// Unit tests for ChainLog — the central error log that
// `~/.fai/logs/studio-errors.log` is the operator-visible
// surface of. The tests redirect the singleton at a temp file
// via `ChainLog.testPathOverride` so the real log under HOME is
// never touched.

import 'dart:convert';
import 'dart:io';

import 'package:chain_studio/data/chain_log.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('ChainLog', () {
    late Directory tmp;
    late File logFile;

    setUp(() {
      tmp = Directory.systemTemp.createTempSync('chain_log_test_');
      logFile = File('${tmp.path}/studio-errors.log');
      ChainLog.testPathOverride = logFile.path;
    });

    tearDown(() {
      ChainLog.testPathOverride = null;
      try {
        tmp.deleteSync(recursive: true);
      } catch (_) {/* best-effort */}
    });

    test('append writes one JSON-shaped line per event', () async {
      await ChainLog.instance.error('flows.run', 'boom');
      final lines = await ChainLog.instance.tail();
      expect(lines, hasLength(1));
      final entry = jsonDecode(lines.single) as Map<String, Object?>;
      expect(entry['source'], 'flows.run');
      expect(entry['error'], 'boom');
      expect(entry['level'], 'error');
      expect(entry['ts'], isA<String>());
    });

    test('context field is preserved when supplied', () async {
      await ChainLog.instance.error(
        'theme.plugin.load',
        Exception('endpoint unreachable'),
        context: 'capability=studio.theme.space',
      );
      final lines = await ChainLog.instance.tail();
      final entry = jsonDecode(lines.single) as Map<String, Object?>;
      expect(entry['context'], 'capability=studio.theme.space');
      expect(entry['error'], contains('endpoint unreachable'));
    });

    test('tail returns oldest first', () async {
      await ChainLog.instance.error('a', '1');
      await ChainLog.instance.error('b', '2');
      await ChainLog.instance.error('c', '3');
      final lines = await ChainLog.instance.tail();
      expect(lines, hasLength(3));
      final sources = lines.map((l) => jsonDecode(l)['source']).toList();
      expect(sources, ['a', 'b', 'c']);
    });

    test('tail caps output at maxLines and keeps the newest', () async {
      for (var i = 0; i < 20; i++) {
        await ChainLog.instance.error('burst', 'event-$i');
      }
      final lines = await ChainLog.instance.tail(maxLines: 5);
      expect(lines, hasLength(5));
      final last = jsonDecode(lines.last) as Map<String, Object?>;
      expect(last['error'], 'event-19');
    });

    test('rotation moves the live log to .log.1 past 256 KiB', () async {
      // Pre-seed the active log just over the cap. The next
      // append should rotate, leaving the rotated file at
      // `.log.1` and a short fresh `.log`.
      logFile.parent.createSync(recursive: true);
      logFile.writeAsBytesSync(List.filled(257 * 1024, 0x20));
      await ChainLog.instance.error('rotation', 'after-cap');
      expect(File('${logFile.path}.1').existsSync(), isTrue);
      final newSize = logFile.lengthSync();
      expect(newSize, lessThan(2 * 1024));
      final newText = logFile.readAsStringSync();
      expect(newText, contains('"source":"rotation"'));
    });

    test('path getter returns the override when set', () {
      expect(ChainLog.instance.path, logFile.path);
    });

    test('writes failing silently does not throw', () async {
      // Redirect to a deliberately impossible path. The error()
      // call must complete cleanly; the operator UI must never
      // crash because the disk is full / read-only / missing.
      ChainLog.testPathOverride = '/this/path/does/not/exist/ever/x.log';
      await expectLater(
        ChainLog.instance.error('bad.path', 'boom'),
        completes,
      );
    });
  });
}