import 'dart:async';

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

import '../../core/api_client.dart';
import '../../core/chat_socket.dart';
import '../../core/msn_api.dart';
import '../../core/session_controller.dart';
import '../../data/message_local_store.dart';
import '../../models/message_model.dart';
import '../../models/room_model.dart';
import '../../models/ws_chat_side_event.dart';
import '../../theme/toss_theme.dart';
import '../profile/user_profile_sheet.dart';

final messageLocalStoreProvider = Provider<MessageLocalStore>((ref) => MessageLocalStore());

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

  final String roomId;
  final String contextId;

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

class _ChatPageState extends ConsumerState<ChatPage> {
  final _controller = TextEditingController();
  final _scroll = ScrollController();
  final List<MessageModel> _items = [];
  StreamSubscription<MessageModel>? _sub;
  bool _loading = true;
  String? _contextName;
  String? _bootstrapError;
  /// From room list; null until loaded.
  bool? _roomIsGroup;
  String? _roomName;
  String? _lastReadByOther;
  StreamSubscription<Object>? _sideSub;
  Timer? _typingDebounce;
  Timer? _typingClear;
  String? _typingUserId;

  @override
  void initState() {
    super.initState();
    _bootstrap();
  }

  Future<void> _bootstrap() async {
    setState(() {
      _bootstrapError = null;
      _loading = true;
    });

    final api = ref.read(msnApiProvider);
    final store = ref.read(messageLocalStoreProvider);

    try {
      try {
        final contexts = await api.listContexts();
        final match = contexts.where((c) => c.id == widget.contextId).toList();
        if (match.isNotEmpty && mounted) {
          setState(() => _contextName = match.first.name);
        }
      } catch (_) {}

      RoomModel? roomMeta;
      try {
        final rooms = await api.listRooms(widget.contextId);
        for (final r in rooms) {
          if (r.id == widget.roomId) {
            roomMeta = r;
            break;
          }
        }
      } catch (_) {}

      await ref.read(chatSocketProvider).connect();
      final list = await api.fetchMessages(widget.roomId);
      await store.upsertMessages(widget.contextId, widget.roomId, list);
      final local = await store.listForRoom(widget.contextId, widget.roomId);
      if (!mounted) return;

      setState(() {
        _items
          ..clear()
          ..addAll(local.isNotEmpty ? local : list);
        _loading = false;
        _roomIsGroup = roomMeta?.isGroup;
        _roomName = roomMeta?.name;
      });

      if (roomMeta?.isGroup == false) {
        unawaited(_refreshReadState());
      }

      ref.read(chatSocketProvider).subscribeRoom(widget.roomId);
      _sub = ref.read(chatSocketProvider).messages.listen((m) {
        if (m.roomId != widget.roomId) return;
        setState(() {
          _items.add(m);
        });
        unawaited(store.upsertMessages(widget.contextId, widget.roomId, [m]));
        unawaited(_markRead(m));
        if (_roomIsGroup == false) {
          unawaited(_refreshReadState());
        }
      });

      _sideSub = ref.read(chatSocketProvider).sideEvents.listen((ev) {
        if (ev is WsTypingEvent) {
          if (ev.roomId != widget.roomId) return;
          final myId = ref.read(sessionProvider).value?.userId;
          if (myId == null || ev.userId == myId) return;
          _typingClear?.cancel();
          if (ev.active) {
            setState(() => _typingUserId = ev.userId);
            _typingClear = Timer(const Duration(seconds: 3), () {
              if (mounted) setState(() => _typingUserId = null);
            });
          } else {
            setState(() => _typingUserId = null);
          }
        } else if (ev is WsReadEvent) {
          if (ev.roomId != widget.roomId) return;
          unawaited(_refreshReadState());
        }
      });

      if (_items.isNotEmpty) {
        unawaited(_markRead(_items.last));
      }
    } catch (e, st) {
      debugPrint('ChatPage _bootstrap: $e\n$st');
      if (!mounted) return;
      setState(() {
        _loading = false;
        _bootstrapError = e.toString();
      });
    }
  }

  Future<void> _refreshReadState() async {
    if (_roomIsGroup == true) return;
    try {
      final id = await ref.read(msnApiProvider).getReadState(widget.roomId);
      if (!mounted) return;
      setState(() => _lastReadByOther = id);
    } catch (_) {}
  }

  Future<void> _markRead(MessageModel last) async {
    try {
      await ref.read(dioProvider).post(
            '/api/messages/read',
            data: {'roomId': widget.roomId, 'upToMessageId': last.id},
          );
    } catch (_) {}
  }

