import 'package:dynamic_color/dynamic_color.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:go_router/go_router.dart';
import 'package:mileograph_flutter/components/login/login.dart';
import 'package:mileograph_flutter/components/pages/calculator.dart';
import 'package:mileograph_flutter/components/pages/calculator_details.dart';
import 'package:mileograph_flutter/components/pages/dashboard.dart';
import 'package:mileograph_flutter/components/pages/legs.dart';
import 'package:mileograph_flutter/components/pages/loco_legs.dart';
import 'package:mileograph_flutter/components/pages/loco_timeline.dart';
import 'package:mileograph_flutter/components/pages/new_entry.dart';
import 'package:mileograph_flutter/components/pages/new_traction.dart';
import 'package:mileograph_flutter/components/pages/settings.dart';
import 'package:mileograph_flutter/components/pages/traction.dart';
import 'package:mileograph_flutter/components/pages/trips.dart';
import 'package:mileograph_flutter/services/authservice.dart';
import 'package:mileograph_flutter/services/data_service.dart';
import 'package:mileograph_flutter/services/navigation_guard.dart';
import 'package:provider/provider.dart';

final GlobalKey<NavigatorState> _shellNavigatorKey = GlobalKey<NavigatorState>();

const List<String> _contentPages = [
  "/",
  "/calculator",
  "/legs",
  "/traction",
  "/trips",
  "/add",
];

const int _addTabIndex = 5;

class _NavItem {
  final String label;
  final IconData icon;
  const _NavItem(this.label, this.icon);
}

const List<_NavItem> _navItems = [
  _NavItem("Home", Icons.home),
  _NavItem("Calculator", Icons.route),
  _NavItem("Entries", Icons.list),
  _NavItem("Traction", Icons.train),
  _NavItem("Trips", Icons.book),
  _NavItem("Add", Icons.add),
];

int tabIndexForPath(String path) {
  final newIndex = _contentPages.indexWhere((routePath) {
    if (path == routePath) return true;
    if (routePath == '/') return path == '/';
    return path.startsWith('$routePath/');
  });
  return newIndex < 0 ? 0 : newIndex;
}

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late final GoRouter _router;
  bool _routerInitialized = false;

  final ColorScheme defaultLight = ColorScheme.fromSeed(seedColor: Colors.red);
  final ColorScheme defaultDark = ColorScheme.fromSeed(
    seedColor: Colors.red,
    brightness: Brightness.dark,
  );

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (_routerInitialized) return;
    _routerInitialized = true;
    final auth = context.read<AuthService>();
    _router = GoRouter(
      refreshListenable: auth,
      redirect: (context, state) {
        final loggedIn = auth.isLoggedIn;
        final loggingIn = state.uri.toString() == '/login';
        final atSettings = state.uri.toString() == '/settings';

