Show network offline banner

src/application.vala

@@ -21,6 +21,9 @@
 public class Allesapp.Application : Adw.Application {
     public signal void toast (string message, int timeout = 5);
 
+    public bool network_online { get; private set; default=true; }
+    public signal void network_online_changed ();
+
     public Application () {
         Object (
             application_id: "de.clerie.allesapp",
@@ -37,6 +40,10 @@ public class Allesapp.Application : Adw.Application {
         };
         this.add_action_entries (action_entries, this);
         this.set_accels_for_action ("app.quit", {"<primary>q"});
+
+        this.network_online_changed.connect(on_network_online_changed);
+
+        GLib.Idle.add_once (on_check_network_online_loop);
     }
 
     public override void activate () {
@@ -64,4 +71,40 @@ public class Allesapp.Application : Adw.Application {
         message ("app.preferences action activated");
     }
 
+    private void on_check_network_online_loop () {
+        on_check_network_online ();
+
+        GLib.Timeout.add_seconds_once (5, on_check_network_online_loop_cooldown_elapsed);
+    }
+
+    private void on_check_network_online_loop_cooldown_elapsed () {
+        GLib.Idle.add_once (on_check_network_online_loop);
+    }
+
+    private void on_check_network_online () {
+        var session = new Soup.Session ();
+        var msg = new Soup.Message ("GET", "http://ping.clerie.de/ping");
+
+        var old_network_online = app.network_online;
+
+        try {
+            session.send (msg);
+            app.network_online = msg.status_code == 201;
+        } catch (Error e) {
+            app.network_online = false;
+        }
+
+        if (old_network_online != app.network_online) {
+            app.network_online_changed ();
+        }
+    }
+
+    private void on_network_online_changed () {
+        if (app.network_online) {
+            message ("Network online");
+        } else {
+            message ("Network offline");
+        }
+    }
+
 }

src/window.ui

@@ -27,9 +27,8 @@
               <object class="GtkBox">
                 <property name="orientation">vertical</property>
                 <child>
-                  <object class="AdwBanner">
-                    <property name="revealed">True</property>
-                    <property name="title">Meow meow meow</property>
+                  <object class="AdwBanner" id="network_offline">
+                    <property name="title">Network offline</property>
                   </object>
                 </child>
                 <child>

src/window.vala

@@ -26,12 +26,16 @@ public class Allesapp.Window : Adw.ApplicationWindow {
     [GtkChild]
     private unowned Adw.ToastOverlay toast_overlay;
 
+    [GtkChild]
+    private unowned Adw.Banner network_offline;
+
     public Window (Gtk.Application app) {
         Object (application: app);
     }
 
     construct {
         app.toast.connect (add_toast);
+        app.network_online_changed.connect (on_network_online_changed);
     }
 
     [GtkCallback]
@@ -52,4 +56,8 @@ public class Allesapp.Window : Adw.ApplicationWindow {
             timeout = timeout
         });
     }
+
+    private void on_network_online_changed () {
+        network_offline.set_revealed (!app.network_online);
+    }
 }