merge: T95 delete-impact computation service

chat/services/branching.py

@@ -0,0 +1,107 @@
+"""Branching service (T94, Phase 4).
+
+Wraps branches state with validation + event emission. Phase 4 ships
+the data model and creation/switching APIs; the read-side filter
+(event readers consulting is_active) is a Phase 4.5+ follow-up — for
+now branches are metadata-only and the existing event readers remain
+branch-agnostic. The drawer UI (T98) drives create/switch via these
+helpers.
+"""
+
+from __future__ import annotations
+from sqlite3 import Connection
+
+from chat.eventlog.log import append_and_apply
+from chat.state.branches import get_branch, list_branches, active_branch  # noqa: F401
+
+
+def branch_from_event(
+    conn: Connection,
+    *,
+    name: str,
+    origin_event_id: int,
+    chat_id: str | None = None,
+) -> int:
+    """Create a new named branch forking from origin_event_id.
+
+    Emits a branch_created event. Returns the new branch's row id.
+    Raises ValueError if name already exists or origin_event_id doesn't
+    correspond to a real event."""
+    if not name or not name.strip():
+        raise ValueError("branch name must be non-empty")
+
+    if get_branch(conn, name) is not None:
+        raise ValueError(f"branch {name!r} already exists")
+
+    # Validate origin_event_id is a real event id (or 0 for the bootstrap case
+    # which only main uses).
+    if origin_event_id < 0:
+        raise ValueError(f"origin_event_id must be >= 0, got {origin_event_id}")
+    if origin_event_id > 0:
+        row = conn.execute(
+            "SELECT 1 FROM event_log WHERE id = ?", (origin_event_id,)
+        ).fetchone()
+        if row is None:
+            raise ValueError(
+                f"origin_event_id {origin_event_id} does not exist in event_log"
+            )
+
+    append_and_apply(
+        conn,
+        kind="branch_created",
+        payload={
+            "name": name,
+            "origin_event_id": origin_event_id,
+            "head_event_id": origin_event_id,  # head starts at origin
+            "chat_id": chat_id,
+        },
+    )
+
+    branch = get_branch(conn, name)
+    if branch is None:
+        # Should be unreachable if append_and_apply worked.
+        raise RuntimeError(f"branch {name!r} not found after creation")
+    return branch["id"]
+
+
+def switch_active_branch(conn: Connection, *, name: str) -> None:
+    """Make the named branch active. Emits branch_switched."""
+    if get_branch(conn, name) is None:
+        raise ValueError(f"branch {name!r} does not exist")
+
+    append_and_apply(
+        conn,
+        kind="branch_switched",
+        payload={"name": name},
+    )
+
+
+def list_branches_with_metadata(
+    conn: Connection, chat_id: str | None = None
+) -> list[dict]:
+    """List branches with computed event_count metadata.
+
+    event_count = head_event_id - origin_event_id + 1 (when both are set)
+                  OR head_event_id (when origin is 0, e.g., main branch)
+                  OR 0 (when head <= origin, which is the bootstrap state)
+    """
+    branches = list_branches(conn, chat_id)
+    enriched = []
+    for b in branches:
+        origin = b["origin_event_id"]
+        head = b["head_event_id"]
+        if head < origin:
+            event_count = 0
+        elif origin == 0:
+            event_count = head
+        else:
+            event_count = head - origin + 1
+        enriched.append({**b, "event_count": event_count})
+    return enriched
+
+
+__all__ = [
+    "branch_from_event",
+    "switch_active_branch",
+    "list_branches_with_metadata",
+]

