feat(wiki): reembed_wiki_page durable task

Per-page re-embed (Unit 2 of F-Wiki): targeted delete of the page's old chunks, re-chunk via the source's chunking config, add_chunk with reingest-matching metadata (source=path), set embed_status embedded/failed. Durable + idempotent (key=content_hash), mirroring reingest_source_task. Missing page => purge only.

tests/worker/test_reembed_wiki_page.py

@@ -0,0 +1,183 @@
+"""Tests for the per-page wiki re-embed worker and Celery task.
+
+The worker loads the source row from the ephemeral DB, then re-embeds (or
+purges) one wiki page. The vector store, ``ChunkerCreator``, and the page
+lookup are mocked so no live embeddings run; the ``sources`` row is real so
+``SourcesRepository.get_any`` resolves.
+"""
+
+from __future__ import annotations
+
+from contextlib import contextmanager
+from unittest.mock import MagicMock
+
+import pytest
+
+from application.parser.schema.base import Document
+from application.storage.db.repositories.sources import SourcesRepository
+
+
+def _seed_source(pg_conn) -> str:
+    src = SourcesRepository(pg_conn).create(
+        "wiki-set",
+        user_id="alice",
+        type="wiki",
+        config={"kind": "wiki"},
+    )
+    return str(src["id"])
+
+
+def _patch_store(monkeypatch, store):
+    monkeypatch.setattr(
+        "application.vectorstore.vector_creator.VectorCreator.create_vectorstore",
+        lambda *a, **kw: store,
+    )
+
+
+def _patch_repo(monkeypatch, page):
+    """Replace ``WikiPagesRepository`` with one returning ``page`` and a stub setter."""
+    repo = MagicMock(name="wiki_repo")
+    repo.get_by_path.return_value = page
+    repo.set_embed_status.return_value = True
+    monkeypatch.setattr(
+        "application.worker.WikiPagesRepository", lambda conn: repo
+    )
+    return repo
+
+
+def _patch_chunker(monkeypatch, chunks):
+    calls: list[dict] = []
+
+    def _create_chunker(strategy, **kwargs):
+        calls.append({"strategy": strategy, **kwargs})
+        chunker = MagicMock(name="chunker")
+        chunker.chunk.return_value = chunks
+        return chunker
+
+    monkeypatch.setattr(
+        "application.worker.ChunkerCreator.create_chunker",
+        staticmethod(_create_chunker),
+    )
+    return calls
+
+
+@pytest.mark.unit
+class TestReembedWikiPageWorker:
+    def test_page_exists_reembeds(
+        self, pg_conn, patch_worker_db, task_self, monkeypatch
+    ):
+        from application import worker
+
+        source_id = _seed_source(pg_conn)
+
+        store = MagicMock(name="vector_store")
+        store.delete_chunks_by_source_path.return_value = 3
+        _patch_store(monkeypatch, store)
+
+        repo = _patch_repo(
+            monkeypatch,
+            {"content": "page body", "title": "Page Title"},
+        )
+        _patch_chunker(
+            monkeypatch,
+            [Document(text="c1"), Document(text="c2")],
+        )
+
+        result = worker.reembed_wiki_page_worker(
+            task_self, source_id, "guide/intro.md", "hash-1", "alice"
+        )
+
+        store.delete_chunks_by_source_path.assert_called_once_with(
+            "guide/intro.md"
+        )
+        assert store.add_chunk.call_count == 2
+        for call in store.add_chunk.call_args_list:
+            assert call.kwargs["metadata"]["source"] == "guide/intro.md"
+            assert call.kwargs["metadata"]["title"] == "Page Title"
+            assert call.kwargs["metadata"]["filename"] == "guide/intro.md"
+        repo.set_embed_status.assert_called_once_with(
+            source_id, "guide/intro.md", "embedded"
+        )
+        assert result == {"status": "embedded", "added": 2, "deleted": 3}
+
+    def test_page_missing_purges(
+        self, pg_conn, patch_worker_db, task_self, monkeypatch
+    ):
+        from application import worker
+
+        source_id = _seed_source(pg_conn)
+
+        store = MagicMock(name="vector_store")
+        store.delete_chunks_by_source_path.return_value = 4
+        _patch_store(monkeypatch, store)
+
+        repo = _patch_repo(monkeypatch, None)
+
+        result = worker.reembed_wiki_page_worker(
+            task_self, source_id, "old/page.md", "hash-x", "alice"
+        )
+
+        store.delete_chunks_by_source_path.assert_called_once_with("old/page.md")
+        store.add_chunk.assert_not_called()
+        repo.set_embed_status.assert_not_called()
+        assert result == {"status": "deleted", "deleted": 4}
+
+    def test_embed_failure_sets_failed_and_reraises(
+        self, pg_conn, patch_worker_db, task_self, monkeypatch
+    ):
+        from application import worker
+
+        source_id = _seed_source(pg_conn)
+
+        store = MagicMock(name="vector_store")
+        store.delete_chunks_by_source_path.return_value = 0
+        store.add_chunk.side_effect = RuntimeError("embed boom")
+        _patch_store(monkeypatch, store)
+
+        repo = _patch_repo(
+            monkeypatch, {"content": "page body", "title": "T"}
+        )
+        _patch_chunker(monkeypatch, [Document(text="c1")])
+
+        with pytest.raises(RuntimeError, match="embed boom"):
+            worker.reembed_wiki_page_worker(
+                task_self, source_id, "p.md", "hash-2", "alice"
+            )
+
+        repo.set_embed_status.assert_called_once_with(source_id, "p.md", "failed")
+
+
+@pytest.mark.unit
+class TestReembedWikiPageTask:
+    def test_idempotency_key_is_content_hash(self, pg_conn, monkeypatch):
+        """A redelivery with the same content_hash key short-circuits the worker."""
+        from application.api.user import tasks
+
+        @contextmanager
+        def _yield():
+            yield pg_conn
+
+        monkeypatch.setattr(
+            "application.api.user.idempotency.db_session", _yield
+        )
+        monkeypatch.setattr(
+            "application.api.user.idempotency.db_readonly", _yield
+        )
+
+        calls: list[str] = []
+
+        def _fake_worker(self, source_id, path, content_hash, user):
+            calls.append(content_hash)
+            return {"status": "embedded", "added": 1, "deleted": 0}
+
+        monkeypatch.setattr(tasks, "reembed_wiki_page_worker", _fake_worker)
+
+        first = tasks.reembed_wiki_page(
+            "src-1", "p.md", "abc123", "alice", idempotency_key="abc123",
+        )
+        second = tasks.reembed_wiki_page(
+            "src-1", "p.md", "abc123", "alice", idempotency_key="abc123",
+        )
+
+        assert first == second
+        assert len(calls) == 1