import 'dart:io';
import 'dart:async';

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:chepuhagram/logic/auth_provider.dart';
import 'package:chepuhagram/data/models/session_model.dart';
import 'package:chepuhagram/presentation/screens/qr_scan_screen.dart';
import 'package:timeago/timeago.dart' as timeago;

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

  @override
  State<SessionsScreen> createState() => _SessionsScreenState();
}

class _SessionsScreenState extends State<SessionsScreen> {
  Timer? _refreshTimer;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (mounted) {
        Provider.of<AuthProvider>(context, listen: false).fetchSessions();
      }
    });
    // Периодическое обновление списка сессий каждые 5 секунд (фоновое)
    _refreshTimer = Timer.periodic(const Duration(seconds: 5), (_) {
      if (mounted) {
        Provider.of<AuthProvider>(context, listen: false).fetchSessions(silent: true);
      }
    });
  }

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

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    return Scaffold(
      backgroundColor: colorScheme.background,
      appBar: AppBar(
        title: Text(
          'Активные сеансы',
          style: TextStyle(
            fontWeight: FontWeight.bold,
            color: Theme.of(context).colorScheme.onSurface,
          ),
        ),
        iconTheme: IconThemeData(
          color: Theme.of(context).colorScheme.onSurface,
        ),
        elevation: 0,
        backgroundColor: Colors.transparent,
      ),
      body: Consumer<AuthProvider>(
        builder: (context, auth, child) {
          if (auth.isLoading && auth.sessions.isEmpty) {
            return const Center(child: CircularProgressIndicator());
          }

          if (auth.error != null) {
            return Center(
              child: Padding(
                padding: const EdgeInsets.all(16.0),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    Text('Ошибка: ${auth.error}', textAlign: TextAlign.center),
                    const SizedBox(height: 20),
                    ElevatedButton(
                      onPressed: () => auth.fetchSessions(),
                      child: const Text('Попробовать снова'),
                    ),
                  ],
                ),
              ),
            );
          }

          return RefreshIndicator(
            onRefresh: () => auth.fetchSessions(),
            child: _SessionsList(sessions: auth.sessions),
          );
        },
      ),
    );
  }
}

class _SessionsList extends StatelessWidget {
  final List<Session> sessions;

  const _SessionsList({required this.sessions});

  Future<void> _revokeSession(BuildContext context, int sessionId) async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Завершить сеанс?'),
        content: const Text(
          'Вы уверены, что хотите завершить этот сеанс? Это действие нельзя будет отменить.',
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(context).pop(false),
            child: const Text('Отмена'),
          ),
          TextButton(
            onPressed: () => Navigator.of(context).pop(true),
            style: TextButton.styleFrom(
              foregroundColor: Theme.of(context).colorScheme.error,
            ),
            child: const Text('Завершить'),
          ),
        ],
      ),
    );

    if (confirmed == true && context.mounted) {
      await Provider.of<AuthProvider>(
        context,
        listen: false,
      ).revokeSession(sessionId);
    }
  }

  Future<void> _revokeAllOtherSessions(BuildContext context) async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Завершить все другие сеансы?'),
        content: const Text(
          'Это завершит все сеансы на всех устройствах, кроме текущего.',
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(context).pop(false),
            child: const Text('Отмена'),
          ),
          TextButton(
            onPressed: () => Navigator.of(context).pop(true),
            style: TextButton.styleFrom(
              foregroundColor: Theme.of(context).colorScheme.error,
            ),
            child: const Text('Завершить'),
          ),
        ],
      ),
    );

    if (confirmed == true && context.mounted) {
      await Provider.of<AuthProvider>(
        context,
        listen: false,
      ).revokeAllOtherSessions();
    }
  }

  IconData _getIconForDevice(String deviceName) {
    final name = deviceName.toLowerCase();
    if (name.contains('windows') ||
        name.contains('linux') ||
        name.contains('macos')) {
      return Icons.desktop_windows_outlined;
    }
    if (name.contains('web') || name.contains('chrome')) {
      return Icons.language_outlined;
    }
    if (name.contains('android') ||
        name.contains('ios') ||
        name.contains('mobile')) {
      return Icons.phone_android_outlined;
    }
    return Icons.device_unknown_outlined;
  }

