import 'dart:async';
import 'package:flutter/material.dart';
import 'models/client.dart';
import 'models/activity.dart';
import 'models/app_stats.dart';
import 'screens/dashboard_screen.dart';
import 'screens/clients_screen.dart';
import 'screens/survey_screen.dart';
import 'screens/surveys_list_screen.dart';
import 'screens/pricing_screen.dart';
import 'services/crm_api_service.dart';
import 'services/auth_service.dart';

class AppShell extends StatefulWidget {
  final AuthUser currentUser;
  final VoidCallback onLogout;

  const AppShell({
    super.key,
    required this.currentUser,
    required this.onLogout,
  });

  @override
  State<AppShell> createState() => _AppShellState();
}

class _AppShellState extends State<AppShell> {
  int _currentIndex = 0;
  bool _backendReady = false;

  List<Client> _clients = [];
  List<Activity> _activities = [];
  List<dynamic> _surveys = [];
  List<dynamic> _pricing = [];
  AppStats _stats = const AppStats(
    totalClients: 0,
    avgVolume: 0,
    revenueOpportunity: 0,
    todayEntries: 0,
    pendingFollowups: 0,
  );

  final _api = CrmApiService();

  Timer? _pollingTimer;

  @override
  void initState() {
    super.initState();
    _api.setToken(widget.currentUser.token);
    _loadFromBackend();
    _startPolling();
  }

  void _startPolling() {
    _pollingTimer = Timer.periodic(const Duration(seconds: 10), (_) {
      _loadFromBackend(silent: true);
    });
  }

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

  Future<void> _loadFromBackend({bool silent = false}) async {
    try {
      final results = await Future.wait([
        _api.loadClients(),
        _api.fetchSurveys(),
        _api.fetchPricing(),
      ]);
      final clients = results[0] as List<Client>;
      final surveys = results[1];
      final pricing = results[2];
      
      if (!mounted) return;
      setState(() {
        _clients = clients;
        _surveys = surveys;
        _pricing = pricing;
        _stats = _computeStats(clients);
        _backendReady = true;
      });
    } catch (_) {
      if (mounted && !silent) setState(() => _backendReady = false);
    }
  }

  AppStats _computeStats(List<Client> clients) {
    if (clients.isEmpty) {
      return const AppStats(
        totalClients: 0,
        avgVolume: 0,
        revenueOpportunity: 0,
        todayEntries: 0,
        pendingFollowups: 0,
      );
    }
    final totalVolume = clients.fold(0.0, (acc, c) => acc + c.parcelVolume);
    final avg = (totalVolume / clients.length).round();
    return AppStats(
      totalClients: clients.length,
      avgVolume: avg,
      revenueOpportunity: double.parse((totalVolume * 0.01).toStringAsFixed(2)),
      todayEntries: 0,
      pendingFollowups: clients.where((c) => c.dataConsent == DataConsent.basicOnly).length,
    );
  }

  void _handleAddClient(Client incoming) async {
    final newClient = incoming.copyWith(
      recordedByName: widget.currentUser.name,
      recordedByEmail: widget.currentUser.email,
      recordedByRole: widget.currentUser.role,
    );

    // Optimistic UI update with a temp ID
    setState(() {
      _clients = [newClient, ..._clients];
      _activities = [
        Activity(
          id: 'act_${DateTime.now().millisecondsSinceEpoch}',
          clientName: newClient.name,
          action: 'Survey submitted just now',
          icon: ActivityIcon.shipping,
          status: ActivityStatus.newStatus,
        ),
        ..._activities,
      ];
      _stats = _computeStats(_clients);
    });

