import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:iperf3gui/data/services/iperf3_service.dart';
import 'package:iperf3gui/domain/models/iperf3_result.dart';
import 'package:iperf3gui/domain/models/test_configuration.dart';

/// State of the test run.
enum TestRunState { idle, running, completed, error }

/// ViewModel for managing test run state.
///
/// Subscribes to [Iperf3Service.outputLines] so the transcript grows while the
/// test runs rather than appearing all at once at the end.
class TestRunViewModel extends ChangeNotifier {
  final Iperf3Service iperf3Service;

  TestRunViewModel({required this.iperf3Service}) {
    _outputSubscription = iperf3Service.outputLines.listen(_onOutputLine);
  }

  StreamSubscription<String>? _outputSubscription;

  TestRunState _state = TestRunState.idle;
  TestRunState get state => _state;

  Iperf3Result? _result;
  Iperf3Result? get result => _result;

  TestConfiguration? _currentConfig;
  TestConfiguration? get currentConfig => _currentConfig;

  final StringBuffer _liveOutput = StringBuffer();

  /// Output accumulated so far. Grows line by line during a run, and holds the
  /// finished transcript once the test completes.
  String get output => _liveOutput.toString();

  /// Whether a test is currently in flight.
  bool get isRunning => _state == TestRunState.running;

  /// Whether the most recent finished run ended because the user stopped it.
  bool get wasStopped => _result?.stopped ?? false;

  /// Start a test with the given configuration.
  Future<void> runTest(TestConfiguration config) async {
    if (_state == TestRunState.running) return;

    if (!config.isValid) {
      _liveOutput
        ..clear()
        ..writeln('Invalid configuration: check the server address and port.');
      _state = TestRunState.error;
      _result = null;
      notifyListeners();
      return;
    }

    _state = TestRunState.running;
    _currentConfig = config;
    _result = null;
    _liveOutput.clear();
    notifyListeners();

    try {
      final result = await iperf3Service.run(config);
      _result = result;
      // Prefer the streamed transcript — it is what the user watched build up.
      // Fall back to the service's copy if nothing streamed through.
      if (_liveOutput.isEmpty && result.rawOutput.isNotEmpty) {
        _liveOutput.write(result.rawOutput);
      }
      _state =
          result.exitCode == 0 ? TestRunState.completed : TestRunState.error;
    } catch (e) {
      _liveOutput.writeln('Test failed: $e');
      _state = TestRunState.error;
    } finally {
      notifyListeners();
    }
  }

  /// Request that a running test stop early.
  Future<void> stopTest() async {
    if (_state != TestRunState.running) return;
    await iperf3Service.stop();
  }

  /// Reset to idle state.
  void reset() {
    _state = TestRunState.idle;
    _result = null;
    _currentConfig = null;
    _liveOutput.clear();
    notifyListeners();
  }

  void _onOutputLine(String line) {
    _liveOutput.write(line.endsWith('\n') ? line : '$line\n');
    notifyListeners();
  }

  @override
  void dispose() {
    _outputSubscription?.cancel();
    iperf3Service.dispose();
    super.dispose();
  }
}