Add Reddit video support

Reddit links now download and post like the other platforms.

Two changes were needed, not just the URL pattern:

- Regex: yt-dlp's Reddit extractor only matches /comments/ permalinks, so
  the app's /r/<sub>/s/<code> share links and redd.it / v.redd.it
  shortlinks are listed explicitly — they redirect to the canonical URL,
  which yt-dlp follows. Without them the link is silently dropped.

- Format selector: Reddit publishes video and audio as separate DASH/HLS
  streams with no muxed rendition, so every `best...` term failed and
  yt-dlp aborted with "Requested format is not available". Added a
  bv*+ba merge tail (and a bare bv* for silent videos) to the normal and
  /force selectors. Muxed hosts still resolve at the earlier terms, so
  YouTube/IG/TikTok/X selection is unchanged.

Posts with no video report "No media found", already in the silent list,
so ordinary Reddit links shared in chat draw no reply.

README.md

@@ -1,8 +1,8 @@
 # signal-bot
 
 A Signal group-chat bot that grabs videos from links people post (X/Twitter,
-Instagram, YouTube, TikTok) and posts them back into the chat, plus a couple of
+Instagram, YouTube, TikTok, Reddit) and posts them back into the chat, plus a
-toys for messing with the last video.
+couple of toys for messing with the last video.
 
 ## What it does
 
@@ -16,7 +16,9 @@ toys for messing with the last video.
   to refresh Instagram auth without touching the server.
 
 Supported links: `x.com` / `twitter.com` (and `fxtwitter`/`vxtwitter`/`fixupx`
-wrappers), `instagram.com/reel|p`, `youtube.com` / `youtu.be` / Shorts, and TikTok.
+wrappers), `instagram.com/reel|p`, `youtube.com` / `youtu.be` / Shorts, TikTok,
+and Reddit (`/comments/` permalinks, `/s/` app share links, `redd.it` and
+`v.redd.it` shortlinks). Reddit posts with no video stay silent.
 
 ## How it's wired
 

bot.py

@@ -30,7 +30,19 @@ TWITTER_URL_PATTERN = r"https?://(?:www\.)?(?:twitter\.com|x\.com|fxtwitter\.com
 INSTAGRAM_URL_PATTERN = r"https?://(?:www\.)?instagram\.com/(?:share/)?(?:reels?|p|tv)/[\w-]+"
 YOUTUBE_URL_PATTERN = r"https?://(?:www\.)?(?:youtube\.com/(?:watch\?v=|shorts/)|youtu\.be/)[\w-]+"
 TIKTOK_URL_PATTERN = r"https?://(?:(?:www|m)\.tiktok\.com/(?:@[\w.-]+/video/\d+|t/\w+|v/\d+)|(?:vm|vt)\.tiktok\.com/\w+)"
-VIDEO_URL_PATTERN = rf"(?:{TWITTER_URL_PATTERN}|{INSTAGRAM_URL_PATTERN}|{YOUTUBE_URL_PATTERN}|{TIKTOK_URL_PATTERN})"
+# Reddit's canonical form is /r/<sub>/comments/<id>/<slug>, but the mobile share
+# sheet emits /r/<sub>/s/<code> and older shares use redd.it/<id>; both are plain
+# redirects to the canonical URL, which yt-dlp follows. v.redd.it/<id> is the bare
+# media host. Any subdomain (www/old/new/np/m) is valid. yt-dlp's own extractor
+# only matches the /comments/ form, so the redirecting shapes must be listed here
+# explicitly or the link is silently dropped (regex never matches -> no download,
+# no error reply). Most Reddit links carry no video at all; the extractor reports
+# "No media found" for those, which _NO_MEDIA_ERROR_PATTERNS already keeps quiet.
+REDDIT_URL_PATTERN = (
+    r"https?://(?:(?:\w+\.)?reddit\.com/(?:(?:r|user|u)/[^/\s]+/)?(?:comments|s)/[\w-]+"
+    r"|(?:v\.)?redd\.it/[\w-]+)"
+)
+VIDEO_URL_PATTERN = rf"(?:{TWITTER_URL_PATTERN}|{INSTAGRAM_URL_PATTERN}|{YOUTUBE_URL_PATTERN}|{TIKTOK_URL_PATTERN}|{REDDIT_URL_PATTERN})"
 MAX_FILE_SIZE = 100 * 1024 * 1024  # 100 MB
 CLIP_DURATION = 60  # default seconds to grab around a shared ?t= timestamp
 MAX_CLIP_DURATION = 600  # ceiling for a user-supplied /clip override
@@ -543,8 +555,15 @@ def _run_ytdlp(url: str, outpath: str, tmpdir: str,
         # Prefer the largest mp4 that already fits under 95 MB, so we avoid
         # re-encoding when a smaller variant exists (e.g. a 4K rendition
         # >100 MB alongside a 1080p ~50 MB).
+        # The bv*+ba tail is required for hosts that never publish a muxed
+        # rendition — Reddit serves video and audio as separate DASH/HLS
+        # streams, so every `best...` term above fails and yt-dlp aborts with
+        # "Requested format is not available" unless we merge them ourselves.
+        # The bare bv* last resort covers silent videos (no audio to merge).
         cmd += [
-            "-f", "best[ext=mp4][filesize<95M]/best[ext=mp4][filesize_approx<95M]/best[ext=mp4]/best",
+            "-f",
+            "best[ext=mp4][filesize<95M]/best[ext=mp4][filesize_approx<95M]/best[ext=mp4]/best"
+            "/bv*[filesize<95M]+ba/bv*[filesize_approx<95M]+ba/bv*+ba/bv*",
         ]
     cmd += [
         "--merge-output-format", "mp4",
@@ -704,7 +723,8 @@ def _force_download_and_publish(url: str, token: str) -> tuple[str | None, int |
         cmd = [
             *_NICE,
             YTDLP, "--no-playlist", "--no-warnings", "--js-runtimes", JS_RUNTIME,
-            "-f", "best[ext=mp4]/best", "--merge-output-format", "mp4",
+            # bv*+ba tail: split-stream hosts (Reddit) have no muxed rendition.
+            "-f", "best[ext=mp4]/best/bv*+ba/bv*", "--merge-output-format", "mp4",
             "--max-filesize", FORCE_MAX_FILESIZE,
             *_cookie_args(url),
             "-o", os.path.join(tokdir, "video.%(ext)s"),
@@ -1109,7 +1129,7 @@ class ForceCommand(Command):
 
 HELP_TEXT = f"""🎬 Video bot — what I can do
 
-Share a video link (X/Twitter, Instagram, YouTube, TikTok) and I'll post the video back to the group.
+Share a video link (X/Twitter, Instagram, YouTube, TikTok, Reddit) and I'll post the video back to the group.
   e.g.  https://x.com/user/status/123456789
 
 A YouTube link with a timestamp → I post a {CLIP_DURATION}s clip starting at that moment.