import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:riverpod_annotation/riverpod_annotation.dart';
import 'package:tatlock_ui/core/auth/auth_provider.dart';
import 'package:tatlock_ui/core/config/app_config.dart';
import 'package:tatlock_ui/features/control_room/router.dart';
import 'package:tatlock_ui/features/front_hall/presentation/pages/front_hall_page.dart';
import 'package:tatlock_ui/features/security/router.dart';
import 'package:tatlock_ui/shared/layouts/app_scaffold.dart';

part 'app_router.g.dart';

/// Route paths as constants.
abstract class AppRoutes {
  static const frontHall = '/';
  static const parlor = '/parlor';
  static const settings = '/settings';
  static const login = '/login';
  static const callback = '/callback';
}

/// Provides the GoRouter instance.
@riverpod
GoRouter appRouter(Ref ref) {
  final authState = ref.watch(authProvider);

  return GoRouter(
    initialLocation: AppRoutes.frontHall,
    debugLogDiagnostics: true,
    redirect: (context, state) {
      // No auth required in LAN mode
      if (!AppConfig.requiresAuth) {
        return null;
      }

      // Allow callback route through without auth check (must be checked FIRST!)
      if (state.matchedLocation == AppRoutes.callback) {
        return null;
      }

      final isAuthenticated = authState.value?.isAuthenticated ?? false;
      final isLoginRoute = state.matchedLocation == AppRoutes.login;

      // If not authenticated, redirect to login (except if already on login)
      if (!isAuthenticated && !isLoginRoute) {
        return AppRoutes.login;
      }

      // If authenticated and on login page, redirect to home
      if (isAuthenticated && isLoginRoute) {
        return AppRoutes.frontHall;
      }

      return null;
    },
    routes: [
      // Login route (outside shell - no app scaffold)
      GoRoute(
        path: AppRoutes.login,
        name: 'login',
        builder: (context, state) => const _LoginPage(),
      ),
      // OIDC callback route (handles auth code exchange)
      GoRoute(
        path: AppRoutes.callback,
        name: 'callback',
        builder: (context, state) => _OidcCallbackPage(
          code: state.uri.queryParameters['code'],
          callbackState: state.uri.queryParameters['state'],
          error: state.uri.queryParameters['error'],
          errorDescription: state.uri.queryParameters['error_description'],
        ),
      ),
      // Main app routes (inside shell with app scaffold)
      ShellRoute(
        builder: (context, state, child) => AppScaffold(child: child),
        routes: [
          GoRoute(
            path: AppRoutes.frontHall,
            name: 'frontHall',
            builder: (context, state) => const FrontHallPage(),
          ),
          ...controlRoomRoutes(),
          ...securityRoutes(),
          GoRoute(
            path: AppRoutes.parlor,
            name: 'parlor',
            builder: (context, state) =>
                const _PlaceholderPage(title: 'Parlor'),
          ),
          GoRoute(
            path: AppRoutes.settings,
            name: 'settings',
            builder: (context, state) =>
                const _PlaceholderPage(title: 'Settings'),
          ),
        ],
      ),
    ],
  );
}

/// Placeholder page for routes not yet implemented.
class _PlaceholderPage extends StatelessWidget {
  const _PlaceholderPage({required this.title});

  final String title;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Icon(
            Icons.construction,
            size: 64,
            color: Theme.of(context).colorScheme.outline,
          ),
          const SizedBox(height: 16),
          Text(
            title,
            style: Theme.of(context).textTheme.headlineMedium,
          ),
          const SizedBox(height: 8),
          Text(
            'Coming soon',
            style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                  color: Theme.of(context).colorScheme.outline,
                ),
          ),
        ],
      ),
    );
  }
}

/// Login page displayed when user is not authenticated.
class _LoginPage extends ConsumerWidget {
  const _LoginPage();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final authAsync = ref.watch(authProvider);
    final colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: Center(
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: 400),
          child: Card(
            child: Padding(
              padding: const EdgeInsets.all(32),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  Icon(
                    Icons.home_work_outlined,
                    size: 64,
                    color: colorScheme.primary,
                  ),
                  const SizedBox(height: 24),
                  Text(
                    'Tatlock Estate',
                    style: Theme.of(context).textTheme.headlineMedium?.copyWith(
                          fontWeight: FontWeight.w600,
                        ),
                  ),
                  const SizedBox(height: 8),
                  Text(
                    'Sign in to access the estate management system',
                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                          color: colorScheme.onSurfaceVariant,
                        ),
                    textAlign: TextAlign.center,
                  ),
                  const SizedBox(height: 32),
                  authAsync.when(
                    data: (_) => _buildSignInContent(context, ref),
                    loading: () => const Column(
                      children: [
                        SizedBox(
                          width: 24,
                          height: 24,
                          child: CircularProgressIndicator(strokeWidth: 2),
                        ),
                        SizedBox(height: 16),
                        Text('Checking authentication...'),
                      ],
                    ),
                    error: (error, _) => _buildErrorContent(context, ref, error),
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildSignInContent(BuildContext context, WidgetRef ref) {
    // Same sign in button for both web and mobile
    return FilledButton.icon(
      onPressed: () => ref.read(authProvider.notifier).signIn(),
      icon: const Icon(Icons.login),
      label: const Text('Sign in with Authentik'),
      style: FilledButton.styleFrom(
        minimumSize: const Size(double.infinity, 48),
      ),
    );
  }