  @override
  void dispose() {
    _sub?.cancel();
    _sideSub?.cancel();
    _typingDebounce?.cancel();
    _typingClear?.cancel();
    ref.read(chatSocketProvider).sendTyping(widget.roomId, false);
    _controller.dispose();
    _scroll.dispose();
    super.dispose();
  }

  void _onInputChanged(String text) {
    if (_roomIsGroup == true) return;
    _typingDebounce?.cancel();
    final socket = ref.read(chatSocketProvider);
    if (text.trim().isEmpty) {
      socket.sendTyping(widget.roomId, false);
      return;
    }
    _typingDebounce = Timer(const Duration(milliseconds: 400), () {
      socket.sendTyping(widget.roomId, true);
    });
  }

  int? _lastMyMessageIndex(String me) {
    for (var i = _items.length - 1; i >= 0; i--) {
      if (_items[i].senderId == me) return i;
    }
    return null;
  }

  bool _showReadReceipt(String me) {
    if (_roomIsGroup == true || _lastReadByOther == null) return false;
    final myIdx = _lastMyMessageIndex(me);
    if (myIdx == null) return false;
    final readIdx = _items.indexWhere((m) => m.id == _lastReadByOther);
    if (readIdx < 0) return false;
    return readIdx >= myIdx;
  }

  void _send() {
    final text = _controller.text.trim();
    if (text.isEmpty) return;
    ref.read(chatSocketProvider).sendTyping(widget.roomId, false);
    final sent = ref.read(chatSocketProvider).sendMessage(widget.roomId, text);
    _controller.clear();
    if (!sent && mounted) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('연결을 기다리는 중입니다. 복구되면 자동으로 전송됩니다.')),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    final me = ref.watch(sessionProvider).value?.userId ?? '';
    final theme = Theme.of(context);

