J2.5:Creating a System Plugin to augment JRouter

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The Joomla! Router can be modified with additional rules by using the attatchXRules methods. Ideally, this can be done from a system plugin so these rules can affect be used by others.

2 possibilities when adding rules would be that you want to augment the router functionality, or you want to replace it.

Augmentation

class plgSystemMyRouterAugmentor extends JPlugin {

   public function onAfterInitialize()
   {
      global $app;
   // should we  use $app = JFactory::getApplication('site'); ?

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

   // add my own rules
   // create a callback array to call the augmentRoute method of this object
   $augmentCallback = array($this, 'augmentRoute ');
   // attach the callback to the router
   $router->attachBuildRule($myRouterCallback);

   }
   /**
    * @param   JRouterSite &$router  The Joomla Site Router
    * @param   JURI  &$uri  The URI to parse
    *
    * @return  array  $vars The array of processed URI variables
   */
   public function augmentRoute ($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

define('ROUTER_MODE_SKIP_SEF', 2); define('ROUTER_MODE_SKIP_RAW', -1); class plgSystemMyRouterReplacor extends JPlugin {

   public function onAfterInitialize()
   {
      global $app;
     // should we  use $app = JFactory::getApplication('site'); ?
     // get the router
     $router = $app->getRouter();
     // add my own rules
     // create a callback array to call the replaceRoute method of this object
     $augmentCallback = array($this, 'replaceRoute ');
     // attach the callback to the router
     $router->attachBuildRule($myRouterCallback);
   }
   /**
    * @param   JRouterSite &$router  The Joomla Site Router
    * @param   JURI  &$uri  The URI to parse
    *
    * @return  array  $vars The array of processed URI variables
    */
   public function replaceRoute ($router, $uri)
   {
     global $app;
     // should we  use $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)) {
      // oh no!  Abort, 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 = $myRouter->parse($vars);
     //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;
   }

}

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