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

import '../../core/constants.dart';
import '../../core/exceptions.dart';
import '../../providers/chat_provider.dart';

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

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final convsAsync = ref.watch(conversationsProvider);

    return Scaffold(
      body: convsAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, _) => Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Icon(Icons.cloud_off, size: 48),
              const SizedBox(height: 12),
              const Text('Could not load conversations.'),
              const SizedBox(height: 4),
              TextButton(
                onPressed: () => ref.invalidate(conversationsProvider),
                child: const Text('Retry'),
              ),
            ],
          ),
        ),
        data: (convs) {
          if (convs.isEmpty) {
            return const Center(
                child: Text('No conversations yet. Tap + to start one.'));
          }
          return RefreshIndicator(
            onRefresh: () => ref.refresh(conversationsProvider.future),
            child: ListView.separated(
              itemCount: convs.length,
              separatorBuilder: (_, _) => const Divider(height: 1),
              itemBuilder: (context, i) {
                final conv = convs[i];
                return ListTile(
                  leading: const Icon(Icons.chat_bubble_outline),
                  title: Text(
                    conv.title.isNotEmpty ? conv.title : 'New conversation',
                  ),
                  subtitle: Text(
                    conv.updatedAt.toLocal().toString().substring(0, 16),
                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
                          color: Theme.of(context).colorScheme.onSurfaceVariant,
                        ),
                  ),
                  onTap: () => context.push(
                    Routes.chat.replaceFirst(':id', '${conv.id}'),
                  ),
                  onLongPress: () async {
                    final confirm = await showDialog<bool>(
                      context: context,
                      builder: (dialogContext) => AlertDialog(
                        title: const Text('Delete conversation?'),
                        content: Text(
                          conv.title.isNotEmpty
                              ? conv.title
                              : 'New conversation',
                        ),
                        actions: [
                          TextButton(
                            onPressed: () =>
                                Navigator.pop(dialogContext, false),
                            child: const Text('Cancel'),
                          ),
                          TextButton(
                            onPressed: () => Navigator.pop(dialogContext, true),
                            child: const Text('Delete'),
                          ),
                        ],
                      ),
                    );
                    if (confirm == true) {
                      await ref
                          .read(conversationsProvider.notifier)
                          .delete(conv.id);
                    }
                  },
                );
              },
            ),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        heroTag: 'chat_fab',
        onPressed: () => _newConversation(context, ref),
        child: const Icon(Icons.add),
      ),
    );
  }

  Future<void> _newConversation(BuildContext context, WidgetRef ref) async {
    try {
      final conv = await ref.read(conversationsProvider.notifier).create('');
      if (context.mounted) {
        context.push(Routes.chat.replaceFirst(':id', '${conv.id}'));
      }
    } on AppException catch (e) {
      if (context.mounted) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text(e.message)));
      }
    }
  }
}