    return Scaffold(
      backgroundColor: TossColors.bg,
      appBar: AppBar(
        title: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(
              _roomIsGroup == true ? (_roomName ?? '그룹 채팅') : '채팅',
              style: theme.textTheme.titleLarge,
            ),
            if (_typingUserId != null)
              Padding(
                padding: const EdgeInsets.only(top: 4),
                child: Text(
                  '상대가 입력 중…',
                  style: theme.textTheme.labelSmall?.copyWith(
                    color: TossColors.blue,
                    fontWeight: FontWeight.w600,
                  ),
                ),
              ),
            if (_contextName != null)
              Padding(
                padding: const EdgeInsets.only(top: 2),
                child: Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Container(
                      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
                      decoration: BoxDecoration(
                        color: TossColors.blue.withValues(alpha: 0.12),
                        borderRadius: BorderRadius.circular(6),
                      ),
                      child: Text(
                        _contextName!,
                        style: theme.textTheme.labelSmall?.copyWith(
                          color: TossColors.blueDark,
                          fontWeight: FontWeight.w600,
                        ),
                      ),
                    ),
                  ],
                ),
              ),
          ],
        ),
        actions: [
          if (_roomIsGroup == true)
            IconButton(
              tooltip: '그룹 정보',
              icon: const Icon(Icons.groups_outlined),
              onPressed: _showGroupRoomSheet,
            )
          else if (_roomIsGroup == false)
            IconButton(
              tooltip: '프로필',
              icon: const Icon(Icons.person_outline_rounded),
              onPressed: () async {
                final other = await _resolveOtherUserId();
                if (!context.mounted || other == null) return;
                await showUserProfileSheet(
                  context,
                  ref,
                  contextId: widget.contextId,
                  userId: other,
                );
              },
            ),
        ],
      ),
      body: Column(
        children: [
          Expanded(
            child: _loading
                ? const Center(child: CircularProgressIndicator(color: TossColors.blue))
                : _bootstrapError != null && _items.isEmpty
                    ? Center(
                        child: Padding(
                          padding: const EdgeInsets.all(24),
                          child: Column(
                            mainAxisSize: MainAxisSize.min,
                            children: [
                              Icon(Icons.wifi_off_rounded, size: 48, color: theme.colorScheme.error),
                              const SizedBox(height: 16),
                              Text(
                                '불러오지 못했어요',
                                style: theme.textTheme.titleMedium,
                              ),
                              const SizedBox(height: 8),
                              Text(
                                _bootstrapError!,
                                textAlign: TextAlign.center,
                                style: theme.textTheme.bodySmall,
                              ),
                              const SizedBox(height: 20),
                              FilledButton(
                                onPressed: () {
                                  _sub?.cancel();
                                  _sub = null;
                                  _bootstrap();
                                },
                                child: const Text('다시 시도'),
                              ),
                            ],
                          ),
                        ),
                      )
                    : ListView.builder(
                    controller: _scroll,
                    padding: const EdgeInsets.symmetric(vertical: 12, horizontal: 8),
                    itemCount: _items.length,
                    itemBuilder: (context, i) {
                      final m = _items[i];
                      final mine = m.senderId == me;
                      final lastMy = _lastMyMessageIndex(me);
                      final showRead = mine &&
                          lastMy == i &&
                          _showReadReceipt(me);
                      return Align(
                        alignment: mine ? Alignment.centerRight : Alignment.centerLeft,
                        child: Column(
                          crossAxisAlignment:
                              mine ? CrossAxisAlignment.end : CrossAxisAlignment.start,
                          mainAxisSize: MainAxisSize.min,
                          children: [
                            Container(
                              margin: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
                              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
                              constraints: BoxConstraints(
                                maxWidth: MediaQuery.sizeOf(context).width * 0.78,
                              ),
                              decoration: BoxDecoration(
                                color: mine ? TossColors.blue : TossColors.surface,
                                borderRadius: BorderRadius.only(
                                  topLeft: const Radius.circular(20),
                                  topRight: const Radius.circular(20),
                                  bottomLeft: Radius.circular(mine ? 20 : 6),
                                  bottomRight: Radius.circular(mine ? 6 : 20),
                                ),
                                border: mine ? null : Border.all(color: TossColors.line),
                                boxShadow: [
                                  BoxShadow(
                                    color: Colors.black.withValues(alpha: 0.05),
                                    blurRadius: 8,
                                    offset: const Offset(0, 2),
                                  ),
                                ],
                              ),
                              child: Text(
                                m.body,
                                style: theme.textTheme.bodyLarge?.copyWith(
                                  color: mine ? Colors.white : TossColors.textPrimary,
                                  height: 1.35,
                                ),
                              ),
                            ),
                            if (showRead)
                              Padding(
                                padding: const EdgeInsets.only(right: 12, bottom: 4),
                                child: Text(
                                  '읽음',
                                  style: theme.textTheme.labelSmall?.copyWith(
                                    color: TossColors.textSecondary,
                                  ),
                                ),
                              ),
                          ],
                        ),
                      );
                    },
                  ),
          ),
          Container(
            color: TossColors.surface,
            padding: EdgeInsets.fromLTRB(
              12,
              8,
              12,
              8 + MediaQuery.paddingOf(context).bottom,
            ),
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.end,
              children: [
                Expanded(
                  child: TextField(
                    controller: _controller,
                    decoration: InputDecoration(
                      hintText: '메시지를 입력하세요',
                      hintStyle: theme.textTheme.bodyMedium,
                      filled: true,
                      fillColor: TossColors.bg,
                      contentPadding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(22),
                        borderSide: BorderSide.none,
                      ),
                    ),
                    minLines: 1,
                    maxLines: 4,
                    onChanged: _onInputChanged,
                    onSubmitted: (_) => _send(),
                  ),
                ),
                const SizedBox(width: 8),
                Material(
                  color: TossColors.blue,
                  borderRadius: BorderRadius.circular(22),
                  child: InkWell(
                    onTap: _send,
                    borderRadius: BorderRadius.circular(22),
                    child: const Padding(
                      padding: EdgeInsets.all(12),
                      child: Icon(Icons.arrow_upward_rounded, color: Colors.white, size: 22),
                    ),
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Future<void> _showGroupRoomSheet() async {
    try {
      final res = await ref.read(dioProvider).get<Map<String, dynamic>>(
            '/api/rooms/${widget.roomId}/participants',
          );
      final ids = (res.data!['userIds'] as List<dynamic>).cast<String>();
      if (!mounted) return;
      await showModalBottomSheet<void>(
        context: context,
        showDragHandle: true,
        backgroundColor: TossColors.surface,
        shape: const RoundedRectangleBorder(
          borderRadius: BorderRadius.vertical(top: Radius.circular(20)),
        ),
        builder: (ctx) {
          final tt = Theme.of(ctx).textTheme;
          return SafeArea(
            child: Padding(
              padding: const EdgeInsets.fromLTRB(24, 8, 24, 24),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  Text(
                    _roomName ?? '그룹 채팅',
                    style: tt.titleLarge,
                  ),
                  const SizedBox(height: 8),
                  Text(
                    '참여자 ${ids.length}명',
                    style: tt.bodyLarge,
                  ),
                  const SizedBox(height: 12),
                  Text(
                    '이 맥락에서만 보이는 그룹 대화입니다.',
                    style: tt.bodySmall,
                  ),
                ],
              ),
            ),
          );
        },
      );
    } catch (_) {}
  }

  Future<String?> _resolveOtherUserId() async {
    try {
      final res = await ref.read(dioProvider).get<Map<String, dynamic>>(
            '/api/rooms/${widget.roomId}/participants',
          );
      final ids = (res.data!['userIds'] as List<dynamic>).cast<String>();
      final session = ref.read(sessionProvider).value;
      final meId = session?.userId;
      for (final id in ids) {
        if (id != meId) return id;
      }
      return ids.isNotEmpty ? ids.first : null;
    } catch (_) {
      return null;
    }
  }
}