Add option for showing bookmark favicons (#390)

* Implement favicon loader

* Implement load favicon task

* Show favicons in bookmark list

* Add missing migration

* Load missing favicons on import

* Automatically refresh favicons

* Add enable favicon setting

* Update uwsgi config to host favicons

* Improve settings wording

* Fix favicon loader test setup

* Document LD_FAVICON_PROVIDER setting

* Add refresh favicons button

bookmarks/services/favicon_loader.py

@@ -0,0 +1,57 @@
+import os.path
+import re
+import shutil
+import time
+from pathlib import Path
+from urllib.parse import urlparse
+
+import requests
+from django.conf import settings
+
+max_file_age = 60 * 60 * 24  # 1 day
+
+
+def _ensure_favicon_folder():
+    Path(settings.LD_FAVICON_FOLDER).mkdir(parents=True, exist_ok=True)
+
+
+def _url_to_filename(url: str) -> str:
+    name = re.sub(r'\W+', '_', url)
+    return f'{name}.png'
+
+
+def _get_base_url(url: str) -> str:
+    parsed_uri = urlparse(url)
+    return f'{parsed_uri.scheme}://{parsed_uri.hostname}'
+
+
+def _get_favicon_path(favicon_file: str) -> Path:
+    return Path(os.path.join(settings.LD_FAVICON_FOLDER, favicon_file))
+
+
+def _is_stale(path: Path) -> bool:
+    stat = path.stat()
+    file_age = time.time() - stat.st_mtime
+    return file_age >= max_file_age
+
+
+def load_favicon(url: str) -> str:
+    # Get base URL so that we can reuse favicons for multiple bookmarks with the same host
+    base_url = _get_base_url(url)
+    favicon_name = _url_to_filename(base_url)
+    favicon_path = _get_favicon_path(favicon_name)
+
+    # Load icon if it doesn't exist yet or has become stale
+    if not favicon_path.exists() or _is_stale(favicon_path):
+        # Create favicon folder if not exists
+        _ensure_favicon_folder()
+        # Load favicon from provider, save to file
+        favicon_url = settings.LD_FAVICON_PROVIDER.format(url=base_url)
+        response = requests.get(favicon_url, stream=True)
+
+        with open(favicon_path, 'wb') as file:
+            shutil.copyfileobj(response.raw, file)
+
+        del response
+
+    return favicon_name