build available theme list dynamically

app/__init__.py

@@ -83,6 +83,18 @@ def create_app():
     app.config['MAX_CONTENT_LENGTH'] = 1000 * 1000
 
     os.makedirs(os.path.dirname(app.config["DB_PATH"]), exist_ok = True)
+
+    css_dir = 'data/static/css/'
+    allowed_themes = []
+    for f in os.listdir(css_dir):
+        if not os.path.isfile(os.path.join(css_dir, f)):
+            continue
+        theme_name = os.path.splitext(os.path.basename(f))[0]
+        allowed_themes.append(theme_name)
+
+    allowed_themes.sort(key=(lambda x: (x != 'style', x)))
+    app.config['allowed_themes'] = allowed_themes
+
     with app.app_context():
         from .schema import create as create_tables
         from .migrations import run_migrations
@@ -179,4 +191,11 @@ def create_app():
     def cachebust(subject):
         return f"{subject}?v={str(int(time.time()))}"
 
+    @app.template_filter('theme_name')
+    def get_theme_name(subject: str):
+        if subject == 'style':
+            return 'Default'
+
+        return f'{subject.removeprefix('theme-').capitalize()} (beta)'
+
     return app

app/routes/users.py

@@ -169,6 +169,9 @@ def get_prefers_theme():
     if not 'theme' in session:
         return 'style'
 
+    if session['theme'] not in current_app.config['allowed_themes']:
+        return 'style'
+
     return session['theme']
 
 @bp.get("/log_in")
@@ -294,8 +297,8 @@ def settings_form(username):
     # we silently ignore the passed username
     # and grab the correct user from the session
     user = get_active_user()
-    theme = request.form.get('theme', default='default')
-    if theme == 'default':
+    theme = request.form.get('theme', default='style')
+    if theme == 'style':
         if 'theme' in session:
             session.pop('theme')
     else:

app/templates/users/settings.html

@@ -17,8 +17,9 @@
   <form method='post'>
     <label for='theme'>Theme (beta)</label>
     <select autocomplete='off' id='theme' name='theme'>
-      <option value='default' {{ 'selected' if get_prefers_theme() == 'style' }}>Default</option>
-      <option value='theme-otomotone' {{ 'selected' if get_prefers_theme() == 'theme-otomotone' }}>Otomotone (beta)</option>
+      {% for theme in config.allowed_themes %}
+        <option value="{{ theme }}" {{ 'selected' if get_prefers_theme() == theme }}>{{ theme | theme_name }}</option>
+      {% endfor %}
     </select>
     <label for='topic_sort_by'>Sort threads by:</label>
     <select id='topic_sort_by' name='topic_sort_by'>