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

import '../../data/models/briefing_conversation.dart';
import '../../data/models/message.dart';
import '../../providers/api_client_provider.dart';
import '../../widgets/chat_message_bubble.dart';

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

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

    return Scaffold(
      appBar: AppBar(title: const Text('Past Briefings')),
      body: historyAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, _) =>
            const Center(child: Text('Could not load briefing history.')),
        data: (convs) {
          if (convs.isEmpty) {
            return const Center(child: Text('No past briefings.'));
          }
          return ListView.builder(
            itemCount: convs.length,
            itemBuilder: (context, i) {
              final conv = convs[i];
              final label = conv.briefingDate ?? conv.title;
              return ListTile(
                leading: const Icon(Icons.wb_sunny_outlined),
                title: Text(label),
                trailing: const Icon(Icons.chevron_right),
                onTap: () => Navigator.of(context).push(
                  MaterialPageRoute(
                    builder: (_) => _BriefingDetailScreen(conv: conv),
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }
}

/// Lazily loads and displays all messages for a past briefing.
class _BriefingDetailScreen extends ConsumerWidget {
  final BriefingConversation conv;
  const _BriefingDetailScreen({required this.conv});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final messagesAsync = ref.watch(_briefingMessagesProvider(conv.id));

    return Scaffold(
      appBar: AppBar(title: Text(conv.briefingDate ?? conv.title)),
      body: messagesAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, _) => const Center(child: Text('Could not load messages.')),
        data: (messages) {
          if (messages.isEmpty) {
            return const Center(child: Text('No messages.'));
          }
          return ListView.builder(
            padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 12),
            itemCount: messages.length,
            itemBuilder: (_, i) => ChatMessageBubble(message: messages[i]),
          );
        },
      ),
    );
  }
}

// ── Private providers (scoped to this file) ──────────────────────────────────

final _briefingHistoryProvider =
    FutureProvider<List<BriefingConversation>>((ref) async {
  return ref.watch(briefingApiProvider).getHistory();
});

final _briefingMessagesProvider =
    FutureProvider.family<List<Message>, int>((ref, convId) async {
  return ref.watch(briefingApiProvider).getMessages(convId);
});