chat/services/delete_impact.py

@@ -0,0 +1,147 @@
+"""Delete-impact computation service (T95, Phase 4).
+
+Walks event_log forward from a target event_id and produces an ImpactReport
+describing what would be removed if rewind-to-target were invoked. Pure
+computation — does NOT mutate the database. Used by T98's drawer surgical-
+delete UI to render an 'are you sure?' modal before invoking the actual
+rewind path (chat/services/rewind.py).
+"""
+
+from __future__ import annotations
+import json
+from sqlite3 import Connection
+
+from pydantic import BaseModel, Field
+
+
+class DeletedItem(BaseModel):
+    kind: str
+    description: str
+    target_id: int | str | None = None
+
+
+class ImpactReport(BaseModel):
+    target_event_id: int
+    cascading: list[DeletedItem] = Field(default_factory=list)
+    notes: list[str] = Field(default_factory=list)
+
+
+def _excerpt(text: str, n: int = 60) -> str:
+    text = (text or "").strip().replace("\n", " ")
+    return text if len(text) <= n else text[: n - 1] + "…"
+
+
+def compute_delete_impact(
+    conn: Connection,
+    *,
+    target_event_id: int,
+) -> ImpactReport:
+    """Compute the cascading impact of rewinding to target_event_id."""
+    # Verify target exists.
+    target_row = conn.execute(
+        "SELECT id, kind, payload_json FROM event_log WHERE id = ?",
+        (target_event_id,),
+    ).fetchone()
+    if target_row is None:
+        return ImpactReport(
+            target_event_id=target_event_id,
+            cascading=[],
+            notes=[f"target event_id {target_event_id} not found"],
+        )
+
+    # Walk forward: every event with id >= target_event_id is in scope.
+    rows = conn.execute(
+        "SELECT id, kind, payload_json FROM event_log "
+        "WHERE id >= ? ORDER BY id ASC",
+        (target_event_id,),
+    ).fetchall()
+
+    cascading: list[DeletedItem] = []
+    notes: list[str] = []
+    scene_close_present = False
+    regenerated_from = None
+
+    for row_id, kind, payload_json in rows:
+        try:
+            payload = json.loads(payload_json) if payload_json else {}
+        except (json.JSONDecodeError, TypeError):
+            payload = {}
+
+        if kind == "memory_written":
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"memory: {_excerpt(payload.get('pov_summary', ''))}",
+                    target_id=payload.get("memory_id"),
+                )
+            )
+        elif kind == "edge_update":
+            src = payload.get("source_id", "?")
+            tgt = payload.get("target_id", "?")
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"edge update: {src} -> {tgt}",
+                    target_id=f"{src}->{tgt}",
+                )
+            )
+        elif kind == "scene_closed":
+            scene_close_present = True
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"scene close at {payload.get('closed_at', '?')}",
+                    target_id=payload.get("scene_id"),
+                )
+            )
+        elif kind in ("user_turn", "user_turn_edit", "assistant_turn"):
+            speaker = payload.get("speaker_id") or ("you" if kind.startswith("user") else "?")
+            prose = payload.get("prose") or payload.get("text") or ""
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"turn {row_id} ({speaker}: {_excerpt(prose, 50)})",
+                    target_id=row_id,
+                )
+            )
+            if regenerated_from is None and payload.get("regenerated_from"):
+                regenerated_from = payload["regenerated_from"]
+        elif kind == "manual_edit":
+            target_kind = payload.get("target_kind", "?")
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"manual edit: {target_kind}",
+                    target_id=payload.get("target_id"),
+                )
+            )
+        else:
+            cascading.append(
+                DeletedItem(
+                    kind=kind,
+                    description=f"{kind} event",
+                    target_id=row_id,
+                )
+            )
+
+    # Notes / warnings.
+    notes.append(f"{len(rows)} events would be discarded total")
+    if scene_close_present:
+        notes.append(
+            "scene close events are in scope — closing-scene per-POV summaries "
+            "and group_node updates will be reverted"
+        )
+    if regenerated_from is not None:
+        notes.append(
+            f"target turn was regenerated from event_id {regenerated_from}; "
+            f"the original turn remains intact"
+        )
+
+    return ImpactReport(
+        target_event_id=target_event_id,
+        cascading=cascading,
+        notes=notes,
+    )
+
+
+__all__ = ["DeletedItem", "ImpactReport", "compute_delete_impact"]

