Add URL previews for chat messages (#43)

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>
2026-08-17 17:50:55 -06:00
parent 752da74c5a
commit 760d2cf5dd
18 changed files with 835 additions and 21 deletions
@@ -0,0 +1,266 @@
+import asyncio
+import uuid
+
+import pytest_asyncio
+
+from app.database import engine as _link_preview_engine
+from app.schemas.user import UserCreate
+from app.services.auth_service import register_user
+from app.services.link_preview_service import extract_first_url
+from tests.conftest import register_and_login
+
+
+@pytest_asyncio.fixture(autouse=True)
+async def _dispose_engine_between_tests():
+    # link_preview_service's background task uses app.database's module-
+    # level engine directly (see test_cli.py's identical fixture for why:
+    # pytest-asyncio's per-test event loops make a stale pooled connection
+    # from an earlier test's loop fail with asyncpg "another operation is
+    # in progress" -- silently, in this file's case, since
+    # fetch_and_broadcast_link_preview catches and logs rather than raises).
+    yield
+    await _link_preview_engine.dispose()
+
+
+def _unique(prefix: str) -> str:
+    return f"{prefix}-{uuid.uuid4().hex[:8]}"
+
+
+def _unique_url() -> str:
+    # link_previews rows are written via the background task's own,
+    # separately-committed DB session (see link_preview_service.py), not
+    # the db_session fixture's rollback-at-teardown transaction -- they're
+    # real, permanent rows that persist across test runs. A literal URL
+    # shared between tests (or repeated suite runs) would silently hit an
+    # earlier run's cached row instead of exercising a fresh fetch.
+    return f"http://8.8.8.8/{uuid.uuid4().hex}"
+
+
+def _recv(ws) -> dict:
+    """Reads the next frame, discarding member_updated presence-change
+    broadcasts -- same convention as test_message_edit.py."""
+    while True:
+        msg = ws.receive_json()
+        if msg.get("type") != "member_updated":
+            return msg
+
+
+def _register_ws(ws_client, username: str) -> dict:
+    async def _seed():
+        async with ws_client.session_factory() as session:
+            await register_user(
+                session,
+                UserCreate(username=username, email=f"{username}@example.com", password="password123"),
+            )
+
+    ws_client.portal.call(_seed)
+    resp = ws_client.post(
+        "/api/auth/login", json={"username_or_email": username, "password": "password123"}
+    )
+    assert resp.status_code == 200, resp.text
+    return resp.json()
+
+
+class _FakeResponse:
+    def __init__(self, status_code=200, headers=None, body=b""):
+        self.status_code = status_code
+        self.headers = headers or {}
+        self.is_redirect = status_code in (301, 302, 303, 307, 308)
+        self._body = body
+
+    async def aiter_bytes(self):
+        yield self._body
+
+
+class _FakeStreamCtx:
+    def __init__(self, response):
+        self._response = response
+
+    async def __aenter__(self):
+        return self._response
+
+    async def __aexit__(self, *args):
+        return False
+
+
+_OG_HTML = (
+    b"<html><head>"
+    b'<meta property="og:title" content="Example Article">'
+    b'<meta property="og:description" content="A description of the article.">'
+    b'<meta property="og:image" content="https://8.8.8.8/image.png">'
+    b'<meta property="og:site_name" content="Example">'
+    b"</head></html>"
+)
+
+
+def _fake_client_factory(html=_OG_HTML, status_code=200, call_log=None):
+    class _FakeAsyncClient:
+        def __init__(self, *args, **kwargs):
+            pass
+
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, *args):
+            return False
+
+        def stream(self, method, url, headers=None):
+            if call_log is not None:
+                call_log.append(url)
+            return _FakeStreamCtx(_FakeResponse(status_code, {"content-type": "text/html"}, html))
+
+    return _FakeAsyncClient
+
+
+def test_extract_first_url_finds_url_in_content():
+    assert extract_first_url("check out https://example.com for more") == "https://example.com"
+
+
+def test_extract_first_url_strips_trailing_punctuation():
+    assert extract_first_url("see (https://example.com/page).") == "https://example.com/page"
+
+
+def test_extract_first_url_returns_none_without_url():
+    assert extract_first_url("no links here") is None
+
+
+def test_extract_first_url_returns_none_for_empty_content():
+    assert extract_first_url(None) is None
+    assert extract_first_url("") is None
+
+
+def test_ws_message_with_url_triggers_link_preview_broadcast(ws_client, monkeypatch):
+    monkeypatch.setattr("app.services.link_preview_service.httpx.AsyncClient", _fake_client_factory())
+    url = _unique_url()
+
+    username = _unique("alice")
+    _register_ws(ws_client, username=username)
+    room = ws_client.post("/api/rooms", json={"name": _unique("general")}).json()
+
+    with ws_client.websocket_connect("/ws/chat") as ws:
+        ws.send_json({"type": "join", "room_id": room["id"]})
+        assert _recv(ws)["type"] == "joined"
+
+        ws.send_json({"type": "message", "room_id": room["id"], "content": f"check this out {url}"})
+        message = _recv(ws)
+        assert message["type"] == "message"
+        # Never populated on the initial broadcast -- fetching is async.
