import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:path_provider/path_provider.dart';

/// Persistent protocol log for field debugging without a USB cable.
///
/// Every line is kept in a bounded in-memory ring (viewable in-app) and, once
/// [init] has run, appended to a file that can be pulled with adb:
///
///   adb pull /sdcard/Android/data/dev.teamhydra.openscooter/files/openscooter.log
///
/// Before [init], or in tests, only the in-memory ring is used.
/// The PIN is never written here; callers mask it first.
class ProtocolLog extends ChangeNotifier {
  ProtocolLog._();
  static final ProtocolLog instance = ProtocolLog._();

  static const maxLines = 2000;

  final List<String> _lines = <String>[];
  File? _file;
  IOSink? _sink;

  List<String> get lines => List.unmodifiable(_lines);
  String? get path => _file?.path;

  Future<void> init() async {
    if (_file != null) return;
    try {
      Directory? dir;
      if (Platform.isAndroid) dir = await getExternalStorageDirectory();
      dir ??= await getApplicationDocumentsDirectory();
      _file = File('${dir.path}/openscooter.log');
      _sink = _file!.openWrite(mode: FileMode.append);
      log('LOG', 'opened ${_file!.path}');
    } catch (e) {
      debugPrint('ProtocolLog: could not open log file: $e');
    }
  }

  void log(String tag, String message) {
    final line = '${DateTime.now().toIso8601String()} [$tag] $message';
    if (kDebugMode) debugPrint(line);
    _lines.add(line);
    if (_lines.length > maxLines) _lines.removeRange(0, _lines.length - maxLines);
    _sink?.writeln(line);
    notifyListeners();
  }

  Future<void> clear() async {
    _lines.clear();
    await _sink?.flush();
    await _sink?.close();
    _sink = null;
    final f = _file;
    if (f != null) {
      try {
        await f.writeAsString('');
      } catch (_) {}
      _sink = f.openWrite(mode: FileMode.append);
    }
    notifyListeners();
  }

  Future<void> flush() async => _sink?.flush();
}