import 'dart:async';
import 'dart:js_interop';
import 'dart:js_interop_unsafe';
import 'dart:ui_web' as ui_web;

import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import 'package:userfront/i18n.dart';
import 'package:web/web.dart' as web;

import 'qr_camera_bootstrap_policy.dart';
import 'qr_scan_route.dart';

@JS('BarcodeDetector')
extension type _BarcodeDetector._(JSObject _) implements JSObject {
  external factory _BarcodeDetector();
  external JSPromise<JSArray<_DetectedBarcode>> detect(JSObject source);
}

extension type _DetectedBarcode._(JSObject _) implements JSObject {
  external String? get rawValue;
}

class QRScanScreen extends StatefulWidget {
  const QRScanScreen({super.key});

  @override
  State<QRScanScreen> createState() => _QRScanScreenState();
}

class _QRScanScreenState extends State<QRScanScreen> {
  late final web.HTMLVideoElement _videoElement;
  late final String _viewType;
  final TextEditingController _manualController = TextEditingController();

  web.MediaStream? _stream;
  _BarcodeDetector? _detector;
  Timer? _scanTimer;
  bool _scanInFlight = false;
  bool _navigated = false;
  bool _initializing = true;
  String? _error;
  String? _status;

  @override
  void initState() {
    super.initState();
    _viewType = 'qr-camera-${DateTime.now().microsecondsSinceEpoch}';
    _videoElement = web.HTMLVideoElement()
      ..autoplay = true
      ..muted = true
      ..playsInline = true
      ..style.border = '0'
      ..style.width = '100%'
      ..style.height = '100%'
      ..style.objectFit = 'cover';

    ui_web.platformViewRegistry.registerViewFactory(_viewType, (int viewId) {
      return _videoElement;
    });

    unawaited(_initializeScanner());
  }

  @override
  void dispose() {
    _scanTimer?.cancel();
    _stopCamera();
    _manualController.dispose();
    super.dispose();
  }

  Future<void> _initializeScanner() async {
    setState(() {
      _initializing = true;
      _error = null;
      _status = tr('ui.userfront.qr.title', fallback: 'Scan QR Code');
    });
    final hasBarcodeDetector = globalContext
        .hasProperty('BarcodeDetector'.toJS)
        .toDart;

    final result = await bootstrapQrCamera(
      hasBarcodeDetector: hasBarcodeDetector,
      openCameraAndPlay: () async {
        final constraints = web.MediaStreamConstraints(
          video: web.MediaTrackConstraints(facingMode: 'environment'.toJS),
          audio: false.toJS,
        );
        _stream = await web.window.navigator.mediaDevices
            .getUserMedia(constraints)
            .toDart;
        _videoElement.srcObject = _stream;
        await _videoElement.play().toDart;
      },
      stopCamera: () async {
        _stopCamera();
      },
    );

    if (!mounted) {
      return;
    }

    switch (result.status) {
      case QrCameraBootstrapStatus.ready:
        _detector = _BarcodeDetector();
        setState(() {
          _initializing = false;
          _status = tr(
            'msg.userfront.login.qr.scan_hint',
            fallback: 'QR 코드를 카메라 중앙에 맞춰주세요.',
          );
        });
        _startScanLoop();
        break;
      case QrCameraBootstrapStatus.detectorUnsupported:
        setState(() {
          _initializing = false;
          _status = tr(
            'msg.userfront.login.qr.scan_hint',
            fallback: 'QR 코드를 카메라 중앙에 맞춰주세요.',
          );
          _error = tr(
            'msg.userfront.qr.camera_error',
            fallback: 'Camera error: {{error}}',
            params: {'error': result.errorDetail},
          );
        });
        break;
      case QrCameraBootstrapStatus.permissionError:
        setState(() {
          _initializing = false;
          _error = tr(
            'msg.userfront.qr.permission_error',
            fallback: 'Permission request failed. Check browser/OS settings.',
          );
        });
        break;
      case QrCameraBootstrapStatus.cameraError:
        setState(() {
          _initializing = false;
          _error = tr(
            'msg.userfront.qr.camera_error',
            fallback: 'Camera error: {{error}}',
            params: {'error': result.errorDetail},
          );
        });
        break;
    }
  }

