed URI variables
	 */
	public function augmentRoute($router, $uri)
	{
		$vars = array();

		// Do something to the vars
		$vars['augment'] = 'succeeded';

		/**
		 * In this case, now to any Joomla! component/module it will look like
		 * ?augment=succeeded was in the url
		 */
		return $vars;
	}
}

Replacement

JRouter returns an array of variables which are then used through the API by JInput to override the actual _GET/_POST/_REQUEST variables. If you want to completely replace these variables, this takes a bit more work. In this case you may need to call the parse method in a sandbox to find out what would have been the results. You can then add/delete/modify those results. Finally, before returning those results to JRouter for the site itself, you need to flag JRouter so it doesn't continue to process the results.

define('ROUTER_MODE_SKIP_SEF', 2);
define('ROUTER_MODE_SKIP_RAW', -1);

class plgSystemMyRouterReplacor extends JPlugin
{
	/**
	 * @return  void
	 */
	public function onAfterInitialise()
	{
		$app = JFactory::getApplication();

		// Get the router
		$router = $app->getRouter();

		// Create a callback array to call the replaceRoute method of this object
		$replaceRouteCallback = array($this, 'replaceRoute');

		// Attach the callback to the router
		$router->attachBuildRule($replaceRouteCallback);
	}

	/**
	 * @param   JRouterSite  &$router  The Joomla Site Router
	 * @param   JURI         &$uri     The URI to parse
	 *
	 * @return  array  The array of processed URI variables
	 */
	public function replaceRoute($router, $uri)
	{
		$app = JFactory::getApplication('site');
		$vars = array();

		// Get the true router
		$siteRouter = $app->getRouter();

		/**
		 * to avoid a recursion trap, we need to make sure that only
		 * the site router can call us!  We could have removed our own
		 * rule the myRouter...but that would only work
		 * inside our own method!  If someone else is also
		 * doing the same thing, we would have an ugly little
		 * recursion where they call parse which calls us
		 * and then we clone router and call parse which calls them
		 * back, and forth and back and forth
		 * friends don't let friends use recursion!
		 */

		if (spl_object_hash($router) != spl_object_hash($siteRouter))
		{
			// Recursion detected -> abort!
			return $vars;
		}

		/**
		 * we still want to clone the router passed to us, not the true router
		 * since the rules might be different
		 */

		$myRouter = clone $router;

		// Now use the power of Joomla! to parse this uri!
		$vars = $myRouter->parse($uri);

		// What is the menu id?  What is the airspeed velocity of an unladen swallow?
		$menuId = isset($vars['itemId']) ? $vars['itemId'] : 0;

		// Please be smarter than this.  Load the menu and check the config.  Do something
		if ($menuId == 67)
		{
			// Change the option to be a different component.
			$vars['option'] == 'com_my_custom_component';
		}

		/**
		 * $vars has both the merged values of what would have been calculated and our changes
		 * So force the siteRouter to skip more processing - no reason to process it twice!
		 * $router->setMode(JROUTER_MODE_RAW);
		 * if the router mode is RAW - integer 0, then _parseRawRoute will be called by JRouter
		 * $router->setMode(JROUTER_MODE_SEF);
		 * if the router mode is SEF - integer 1, then _parseSEFRoute will be called by JRouter
		 * if we set it to something which is NOT SEF or RAW, nothing is done to it
		 * false or null would be a logical choice,
		 * but since the comparison is == not === false, null and 0/RAW are the same
		 * therefore we defined our own constants.
		 * SEF/RAW is a binary condition of either a positive integer or not a positive integer[0]
		 * so we extend that so SKIP_SEF becomes 2 so the if clause will fail, but anything else
		 * counting on checking for if mode > 0 will work
		 * and SKIP_RAW is -1, so anything counting on checking mode <=0 will work
		 * if it is not 0 or 1, then we don't change it because something else
		 * already triggered the skip.
		 */

		$mode = $router->getMode();

		if ($mode == JROUTER_MODE_RAW)
		{
			$router->setMode(ROUTER_MODE_SKIP_RAW);
		}

		if ($mode == JROUTER_MODE_SEF)
		{
			$router->setMode(ROUTER_MODE_SKIP_SEF);
		}

		// Return our custom variables
		return $vars;
	}
}