import 'package:flutter/foundation.dart';

import '../../../../api/demo/demo_mode.dart';
import '../../../../api/marianumcloud/search/search_chat_messages.dart';
import '../../../../api/marianumcloud/talk/chat/get_chat_response.dart';
import '../../../../utils/debouncer.dart';
import '../data/chat_message_matcher.dart';

/// Live state of a search inside one chat, mirroring `FilesSearchController`:
/// hits from the loaded history appear immediately, the server-side search
/// over the full history follows debounced and can be paged further.
class ChatSearchController extends ChangeNotifier {
  ChatSearchController({
    required this.chatToken,
    required GetChatResponse? Function() loadedMessages,
  }) : _loadedMessages = loadedMessages;

  final String chatToken;
  final GetChatResponse? Function() _loadedMessages;

  static const Duration _serverDebounce = Duration(seconds: 1);
  final String _debounceTag =
      'chat-search-${DateTime.now().microsecondsSinceEpoch}';
  final SearchChatMessages _api = SearchChatMessages();

  String _query = '';
  List<ChatSearchHit> _localResults = const [];
  List<ChatSearchHit> _serverResults = const [];
  Object? _serverCursor;
  bool _serverLoading = false;
  bool _loadingMore = false;
  Object? _serverError;
  int _serverEpoch = 0;
  bool _disposed = false;

  void _safeNotify() {
    if (_disposed) return;
    notifyListeners();
  }

  String get query => _query;
  bool get serverLoading => _serverLoading;
  bool get loadingMore => _loadingMore;
  bool get canLoadMore => _serverCursor != null;
  Object? get serverError => _serverError;

  List<ChatSearchHit> get combinedResults =>
      ChatMessageMatcher.merge(_localResults, _serverResults);

  void setQuery(String value) {
    if (value == _query) return;
    _query = value;
    // Invalidates in-flight server calls of the previous query.
    ++_serverEpoch;
    _serverResults = const [];
    _serverCursor = null;
    _loadingMore = false;
    _serverError = null;
    if (_query.trim().isEmpty) {
      Debouncer.cancel(_debounceTag);
      _localResults = const [];
      _serverLoading = false;
      _safeNotify();
      return;
    }
    final loaded = _loadedMessages();
    _localResults = loaded == null
        ? const []
        : ChatMessageMatcher.findMatches(loaded, _query);
    // Demo sessions must not hit the real Nextcloud (see DemoHttpClient).
    _serverLoading = !DemoMode.active;
    _safeNotify();
    if (_serverLoading) {
      Debouncer.debounce(_debounceTag, _serverDebounce, _runServerCall);
    }
  }

  void retry() {
    if (_query.trim().isEmpty || DemoMode.active) return;
    ++_serverEpoch;
    Debouncer.cancel(_debounceTag);
    _serverResults = const [];
    _serverCursor = null;
    _loadingMore = false;
    _serverLoading = true;
    _serverError = null;
    _safeNotify();
    _runServerCall();
  }

  void loadMore() {
    if (_serverCursor == null || _serverLoading || _loadingMore) return;
    _loadingMore = true;
    _safeNotify();
    _runServerCall(cursor: _serverCursor);
  }

  Future<void> _runServerCall({Object? cursor}) async {
    final epoch = _serverEpoch;
    try {
      final response = await _api.run(
        chatToken: chatToken,
        term: _query.trim(),
        cursor: cursor,
      );
      if (epoch != _serverEpoch) return;
      _serverResults = [
        ..._serverResults,
        ...response.entries.map(ChatSearchHit.fromServer),
      ];
      _serverCursor = response.cursor;
      _serverError = null;
    } on Object catch (e) {
      if (epoch != _serverEpoch) return;
      _serverCursor = null;
      _serverError = e;
    }
    _serverLoading = false;
    _loadingMore = false;
    _safeNotify();
  }

  @override
  void dispose() {
    _disposed = true;
    Debouncer.cancel(_debounceTag);
    super.dispose();
  }
}