import pytest

from fam_edge.disk_guard import DiskGuard


def _cfg(**overrides):
    base = {
        "enabled": True,
        "min_free_gb": 10,
        "target_free_gb": 15,
        "watch_path": "/opt/fam-edge",
        "max_delete_per_round": 50,
        "check_interval_sec": 300,
    }
    base.update(overrides)
    return base


class _FakeDB:
    def __init__(self, candidates=None):
        self._candidates = list(candidates or [])
        self.deleted_ids = []
        self.activities = []

    def get_oldest_purgeable_material(self):
        if not self._candidates:
            return None
        return self._candidates.pop(0)

    def delete_video(self, video_id):
        self.deleted_ids.append(video_id)
        return None

    def record_activity(self, service, action, detail=''):
        self.activities.append((service, action, detail))


def _guard(monkeypatch, db, free_gb_sequence, **cfg_overrides):
    """free_gb_sequence: 每次调用 _free_gb() 依次返回的值列表（最后一个值
    耗尽后保持不变），用来模拟"清理一个文件后空间逐步恢复"的过程。"""
    monkeypatch.setattr(
        "fam_edge.disk_guard.load_config",
        lambda: {"disk_guard": _cfg(**cfg_overrides)})
    guard = DiskGuard(db)
    seq = list(free_gb_sequence)

    def fake_free_gb():
        if len(seq) > 1:
            return seq.pop(0)
        return seq[0]

    monkeypatch.setattr(guard, "_free_gb", fake_free_gb)
    return guard


def test_check_once_does_nothing_when_space_sufficient(monkeypatch):
    db = _FakeDB()
    guard = _guard(monkeypatch, db, [20.0])

    guard.check_once()

    assert db.deleted_ids == []
    assert db.activities == []


def test_check_once_cleans_until_target_reached(monkeypatch):
    """核心诉求: 低于 min_free_gb 触发清理，一直清到 target_free_gb 为止，
    不是清一个就停（否则马上又会跌破阈值，频繁触发）。"""
    db = _FakeDB(candidates=[
        {"id": 1, "local_path": "/tmp/a.mp4"},
        {"id": 2, "local_path": "/tmp/b.mp4"},
        {"id": 3, "local_path": "/tmp/c.mp4"},
    ])
    # 初始 8GB（< min_free_gb=10），每删一个恢复到 8/12/16GB（16 >= target=15 时停）
    guard = _guard(monkeypatch, db, [8.0, 8.0, 12.0, 16.0])

    guard.check_once()

    assert db.deleted_ids == [1, 2]
    actions = [a[1] for a in db.activities]
    assert "low_space" in actions
    assert "cleaned" in actions


def test_check_once_stops_when_no_candidate_left(monkeypatch):
    """核心诉求: 候选清空了但空间依然不足，不能死循环，要停下来并记录一条
    "没有可清理素材"的警告，让人能在服务状态页看到这个异常情况——即便如此，
    已经发生的清理动作本身也要记录（能看到确实清过、释放了多少），不因为
    没完全达标就把 cleaned 记录吞掉。"""
    db = _FakeDB(candidates=[{"id": 1, "local_path": "/tmp/a.mp4"}])
    guard = _guard(monkeypatch, db, [8.0, 8.0, 9.0])  # 删完仅 1 个后仍然 <15GB

    guard.check_once()

    assert db.deleted_ids == [1]
    actions = [a[1] for a in db.activities]
    assert "no_candidate" in actions
    assert "cleaned" in actions


def test_check_once_respects_max_delete_per_round(monkeypatch):
    """核心诉求: 单轮清理有上限，防止候选异常多时一次性删太多——下一轮检查
    很快就会再触发，没必要在一轮里清空所有候选。"""
    candidates = [{"id": i, "local_path": f"/tmp/{i}.mp4"} for i in range(1, 6)]
    db = _FakeDB(candidates=candidates)
    # 空间一直卡在 8GB 不涨（模拟每个文件都很小，删多少都到不了 target）
    guard = _guard(monkeypatch, db, [8.0], max_delete_per_round=3)

    guard.check_once()

    assert db.deleted_ids == [1, 2, 3]


def test_disabled_guard_does_not_start(monkeypatch):
    db = _FakeDB()
    guard = _guard(monkeypatch, db, [1.0], enabled=False)

    guard.start()

    assert guard.is_alive() is False