import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:tatlock_ui/core/auth/auth_provider.dart';
import 'package:tatlock_ui/core/config/app_config.dart';
import 'package:tatlock_ui/routing/room_registry.dart';
import 'package:tatlock_ui/shared/layouts/widgets/top_header_bar.dart';

/// Main application scaffold with top header navigation.
///
/// Handles authentication automatically:
/// - If not authenticated, auto-initiates OIDC flow
/// - Shows loading state during authentication
/// - Shows error state if auth fails (with retry)
///
/// Layout structure per UI_LAYOUT.md:
/// ```
/// ┌─────────────────────────────────────────────────────────────────┐
/// │  HEADER: [Logo] [Room Tabs] [Profile]                           │
/// ├─────────────────────────────────────────────────────────────────┤
/// │  BODY: Room page content (may include room-specific sidebar)    │
/// └─────────────────────────────────────────────────────────────────┘
/// ```
class AppScaffold extends ConsumerStatefulWidget {
  const AppScaffold({super.key, required this.child});

  final Widget child;

  @override
  ConsumerState<AppScaffold> createState() => _AppScaffoldState();
}

class _AppScaffoldState extends ConsumerState<AppScaffold> {
  // Header height must match TopHeaderBar._headerHeight
  static const double _headerHeight = 56.0;

  bool _authInitiated = false;

  @override
  Widget build(BuildContext context) {
    // No auth required in LAN mode - show content directly
    if (!AppConfig.requiresAuth) {
      return _buildScaffold(context);
    }

    // Watch auth state (works for both web and mobile)
    final authAsync = ref.watch(authProvider);

    return authAsync.when(
      data: (authState) {
        if (authState.isAuthenticated) {
          // Authenticated - show the app
          _authInitiated = false; // Reset for next time
          return _buildScaffold(context);
        }

        // On web, NPM handles auth - if we're here without auth, something is wrong
        // (NPM should have redirected to Authentik before we loaded)
        if (kIsWeb) {
          return _buildAuthErrorScreen(context, 'Authentication required');
        }

        // Mobile: Not authenticated - auto-initiate OIDC
        if (!_authInitiated) {
          _authInitiated = true;
          WidgetsBinding.instance.addPostFrameCallback((_) {
            ref.read(authProvider.notifier).signIn();
          });
        }

        // Show loading while redirecting to Authentik
        return _buildAuthLoadingScreen(context, 'Redirecting to sign in...');
      },
      loading: () => _buildAuthLoadingScreen(context, 'Loading user info...'),
      error: (error, _) => _buildAuthErrorScreen(context, error),
    );
  }

  Widget _buildScaffold(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          // Main content area with top padding for header
          Positioned.fill(
            child: Padding(
              padding: const EdgeInsets.only(top: _headerHeight),
              child: widget.child,
            ),
          ),

          // Top header overlays content (bulge extends into content area)
          Positioned(
            top: 0,
            left: 0,
            right: 0,
            child: TopHeaderBar(
              selectedIndex: _selectedIndex(context),
              onRoomSelected: (index) => _onNavSelected(context, index),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildAuthLoadingScreen(BuildContext context, String message) {
    final colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          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: 32),
            const SizedBox(
              width: 24,
              height: 24,
              child: CircularProgressIndicator(strokeWidth: 2),
            ),
            const SizedBox(height: 16),
            Text(
              message,
              style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                    color: colorScheme.onSurfaceVariant,
                  ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildAuthErrorScreen(BuildContext context, Object error) {
    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.error_outline,
                    size: 64,
                    color: colorScheme.error,
                  ),
                  const SizedBox(height: 24),
                  Text(
                    'Authentication Failed',
                    style: Theme.of(context).textTheme.headlineMedium?.copyWith(
                          fontWeight: FontWeight.w600,
                        ),
                  ),
                  const SizedBox(height: 16),
                  Container(
                    padding: const EdgeInsets.all(12),
                    decoration: BoxDecoration(
                      color: colorScheme.errorContainer,
                      borderRadius: BorderRadius.circular(8),
                    ),
                    child: Text(
                      _formatError(error),
                      style: TextStyle(color: colorScheme.onErrorContainer),
                      textAlign: TextAlign.center,
                    ),
                  ),
                  const SizedBox(height: 24),
                  FilledButton.icon(
                    onPressed: () {
                      _authInitiated = false;
                      ref.read(authProvider.notifier).signIn();
                    },
                    icon: const Icon(Icons.refresh),
                    label: const Text('Try again'),
                    style: FilledButton.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.';
  }

  int _selectedIndex(BuildContext context) {
    final location = GoRouterState.of(context).matchedLocation;
    return roomRegistry.indexOfRoute(location);
  }

  void _onNavSelected(BuildContext context, int index) {
    final rooms = roomRegistry.all;
    if (index >= 0 && index < rooms.length) {
      context.go(rooms[index].defaultRoute);
    }
  }
}