  @override
  Widget build(BuildContext context) {
    final Session? currentSession = sessions.isEmpty
        ? null
        : sessions.firstWhere((s) => s.isCurrent, orElse: () => sessions.first);
    final otherSessions = sessions
        .where((s) => s.id != currentSession?.id)
        .toList();

    final colorScheme = Theme.of(context).colorScheme;

    return ListView(
      padding: EdgeInsets.zero,
      children: [
        if (Platform.isAndroid) ...[
          const SizedBox(height: 16),
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: Container(
              decoration: BoxDecoration(
                color: colorScheme.surfaceVariant.withOpacity(0.2),
                borderRadius: BorderRadius.circular(24),
                border: Border.all(
                  color: colorScheme.outlineVariant.withOpacity(0.15),
                ),
              ),
              child: Material(
                color: Colors.transparent,
                child: InkWell(
                  borderRadius: BorderRadius.circular(24),
                  onTap: () {
                    Navigator.push(
                      context,
                      MaterialPageRoute(builder: (_) => const QrScanScreen()),
                    );
                  },
                  child: Padding(
                    padding: const EdgeInsets.all(20.0),
                    child: Row(
                      children: [
                        Container(
                          padding: const EdgeInsets.all(10),
                          decoration: BoxDecoration(
                            color: colorScheme.primary.withOpacity(0.1),
                            shape: BoxShape.circle,
                          ),
                          child: Icon(
                            Icons.qr_code_scanner,
                            color: colorScheme.primary,
                            size: 24,
                          ),
                        ),
                        const SizedBox(width: 16),
                        Expanded(
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Text(
                                'Подключить устройство',
                                style: TextStyle(
                                  color: colorScheme.onSurface,
                                  fontWeight: FontWeight.bold,
                                  fontSize: 16,
                                ),
                              ),
                              const SizedBox(height: 4),
                              Text(
                                'Сканируйте QR-код для входа на ПК или планшете',
                                style: TextStyle(
                                  color: colorScheme.outline,
                                  fontSize: 12,
                                ),
                              ),
                            ],
                          ),
                        ),
                        Icon(Icons.chevron_right, color: colorScheme.outline),
                      ],
                    ),
                  ),
                ),
              ),
            ),
          ),
        ],
        const SizedBox(height: 16),
        if (currentSession != null) ...[
          _buildSectionHeader(context, 'Текущий сеанс'),
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: _buildGroupContainer(
              context,
              child: _buildSessionTile(
                context,
                currentSession,
                isCurrent: true,
              ),
            ),
          ),
        ],
        const SizedBox(height: 24),
        if (otherSessions.isNotEmpty) ...[
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: _buildGroupContainer(
              context,
              isError: true,
              child: ListTile(
                contentPadding: const EdgeInsets.symmetric(
                  horizontal: 20,
                  vertical: 4,
                ),
                leading: Icon(
                  Icons.phonelink_erase_outlined,
                  color: Theme.of(context).colorScheme.error,
                ),
                title: Text(
                  'Завершить все остальные сеансы',
                  style: TextStyle(
                    color: Theme.of(context).colorScheme.error,
                    fontWeight: FontWeight.w600,
                  ),
                ),
                onTap: () => _revokeAllOtherSessions(context),
              ),
            ),
          ),
          const SizedBox(height: 24),
          _buildSectionHeader(context, 'Активные сеансы'),
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: _buildGroupContainer(
              context,
              child: Column(
                children: otherSessions.map((session) {
                  return Column(
                    children: [
                      _buildSessionTile(context, session),
                      if (otherSessions.last != session) _buildDivider(context),
                    ],
                  );
                }).toList(),
              ),
            ),
          ),
        ] else if (sessions.isNotEmpty) ...[
          Center(
            child: Padding(
              padding: const EdgeInsets.all(16.0),
              child: Text(
                'Нет других активных сеансов.',
                style: Theme.of(context).textTheme.bodySmall,
              ),
            ),
          ),
        ],
        if (sessions.isEmpty &&
            !Provider.of<AuthProvider>(context, listen: false).isLoading)
          Center(
            child: Padding(
              padding: const EdgeInsets.all(32.0),
              child: Text(
                'Нет информации о сеансах.',
                style: Theme.of(context).textTheme.bodySmall,
              ),
            ),
          ),
      ],
    );
  }

