peter
40acf104a1
The iPad Messenger app unfurls a share link on-device (fetches + renders the OG tags itself), but messenger.com desktop shows only what Facebook's server-side scraper cached — which is pickier. Add og:image:secure_url (public HTTPS) and og:image:type=image/jpeg for our poster so the card renders even when the scraper won't sniff the bytes. Reachability/stale-cache is a separate, live-diagnosis step.
100 lines
4.5 KiB
Python
100 lines
4.5 KiB
Python
"""Server-rendered Open Graph tags for the public /watch/{token} page.
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The watch page is a client-side SPA, so a social crawler (facebookexternalhit, Twitterbot, …) that
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fetches /watch/{token} would otherwise only see the generic index.html — a blank/greyed link card.
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This injects per-video OG/Twitter tags into the served HTML so a shared link unfurls with the
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video's title, channel and thumbnail. Real browsers ignore the extra tags and hydrate the SPA as
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usual. Password-protected / expired / invalid links fall back to the generic card (no metadata leak).
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"""
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import html
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import re
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from pathlib import Path
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from sqlalchemy import select
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from sqlalchemy.orm import Session
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from app.config import settings
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from app.downloads import links as linksmod
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from app.models import DownloadJob, DownloadLink, MediaAsset
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_OG_BLOCK = re.compile(r"<!--OG:START-->.*?<!--OG:END-->", re.DOTALL)
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def _tag(prop: str, content: str, attr: str = "property") -> str:
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return f'<meta {attr}="{prop}" content="{html.escape(content, quote=True)}" />'
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def _watch_tags(token: str, db: Session) -> str | None:
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"""Build the OG/Twitter meta block for a watch token, or None to keep the generic card."""
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link = db.execute(
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select(DownloadLink).where(DownloadLink.token == token)
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).scalar_one_or_none()
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if link is None or linksmod.is_expired(link):
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return None
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url = f"{settings.app_base}/watch/{token}"
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if link.password_hash:
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# Password-gated: don't leak the title/thumbnail in the unfurl.
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return "\n ".join(
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[
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"<title>Siftlode</title>",
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_tag("og:title", "Password-protected video"),
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_tag("og:description", "Shared via Siftlode"),
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_tag("og:type", "video.other"),
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_tag("og:url", url),
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_tag("og:site_name", "Siftlode"),
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]
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)
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job = db.get(DownloadJob, link.job_id)
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asset = db.get(MediaAsset, job.asset_id) if job and job.asset_id else None
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if job is None or asset is None or asset.status != "ready":
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return None
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title = (job.display_name or asset.title or "Video").strip()
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channel = (job.display_uploader or asset.uploader or "").strip()
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# Prefer our self-hosted poster for the link-preview image: a remote thumbnail (Facebook's
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# signed CDN URL especially) expires and isn't reliably fetchable cross-origin by the crawler.
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# (This block only runs for non-password links, so the poster needs no grant.) Fall back to the
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# remote thumbnail only if we somehow have no poster.
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image = (
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f"{settings.app_base}/api/public/watch/{token}/poster.jpg"
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if asset.poster_path
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else asset.thumbnail_url
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)
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tags = [
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f"<title>{html.escape(title)}</title>",
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_tag("og:title", title),
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_tag("og:description", channel or "Shared via Siftlode"),
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_tag("og:type", "video.other"),
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_tag("og:url", url),
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_tag("og:site_name", "Siftlode"),
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_tag("twitter:title", title, attr="name"),
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]
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if channel:
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tags.append(_tag("twitter:description", channel, attr="name"))
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if image:
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# A real thumbnail → a large image card; without one, a plain (text) card is served.
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tags.append(_tag("og:image", image))
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# Facebook's scraper is pickier than Apple's on-device unfurl: spell out that the image is a
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# public HTTPS JPEG so it renders the card even when it won't fetch/sniff the bytes itself.
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if image.startswith("https://"):
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tags.append(_tag("og:image:secure_url", image))
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if image.endswith("poster.jpg"):
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tags.append(_tag("og:image:type", "image/jpeg"))
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tags.append(_tag("twitter:card", "summary_large_image", attr="name"))
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tags.append(_tag("twitter:image", image, attr="name"))
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else:
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tags.append(_tag("twitter:card", "summary", attr="name"))
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return "\n ".join(tags)
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def render_watch_html(token: str, index_html: Path, db: Session) -> str | None:
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"""Return index.html with the OG block replaced for this watch token, or None to serve the
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generic page unchanged (invalid/expired/not-ready link, or a template without the markers)."""
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tags = _watch_tags(token, db)
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if tags is None:
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return None
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text = index_html.read_text(encoding="utf-8")
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if "<!--OG:START-->" not in text:
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return None
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# A function replacement avoids re.sub interpreting backslashes/group refs in `tags`.
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return _OG_BLOCK.sub(lambda _m: tags, text, count=1)
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