"""归档保留策略（`app.cli.prune_experiments`）的候选选择单测。

删除归档是**不可恢复**操作，因此候选集合的判定必须被测试钉住：多删一条就是丢了
一份研究结论，少删一条则保留策略失效。这里只测纯函数与参数护栏（不连数据库）。
"""

from __future__ import annotations

from datetime import datetime, timedelta

import pytest
from app.cli.prune_experiments import _parse_args, select_prune_candidates


class _Row:
    """最小归档摘要替身（只有 id / created_at 参与判定）。"""

    def __init__(self, id_: str, age_days: float | None) -> None:
        self.id = id_
        self.created_at = None if age_days is None else NOW - timedelta(days=age_days)


NOW = datetime(2026, 9, 20, 12, 0, 0)


def _rows() -> list[_Row]:
    return [_Row("E1", 1), _Row("E2", 2), _Row("E3", 10), _Row("E4", 30), _Row("E5", None)]


class TestSelectPruneCandidates:
    def test_keep_newest_n(self) -> None:
        got = [e.id for e in select_prune_candidates(_rows(), keep=2, older_than_days=None, now=NOW)]
        assert got == ["E3", "E4", "E5"], "只保留最新 2 条（E1/E2），其余都是候选"

    def test_keep_zero_deletes_all(self) -> None:
        got = [e.id for e in select_prune_candidates(_rows(), keep=0, older_than_days=None, now=NOW)]
        assert set(got) == {"E1", "E2", "E3", "E4", "E5"}

    def test_older_than_only(self) -> None:
        got = [e.id for e in select_prune_candidates(_rows(), keep=None, older_than_days=5, now=NOW)]
        assert got == ["E3", "E4", "E5"], "5 天内创建的 E1/E2 必须保留"

    def test_intersection_of_both_conditions(self) -> None:
        got = [e.id for e in select_prune_candidates(_rows(), keep=4, older_than_days=5, now=NOW)]
        # older_than 选出 E3/E4/E5，keep=4 保留 E1..E4 → 交集只剩 E5
        assert got == ["E5"]

    def test_missing_created_at_treated_as_oldest(self) -> None:
        """created_at 为空按最旧处理：不能被当作「最新」从而永久留库。"""
        got = [e.id for e in select_prune_candidates(_rows(), keep=4, older_than_days=None, now=NOW)]
        assert "E5" in got

    def test_result_is_newest_first(self) -> None:
        got = [e.id for e in select_prune_candidates(_rows(), keep=0, older_than_days=None, now=NOW)]
        assert got == ["E1", "E2", "E3", "E4", "E5"], "输出按新→旧，便于人工核对"


class TestArgGuard:
    def test_requires_keep_or_older_than(self) -> None:
        with pytest.raises(SystemExit):
            _parse_args([])  # 两个条件都不给 → 拒绝执行（避免误删全部）

    def test_negative_keep_rejected(self) -> None:
        with pytest.raises(SystemExit):
            _parse_args(["--keep", "-1"])

    def test_default_is_dry_run(self) -> None:
        args = _parse_args(["--keep", "10"])
        assert args.apply is False, "默认必须 dry-run，只有显式 --apply 才写库"