    // Persist to backend and swap temp ID with server-assigned ID
    final saved = await _api.createClient(newClient);
    if (saved != null && mounted) {
      setState(() {
        _clients = _clients
            .map((c) => c.id == newClient.id ? saved : c)
            .toList();
      });
    }
  }

  void _handleUpdateNotes(String clientId, String newNotes) async {
    setState(() {
      _clients = _clients.map((c) {
        if (c.id == clientId) {
          return c.copyWith(notes: newNotes, lastUpdated: 'Updated just now');
        }
        return c;
      }).toList();

      final updated = _clients.firstWhere((c) => c.id == clientId);
      _activities = [
        Activity(
          id: 'act_${DateTime.now().millisecondsSinceEpoch}',
          clientName: updated.name,
          action: 'Profile updated by Rep',
          icon: ActivityIcon.edit,
        ),
        ..._activities,
      ];
    });

    final updated = _clients.firstWhere((c) => c.id == clientId);
    await _api.updateClient(updated);
  }

  void _handleCompleteClientProfile(
    String clientId,
    double parcelVolume,
    int activeContracts,
    String provider,
    String notes,
  ) async {
    String efficiency = 'High Efficiency';
    if (provider == 'Blue Dart Express') efficiency = 'Premium Service';
    if (provider == 'Gati-KWE') efficiency = 'Cost Leader';
    if (provider == 'Delhivery') efficiency = 'Local Last Mile';

    setState(() {
      _clients = _clients.map((c) {
        if (c.id != clientId) return c;
        return c.copyWith(
          parcelVolume: parcelVolume,
          activeContracts: activeContracts,
          provider: provider,
          efficiency: efficiency,
          notes: notes,
          dataConsent: DataConsent.full,
          lastUpdated: 'Just now',
          surveySubmitted: true,
          recordedByName: widget.currentUser.name,
          recordedByEmail: widget.currentUser.email,
          recordedByRole: widget.currentUser.role,
        );
      }).toList();
      _stats = _computeStats(_clients);
    });

    final updated = _clients.firstWhere((c) => c.id == clientId);
    await _api.updateClient(updated);
  }

  void _navigateTo(int index) {
    if (index == 4) {
      Navigator.push(context, MaterialPageRoute(
        builder: (ctx) => Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.white,
            elevation: 0,
            iconTheme: const IconThemeData(color: Colors.black87),
            title: const Text('Add Client', style: TextStyle(color: Colors.black87, fontWeight: FontWeight.bold)),
          ),
          body: SurveyScreen(
            clients: _clients,
            onAddClient: _handleAddClient,
            onNavigate: (i) {
              Navigator.pop(ctx);
              _navigateTo(i);
            },
            backendReady: _backendReady,
            isActive: true,
          ),
        ),
      ));
      return;
    }
    setState(() => _currentIndex = index);
  }

  @override
  Widget build(BuildContext context) {
    final screens = [
      DashboardScreen(
        stats: _stats,
        activities: _activities,
        clients: _clients,
        surveys: _surveys,
        pricing: _pricing,
        onNavigate: _navigateTo,
        onDataChanged: _loadFromBackend,
        backendReady: _backendReady,
        onLogout: widget.onLogout,
        isActive: _currentIndex == 0,
      ),
      ClientsScreen(
        clients: _clients,
        onUpdateClientNotes: _handleUpdateNotes,
        onCompleteClientProfile: _handleCompleteClientProfile,
        onNavigate: _navigateTo,
        backendReady: _backendReady,
        isActive: _currentIndex == 1,
      ),
      SurveysListScreen(
        surveys: _surveys,
        onDataChanged: _loadFromBackend,
        isActive: _currentIndex == 2,
      ),
      PricingScreen(
        pricing: _pricing,
        backendReady: _backendReady,
        onDataChanged: _loadFromBackend,
        isActive: _currentIndex == 3,
      ),
    ];

    return Scaffold(
      body: SafeArea(
        child: IndexedStack(
          index: _currentIndex,
          children: screens,
        ),
      ),
      bottomNavigationBar: NavigationBar(
        selectedIndex: _currentIndex,
        onDestinationSelected: _navigateTo,
        height: 68,
        destinations: const [
          NavigationDestination(icon: Icon(Icons.dashboard_outlined), selectedIcon: Icon(Icons.dashboard), label: 'Home'),
          NavigationDestination(icon: Icon(Icons.people_outline), selectedIcon: Icon(Icons.people), label: 'Clients'),
          NavigationDestination(icon: Icon(Icons.storefront_outlined), selectedIcon: Icon(Icons.storefront), label: 'Surveys'),
          NavigationDestination(icon: Icon(Icons.local_shipping_outlined), selectedIcon: Icon(Icons.local_shipping), label: 'Pricing'),
        ],
      ),
    );
  }
}