"""Tests for io_utils."""

from __future__ import annotations

import json
from pathlib import Path

from app.io_utils import read_json, write_json_atomic


def test_read_json_missing_returns_default(tmp_path: Path) -> None:
    assert read_json(tmp_path / "missing.json", default={}) == {}


def test_read_json_corrupt_returns_default(tmp_path: Path) -> None:
    path = tmp_path / "bad.json"
    path.write_text("not json", encoding="utf-8")
    assert read_json(path, default=None) is None


def test_write_json_atomic_roundtrip(tmp_path: Path) -> None:
    path = tmp_path / "data.json"
    payload = {"job_id": "photo", "variants": []}
    write_json_atomic(path, payload)
    assert json.loads(path.read_text(encoding="utf-8")) == payload
    assert not path.with_suffix(path.suffix + ".tmp").exists()


def test_file_lock_exclusive(tmp_path: Path) -> None:
    from concurrent.futures import ThreadPoolExecutor

    from app.io_utils import file_lock

    lock_path = tmp_path / "job.lock"
    counter = {"n": 0}

    def bump() -> None:
        with file_lock(lock_path):
            current = counter["n"]
            counter["n"] = current + 1

    with ThreadPoolExecutor(max_workers=8) as pool:
        list(pool.map(lambda _: bump(), range(40)))
    assert counter["n"] == 40