Disable the ``last`` button when filtering groups

Since we cannot effectively filter for groups and have to work with
incremental prefetching, the ``last`` button is mostly broken/buggy.
Hence it is disabled in this usecase.

lib/plugins/authad/auth.php

@@ -387,12 +387,16 @@ class auth_plugin_authad extends DokuWiki_Auth_Plugin {
             if (isset($filter['grps'])) {
                 $this->users = array_fill_keys($result, false);
                 $usermanager = plugin_load("admin", "usermanager", false);
+                $usermanager->setLastdisabled(true);
                 if (!isset($this->_grpsusers[$this->_filterToString($filter)])){
                     $this->_fillGroupUserArray($filter,$usermanager->getStart() + 3*$usermanager->getPagesize());
                 } elseif (count($this->_grpsusers[$this->_filterToString($filter)]) < getStart() + 3*$usermanager->getPagesize()) {
                     $this->_fillGroupUserArray($filter,$usermanager->getStart() + 3*$usermanager->getPagesize() - count($this->_grpsusers[$this->_filterToString($filter)]));
                 }
                 $result = $this->_grpsusers[$this->_filterToString($filter)];
+            } else {
+                $usermanager = plugin_load("admin", "usermanager", false);
+                $usermanager->setLastdisabled(false);
             }
 
         }
@@ -470,6 +474,8 @@ class auth_plugin_authad extends DokuWiki_Auth_Plugin {
         $result = array();
 
         if (!isset($filter['grps'])) {
+            $usermanager = plugin_load("admin", "usermanager", false);
+            $usermanager->setLastdisabled(false);
             foreach($this->users as $user => &$info) {
                 if($i++ < $start) {
                     continue;
@@ -483,6 +489,8 @@ class auth_plugin_authad extends DokuWiki_Auth_Plugin {
                 }
             }
         } else {
+            $usermanager = plugin_load("admin", "usermanager", false);
+            $usermanager->setLastdisabled(true);
             if (!isset($this->_grpsusers[$this->_filterToString($filter)]) || count($this->_grpsusers[$this->_filterToString($filter)]) < ($start+$limit)) {
                 $this->_fillGroupUserArray($filter,$start+$limit - count($this->_grpsusers[$this->_filterToString($filter)]) +1);
             }

lib/plugins/usermanager/admin.php

@@ -31,6 +31,7 @@ class admin_plugin_usermanager extends DokuWiki_Admin_Plugin {
     protected $_edit_userdata = array();
     protected $_disabled = '';      // if disabled set to explanatory string
     protected $_import_failures = array();
+    protected $_lastdisabled = false; // set to true if last user is unknown and last button is hence buggy
 
     /**
      * Constructor
@@ -95,6 +96,13 @@ class admin_plugin_usermanager extends DokuWiki_Admin_Plugin {
         return $this->_pagesize;
     }
 
+    /**
+     * @param boolean $lastdisabled
+     */
+    public function setLastdisabled($lastdisabled) {
+        $this->_lastdisabled = $lastdisabled;
+    }
+
     /**
      * Handle user request
      *
@@ -850,6 +858,10 @@ class admin_plugin_usermanager extends DokuWiki_Admin_Plugin {
             $buttons['last'] = $buttons['next'] = (($this->_start + $this->_pagesize) >= $this->_user_total) ? $disabled : '';
         }
 
+        if ($this->_lastdisabled) {
+            $buttons['last'] = $disabled;
+        }
+
         return $buttons;
     }