+        assert message["link_preview"] is None
+
+        preview = _recv(ws)
+        assert preview["type"] == "link_preview"
+        assert preview["id"] == message["id"]
+        assert preview["url"] == url
+        assert preview["title"] == "Example Article"
+        assert preview["description"] == "A description of the article."
+        assert preview["image_url"] == "https://8.8.8.8/image.png"
+        assert preview["site_name"] == "Example"
+
+
+def test_ws_message_with_private_url_gets_no_preview(ws_client, monkeypatch):
+    calls: list[str] = []
+    monkeypatch.setattr(
+        "app.services.link_preview_service.httpx.AsyncClient",
+        _fake_client_factory(call_log=calls),
+    )
+
+    username = _unique("alice")
+    _register_ws(ws_client, username=username)
+    room = ws_client.post("/api/rooms", json={"name": _unique("general")}).json()
+
+    with ws_client.websocket_connect("/ws/chat") as ws:
+        ws.send_json({"type": "join", "room_id": room["id"]})
+        assert _recv(ws)["type"] == "joined"
+
+        ws.send_json(
+            {
+                "type": "message",
+                "room_id": room["id"],
+                "content": "internal link http://127.0.0.1/secret",
+            }
+        )
+        message = _recv(ws)
+        assert message["link_preview"] is None
+
+        # Sync barrier: an idempotent second frame's ack proves the first
+        # message's entire async handling (including the spawned link-
+        # preview task, which is rejected before any real I/O) has settled
+        # without ever publishing a link_preview envelope.
+        ws.send_json({"type": "join", "room_id": room["id"]})
+        assert _recv(ws)["type"] == "joined"
+
+    assert calls == []
+
+
+async def test_message_history_includes_cached_link_preview(client, db_session, monkeypatch):
+    captured_tasks: list[asyncio.Task] = []
+    real_create_task = asyncio.create_task
+
+    def fake_create_task(coro):
+        task = real_create_task(coro)
+        captured_tasks.append(task)
+        return task
+
+    monkeypatch.setattr("app.services.message_events.asyncio.create_task", fake_create_task)
+    monkeypatch.setattr("app.services.link_preview_service.httpx.AsyncClient", _fake_client_factory())
+    url = _unique_url()
+
+    await register_and_login(client, db_session, username="alice")
+    room = (await client.post("/api/rooms", json={"name": "general"})).json()
+    webhook = (await client.post(f"/api/rooms/{room['id']}/webhooks/incoming", json={})).json()
+
+    resp = await client.post(
+        f"/api/webhooks/incoming/{webhook['token']}",
+        json={"content": f"see {url}"},
+    )
+    assert resp.status_code == 204
+    await asyncio.gather(*captured_tasks)
+
+    history = (await client.get(f"/api/rooms/{room['id']}/messages")).json()
+    assert len(history) == 1
+    assert history[0]["link_preview"]["title"] == "Example Article"
+    assert history[0]["link_preview"]["url"] == url
+
+
+async def test_link_preview_reused_across_messages_with_same_url(client, db_session, monkeypatch):
+    captured_tasks: list[asyncio.Task] = []
+    real_create_task = asyncio.create_task
+
+    def fake_create_task(coro):
+        task = real_create_task(coro)
+        captured_tasks.append(task)
+        return task
+
+    monkeypatch.setattr("app.services.message_events.asyncio.create_task", fake_create_task)
+    calls: list[str] = []
+    monkeypatch.setattr(
+        "app.services.link_preview_service.httpx.AsyncClient",
+        _fake_client_factory(call_log=calls),
+    )
+    url = _unique_url()
+
+    await register_and_login(client, db_session, username="alice")
+    room = (await client.post("/api/rooms", json={"name": "general"})).json()
+    webhook = (await client.post(f"/api/rooms/{room['id']}/webhooks/incoming", json={})).json()
+
+    # Awaited one at a time so the second send's cache check happens after
+    # the first's fetch has actually committed -- otherwise both could race
+    # past the "not cached yet" check concurrently and this would flake.
+    resp1 = await client.post(
+        f"/api/webhooks/incoming/{webhook['token']}", json={"content": f"see {url}"}
+    )
+    assert resp1.status_code == 204
+    await asyncio.gather(*captured_tasks)
+    captured_tasks.clear()
+
+    resp2 = await client.post(
+        f"/api/webhooks/incoming/{webhook['token']}", json={"content": f"again: {url}"}
+    )
+    assert resp2.status_code == 204
+    await asyncio.gather(*captured_tasks)
+
+    assert len(calls) == 1
+
+    history = (await client.get(f"/api/rooms/{room['id']}/messages")).json()
+    assert len(history) == 2
+    assert all(m["link_preview"]["title"] == "Example Article" for m in history)