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

import '../../core/constants.dart';
import '../../data/models/briefing_feed.dart';
import '../../providers/api_client_provider.dart';
import '../../providers/news_provider.dart';
import '../../widgets/news_card.dart';

class NewsScreen extends ConsumerStatefulWidget {
  const NewsScreen({super.key});

  @override
  ConsumerState<NewsScreen> createState() => _NewsScreenState();
}

class _NewsScreenState extends ConsumerState<NewsScreen> {
  final Set<int> _openingChat = {};

  Future<void> _handleDiscuss(int itemId) async {
    if (_openingChat.contains(itemId)) return;
    setState(() => _openingChat.add(itemId));
    try {
      final conversationId =
          await ref.read(chatApiProvider).openArticleInChat(itemId);
      if (mounted) {
        context.push(Routes.chat.replaceFirst(':id', '$conversationId'));
      }
    } catch (_) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Failed to open article in chat.')),
        );
      }
    } finally {
      if (mounted) setState(() => _openingChat.remove(itemId));
    }
  }

  Future<void> _loadMore() async {
    try {
      await ref.read(newsProvider.notifier).loadMore();
    } catch (_) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Failed to load more articles.')),
        );
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    final newsAsync = ref.watch(newsProvider);
    final feedsAsync = ref.watch(feedsProvider);
    final scheme = Theme.of(context).colorScheme;

    return Scaffold(
      appBar: AppBar(
        title: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text('News', style: Theme.of(context).textTheme.titleLarge),
            Text(
              'Last 90 days',
              style: Theme.of(context).textTheme.labelSmall?.copyWith(
                    color: scheme.onSurfaceVariant,
                  ),
            ),
          ],
        ),
      ),
      body: newsAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (e, _) => Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Text('Could not load news.'),
              const SizedBox(height: 12),
              FilledButton.tonal(
                onPressed: () => ref.invalidate(newsProvider),
                child: const Text('Retry'),
              ),
            ],
          ),
        ),
        data: (news) => Column(
          children: [
            _FeedFilter(
              feeds: feedsAsync.value ?? [],
              selectedFeedId: news.selectedFeedId,
              onChanged: (feedId) =>
                  ref.read(newsProvider.notifier).setFeed(feedId),
            ),
            const Divider(height: 1),
            Expanded(
              child: RefreshIndicator(
                onRefresh: () => ref.read(newsProvider.notifier).refresh(),
                child: ListView.builder(
                padding:
                    const EdgeInsets.symmetric(horizontal: 8, vertical: 8),
                itemCount: news.items.length + 1,
                itemBuilder: (_, i) {
                  if (i == news.items.length) {
                    if (!news.hasMore) return const SizedBox.shrink();
                    return Padding(
                      padding: const EdgeInsets.symmetric(vertical: 8),
                      child: Center(
                        child: news.loadingMore
                            ? const CircularProgressIndicator()
                            : FilledButton.tonal(
                                onPressed: _loadMore,
                                child: const Text('Load more'),
                              ),
                      ),
                    );
                  }
                  final item = news.items[i];
                  return NewsCard(
                    item: RssItemMeta.fromNewsItem(item),
                    reaction: news.reactions[item.id],
                    onReaction: (itemId, reaction) => ref
                        .read(newsProvider.notifier)
                        .toggleReaction(itemId, reaction),
                    onDiscuss: _openingChat.contains(item.id)
                        ? null
                        : () => _handleDiscuss(item.id),
                  );
                },
              ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _FeedFilter extends StatelessWidget {
  final List<BriefingFeed> feeds;
  final int? selectedFeedId;
  final void Function(int? feedId) onChanged;

  const _FeedFilter({
    required this.feeds,
    required this.selectedFeedId,
    required this.onChanged,
  });

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 6, 16, 6),
      child: Row(
        children: [
          Text(
            'Feed:',
            style: Theme.of(context).textTheme.labelMedium?.copyWith(
                  color: Theme.of(context).colorScheme.onSurfaceVariant,
                ),
          ),
          const SizedBox(width: 8),
          DropdownButton<int?>(
            value: selectedFeedId,
            underline: const SizedBox.shrink(),
            items: [
              const DropdownMenuItem<int?>(
                value: null,
                child: Text('All feeds'),
              ),
              ...feeds.map(
                (f) => DropdownMenuItem<int?>(
                  value: f.id,
                  child: Text(f.title),
                ),
              ),
            ],
            onChanged: (v) => onChanged(v),
          ),
        ],
      ),
    );
  }
}