feat: rewind with impact preview, pre-rewind snapshot, undo toast

tests/test_rewind.py

@@ -0,0 +1,164 @@
+"""Tests for Task 28 — rewind with snapshot, impact preview, and re-projection.
+
+Per Requirements §10.1, rewind must:
+
+* take a pre-rewind snapshot of all projected tables (so the user can recover),
+* truncate the event log past a chosen event id,
+* clear projected tables and re-project from the truncated log so live state
+  matches "what the world looked like at turn N" (no stale rows from rewound
+  events).
+
+These tests cover the functional core. The HTTP route surface is left to the
+plan's polish pass — tests exercise via direct service calls.
+"""
+
+from __future__ import annotations
+
+import json
+
+from chat.db.connection import open_db
+from chat.db.migrate import apply_migrations
+from chat.eventlog.log import append_event
+from chat.eventlog.projector import project
+from chat.services.rewind import compute_rewind_preview, execute_rewind
+from chat.services.snapshot import take_snapshot
+
+# Importing the state modules registers their projector handlers as a
+# side effect — the test would otherwise see an unprojected db after
+# re-projection because the registry would be empty.
+import chat.state.entities  # noqa: F401
+import chat.state.edges  # noqa: F401
+import chat.state.memory  # noqa: F401
+import chat.state.world  # noqa: F401
+import chat.state.manual_edit  # noqa: F401
+
+
+def _seed_5_turns(db):
+    """Seed: bot + chat + 5 mock user/assistant turn pairs.
+
+    user_turn / assistant_turn have no projector handlers — they live in
+    the event_log purely for transcript rendering — so the only
+    projection-bearing events are bot_authored and chat_created. That
+    makes the post-rewind invariants easy to assert without needing the
+    real classifier pass.
+    """
+    apply_migrations(db)
+    with open_db(db) as conn:
+        append_event(
+            conn,
+            kind="bot_authored",
+            payload={
+                "id": "bot_a",
+                "name": "BotA",
+                "persona": "...",
+                "voice_samples": [],
+                "traits": [],
+                "backstory": "",
+                "initial_relationship_to_you": "",
+                "kickoff_prose": "",
+            },
+        )
+        append_event(
+            conn,
+            kind="chat_created",
+            payload={
+                "id": "chat_bot_a",
+                "host_bot_id": "bot_a",
+                "initial_time": "2026-04-26T20:00:00+00:00",
+                "narrative_anchor": "Day 1",
+                "weather": "",
+            },
+        )
+        for i in range(5):
+            append_event(
+                conn,
+                kind="user_turn",
+                payload={
+                    "chat_id": "chat_bot_a",
+                    "prose": f"turn {i}",
+                    "segments": [],
+                },
+            )
+            append_event(
+                conn,
+                kind="assistant_turn",
+                payload={
+                    "chat_id": "chat_bot_a",
+                    "speaker_id": "bot_a",
+                    "text": f"reply {i}",
+                    "truncated": False,
+                    "user_turn_id": i,
+                },
+            )
+        project(conn)
+
+
+def test_take_snapshot_writes_file_to_disk(tmp_path):
+    db = tmp_path / "t.db"
+    _seed_5_turns(db)
+    with open_db(db) as conn:
+        snapshot_path = take_snapshot(
+            conn, data_dir=tmp_path / "data", kind="rewind"
+        )
+    assert snapshot_path.exists()
+    assert snapshot_path.parent == tmp_path / "data" / "snapshots" / "rewind"
+    data = json.loads(snapshot_path.read_text())
+    assert "event_log" in data
+    assert "bots" in data
+    assert "chats" in data
+    # Bot is in the dump
+    assert any(b["id"] == "bot_a" for b in data["bots"])
+
+
+def test_compute_rewind_preview_counts_kinds(tmp_path):
+    db = tmp_path / "t.db"
+    _seed_5_turns(db)
+    with open_db(db) as conn:
+        # The 1st assistant_turn is the 4th event:
+        # 1 bot_authored, 2 chat_created, 3 user_turn, 4 assistant_turn.
+        # Everything past it should be in the preview (4 user + 4 assistant = 8).
+        first_assistant = conn.execute(
+            "SELECT id FROM event_log WHERE kind='assistant_turn' "
+            "ORDER BY id LIMIT 1"
+        ).fetchone()[0]
+        preview = compute_rewind_preview(conn, after_event_id=first_assistant)
+        assert preview["after_event_id"] == first_assistant
+        assert preview["total_events"] > 0
+        # by_kind sums to total_events.
+        assert sum(preview["by_kind"].values()) == preview["total_events"]
+        # We rewound past assistant_turn #1, so 4 user + 4 assistant remain.
+        assert preview["by_kind"].get("user_turn") == 4
+        assert preview["by_kind"].get("assistant_turn") == 4
+
+
+def test_execute_rewind_truncates_and_reprojects(tmp_path):
+    db = tmp_path / "t.db"
+    data_dir = tmp_path / "data"
+    _seed_5_turns(db)
+    with open_db(db) as conn:
+        first_assistant = conn.execute(
+            "SELECT id FROM event_log WHERE kind='assistant_turn' "
+            "ORDER BY id LIMIT 1"
+        ).fetchone()[0]
+
+    snapshot_path = execute_rewind(
+        db_path=db, data_dir=data_dir, after_event_id=first_assistant
+    )
+    # Snapshot is written under data/snapshots/rewind/.
+    assert snapshot_path.exists()
+    assert snapshot_path.parent == data_dir / "snapshots" / "rewind"
+
+    # Verify event_log truncated and projected state matches state-at-turn.
+    with open_db(db) as conn:
+        max_id = conn.execute("SELECT MAX(id) FROM event_log").fetchone()[0]
+        assert max_id == first_assistant
+        # Bot still exists (re-projected from preserved bot_authored event).
+        bot = conn.execute(
+            "SELECT id FROM bots WHERE id = 'bot_a'"
+        ).fetchone()
+        assert bot is not None
+        # Chat still exists (re-projected from preserved chat_created event).
+        chat = conn.execute(
+            "SELECT id FROM chats WHERE id = 'chat_bot_a'"
+        ).fetchone()
+        assert chat is not None