import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:formz/formz.dart';
import 'package:go_router/go_router.dart';

import '../../../../core/router/app_routes.dart';
import '../../../../core/theme/design_tokens.dart';
import '../../../../shared/widgets/app_button.dart';
import '../../../../shared/widgets/banner/app_banner.dart';
import '../../../../shared/widgets/fixed_length_code_input.dart';
import '../../../../shared/widgets/link_button.dart';
import '../../../../shared/widgets/toast/toast.dart';
import '../../../../shared/widgets/toast/toast_type.dart';
import '../../presentation/bloc/auth_bloc.dart';
import '../../presentation/bloc/auth_event.dart';
import '../../presentation/cubits/register_cubit.dart';
import '../widgets/auth_page_scaffold.dart';

class RegisterVerificationScreen extends StatelessWidget {
  const RegisterVerificationScreen({super.key, this.cubit});

  final RegisterCubit? cubit;

  @override
  Widget build(BuildContext context) {
    final registerCubit =
        cubit ?? (GoRouterState.of(context).extra as RegisterCubit?);

    if (registerCubit == null) {
      return const Scaffold(
        body: Center(child: Text('RegisterCubit not found')),
      );
    }

    return BlocProvider.value(
      value: registerCubit,
      child: const RegisterVerificationView(),
    );
  }
}

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

  @override
  State<RegisterVerificationView> createState() =>
      _RegisterVerificationViewState();
}

class _RegisterVerificationViewState extends State<RegisterVerificationView> {
  final _codeController = TextEditingController();
  Timer? _countdownTimer;
  int _countdown = 0;
  bool _firstSendCompleted = false;

  @override
  void dispose() {
    _countdownTimer?.cancel();
    _codeController.dispose();
    super.dispose();
  }

  void _startCountdown() {
    setState(() {
      _countdown = 60;
    });
    _countdownTimer?.cancel();
    _countdownTimer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (_countdown > 0) {
        setState(() {
          _countdown--;
        });
      } else {
        timer.cancel();
      }
    });
  }

  Future<void> _handleComplete() async {
    final cubit = context.read<RegisterCubit>();
    cubit.verificationCodeChanged(_codeController.text);

    if (!cubit.state.isStep2Valid) {
      Toast.show(
        context,
        _codeController.text.isEmpty ? '请输入验证码' : '验证码必须是 6 位数字',
        type: ToastType.warning,
      );
      return;
    }

    final response = await cubit.submitStep2();
    if (response != null && mounted) {
      context.read<AuthBloc>().add(AuthLoggedIn(user: response.user));
      context.go(AppRoutes.homeMain);
    }
  }

  Future<void> _handleResendCode() async {
    final cubit = context.read<RegisterCubit>();
    final success = await cubit.resendCode();

    if (success && mounted) {
      _startCountdown();
      Toast.show(context, '验证码已发送', type: ToastType.success);
    }
  }

  @override
  Widget build(BuildContext context) {
    return AuthPageScaffold(
      mainContent: Padding(
        padding: const EdgeInsets.symmetric(horizontal: AppSpacing.sm),
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: 388),
          child: BlocConsumer<RegisterCubit, RegisterState>(
            listener: (context, state) {
              if (!mounted) {
                return;
              }

              if (state.status == FormzSubmissionStatus.failure &&
                  state.errorMessage != null) {
                Toast.show(context, state.errorMessage!, type: ToastType.error);

                if (!_firstSendCompleted) {
                  _firstSendCompleted = true;
                  setState(() {
                    _countdown = 0;
                  });
                }
              }

              if (state.status == FormzSubmissionStatus.success &&
                  !_firstSendCompleted) {
                _firstSendCompleted = true;
                _startCountdown();
                Toast.show(context, '验证码已发送', type: ToastType.info);
              }
            },
            builder: (context, state) {
              final isSubmitting =
                  state.status == FormzSubmissionStatus.inProgress;
              final canResend = _countdown == 0 && !isSubmitting;

              return Column(
                mainAxisSize: MainAxisSize.min,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  const AuthHeroHeader(showBrand: true),
                  SizedBox(height: AppSpacing.xl),
                  AuthSurfaceCard(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: [
                        const Text(
                          '验证邮箱',
                          style: TextStyle(
                            fontSize: 20,
                            fontWeight: FontWeight.w700,
                            color: AppColors.slate900,
                          ),
                        ),
                        SizedBox(height: AppSpacing.lg),
                        AuthSection(
                          title: '验证码',
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.stretch,
                            children: [
                              FixedLengthCodeInput(
                                controller: _codeController,
                                length: 6,
                                semanticLabel: '邮箱验证码输入框',
                                keyboardType: TextInputType.number,
                                allowedCharacters: const {
                                  '0',
                                  '1',
                                  '2',
                                  '3',
                                  '4',
                                  '5',
                                  '6',
                                  '7',
                                  '8',
                                  '9',
                                },
                                onChanged: (value) {
                                  context
                                      .read<RegisterCubit>()
                                      .verificationCodeChanged(value);
                                },
                              ),
                              SizedBox(height: AppSpacing.md),
                              AppBanner(
                                title: '验证码',
                                message: canResend
                                    ? '6 位数字验证码。'
                                    : '$_countdown 秒后可重新发送。',
                                type: ToastType.info,
                              ),
                            ],
                          ),
                        ),
                        SizedBox(height: AppSpacing.lg),
                        AppButton(
                          text: '完成注册',
                          onPressed: isSubmitting ? null : _handleComplete,
                          isLoading: isSubmitting,
                        ),
                        SizedBox(height: AppSpacing.sm),
                        Center(
                          child: LinkButton(
                            text: canResend ? '重新发送验证码' : '$_countdown 秒后重发',
                            onTap: canResend ? _handleResendCode : null,
                            enabled: canResend,
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              );
            },
          ),
        ),
      ),
      footer: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          const Text(
            '已有账号？',
            style: TextStyle(fontSize: 14, color: AppColors.authLinkMuted),
          ),
          LinkButton(text: '去登录', onTap: () => context.go('/')),
        ],
      ),
    );
  }
}