from __future__ import annotations

from dataclasses import dataclass
from datetime import UTC, datetime, timedelta

import pytest
from backup_tool.retention import RetentionError, RetentionPolicy, retained_ids


@dataclass
class Backup:
    id: str
    created_at: datetime
    pinned: bool = False
    tombstoned_at: datetime | None = None


def test_retention_is_union_and_protects_newest() -> None:
    now = datetime(2026, 7, 29, tzinfo=UTC)
    backups = [Backup(str(index), now - timedelta(days=index)) for index in range(6)]
    backups[-1].pinned = True

    kept = retained_ids(backups, RetentionPolicy(keep_last=2, keep_daily=3), now)

    assert {"0", "1", "2", "5"} <= kept


def test_newest_is_kept_even_when_policy_is_zero() -> None:
    now = datetime(2026, 7, 29, tzinfo=UTC)
    assert retained_ids([Backup("new", now)], RetentionPolicy(keep_last=0), now) == {"new"}


@pytest.mark.parametrize("policy", [{"keep_last": -1}, {"unknown": 1}, {"keep_days": True}])
def test_invalid_retention_policy_is_rejected(policy: dict[str, object]) -> None:
    with pytest.raises(RetentionError):
        RetentionPolicy.from_dict(policy)