  Widget _buildErrorContent(BuildContext context, WidgetRef ref, Object error) {
    final colorScheme = Theme.of(context).colorScheme;

    return Column(
      children: [
        Container(
          padding: const EdgeInsets.all(12),
          decoration: BoxDecoration(
            color: colorScheme.errorContainer,
            borderRadius: BorderRadius.circular(8),
          ),
          child: Row(
            children: [
              Icon(Icons.error_outline, color: colorScheme.onErrorContainer),
              const SizedBox(width: 12),
              Expanded(
                child: Text(
                  _formatError(error),
                  style: TextStyle(color: colorScheme.onErrorContainer),
                ),
              ),
            ],
          ),
        ),
        const SizedBox(height: 16),
        OutlinedButton.icon(
          onPressed: () => ref.read(authProvider.notifier).signIn(),
          icon: const Icon(Icons.refresh),
          label: const Text('Try again'),
          style: OutlinedButton.styleFrom(
            minimumSize: const Size(double.infinity, 48),
          ),
        ),
      ],
    );
  }

  String _formatError(Object error) {
    final message = error.toString();
    if (message.contains('user_cancelled')) {
      return 'Sign in was cancelled';
    }
    if (message.contains('network')) {
      return 'Network error. Please check your connection.';
    }
    return 'Authentication failed. Please try again.';
  }
}

/// OIDC callback page that handles the authorization code exchange.
class _OidcCallbackPage extends ConsumerStatefulWidget {
  const _OidcCallbackPage({
    this.code,
    this.callbackState,
    this.error,
    this.errorDescription,
  });

  final String? code;
  final String? callbackState;
  final String? error;
  final String? errorDescription;

  @override
  ConsumerState<_OidcCallbackPage> createState() => _OidcCallbackPageState();
}

class _OidcCallbackPageState extends ConsumerState<_OidcCallbackPage> {
  bool _isProcessing = true;
  String? _error;

  @override
  void initState() {
    super.initState();
    // Defer callback processing to avoid Riverpod state modification during build
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _processCallback();
    });
  }

  Future<void> _processCallback() async {
    // Check for error from Authentik
    if (widget.error != null) {
      setState(() {
        _isProcessing = false;
        _error = widget.errorDescription ?? widget.error;
      });
      return;
    }

    // Check for required parameters
    if (widget.code == null || widget.callbackState == null) {
      setState(() {
        _isProcessing = false;
        _error = 'Invalid callback - missing code or state parameter';
      });
      return;
    }

    // Exchange code for tokens
    try {
      await ref.read(authProvider.notifier).handleOidcCallback(
            widget.code!,
            widget.callbackState!,
          );

      // Navigate to home on success
      if (mounted) {
        context.go(AppRoutes.frontHall);
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _isProcessing = false;
          _error = e.toString();
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: Center(
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: 400),
          child: Card(
            child: Padding(
              padding: const EdgeInsets.all(32),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  Icon(
                    _error != null ? Icons.error_outline : Icons.home_work_outlined,
                    size: 64,
                    color: _error != null ? colorScheme.error : colorScheme.primary,
                  ),
                  const SizedBox(height: 24),
                  Text(
                    _error != null ? 'Authentication Failed' : 'Signing in...',
                    style: Theme.of(context).textTheme.headlineMedium?.copyWith(
                          fontWeight: FontWeight.w600,
                        ),
                  ),
                  const SizedBox(height: 16),
                  if (_isProcessing)
                    const CircularProgressIndicator()
                  else if (_error != null) ...[
                    Container(
                      padding: const EdgeInsets.all(12),
                      decoration: BoxDecoration(
                        color: colorScheme.errorContainer,
                        borderRadius: BorderRadius.circular(8),
                      ),
                      child: Text(
                        _error!,
                        style: TextStyle(color: colorScheme.onErrorContainer),
                        textAlign: TextAlign.center,
                      ),
                    ),
                    const SizedBox(height: 16),
                    OutlinedButton.icon(
                      onPressed: () => context.go(AppRoutes.login),
                      icon: const Icon(Icons.arrow_back),
                      label: const Text('Back to Login'),
                      style: OutlinedButton.styleFrom(
                        minimumSize: const Size(double.infinity, 48),
                      ),
                    ),
                  ],
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}