tests/test_branching.py

@@ -0,0 +1,131 @@
+"""Tests for the branching service (T94, Phase 4)."""
+
+from __future__ import annotations
+
+import pytest
+
+from chat.db.connection import open_db
+from chat.db.migrate import apply_migrations
+from chat.eventlog.log import append_and_apply
+import chat.state.branches  # noqa: F401  registers handlers
+from chat.services.branching import (
+    branch_from_event,
+    list_branches_with_metadata,
+    switch_active_branch,
+)
+from chat.state.branches import active_branch, get_branch
+
+
+def _seed_event(conn) -> int:
+    """Append a benign event so we have a real event_log row to fork from.
+
+    ``user_turn`` is a transcript-only kind with no registered projector
+    handler, so ``append_and_apply`` is a clean no-op on the projector
+    side regardless of what other handlers are imported by the suite.
+    """
+    return append_and_apply(
+        conn,
+        kind="user_turn",
+        payload={"chat_id": "c1", "text": "hi"},
+    )
+
+
+def test_branch_from_event_creates_branch_via_event(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        seed_id = _seed_event(conn)
+
+        new_id = branch_from_event(
+            conn,
+            name="experiment",
+            origin_event_id=seed_id,
+            chat_id="c1",
+        )
+        assert isinstance(new_id, int) and new_id > 0
+
+        b = get_branch(conn, "experiment")
+        assert b is not None
+        assert b["id"] == new_id
+        assert b["origin_event_id"] == seed_id
+        assert b["head_event_id"] == seed_id
+        assert b["chat_id"] == "c1"
+        assert b["is_active"] is False
+
+        # branch_created event landed in event_log
+        row = conn.execute(
+            "SELECT COUNT(*) FROM event_log WHERE kind = 'branch_created'"
+        ).fetchone()
+        assert row[0] == 1
+
+
+def test_branch_from_event_duplicate_name_raises(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        seed_id = _seed_event(conn)
+        branch_from_event(conn, name="dup", origin_event_id=seed_id)
+
+        with pytest.raises(ValueError, match="already exists"):
+            branch_from_event(conn, name="dup", origin_event_id=seed_id)
+
+
+def test_branch_from_event_invalid_origin_raises(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        with pytest.raises(ValueError, match="does not exist"):
+            branch_from_event(conn, name="ghost", origin_event_id=99999)
+
+
+def test_switch_active_branch_changes_active(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        seed_id = _seed_event(conn)
+        branch_from_event(conn, name="experiment", origin_event_id=seed_id)
+
+        switch_active_branch(conn, name="experiment")
+        active = active_branch(conn)
+        assert active is not None
+        assert active["name"] == "experiment"
+
+        # Switch back to main.
+        switch_active_branch(conn, name="main")
+        active2 = active_branch(conn)
+        assert active2 is not None
+        assert active2["name"] == "main"
+
+
+def test_switch_active_branch_unknown_name_raises(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        with pytest.raises(ValueError, match="does not exist"):
+            switch_active_branch(conn, name="nope")
+
+
+def test_list_branches_with_metadata_includes_event_count(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        # Seed enough events to cover origin=10 and head=15.
+        for _ in range(15):
+            _seed_event(conn)
+
+        # Create the branch at origin=10, then bump its head to 15.
+        branch_from_event(conn, name="exp", origin_event_id=10)
+        append_and_apply(
+            conn,
+            kind="branch_head_updated",
+            payload={"name": "exp", "head_event_id": 15},
+        )
+
+        rows = {b["name"]: b for b in list_branches_with_metadata(conn)}
+
+        # main: bootstrap state — origin=0, head=0 — event_count == 0.
+        assert rows["main"]["event_count"] == 0
+        # exp: origin=10, head=15 — event_count == 6 (inclusive).
+        assert rows["exp"]["origin_event_id"] == 10
+        assert rows["exp"]["head_event_id"] == 15
+        assert rows["exp"]["event_count"] == 6

