"""Settings commits retain valid files on failure and concurrent writes."""

from concurrent.futures import ThreadPoolExecutor
import json
from pathlib import Path
import tempfile
import unittest
from unittest import mock

from python_app.file_io import atomic_write_json
from python_app.orchestration.gui_session_state import GuiSessionStateStore


class AtomicJsonTest(unittest.TestCase):
    def setUp(self) -> None:
        directory = tempfile.TemporaryDirectory()
        self.addCleanup(directory.cleanup)
        self.path = Path(directory.name) / "settings.json"
        atomic_write_json(self.path, {"old": True})

    def test_failed_sync_or_commit_preserves_previous_file(self) -> None:
        for operation in ('fsync', 'replace'):
            with self.subTest(operation=operation), \
                    mock.patch(f'python_app.file_io.os.{operation}', side_effect=OSError('disk failure')), \
                    self.assertRaises(OSError):
                atomic_write_json(self.path, {'new': True}, durable=True)
            self.assertEqual(json.loads(self.path.read_text()), {'old': True})
            self.assertEqual(list(self.path.parent.glob('*.tmp')), [])

    def test_nonfinite_json_cannot_overwrite_settings(self) -> None:
        with self.assertRaises(ValueError):
            atomic_write_json(self.path, {'bad': float('nan')})
        self.assertEqual(json.loads(self.path.read_text()), {'old': True})

    def test_concurrent_writers_publish_complete_json_and_leave_no_temp_files(self) -> None:
        payloads = [{'index': i, 'values': [i] * 1000} for i in range(32)]
        with ThreadPoolExecutor(max_workers=8) as executor:
            list(executor.map(lambda payload: atomic_write_json(self.path, payload), payloads))
        self.assertIn(json.loads(self.path.read_text()), payloads)
        self.assertEqual(list(self.path.parent.glob('*.tmp')), [])

    def test_invalid_utf8_session_cache_uses_defaults(self) -> None:
        self.path.write_bytes(b'\xff')
        self.assertEqual(GuiSessionStateStore(self.path).load().last_profile_path, '')