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ksmithandClaude Sonnet 5
760d2cf5dd
Slack/Discord-style link unfurling: the first http(s) URL in a message's content gets a small preview card (title/description/image/site name) fetched from the page's Open Graph tags. Backend: - Message.preview_url (extracted at create/edit time, cheap regex, no I/O) points at a link_previews cache row keyed by URL -- the same URL posted in different messages/rooms fetches once, and a failed fetch is cached too so a dead URL isn't retried on every reference. - The actual fetch runs in a background asyncio.create_task from broadcast_new_message/broadcast_message_update, on its own DB session, so a slow third-party site never delays message delivery. A separate "link_preview" WS envelope carries the result once it resolves. - SSRF protection reuses app/services/ssrf.py's validate_target_url (renamed from UnsafeWebhookUrlError to UnsafeUrlError now that it's shared with webhooks), but re-validates before every hop of a redirect chain rather than once up front -- redirects are followed manually so each intermediate URL is checked before it's ever connected to. - Parsed with stdlib html.parser -- no new dependency. Frontend: a LinkPreviewCard rendered under message content when present, patched into state live via the new WS envelope and included in message history for reloads. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
33 lines
1.5 KiB
Python
33 lines
1.5 KiB
Python
import uuid
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from datetime import datetime
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from sqlalchemy import Boolean, DateTime, String, func
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from sqlalchemy.orm import Mapped, mapped_column
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from app.models.base import Base
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class LinkPreview(Base):
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"""A cache keyed by URL, not by message -- multiple messages (in the
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same room or different ones) linking the same URL share one fetch
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instead of each triggering their own. link_preview_service is the only
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writer; Message.preview_url (the first URL found in a message's
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content, set at creation time) is the join key a caller looks this up
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by."""
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__tablename__ = "link_previews"
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id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
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url: Mapped[str] = mapped_column(String(2048), unique=True, index=True, nullable=False)
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title: Mapped[str | None] = mapped_column(String(500))
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description: Mapped[str | None] = mapped_column(String(1000))
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image_url: Mapped[str | None] = mapped_column(String(2048))
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site_name: Mapped[str | None] = mapped_column(String(200))
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# Cached separately from a "no row yet" state so a URL that genuinely
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# doesn't unfurl (no title, fetch error, blocked by SSRF checks) isn't
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# re-fetched on every message that references it within the TTL.
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fetch_failed: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
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fetched_at: Mapped[datetime] = mapped_column(
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DateTime(timezone=True), server_default=func.clock_timestamp(), nullable=False
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)
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