        if (!loggedIn && !loggingIn && !atSettings) return '/login';
        if (loggedIn && loggingIn) return '/';
        return null;
      },
      routes: [
        ShellRoute(
          navigatorKey: _shellNavigatorKey,
          builder: (context, state, child) => MyHomePage(child: child),
          routes: [
            GoRoute(path: '/', builder: (context, state) => const Dashboard()),
            GoRoute(
              path: '/calculator',
              builder: (context, state) => CalculatorPage(),
            ),
            GoRoute(
              path: '/calculator/details',
              builder: (context, state) =>
                  CalculatorDetailsPage(result: state.extra),
            ),
            GoRoute(path: '/legs', builder: (context, state) => LegsPage()),
            GoRoute(
              path: '/traction',
              builder: (context, state) => TractionPage(),
            ),
            GoRoute(
              path: '/traction/:id/timeline',
              builder: (_, state) {
                final idParam = state.pathParameters['id'];
                final locoId = int.tryParse(idParam ?? '') ?? 0;
                final extra = state.extra;
                String label = state.uri.queryParameters['label'] ?? '';
                if (extra is Map && extra['label'] is String) {
                  label = extra['label'] as String;
                } else if (extra is String && extra.isNotEmpty) {
                  label = extra;
                }
                if (label.trim().isEmpty) label = 'Loco $locoId';
                return LocoTimelinePage(locoId: locoId, locoLabel: label);
              },
            ),
            GoRoute(
              path: '/traction/:id/legs',
              builder: (_, state) {
                final idParam = state.pathParameters['id'];
                final locoId = int.tryParse(idParam ?? '') ?? 0;
                final extra = state.extra;
                String label = state.uri.queryParameters['label'] ?? '';
                if (extra is Map && extra['label'] is String) {
                  label = extra['label'] as String;
                } else if (extra is String && extra.isNotEmpty) {
                  label = extra;
                }
                if (label.trim().isEmpty) label = 'Loco $locoId';
                return LocoLegsPage(locoId: locoId, locoLabel: label);
              },
            ),
            GoRoute(
              path: '/traction/new',
              builder: (context, state) => const NewTractionPage(),
            ),
            GoRoute(path: '/trips', builder: (context, state) => TripsPage()),
            GoRoute(path: '/add', builder: (context, state) => NewEntryPage()),
            GoRoute(
              path: '/legs/edit/:id',
              builder: (_, state) {
                final idParam = state.pathParameters['id'];
                final legId = idParam == null ? null : int.tryParse(idParam);
                return NewEntryPage(editLegId: legId);
              },
            ),
          ],
        ),
        GoRoute(path: '/login', builder: (context, state) => const LoginScreen()),
        GoRoute(
          path: '/settings',
          builder: (context, state) => const SettingsPage(),
        ),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return DynamicColorBuilder(
      builder: (ColorScheme? lightDynamic, ColorScheme? darkDynamic) {
        return MaterialApp.router(
          title: 'Mileograph',
          routerConfig: _router,
          theme: ThemeData(
            useMaterial3: true,
            colorScheme: lightDynamic ?? defaultLight,
          ),
          darkTheme: ThemeData(
            useMaterial3: true,
            colorScheme: darkDynamic ?? defaultDark,
          ),
          themeMode: ThemeMode.system,
        );
      },
    );
  }
}

class MyHomePage extends StatefulWidget {
  final Widget child;
  const MyHomePage({super.key, required this.child});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<String> get contentPages => _contentPages;

  Future<void> _onItemTapped(int index, int currentIndex) async {
    if (index < 0 || index >= contentPages.length || index == currentIndex) {
      return;
    }
    await NavigationGuard.attemptNavigation(() async {
      if (!mounted) return;
      context.go(contentPages[index]);
    });
  }

  int? _lastTabIndex;
  final List<int> _tabHistory = [];
  bool _handlingBackNavigation = false;

  bool _fetched = false;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();

    if (_fetched) return;
    _fetched = true;
    WidgetsBinding.instance.addPostFrameCallback((_) {
      Future(() async {
        if (!mounted) return;
        final data = context.read<DataService>();
        final auth = context.read<AuthService>();
        await auth.tryRestoreSession();
        if (!auth.isLoggedIn) return;
        data.fetchEventFields();
        if (data.homepageStats == null) {
          data.fetchHomepageStats();
        }
        if (data.legs.isEmpty) {
          data.fetchLegs();
        }
        if (data.traction.isEmpty) {
          data.fetchHadTraction();
        }
        if (data.latestLocoChanges.isEmpty) {
          data.fetchLatestLocoChanges();
        }
        if (data.onThisDay.isEmpty) {
          data.fetchOnThisDay();
        }
        if (data.tripDetails.isEmpty) {
          data.fetchTripDetails();
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    final uri = GoRouterState.of(context).uri;
    final pageIndex = tabIndexForPath(uri.path);
    _recordTabChange(pageIndex);
    if (pageIndex != _addTabIndex) {
      NavigationGuard.unregister();
    }
    final homepageReady = context.select<DataService, bool>(
      (data) => data.homepageStats != null || !data.isHomepageLoading,
    );
    final auth = context.read<AuthService>();

