spotify: update fetching to current Web API

- OAuth: URL-encode authorize params (scope spaces were unencoded),
  bind loopback redirect server to 127.0.0.1 to match the redirect_uri
  per Spotify's 2025 loopback rules, capture refresh_token.
- Search: URL-encode the query and drop the bogus track=1 param.
- Pagination: follow the paging object's `next` field instead of manual
  offset/total bookkeeping (Spotify's recommended approach).
- Fix invalid `raise "string"` in save_image_from_url.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/backends/spotify/SpotifyAuthenticator.py

@@ -11,6 +11,7 @@ import os.path
 client_id = None
 client_secret = None
 token = None
+refresh_token = None
 
 
 def retrieve_web_api_token(authorization_code):
@@ -44,7 +45,10 @@ def retrieve_web_api_token(authorization_code):
         print(token_response.json())
         raise ValueError
 
-    token = token_response.json()['access_token']
+    global refresh_token
+    response_json = token_response.json()
+    token = response_json['access_token']
+    refresh_token = response_json.get('refresh_token')
 
 
 class RequestHandler(BaseHTTPRequestHandler):
@@ -73,7 +77,7 @@ class RequestHandler(BaseHTTPRequestHandler):
 
 
 def run_redirect_server():
-    httpd = HTTPServer(('localhost', 8888), RequestHandler)
+    httpd = HTTPServer(('127.0.0.1', 8888), RequestHandler)
     print('Starting HTTP redirection server')
     httpd.serve_forever()
 
@@ -88,8 +92,9 @@ def open_authenticate_page():
         "scope": "user-top-read playlist-read-collaborative user-read-email user-library-read user-read-private playlist-read-private",
     }
 
-    auth_url = f"{authorize_url}?client_id={params['client_id']}&response_type={params['response_type']}&redirect_uri={params['redirect_uri']}&scope={params['scope']}"
+    auth_url = f"{authorize_url}?{urllib.parse.urlencode(params)}"
     webbrowser.open(auth_url)
+    print(f"If the browser did not open, visit:\n{auth_url}")
 
 
 def authenticate(id, secret):

src/backends/spotify/SpotifyWebAPI.py

@@ -1,4 +1,5 @@
 import requests
+import urllib.parse
 from PIL import Image
 from io import BytesIO
 
@@ -11,7 +12,7 @@ token = ''
 
 
 def fetch(endpoint, method='GET', body=None):
-    url = f'https://api.spotify.com/{endpoint}'
+    url = endpoint if endpoint.startswith('http') else f'https://api.spotify.com/{endpoint}'
     headers = {
         'Authorization': f'Bearer {token}',
     }
@@ -21,83 +22,52 @@ def fetch(endpoint, method='GET', body=None):
     return response.json()
 
 
+def fetch_paginated(endpoint):
+    """Collect every item of a paging object by following its `next` field,
+    which is Spotify's recommended way to page (more robust than tracking
+    offset/total manually)."""
+    items = []
+    page = fetch(endpoint)
+    while True:
+        items += page.get('items', [])
+        next_url = page.get('next')
+        if not next_url:
+            break
+        page = fetch(next_url)
+    return items
+
+
 def find_song(song_pattern):
-    return fetch(f"v1/search/?type=track&track=1&q={song_pattern}")['tracks']['items']
+    query = urllib.parse.quote(song_pattern)
+    return fetch(f"v1/search?type=track&limit=10&q={query}")['tracks']['items']
 
 
 def fetch_playlists(user_id):
     print("Fetching playlists")
-    endpoint = f"v1/me/playlists"
-    pl_total = fetch(f'{endpoint}?limit=1')['total']
-    pl_count = 0
-    playlists = []
-
-    while pl_count < pl_total:
-        res = fetch(f'{endpoint}?limit={FETCH_STEP}&offset={pl_count}')
-        playlists += res['items']
-        pl_count += FETCH_STEP
-
-    return playlists
+    return fetch_paginated(f"v1/me/playlists?limit={FETCH_STEP}")
 
 
 def fetch_playlist_items(playlist_id):
-    endpoint = f"v1/playlists/{playlist_id}/tracks"
-    items = fetch(f'{endpoint}?fields=total')['total']
-    loaded = 0
-    tracks = []
-
-    while loaded < items:
-        res = fetch(f'{endpoint}?limit={FETCH_STEP}&offset={loaded}')
-        
-        tracks += res['items']
-        loaded += FETCH_STEP
-
-    return tracks
+    return fetch_paginated(f"v1/playlists/{playlist_id}/tracks?limit={FETCH_STEP}")
 
 
 def fetch_tracks(user_id):
     print("Fetching tracks")
-    endpoint = f"v1/me/tracks"
-    total = fetch(f"{endpoint}?limit=1&market=ES")['total']
-    current = 0
-    tracks = []
-
-    while total > current:
-        res = fetch(f"{endpoint}?limit={FETCH_STEP}&offset={current}&market=ES")
-        tracks += res['items']
-        current += FETCH_STEP
-
+    tracks = fetch_paginated(f"v1/me/tracks?limit={FETCH_STEP}&market=ES")
     save_data(tracks, "tracks")
     return tracks
 
 
 def fetch_tracks_top():
     print("Fetching top tracks")
-    total = fetch(f'v1/me/top/tracks?fields=total')['total']
-    current = 0
-    tracks = []
-
-    while current < total:
-        res = fetch(f'v1/me/top/tracks?limit={FETCH_STEP}&offset={current}&time_range=long_term')
-        tracks += res['items']
-        current += FETCH_STEP
-
+    tracks = fetch_paginated(f"v1/me/top/tracks?limit={FETCH_STEP}&time_range=long_term")
     save_data(tracks, "top_tracks")
     return tracks
 
 
 def fetch_artists_top():
     print("Fetching top artists")
-
-    total = fetch(f'v1/me/top/artists?fields=total')['total']
-    current = 0
-    artists = []
-
-    while current < total:
-        res = fetch(f'v1/me/top/artists?limit={FETCH_STEP}&offset={current}&time_range=long_term')
-        artists += res['items']
-        current += FETCH_STEP
-
+    artists = fetch_paginated(f"v1/me/top/artists?limit={FETCH_STEP}&time_range=long_term")
     save_data(artists, "top_artists")
     return artists
 
@@ -140,7 +110,7 @@ def save_image_from_url(url, name, image_dir="playlist_covers"):
     response = requests.get(url)
 
     if response.status_code != 200:
-        raise "Cannot fetch the playlist cover"
+        raise RuntimeError("Cannot fetch the playlist cover")
 
     image = Image.open(BytesIO(response.content))