import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../../models/notification_item.dart';
import '../../models/task.dart';
import '../../providers/notifications_provider.dart';
import '../../providers/profile_provider.dart';
import '../../providers/tasks_provider.dart';
import '../../providers/tickets_provider.dart';
import '../../providers/typing_provider.dart';
import '../../widgets/responsive_body.dart';
import '../../widgets/typing_dots.dart';

class TasksListScreen extends ConsumerWidget {
  const TasksListScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final tasksAsync = ref.watch(tasksProvider);
    final ticketsAsync = ref.watch(ticketsProvider);
    final officesAsync = ref.watch(officesProvider);
    final profileAsync = ref.watch(currentProfileProvider);
    final notificationsAsync = ref.watch(notificationsProvider);

    final canCreate = profileAsync.maybeWhen(
      data: (profile) =>
          profile != null &&
          (profile.role == 'admin' ||
              profile.role == 'dispatcher' ||
              profile.role == 'it_staff'),
      orElse: () => false,
    );

    final ticketById = {
      for (final ticket in ticketsAsync.valueOrNull ?? []) ticket.id: ticket,
    };
    final officeById = {
      for (final office in officesAsync.valueOrNull ?? []) office.id: office,
    };

    return Scaffold(
      body: ResponsiveBody(
        child: tasksAsync.when(
          data: (tasks) {
            if (tasks.isEmpty) {
              return const Center(child: Text('No tasks yet.'));
            }
            return Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                Padding(
                  padding: const EdgeInsets.only(top: 16, bottom: 8),
                  child: Align(
                    alignment: Alignment.center,
                    child: Text(
                      'Tasks',
                      textAlign: TextAlign.center,
                      style: Theme.of(context).textTheme.titleLarge?.copyWith(
                        fontWeight: FontWeight.w700,
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: ListView.separated(
                    padding: const EdgeInsets.only(bottom: 24),
                    itemCount: tasks.length,
                    separatorBuilder: (context, index) =>
                        const SizedBox(height: 12),
                    itemBuilder: (context, index) {
                      final task = tasks[index];
                      final ticketId = task.ticketId;
                      final ticket = ticketId == null
                          ? null
                          : ticketById[ticketId];
                      final officeId = ticket?.officeId ?? task.officeId;
                      final officeName = officeId == null
                          ? 'Unassigned office'
                          : (officeById[officeId]?.name ?? officeId);
                      final subtitle = _buildSubtitle(officeName, task.status);
                      final hasMention = _hasTaskMention(
                        notificationsAsync,
                        task,
                      );
                      final typingChannelId = task.id;
                      final typingState = ref.watch(
                        typingIndicatorProvider(typingChannelId),
                      );
                      final showTyping = typingState.userIds.isNotEmpty;

                      return ListTile(
                        leading: _buildQueueBadge(context, task),
                        title: Text(
                          task.title.isNotEmpty
                              ? task.title
                              : (ticket?.subject ?? 'Task ${task.id}'),
                        ),
                        subtitle: Text(subtitle),
                        trailing: Row(
                          mainAxisSize: MainAxisSize.min,
                          children: [
                            _buildStatusChip(context, task.status),
                            if (showTyping) ...[
                              const SizedBox(width: 6),
                              TypingDots(
                                size: 6,
                                color: Theme.of(context).colorScheme.primary,
                              ),
                            ],
                            if (hasMention)
                              const Padding(
                                padding: EdgeInsets.only(left: 8),
                                child: Icon(
                                  Icons.circle,
                                  size: 10,
                                  color: Colors.red,
                                ),
                              ),
                          ],
                        ),
                        onTap: () => context.go('/tasks/${task.id}'),
                      );
                    },
                  ),
                ),
              ],
            );
          },
          loading: () => const Center(child: CircularProgressIndicator()),
          error: (error, _) =>
              Center(child: Text('Failed to load tasks: $error')),
        ),
      ),
      floatingActionButton: canCreate
          ? FloatingActionButton.extended(
              onPressed: () => _showCreateTaskDialog(context, ref),
              icon: const Icon(Icons.add),
              label: const Text('New Task'),
            )
          : null,
    );
  }

