"""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