import 'dart:async';

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

import 'qr_scan_route.dart';

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

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

class _QRScanScreenState extends State<QRScanScreen> {
  final MobileScannerController _scannerController = MobileScannerController(
    autoStart: true,
    detectionSpeed: DetectionSpeed.noDuplicates,
    facing: CameraFacing.back,
    formats: const <BarcodeFormat>[BarcodeFormat.qrCode],
  );
  final TextEditingController _manualController = TextEditingController();

  bool _isProcessing = false;
  String? _error;
  String? _status;

  @override
  void initState() {
    super.initState();
    _status = tr(
      'msg.userfront.login.qr.scan_hint',
      fallback: 'QR 코드를 카메라 중앙에 맞춰주세요.',
    );
  }

  @override
  void dispose() {
    _manualController.dispose();
    _scannerController.dispose();
    super.dispose();
  }

  Future<void> _navigateToApprove(String rawPayload) async {
    final payload = rawPayload.trim();
    if (payload.isEmpty || _isProcessing || !mounted) {
      return;
    }

    setState(() {
      _isProcessing = true;
      _error = null;
      _status = tr(
        'ui.userfront.qr.result_success',
        fallback: '승인 화면으로 이동 중...',
      );
    });

    try {
      await _scannerController.stop();
    } catch (_) {}

    if (!mounted) {
      return;
    }
    context.go(buildQrApprovePath(payload));
  }

  void _onDetect(BarcodeCapture capture) {
    for (final barcode in capture.barcodes) {
      final raw = barcode.rawValue?.trim();
      if (raw != null && raw.isNotEmpty) {
        unawaited(_navigateToApprove(raw));
        return;
      }
    }
  }

  String _toScannerErrorMessage(MobileScannerException error) {
    switch (error.errorCode) {
      case MobileScannerErrorCode.permissionDenied:
        return tr(
          'msg.userfront.qr.permission_error',
          fallback: '카메라 권한 요청에 실패했습니다. 브라우저/OS 설정을 확인해주세요.',
        );
      case MobileScannerErrorCode.unsupported:
        return tr(
          'msg.userfront.qr.camera_error',
          fallback: '카메라 오류: {{error}}',
          params: {'error': 'QR scanner is not supported in this browser.'},
        );
      default:
        final detail = error.errorDetails?.message;
        return tr(
          'msg.userfront.qr.camera_error',
          fallback: '카메라 오류: {{error}}',
          params: {'error': detail ?? error.errorCode.message},
        );
    }
  }

  void _submitManual() {
    unawaited(_navigateToApprove(_manualController.text));
  }

  Future<void> _retry() async {
    setState(() {
      _isProcessing = false;
      _error = null;
      _status = tr(
        'msg.userfront.login.qr.scan_hint',
        fallback: 'QR 코드를 카메라 중앙에 맞춰주세요.',
      );
    });

    try {
      await _scannerController.start();
    } catch (e) {
      if (!mounted) {
        return;
      }
      setState(() {
        _error = tr(
          'msg.userfront.qr.camera_error',
          fallback: '카메라 오류: {{error}}',
          params: {'error': '$e'},
        );
      });
    }
  }

  void _handleBack() {
    final router = GoRouter.of(context);
    if (router.canPop()) {
      router.pop();
      return;
    }
    router.go(buildQrBackFallbackPath());
  }

  @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: _handleBack,
        ),
      ),
      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: Stack(
                    fit: StackFit.expand,
                    children: [
                      MobileScanner(
                        controller: _scannerController,
                        onDetect: _onDetect,
                        errorBuilder: (context, error) {
                          WidgetsBinding.instance.addPostFrameCallback((_) {
                            if (!mounted) {
                              return;
                            }
                            setState(() {
                              _error = _toScannerErrorMessage(error);
                            });
                          });

                          return Center(
                            child: Padding(
                              padding: const EdgeInsets.all(16),
                              child: Text(
                                _toScannerErrorMessage(error),
                                textAlign: TextAlign.center,
                                style: const TextStyle(color: Colors.white),
                              ),
                            ),
                          );
                        },
                      ),
                      if (_isProcessing)
                        Container(
                          color: Colors.black45,
                          child: const Center(
                            child: CircularProgressIndicator(),
                          ),
                        ),
                    ],
                  ),
                ),
              ),
            ),
            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: _isProcessing ? 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: _isProcessing ? null : _submitManual,
              icon: const Icon(Icons.check_circle),
              label: Text(
                tr('ui.userfront.qr.result_success', fallback: '승인 화면으로 이동'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}