"""Tests for nightly DB backups (T32).

The backup service is intentionally simple: a flat ``data/backups/`` dir
containing timestamped copies of ``chat.db``, with retention of the most
recent 14. The scheduling decision (``should_take_backup``) is a pure
function of clock + filesystem state so it can be unit-tested without
spinning up the BackgroundWorker tick loop.
"""

from __future__ import annotations

from datetime import datetime
from unittest.mock import patch

from chat.services.backup import (
    prune_backups,
    should_take_backup,
    take_backup,
)


def test_take_backup_creates_timestamped_copy(tmp_path):
    db = tmp_path / "chat.db"
    db.write_text("fake db contents")
    backup_path = take_backup(db_path=db, data_dir=tmp_path / "data")
    assert backup_path.exists()
    assert backup_path.name.startswith("chat-")
    assert backup_path.name.endswith(".db")
    # Contents copied
    assert backup_path.read_text() == "fake db contents"
    # Located in data/backups/
    assert backup_path.parent == tmp_path / "data" / "backups"


def test_prune_keeps_last_14(tmp_path):
    backup_dir = tmp_path / "data" / "backups"
    backup_dir.mkdir(parents=True)
    # Create 17 dummy backup files spanning days 1..17 of Jan 2026.
    # Filenames sort lexicographically by the embedded timestamp, so
    # prune_backups should drop the three oldest.
    for i in range(1, 18):
        (backup_dir / f"chat-202601{i:02d}T000000Z.db").write_text(
            f"backup {i}"
        )
    removed = prune_backups(tmp_path / "data", keep=14)
    assert removed == 3
    remaining = sorted(backup_dir.glob("chat-*.db"))
    assert len(remaining) == 14
    # Days 1, 2, 3 removed; day 4 is now the oldest retained backup.
    assert remaining[0].name == "chat-20260104T000000Z.db"


def test_should_take_backup_when_no_prior_and_target_hour_matches(tmp_path):
    from chat.services import backup as backup_mod

    class FakeDateTime(datetime):
        @classmethod
        def now(cls, tz=None):
            return datetime(2026, 4, 26, 3, 0, 0)

    with patch.object(backup_mod, "datetime", FakeDateTime):
        assert should_take_backup(tmp_path / "data") is True


def test_should_not_take_backup_outside_target_hour(tmp_path):
    from chat.services import backup as backup_mod

    class FakeDateTime(datetime):
        @classmethod
        def now(cls, tz=None):
            return datetime(2026, 4, 26, 14, 0, 0)

    with patch.object(backup_mod, "datetime", FakeDateTime):
        assert should_take_backup(tmp_path / "data") is False


def test_should_not_take_backup_when_recent_backup_exists(tmp_path):
    backup_dir = tmp_path / "data" / "backups"
    backup_dir.mkdir(parents=True)
    recent = backup_dir / "chat-recent.db"
    recent.write_text("x")
    # mtime defaults to "now" — within the 23h freshness window so
    # should_take_backup must return False even at the target hour.
    from chat.services import backup as backup_mod

    class FakeDateTime(datetime):
        @classmethod
        def now(cls, tz=None):
            return datetime(2026, 4, 26, 3, 0, 0)

    with patch.object(backup_mod, "datetime", FakeDateTime):
        assert should_take_backup(tmp_path / "data") is False