    final currentPage = homepageReady
        ? widget.child
        : const Center(child: CircularProgressIndicator());

    return PopScope(
      canPop: false,
      onPopInvokedWithResult: (didPop, _) async {
        if (didPop) return;

        final shellNav = _shellNavigatorKey.currentState;
        if (shellNav != null && shellNav.canPop()) {
          shellNav.pop();
          return;
        }

        if (_tabHistory.isNotEmpty) {
          final previousTab = _tabHistory.removeLast();
          if (!mounted) return;
          _handlingBackNavigation = true;
          context.go(contentPages[previousTab]);
          return;
        }

        if (pageIndex != 0) {
          if (!mounted) return;
          _handlingBackNavigation = true;
          context.go(contentPages[0]);
          return;
        }

        SystemNavigator.pop();
      },
      child: LayoutBuilder(
        builder: (context, constraints) {
          final isWide = constraints.maxWidth >= 900;
          final railExtended = constraints.maxWidth >= 1400;
          final navRailDestinations = _navItems
              .map(
                (item) => NavigationRailDestination(
                  icon: Icon(item.icon),
                  label: Text(item.label),
                ),
              )
              .toList();
          final navBarDestinations = _navItems
              .map(
                (item) => NavigationDestination(
                  icon: Icon(item.icon),
                  label: item.label,
                ),
              )
              .toList();

          return Scaffold(
            appBar: AppBar(
              backgroundColor: Theme.of(context).colorScheme.inversePrimary,
              title: Text.rich(
                TextSpan(
                  children: const [
                    TextSpan(text: "Mile"),
                    TextSpan(text: "O", style: TextStyle(color: Colors.red)),
                    TextSpan(text: "graph"),
                  ],
                  style: const TextStyle(
                    decoration: TextDecoration.none,
                    color: Colors.white,
                    fontFamily: "Tomatoes",
                  ),
                ),
              ),
              actions: [
                const IconButton(
                  onPressed: null,
                  icon: Icon(Icons.account_circle),
                ),
                IconButton(
                  tooltip: 'Settings',
                  onPressed: () => context.go('/settings'),
                  icon: const Icon(Icons.settings),
                ),
                IconButton(onPressed: auth.logout, icon: const Icon(Icons.logout)),
              ],
            ),
            bottomNavigationBar: isWide
                ? null
                : NavigationBar(
                    selectedIndex: pageIndex,
                    onDestinationSelected: (int index) =>
                        _onItemTapped(index, pageIndex),
                    destinations: navBarDestinations,
                  ),
            body: isWide
                ? Row(
                    children: [
                      SafeArea(
                        child: NavigationRail(
                          selectedIndex: pageIndex,
                          extended: railExtended,
                          labelType: railExtended
                              ? NavigationRailLabelType.none
                              : NavigationRailLabelType.selected,
                          onDestinationSelected: (int index) =>
                              _onItemTapped(index, pageIndex),
                          destinations: navRailDestinations,
                        ),
                      ),
                      const VerticalDivider(width: 1),
                      Expanded(child: currentPage),
                    ],
                  )
                : currentPage,
          );
        },
      ),
    );
  }

  void _recordTabChange(int pageIndex) {
    final last = _lastTabIndex;
    if (last == null) {
      _lastTabIndex = pageIndex;
      return;
    }
    if (last == pageIndex) return;

    if (_handlingBackNavigation) {
      _handlingBackNavigation = false;
      _lastTabIndex = pageIndex;
      return;
    }

    if (_tabHistory.isEmpty || _tabHistory.last != last) {
      _tabHistory.add(last);
    }
    _lastTabIndex = pageIndex;
  }
}