Introduce save and restore methods

data/music.gschema.xml

@@ -12,6 +12,11 @@
       <summary>An index representing the repeat mode</summary>
       <description>An index representing the repeat mode</description>
     </key>
+    <key type="as" name="previous-queue">
+      <default>['']</default>
+      <summary>The queue from last session to restore</summary>
+      <description>An array of strings representing the files played last</description>
+    </key>
 
     <key name="window-height" type="i">
       <default>475</default>

src/Application.vala

@@ -114,6 +114,10 @@ public class Music.Application : Gtk.Application {
         }
 
         settings.bind ("window-maximized", main_window, "maximized", SettingsBindFlags.SET);
+
+        // This needs to be done after window is constructed
+        // Else music plays but the queue seems empty
+        playback_manager.restore_queue ();
     }
 
     private static File[] list_directory (string directory) {

src/PlaybackManager.vala

@@ -38,6 +38,7 @@ public class Music.PlaybackManager : Object {
     private PlaybackManager () {}
 
     construct {
+        settings = new Settings ("io.elementary.music");
         queue_liststore = new ListStore (typeof (AudioObject));
 
         playbin = Gst.ElementFactory.make ("playbin", "playbin");
@@ -455,4 +456,30 @@ public class Music.PlaybackManager : Object {
         var play_pause_action = (SimpleAction) GLib.Application.get_default ().lookup_action (Application.ACTION_PLAY_PAUSE);
         play_pause_action.set_enabled (current_audio != null);
     }
+
+        public void save_queue () {
+        // Save current queue in gsettings
+        string[] list_uri = new string[queue_liststore.n_items];
+
+        for (var i = 0; i < queue_liststore.n_items; i++) {
+            var item = (Music.AudioObject)queue_liststore.get_item (i);
+            list_uri[i] = item.uri;
+        }
+
+        settings.set_strv ("previous-queue", list_uri);
+    }
+
+    public void restore_queue () {
+        var last_session_uri = settings.get_strv ("previous-queue");
+        var last_session_files = new File[last_session_uri.length];
+
+        for (var i = 0; i < last_session_uri.length; i++) {
+            var uri = last_session_uri[i];
+            var file = File.new_for_uri (uri);
+            last_session_files[i] = file;
+        }
+
+        var files_to_play = Application.loop_through_files (last_session_files);
+        queue_files (files_to_play);
+    }
 }