made steps to shift from gresource to json, the code for json interop working

src/json_config.vala

@@ -1,22 +1,221 @@
-using Json;
+/*
+    example Config file structure :
+    {
+        "playlists": [
+            "playlist1": {
+                "properties": {
+                    "type": 3, // use PlaylistType enum for video-only, audio-only, or an assortment
+                    "playlist_picture": "amazing.png", // store all the playlist_pictures in a given directory
+                }
+                "items": [
+                    "video1": {
+                        "type": 1, // use enum to write in whether it is audio or video
+                        "file": "video1.mp4",
+                        "picture": "video1.png" // store the pictures of playlist items in a good directory
+                    }
+                    "audio2": {
+                        "type": 2,
+                        "file": "audio2.mp3",
+                        "picture": "audio2.png"
+                    }
+                ]
+            }
+        ]
+    }
+
+*/
 
 namespace Song {
 
-    public class JsonConfig : GLib.Object {
+    public enum PlaylistType {
+        VIDEO_ONLY,
+        AUDIO_ONLY,
+        VIDEO_AND_AUDIO_COLLECTION,
+    }
+
+    public enum ItemType {
+        VIDEO,
+        AUDIO,
+    }
+
+    public class Config : GLib.Object {
         
-        private Settings settings = new Settings("com.liyaowhen.Song");
+        private static Config? instance = null;
+        private static string config_file_path;
+        private Json.Object? json_config;
 
-        public class JsonConfig () {
+        public List<PlaylistObject> playlists;
-            var json_text = settings.get_string("songs");
+        public signal void config_changed();
 
-            var parser = new Json.Parser();
+        public static Config get_instance() {
-            try {
+            if (instance == null) {
-                parser.load_from_data (json_text, json_text.length);
+                instance = new Config();
-            } catch (GLib.Error e) {
-                print(e.message);
             }
-            
+            return instance;
+        }
 
+        private Config() {
+            playlists = new List<PlaylistObject>();
+            load();
+        }
+        
+        private async void load() {
+            print("load");
+            File config_file = File.new_for_path(config_file_path);
+            if (config_file.query_exists(null)) {
+                try {
+                    DataInputStream dis = new DataInputStream(config_file.read(null));
+                    
+                    size_t length;
+                    string? content = dis.read_until("", out length, null);
+                    if (content != null) {
+                        Json.Parser parser = new Json.Parser();
+
+                        try {
+                            parser.load_from_file(config_file.get_path());
+                        } catch (GLib.Error e) {
+                            print(e.message);
+                        }
+                        print("\n" + config_file.get_path() + "\n");
+
+                        Json.Node root = parser.get_root();
+                        json_config = root.get_object();
+                        
+                        print(json_config.get_size().to_string());
+    
+                        // Parse settings from JSON
+                        if (json_config.has_member("playlists")) {
+                            Json.Object _playlists = json_config.get_object_member("playlists");
+                            _playlists.foreach_member((object) => {
+                                PlaylistObject _playList = new PlaylistObject();
+
+                                _playList.name = object.get_string_member("name");
+                                // TODO: ADD PROPERTIES _playList.properties = whatever
+                                object.get_object_member("items").foreach_member((item) => {
+                                    PlaylistItem _item = new PlaylistItem();
+                                    _item.item_type = item.get_int_member("item_type");
+                                    _item.name = item.get_string_member("name");
+                                    _item.file = item.get_string_member("file");
+
+                                    if (item.has_member("picture")) {
+                                        _item.picture = item.get_string_member("picture");
+                                    }
+                                    if (item.has_member("source")) {
+                                        _item.picture = item.get_string_member("source");
+                                    }
+                                    _playList.items.append(_item);
+                                });
+                                playlists.append(_playList);
+                            });
+                        }
+                    }
+
+
+                } catch (Error e) {
+                    print("Error reading configuration file: %s\n", e.message);
+                }
+            }
+        }
+    
+        // Save configuration to file
+        public async void save() {
+            print("save");
+            try {
+                Json.Builder builder = new Json.Builder();
+
+                // initialize the root "{}"
+                builder.begin_object();
+
+                // playlists
+                    builder.set_member_name("playlists");
+                    builder.begin_object();
+
+                    foreach (PlaylistObject item in playlists) {
+                        builder.set_member_name(item.name);
+                        builder.begin_object();
+
+                        // name
+                        builder.set_member_name("name");
+                        builder.add_string_value(item.name);
+
+                        // properties
+                        builder.set_member_name("properties");
+                        builder.begin_object();
+                        builder.end_object();
+
+                        // items
+                        builder.set_member_name("items");
+                        builder.begin_object();
+
+                        // foreach item
+                        item.items.foreach((e) => {
+                            builder.set_member_name(e.name);
+                            builder.begin_object();
+
+                            builder.set_member_name("name");
+                            builder.add_string_value("name");
+
+                            builder.set_member_name("item_type");
+                            builder.add_int_value(e.item_type);
+
+                            builder.set_member_name("file");
+                            builder.add_string_value(e.file);
+
+                            if (e.source != null) {
+                                builder.set_member_name("source");
+                                builder.add_string_value(e.source);
+                            }
+
+                            if (e.picture != null) {
+                                builder.set_member_name("picture");
+                                builder.add_string_value(e.picture);
+                            }
+
+                            builder.end_object();
+                        });
+
+                        // items end
+                        builder.end_object();
+
+                        builder.end_object();
+                    }
+
+                    
+                    builder.end_object();
+
+                builder.end_object();
+    
+                Json.Generator generator = new Json.Generator();
+                generator.set_root(builder.get_root());
+                generator.to_file(config_file_path);
+                print("Configuration saved to %s\n", config_file_path);
+            } catch (Error e) {
+                print("Error saving configuration file: %s\n", e.message);
+            }
+            config_changed();
+        }
+
+        public static void init(string app_name) {
+            string config_dir = Environment.get_user_config_dir();
+            string app_config_dir = Path.build_filename(config_dir, app_name);
+            config_file_path = Path.build_filename(app_config_dir, "config.json");
+
+            File app_dir = File.new_for_path(app_config_dir);
+            if (!app_dir.query_exists(null)) {
+                print("directory never existed");
+                try {
+                    app_dir.make_directory_with_parents(null);
+                    print("Created directory: %s\n", app_config_dir);
+                } catch (Error e) {
+                    print("Error creating directory: %s\n", e.message);
+                }
+            }
+
+            File config_file = File.new_for_path(config_file_path);
+            if (!config_file.query_exists(null)) {
+                print("file never existed");
+                Config.get_instance().save(); // Create the file with default values
+            }
         }
     }
 } 

