Start work on themes kitten

kittens/themes/collection.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2021, Kovid Goyal <kovid at kovidgoyal.net>
+
+import datetime
+import http
+import json
+import os
+import shutil
+import zipfile
+from contextlib import suppress
+from urllib.error import HTTPError
+from urllib.request import Request, urlopen
+
+from kitty.constants import cache_dir
+
+
+def fetch_themes(
+    name: str = 'kitty-themes',
+    url: str = 'https://codeload.github.com/kovidgoyal/kitty-themes/zip/master'
+) -> str:
+    now = datetime.datetime.now(datetime.timezone.utc)
+
+    class Metadata:
+        def __init__(self) -> None:
+            self.etag = ''
+            self.timestamp = now
+
+    dest_path = os.path.join(cache_dir(), f'{name}.zip')
+    m = Metadata()
+    with suppress(Exception), zipfile.ZipFile(dest_path, 'r') as zf:
+        q = json.loads(zf.comment)
+        m.etag = str(q.get('etag') or '')
+        m.timestamp = datetime.datetime.fromisoformat(q['timestamp'])
+        if (now - m.timestamp).days < 1:
+            return dest_path
+    rq = Request(url)
+    if m.etag:
+        rq.add_header('If-None-Match', m.etag)
+    try:
+        res = urlopen(rq)
+    except HTTPError as e:
+        if m.etag and e.code == http.HTTPStatus.NOT_MODIFIED:
+            return dest_path
+        raise
+    m.etag = res.headers.get('etag') or ''
+    with open(dest_path, 'wb') as f:
+        shutil.copyfileobj(res, f)
+    with zipfile.ZipFile(dest_path, 'a') as zf:
+        zf.comment = json.dumps({'etag': m.etag, 'timestamp': m.timestamp.isoformat()}).encode('utf-8')
+    return dest_path