Restructure: Make serve a level 4 subsection

README.md

@@ -2,10 +2,11 @@
 
 Tools to manage an UltraStar DX song library. Features include:
 
-1. Deduplication
-2. Organization
-3. Recoding
-4. Jsonification
+1. Web-based catalogue UI
+2. Deduplication
+3. Organization
+4. Recoding
+5. Jsonification
 
 ## Setup
 
@@ -23,6 +24,22 @@ We assume that your song library is stored at `$SONG_LIBRARY`. Replace this plac
 export SONG_LIBRARY=/path/to/library
 ```
 
+### Web-based catalogue UI
+
+**A web-based UI to browse the song library.** It supports searching by title and artist, and allows to mark and unmark favorites on the client side (using local storage).
+
+#### Serve
+
+**Launch a server for the catalogue UI** on localhost. Mostly useful for development purposes.
+
+ℹ️ This is completely risk-free, as it does not change files.
+
+```bash
+python3 -m karaokatalog.ui.serve $SONG_LIBRARY
+```
+
+To speed up the start, use jsonification to create and persist a JSON of all songs in the library root dir before starting this UI.
+
 ### Deduplication
 
 **Find and delete exactly duplicated songs**, i.e., songs with the same title and artist that also consist of exactly the same files in the directory.

karaokatalog/ui/serve/__main__.py

@@ -0,0 +1,32 @@
+import json
+import logging
+
+from karaokatalog.get_parser import get_parser
+from karaokatalog.Library import Library
+from karaokatalog.ui.serve.get_flask_app import get_flask_app
+
+logging.basicConfig(
+    format="%(asctime)s [%(levelname)s] %(message)s", level=logging.INFO
+)
+
+
+if __name__ == "__main__":
+    args = get_parser(
+        "ui.serve", "Serve a web UI to browse the Karaokatalog"
+    ).parse_args()
+
+    songs_json_path = args.library_path / "songs.json"
+
+    if songs_json_path.exists():
+        logging.info(f"Loading {songs_json_path}")
+        with songs_json_path.open("r", encoding="utf-8") as f:
+            songs = json.load(f)
+    else:
+        logging.info("Loading library")
+        library = Library.from_dir(args.library_path)
+        logging.info("Library loaded")
+        songs = [song.as_dict() for song in library.songs]
+
+    logging.info("Starting UI")
+    app = get_flask_app(songs)
+    app.run(port=5657)

karaokatalog/ui/serve/get_flask_app.py

@@ -0,0 +1,20 @@
+from collections.abc import Sequence
+
+from flask import Flask, Response
+
+
+def get_flask_app(songs: Sequence[dict[str, str]]) -> Flask:
+    app = Flask("karaokatalog.ui", static_url_path="/")
+
+    # This is only to make the type checker happy.
+    songs_list = list(songs)
+
+    @app.get("/songs.json")
+    def get_songs() -> list[dict[str, str]]:
+        return songs_list
+
+    @app.get("/")
+    def get_index() -> Response:
+        return app.send_static_file("index.html")
+
+    return app