src/main.vala

@@ -20,6 +20,17 @@
 
 int main (string[] args) {
     Gst.init(ref args);
+
+    Song.Config.init("com.liyaowhen.Song");
+    var config = Song.Config.get_instance ();
+
+    Song.PlaylistObject playlist = new Song.PlaylistObject();
+    playlist.name = "QQ";
+    playlist.add_item(Song.PlaylistItem.load_item(Song.ItemType.AUDIO, "aaa", "eee"));
+
+    config.playlists.append(playlist);
+    config.save();
+
     var app = new Song.Application ();
     return app.run (args);
 }

src/meson.build

@@ -9,14 +9,15 @@ song_sources = [
   'widgets/playlist.vala',
   'controllers/song_controller.vala',
   'widgets/music_list_row.vala',
-  'widgets/song_controls.vala'
+  'widgets/song_controls.vala',
+  'playlist_object.vala'
 ]
 
 song_deps = [
   dependency('gtk4'),
   dependency('libadwaita-1', version: '>= 1.4'),
   dependency('vte-2.91-gtk4'),
-  dependency('jsonrpc-glib-1.0'),
+  dependency('json-glib-1.0'),
   dependency('gstreamer-1.0'),
 ]
 

src/playlist_object.vala

@@ -0,0 +1,29 @@
+namespace Song {
+
+    public class PlaylistObject : Object {
+
+        public string name;
+        public List<PlaylistItem> items; //videos or songs
+
+        public void add_item(PlaylistItem item) {
+            items.append(item);
+        }
+    }
+
+    public class PlaylistItem : Object {
+        public ItemType item_type;
+        public string name;
+        public string? source = null; // null when the source is local
+        public string file;
+        public string? picture = null; // null when the item has no picture
+
+        public static PlaylistItem load_item(ItemType item_type, string file, string picture) {
+            PlaylistItem item = new PlaylistItem();
+            item.item_type = item_type;
+            item.file = file;
+            item.picture = picture;
+
+            return item;
+        }
+    }
+}