Add a backend problem menu item renderer to system menu

refs #4139

modules/monitoring/library/Monitoring/Web/Menu/BackendAvailabilityMenuItemRenderer.php

@@ -0,0 +1,62 @@
+<?php
+/* Icinga Web 2 | (c) 2013-2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Module\Monitoring\Web\Menu;
+
+use Icinga\Web\Menu as Menu;
+use Icinga\Module\Monitoring\Backend\MonitoringBackend;
+use Icinga\Web\Menu\MenuItemRenderer;
+
+class BackendAvailabilityMenuItemRenderer extends MenuItemRenderer
+{
+    /**
+     * Checks whether the monitoring backend is running or not
+     *
+     * @return mixed
+     */
+    protected function isCurrentlyRunning()
+    {
+        return MonitoringBackend::instance()->select()->from(
+            'programstatus',
+            array(
+                'is_currently_running'
+            )
+        )->getQuery()->fetchRow()->is_currently_running;
+    }
+
+    /**
+     * @see MenuItemRenderer::render()
+     */
+    public function render(Menu $menu)
+    {
+        return $this->getBadge() . $this->createLink($menu);
+    }
+
+    protected function getBadge()
+    {
+        if (! (bool)$this->isCurrentlyRunning()) {
+            return sprintf(
+                '<div title="%s" class="badge-container"><span class="badge badge-critical">%s</span></div>',
+                mt('monitoring', 'monitoring backend is not running'),
+                1
+            );
+        }
+        return '';
+    }
+
+    /**
+     * Get the problem data for the summary
+     *
+     * @return array|null
+     */
+    public function getSummary()
+    {
+        if (! (bool)$this->isCurrentlyRunning()) {
+            return array(
+                'problems' => 1,
+                'title' => mt('monitoring', 'monitoring backend is not running')
+            );
+        }
+        return null;
+    }
+}