  Future<void> _showCreateTaskDialog(
    BuildContext context,
    WidgetRef ref,
  ) async {
    final titleController = TextEditingController();
    final descriptionController = TextEditingController();
    String? selectedOfficeId;

    await showDialog<void>(
      context: context,
      builder: (dialogContext) {
        return StatefulBuilder(
          builder: (context, setState) {
            final officesAsync = ref.watch(officesProvider);
            return AlertDialog(
              title: const Text('Create Task'),
              content: SizedBox(
                width: 360,
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    TextField(
                      controller: titleController,
                      decoration: const InputDecoration(
                        labelText: 'Task title',
                      ),
                    ),
                    const SizedBox(height: 12),
                    TextField(
                      controller: descriptionController,
                      decoration: const InputDecoration(
                        labelText: 'Description',
                      ),
                      maxLines: 3,
                    ),
                    const SizedBox(height: 12),
                    officesAsync.when(
                      data: (offices) {
                        if (offices.isEmpty) {
                          return const Text('No offices available.');
                        }
                        selectedOfficeId ??= offices.first.id;
                        return DropdownButtonFormField<String>(
                          initialValue: selectedOfficeId,
                          decoration: const InputDecoration(
                            labelText: 'Office',
                          ),
                          items: offices
                              .map(
                                (office) => DropdownMenuItem(
                                  value: office.id,
                                  child: Text(office.name),
                                ),
                              )
                              .toList(),
                          onChanged: (value) =>
                              setState(() => selectedOfficeId = value),
                        );
                      },
                      loading: () => const Align(
                        alignment: Alignment.centerLeft,
                        child: CircularProgressIndicator(),
                      ),
                      error: (error, _) =>
                          Text('Failed to load offices: $error'),
                    ),
                  ],
                ),
              ),
              actions: [
                TextButton(
                  onPressed: () => Navigator.of(dialogContext).pop(),
                  child: const Text('Cancel'),
                ),
                FilledButton(
                  onPressed: () async {
                    final title = titleController.text.trim();
                    final description = descriptionController.text.trim();
                    final officeId = selectedOfficeId;
                    if (title.isEmpty || officeId == null) {
                      return;
                    }
                    await ref
                        .read(tasksControllerProvider)
                        .createTask(
                          title: title,
                          description: description,
                          officeId: officeId,
                        );
                    if (context.mounted) {
                      Navigator.of(dialogContext).pop();
                    }
                  },
                  child: const Text('Create'),
                ),
              ],
            );
          },
        );
      },
    );
  }

  bool _hasTaskMention(
    AsyncValue<List<NotificationItem>> notificationsAsync,
    Task task,
  ) {
    return notificationsAsync.maybeWhen(
      data: (items) => items.any(
        (item) =>
            item.isUnread &&
            (item.taskId == task.id || item.ticketId == task.ticketId),
      ),
      orElse: () => false,
    );
  }

  Widget _buildQueueBadge(BuildContext context, Task task) {
    final queueOrder = task.queueOrder;
    final isQueued = task.status == 'queued';
    if (!isQueued || queueOrder == null) {
      return const Icon(Icons.fact_check_outlined);
    }
    return Container(
      width: 40,
      height: 40,
      alignment: Alignment.center,
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.primaryContainer,
        borderRadius: BorderRadius.circular(12),
      ),
      child: Text(
        '#$queueOrder',
        style: Theme.of(context).textTheme.labelMedium?.copyWith(
          fontWeight: FontWeight.w700,
          color: Theme.of(context).colorScheme.onPrimaryContainer,
        ),
      ),
    );
  }

  String _buildSubtitle(String officeName, String status) {
    final statusLabel = status.toUpperCase();
    return '$officeName · $statusLabel';
  }

  Widget _buildStatusChip(BuildContext context, String status) {
    return Chip(
      label: Text(status.toUpperCase()),
      backgroundColor: _statusColor(context, status),
      labelStyle: TextStyle(
        color: _statusTextColor(context, status),
        fontWeight: FontWeight.w600,
      ),
    );
  }

  Color _statusColor(BuildContext context, String status) {
    return switch (status) {
      'queued' => Colors.blueGrey.shade200,
      'in_progress' => Colors.blue.shade300,
      'completed' => Colors.green.shade300,
      _ => Theme.of(context).colorScheme.surfaceContainerHighest,
    };
  }

  Color _statusTextColor(BuildContext context, String status) {
    return switch (status) {
      'queued' => Colors.blueGrey.shade900,
      'in_progress' => Colors.blue.shade900,
      'completed' => Colors.green.shade900,
      _ => Theme.of(context).colorScheme.onSurfaceVariant,
    };
  }
}