tests/test_delete_impact.py

@@ -0,0 +1,248 @@
+"""Tests for Task 95 — delete-impact computation service (Phase 4).
+
+`compute_delete_impact` walks event_log forward from a target event_id and
+produces an :class:`ImpactReport` describing what would be removed if
+rewind-to-target were invoked. It is a pure preview — no database mutation.
+T98's drawer surgical-delete UI uses this to render an "are you sure?"
+modal before invoking the actual rewind path.
+"""
+
+from __future__ import annotations
+
+from chat.db.connection import open_db
+from chat.db.migrate import apply_migrations
+from chat.eventlog.log import append_event
+from chat.services.delete_impact import compute_delete_impact
+
+
+def _seed_chat(conn) -> tuple[int, int]:
+    """Append minimal bot + chat events; return their event ids."""
+    bot_id = append_event(
+        conn,
+        kind="bot_authored",
+        payload={
+            "id": "bot_a",
+            "name": "BotA",
+            "persona": "...",
+            "voice_samples": [],
+            "traits": [],
+            "backstory": "",
+            "initial_relationship_to_you": "",
+            "kickoff_prose": "",
+        },
+    )
+    chat_id = 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": "",
+        },
+    )
+    return bot_id, chat_id
+
+
+def test_impact_for_simple_turn_lists_memory_and_edges(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        _seed_chat(conn)
+        user_id = append_event(
+            conn,
+            kind="user_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "prose": "hey there friend",
+                "segments": [],
+            },
+        )
+        append_event(
+            conn,
+            kind="assistant_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "speaker_id": "bot_a",
+                "text": "Hi! Good to see you.",
+                "truncated": False,
+                "user_turn_id": user_id,
+            },
+        )
+        append_event(
+            conn,
+            kind="memory_written",
+            payload={
+                "owner_id": "bot_a",
+                "chat_id": "chat_bot_a",
+                "pov_summary": "You greeted me warmly today.",
+                "witness_you": 1,
+                "witness_host": 1,
+                "witness_guest": 0,
+                "source": "turn",
+                "reliability": 1.0,
+                "significance": 1,
+                "pinned": 0,
+                "auto_pinned": 0,
+            },
+        )
+        append_event(
+            conn,
+            kind="edge_update",
+            payload={
+                "source_id": "you",
+                "target_id": "bot_a",
+                "affinity_delta": 0.1,
+            },
+        )
+
+        report = compute_delete_impact(conn, target_event_id=user_id)
+
+    assert report.target_event_id == user_id
+    kinds = [item.kind for item in report.cascading]
+    # Walk from user_turn forward — user_turn, assistant_turn,
+    # memory_written, edge_update should all be in scope, in order.
+    assert kinds == [
+        "user_turn",
+        "assistant_turn",
+        "memory_written",
+        "edge_update",
+    ]
+    # Memory description includes the pov_summary excerpt.
+    mem_item = report.cascading[2]
+    assert "memory:" in mem_item.description
+    assert "greeted" in mem_item.description
+    # Edge description includes both endpoints.
+    edge_item = report.cascading[3]
+    assert "you" in edge_item.description
+    assert "bot_a" in edge_item.description
+    assert edge_item.target_id == "you->bot_a"
+    # Notes mentions total count.
+    assert any("4 events" in n for n in report.notes)
+
+
+def test_impact_for_scene_opening_turn_warns_about_subsequent(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        _seed_chat(conn)
+        early_id = append_event(
+            conn,
+            kind="user_turn",
+            payload={"chat_id": "chat_bot_a", "prose": "the start", "segments": []},
+        )
+        append_event(
+            conn,
+            kind="assistant_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "speaker_id": "bot_a",
+                "text": "ok",
+                "truncated": False,
+                "user_turn_id": early_id,
+            },
+        )
+        append_event(
+            conn,
+            kind="scene_closed",
+            payload={
+                "scene_id": 1,
+                "closed_at": "2026-04-26T21:00:00+00:00",
+                "significance": 2,
+            },
+        )
+
+        report = compute_delete_impact(conn, target_event_id=early_id)
+
+    # Scene-close warning fires when one is in scope.
+    assert any("scene close" in n.lower() for n in report.notes)
+    # The scene_closed event also appears as a cascading item.
+    assert any(item.kind == "scene_closed" for item in report.cascading)
+
+
+def test_impact_for_missing_event_returns_empty_with_note(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        _seed_chat(conn)
+        report = compute_delete_impact(conn, target_event_id=999_999)
+
+    assert report.cascading == []
+    assert any("not found" in n for n in report.notes)
+
+
+def test_impact_does_not_mutate_database(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        _seed_chat(conn)
+        user_id = append_event(
+            conn,
+            kind="user_turn",
+            payload={"chat_id": "chat_bot_a", "prose": "hi", "segments": []},
+        )
+        append_event(
+            conn,
+            kind="assistant_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "speaker_id": "bot_a",
+                "text": "hello",
+                "truncated": False,
+                "user_turn_id": user_id,
+            },
+        )
+
+        # Snapshot all event_log rows as a tuple-of-tuples.
+        before = conn.execute(
+            "SELECT id, branch_id, ts, kind, payload_json, superseded_by, "
+            "hidden FROM event_log ORDER BY id"
+        ).fetchall()
+
+        compute_delete_impact(conn, target_event_id=user_id)
+
+        after = conn.execute(
+            "SELECT id, branch_id, ts, kind, payload_json, superseded_by, "
+            "hidden FROM event_log ORDER BY id"
+        ).fetchall()
+
+    # Byte-identical: nothing inserted, deleted, or updated.
+    assert before == after
+
+
+def test_impact_includes_regenerated_from_warning(tmp_path):
+    db = tmp_path / "t.db"
+    apply_migrations(db)
+    with open_db(db) as conn:
+        _seed_chat(conn)
+        original_id = append_event(
+            conn,
+            kind="assistant_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "speaker_id": "bot_a",
+                "text": "first try",
+                "truncated": False,
+                "user_turn_id": 0,
+            },
+        )
+        regen_id = append_event(
+            conn,
+            kind="assistant_turn",
+            payload={
+                "chat_id": "chat_bot_a",
+                "speaker_id": "bot_a",
+                "text": "second try",
+                "truncated": False,
+                "user_turn_id": 0,
+                "regenerated_from": original_id,
+            },
+        )
+
+        report = compute_delete_impact(conn, target_event_id=regen_id)
+
+    # The regenerated_from note carries the original event id so the user
+    # knows the original turn isn't lost.
+    assert any("regenerated from" in n for n in report.notes)
+    assert any(str(original_id) in n for n in report.notes)