import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:matrix/matrix.dart';
import 'package:pyramid/features/chat/chat_input.dart';
import 'package:pyramid/features/chat/chat_provider.dart';
import 'package:pyramid/features/chat/message_bubble.dart';

class ChatPage extends ConsumerStatefulWidget {
  final String roomId;
  const ChatPage({super.key, required this.roomId});

  @override
  ConsumerState<ChatPage> createState() => _ChatPageState();
}

class _ChatPageState extends ConsumerState<ChatPage> {
  final _scrollCtrl = ScrollController();
  Event? _replyTo;

  String get _roomId => Uri.decodeComponent(widget.roomId);

  @override
  void initState() {
    super.initState();
    _scrollCtrl.addListener(_onScroll);
  }

  @override
  void dispose() {
    _scrollCtrl.dispose();
    super.dispose();
  }

  void _onScroll() {
    if (_scrollCtrl.position.pixels >=
        _scrollCtrl.position.maxScrollExtent - 300) {
      final timeline = ref.read(timelineProvider(_roomId)).valueOrNull;
      timeline?.requestHistory();
    }
  }

  @override
  Widget build(BuildContext context) {
    final room = ref.watch(roomProvider(_roomId));
    final timelineAsync = ref.watch(timelineProvider(_roomId));

    return Scaffold(
      appBar: AppBar(
        leading: IconButton(
          icon: const Icon(Icons.arrow_back),
          onPressed: () => context.go('/rooms'),
        ),
        title: Text(room?.getLocalizedDisplayname() ?? _roomId),
        actions: [
          IconButton(
            icon: const Icon(Icons.info_outline),
            onPressed: () {},
          ),
        ],
      ),
      body: Column(
        children: [
          Expanded(
            child: timelineAsync.when(
              loading: () => const Center(child: CircularProgressIndicator()),
              error: (e, _) => Center(child: Text('Fehler: $e')),
              data: (timeline) => _MessageList(
                timeline: timeline,
                scrollCtrl: _scrollCtrl,
                currentUserId: room?.client.userID ?? '',
                onReply: (event) => setState(() => _replyTo = event),
              ),
            ),
          ),
          if (room != null)
            ChatInput(
              room: room,
              replyTo: _replyTo,
              onClearReply: () => setState(() => _replyTo = null),
            ),
        ],
      ),
    );
  }
}

class _MessageList extends StatelessWidget {
  final Timeline timeline;
  final ScrollController scrollCtrl;
  final String currentUserId;
  final ValueChanged<Event> onReply;

  const _MessageList({
    required this.timeline,
    required this.scrollCtrl,
    required this.currentUserId,
    required this.onReply,
  });

  @override
  Widget build(BuildContext context) {
    final events = timeline.events
        .where((e) =>
            e.type == EventTypes.Message &&
            e.status != EventStatus.error)
        .toList();

    if (events.isEmpty) {
      return const Center(child: Text('Noch keine Nachrichten'));
    }

    return ListView.builder(
      controller: scrollCtrl,
      reverse: true,
      padding: const EdgeInsets.symmetric(vertical: 8),
      itemCount: events.length,
      itemBuilder: (context, i) {
        final event = events[i];
        final isOwn = event.senderId == currentUserId;

        final showDate = i == events.length - 1 ||
            !_sameDay(event.originServerTs, events[i + 1].originServerTs);

        final replyEventId =
            event.content.tryGetMap<String, dynamic>('m.relates_to')
                ?['m.in_reply_to']?['event_id'] as String?;
        final replyEvent = replyEventId != null
            ? timeline.events.firstWhere(
                (e) => e.eventId == replyEventId,
                orElse: () => event,
              )
            : null;

        return Column(
          children: [
            if (showDate)
              DateSeparator(date: event.originServerTs),
            GestureDetector(
              onLongPress: () => onReply(event),
              child: MessageBubble(
                event: event,
                isOwn: isOwn,
                replyEvent:
                    replyEvent?.eventId != event.eventId ? replyEvent : null,
              ),
            ),
          ],
        );
      },
    );
  }

  bool _sameDay(DateTime a, DateTime b) =>
      a.year == b.year && a.month == b.month && a.day == b.day;
}