  Widget _buildSessionTile(
    BuildContext context,
    Session session, {
    bool isCurrent = false,
  }) {
    final colorScheme = Theme.of(context).colorScheme;

    // Считаем устройство онлайн, если оно текущее или последняя активность была менее 90 секунд назад
    final difference = DateTime.now().toUtc().difference(session.lastActive.toUtc());
    final isOnline = isCurrent || difference.inSeconds < 90;

    final statusText = isOnline 
        ? 'В сети' 
        : 'Активность: ${timeago.format(session.lastActive.toLocal(), locale: 'ru')}';

    return ListTile(
      contentPadding: const EdgeInsets.symmetric(horizontal: 20, vertical: 8),
      leading: Stack(
        clipBehavior: Clip.none,
        children: [
          Container(
            padding: const EdgeInsets.all(8),
            decoration: BoxDecoration(
              color: colorScheme.primary.withOpacity(isCurrent ? 0.12 : 0.08),
              borderRadius: BorderRadius.circular(12),
            ),
            child: Icon(
              _getIconForDevice(session.deviceName),
              color: colorScheme.primary,
              size: 24,
            ),
          ),
          Positioned(
            bottom: -2,
            right: -2,
            child: Container(
              width: 12,
              height: 12,
              decoration: BoxDecoration(
                color: isOnline ? Colors.green : Colors.grey,
                shape: BoxShape.circle,
                border: Border.all(
                  color: Theme.of(context).scaffoldBackgroundColor,
                  width: 2,
                ),
              ),
            ),
          ),
        ],
      ),
      title: Text(
        session.deviceName,
        style: TextStyle(
          fontWeight: isCurrent ? FontWeight.bold : FontWeight.w600,
          fontSize: 16,
        ),
      ),
      subtitle: Text.rich(
        TextSpan(
          children: [
            TextSpan(text: '${session.ipAddress}\n'),
            TextSpan(
              text: statusText,
              style: TextStyle(
                color: isOnline ? Colors.green : colorScheme.outline,
                fontWeight: isOnline ? FontWeight.w500 : FontWeight.normal,
              ),
            ),
          ],
        ),
        style: const TextStyle(fontSize: 13),
      ),
      trailing: isCurrent
          ? null
          : TextButton(
              onPressed: () => _revokeSession(context, session.id),
              child: Text('Выйти', style: TextStyle(color: colorScheme.error)),
            ),
    );
  }

  Widget _buildGroupContainer(
    BuildContext context, {
    required Widget child,
    bool isError = false,
  }) {
    final colorScheme = Theme.of(context).colorScheme;
    return Container(
      decoration: BoxDecoration(
        color: isError
            ? colorScheme.errorContainer.withOpacity(0.15)
            : colorScheme.surfaceVariant.withOpacity(0.2),
        borderRadius: BorderRadius.circular(24),
        border: Border.all(
          color: isError
              ? colorScheme.errorContainer.withOpacity(0.2)
              : colorScheme.outlineVariant.withOpacity(0.1),
        ),
      ),
      child: child,
    );
  }

  Widget _buildDivider(BuildContext context) => Divider(
    height: 1,
    indent: 68,
    color: Theme.of(context).colorScheme.outlineVariant.withOpacity(0.15),
  );

  Widget _buildSectionHeader(BuildContext context, String title) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 8, 16, 12),
      child: Text(
        title.toUpperCase(),
        style: TextStyle(
          fontWeight: FontWeight.bold,
          color: Theme.of(context).colorScheme.primary,
          fontSize: 12,
          letterSpacing: 0.5,
        ),
      ),
    );
  }
}