  void _startScanLoop() {
    _scanTimer?.cancel();
    _scanTimer = Timer.periodic(const Duration(milliseconds: 250), (_) async {
      if (!mounted || _scanInFlight || _navigated) {
        return;
      }
      final detector = _detector;
      if (detector == null) {
        return;
      }
      if (_videoElement.readyState < web.HTMLMediaElement.HAVE_CURRENT_DATA) {
        return;
      }

      _scanInFlight = true;
      try {
        final detected = await detector.detect(_videoElement).toDart;
        final items = detected.toDart;
        for (final item in items) {
          final raw = item.rawValue?.trim();
          if (raw != null && raw.isNotEmpty) {
            _handleScanSuccess(raw);
            break;
          }
        }
      } catch (_) {
      } finally {
        _scanInFlight = false;
      }
    });
  }

  void _stopCamera() {
    final stream = _stream;
    if (stream == null) {
      return;
    }
    final tracks = stream.getTracks().toDart;
    for (final track in tracks) {
      track.stop();
    }
    _videoElement.srcObject = null;
    _stream = null;
  }

  void _handleScanSuccess(String payload) {
    if (_navigated || !mounted) {
      return;
    }
    _navigated = true;
    _scanTimer?.cancel();
    _stopCamera();
    context.go(buildQrApprovePath(payload));
  }

  void _submitManual() {
    final payload = _manualController.text.trim();
    if (payload.isEmpty) {
      return;
    }
    _handleScanSuccess(payload);
  }

  Future<void> _retry() async {
    _scanTimer?.cancel();
    _stopCamera();
    _detector = null;
    await _initializeScanner();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(tr('ui.userfront.qr.title', fallback: 'Scan QR Code')),
        leading: IconButton(
          icon: const Icon(Icons.arrow_back),
          onPressed: () => context.pop(),
        ),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            AspectRatio(
              aspectRatio: 3 / 4,
              child: DecoratedBox(
                decoration: BoxDecoration(
                  color: Colors.black,
                  borderRadius: BorderRadius.circular(12),
                ),
                child: ClipRRect(
                  borderRadius: BorderRadius.circular(12),
                  child: _initializing
                      ? const Center(child: CircularProgressIndicator())
                      : HtmlElementView(viewType: _viewType),
                ),
              ),
            ),
            const SizedBox(height: 12),
            if (_status != null) Text(_status!, textAlign: TextAlign.center),
            if (_error != null) ...[
              const SizedBox(height: 8),
              Text(
                _error!,
                textAlign: TextAlign.center,
                style: const TextStyle(color: Colors.red),
              ),
            ],
            const SizedBox(height: 12),
            FilledButton.icon(
              onPressed: _initializing ? null : _retry,
              icon: const Icon(Icons.refresh),
              label: Text(tr('ui.userfront.qr.rescan', fallback: '다시 스캔')),
            ),
            const SizedBox(height: 12),
            TextField(
              key: const ValueKey('qr_scan_manual_input'),
              controller: _manualController,
              decoration: const InputDecoration(
                labelText: 'QR Payload',
                hintText: 'https://.../ql/{ref} 또는 ref',
              ),
              onSubmitted: (_) => _submitManual(),
            ),
            const SizedBox(height: 8),
            FilledButton.icon(
              key: const ValueKey('qr_scan_submit_button'),
              onPressed: _submitManual,
              icon: const Icon(Icons.check_circle),
              label: Text(
                tr('ui.userfront.qr.result_success', fallback: '승인 화면으로 이동'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}