"""
后端单测统一 runner 的分片与 CI 调用合同。
"""

from pathlib import Path

import pytest

from tests import run as test_runner

ROOT = Path(__file__).resolve().parents[1]
WORKFLOW = ROOT / ".github" / "workflows" / "test.yml"


def _test_files(count: int) -> list[Path]:
    """
    构造按字典序排列的测试文件路径。
    """
    return [Path(f"test_{index:03d}.py") for index in range(count)]


def test_split_test_files_balances_slow_files_deterministically() -> None:
    """
    相邻慢文件必须分散，输入顺序变化也不能造成分片漂移或遗漏。
    """
    test_files = _test_files(10)
    durations = {test_files[0].name: 12.0, test_files[1].name: 11.0}

    shards = test_runner.split_test_files(test_files, shard_count=4, durations=durations)

    assert shards == test_runner.split_test_files(
        list(reversed(test_files)), shard_count=4, durations=durations,
    )
    assert sorted(test_file for shard in shards for test_file in shard) == test_files
    assert all(shard == sorted(shard) for shard in shards)
    assert not any(test_files[0] in shard and test_files[1] in shard for shard in shards)
    assert max(sum(durations.get(path.name, 1.0) for path in shard) for shard in shards) == 12


@pytest.mark.parametrize("file_count, shard_count", [(0, 4), (2, 4), (10, 4), (10, 1)])
def test_split_test_files_covers_unknown_files_and_empty_shards(
    file_count: int, shard_count: int,
) -> None:
    """
    新增无历史耗时文件和空分片均须保留，文件不得重复或漏跑。
    """
    test_files = _test_files(file_count)

    shards = test_runner.split_test_files(test_files, shard_count, durations={})

    assert len(shards) == shard_count
    assert sorted(path for shard in shards for path in shard) == test_files
    assert max(map(len, shards)) - min(map(len, shards)) <= 1


def test_split_test_files_rejects_nonpositive_shard_count() -> None:
    """
    分片数非法时须明确拒绝，不能静默丢失测试。
    """
    with pytest.raises(ValueError, match="shard_count"):
        test_runner.split_test_files(_test_files(1), shard_count=0)


def test_recorded_durations_balance_the_current_ci_suite() -> None:
    """
    慢文件权重必须有效，并将 CI 分片实际运行的文件集的六分片预计耗时维持均衡。
    """
    durations = test_runner.load_test_durations()
    assert all(value > 0 for value in durations.values())
    test_files = test_runner.collect_test_files(exclude_architecture_gate=True)
    shards = test_runner.split_test_files(test_files, shard_count=6)
    totals = [sum(durations.get(path.name, 1.0) for path in shard) for shard in shards]

    assert sorted(path for shard in shards for path in shard) == test_files
    assert max(totals) - min(totals) <= max(durations.values())
    slow_files = sorted(durations, key=durations.get, reverse=True)[:3]
    assert len({index for index, shard in enumerate(shards)
                if any(path.name in slow_files for path in shard)}) == 3


def test_main_defaults_to_four_parallel_shards(monkeypatch) -> None:
    """
    无 runner 参数时应并行执行四个独立 pytest 文件分片。
    """
    test_files = _test_files(10)
    captured = {}
    monkeypatch.setattr(test_runner, "collect_test_files", lambda *_: test_files)

    def fake_run_parallel(shards, pytest_args, _exclude_architecture_gate=False):
        """
        记录默认并行入口接收的分片与 pytest 参数。
        """
        captured["shards"] = shards
        captured["pytest_args"] = pytest_args
        return 0

    monkeypatch.setattr(test_runner, "run_parallel_shards", fake_run_parallel)

    assert test_runner.main(["-q", "--maxfail=1"]) == 0
    assert [len(shard) for shard in captured["shards"]] == [3, 3, 2, 2]
    assert captured["pytest_args"] == ["-q", "--maxfail=1"]


def test_main_runs_requested_ci_shard_in_current_process(monkeypatch) -> None:
    """
    CI 指定分片时只运行该分片，并继续透传 pytest 参数。
    """
    test_files = _test_files(10)
    captured = {}
    monkeypatch.setattr(test_runner, "collect_test_files", lambda *_: test_files)

    def fake_run_pytest(paths, pytest_args):
        """
        记录 pytest 入口接收的文件与透传参数。
        """
        captured["paths"] = paths
        captured["pytest_args"] = pytest_args
        return 0

    monkeypatch.setattr(test_runner, "run_pytest", fake_run_pytest)

    assert test_runner.main(["--shard", "2/4", "-q"]) == 0
    assert captured["paths"] == test_files[1::4]
    assert captured["pytest_args"] == ["-q"]


def test_main_serial_preserves_legacy_full_suite_entry(monkeypatch) -> None:
    """
    串行模式必须保留 tests 根目录加 pytest 参数透传的旧入口。
    """
    captured = {}

    def fake_run_pytest(paths, pytest_args):
        """
        记录 pytest 入口接收的文件与透传参数。
        """
        captured["paths"] = paths
        captured["pytest_args"] = pytest_args
        return 0

    monkeypatch.setattr(test_runner, "run_pytest", fake_run_pytest)

    assert test_runner.main(["--serial", "-q", "--maxfail=1"]) == 0
    assert captured["paths"] == [test_runner.TESTS_DIR]
    assert captured["pytest_args"] == ["-q", "--maxfail=1"]


def test_architecture_gate_files_are_excluded_only_on_request() -> None:
    """
    默认全量包含门禁文件；排除后剩余文件与门禁文件恰好构成全集。
    """
    full = test_runner.collect_test_files()
    remaining = test_runner.collect_test_files(exclude_architecture_gate=True)
    gate = [path for path in full if path.name in test_runner.ARCHITECTURE_GATE_TESTS]

    assert sorted(path.name for path in gate) == sorted(test_runner.ARCHITECTURE_GATE_TESTS)
    assert sorted([*remaining, *gate]) == full


def test_parallel_workers_inherit_architecture_gate_exclusion() -> None:
    """
    并行 worker 必须收到同一排除选项，否则各自划分的分片会遗漏或重复文件。
    """
    command = test_runner._worker_command(2, 4, ["-q"], exclude_architecture_gate=True)

    assert command[2:] == ["--shard", "2/4", "--exclude-architecture-gate", "-q"]
    assert "--exclude-architecture-gate" not in test_runner._worker_command(2, 4, ["-q"])


@pytest.mark.parametrize("value", ["0/4", "5/4", "1/0", "invalid"])
def test_invalid_shard_values_are_rejected(value: str) -> None:
    """
    分片参数必须使用有效的一基 N/TOTAL 范围。
    """
    with pytest.raises(SystemExit, match="2"):
        test_runner.parse_args(["--shard", value])


def test_workflow_uses_the_shared_runner_contract() -> None:
    """
    CI 不得另行维护 shell 分片算法，Coverage 必须复用同一分片入口。
    """
    workflow = WORKFLOW.read_text(encoding="utf-8")

    assert 'run: uv run --locked --no-sync python tests/run.py --shard' not in workflow
    assert "python -m coverage run --parallel-mode tests/run.py --exclude-architecture-gate --shard" in workflow
    assert "mapfile" not in workflow
    assert "SHARD_INDEX" not in workflow