import 'dart:async';
import 'dart:convert';

import 'package:flutter/foundation.dart';
import 'package:p_tits_pas/models/carte_bulle.dart';
import 'package:p_tits_pas/services/api/api_config.dart';
import 'package:p_tits_pas/services/api/tokenService.dart';

import 'cards_stream_connector_stub.dart'
    if (dart.library.html) 'cards_stream_connector_web.dart'
    if (dart.library.io) 'cards_stream_connector_io.dart';

/// Événement temps réel file d'attention — ticket #195.
class CardsStreamEvent {
  final String type;
  final String? cardId;
  final CarteBulle? card;

  const CardsStreamEvent({
    required this.type,
    this.cardId,
    this.card,
  });
}

/// Client SSE `GET /cards/stream` avec reconnexion.
class CardsStreamClient {
  final void Function(CardsStreamEvent event) onEvent;
  final VoidCallback? onReconnectSync;

  CardsStreamClient({
    required this.onEvent,
    this.onReconnectSync,
  });

  final CardsStreamConnector _connector = CardsStreamConnector();
  bool _started = false;
  bool _stopRequested = false;
  int _attempt = 0;
  Timer? _retryTimer;
  bool _hadConnection = false;

  void start() {
    if (_started) return;
    _started = true;
    _stopRequested = false;
    _attempt = 0;
    unawaited(_connect());
  }

  void stop() {
    _stopRequested = true;
    _started = false;
    _retryTimer?.cancel();
    _retryTimer = null;
    _connector.close();
  }

  Future<void> _connect() async {
    if (_stopRequested) return;

    final token = await TokenService.getToken();
    if (token == null || token.isEmpty) {
      _scheduleRetry();
      return;
    }

    final base =
        '${ApiConfig.baseUrl}${ApiConfig.cardsStream}'.replaceAll(
      RegExp(r'/+$'),
      '',
    );

    // Web (EventSource) : token en query. IO : Bearer dans le connecteur.
    final url = kIsWeb
        ? Uri.parse(base).replace(
            queryParameters: {'access_token': token},
          ).toString()
        : base;

    await _connector.connect(
      url: url,
      bearerToken: kIsWeb ? null : token,
      onEvent: _handleRaw,
      onError: (_) {
        if (_stopRequested) return;
        _connector.close();
        _scheduleRetry();
      },
    );
  }

  void _handleRaw(String eventType, String data) {
    if (_stopRequested) return;

    // Premier événement (souvent heartbeat) = connexion OK.
    if (!_hadConnection) {
      _hadConnection = true;
      _attempt = 0;
    } else if (eventType == 'heartbeat') {
      _attempt = 0;
      return;
    }

    if (eventType == 'heartbeat') return;

    try {
      final decoded = jsonDecode(data);
      if (decoded is! Map) return;
      final map = Map<String, dynamic>.from(decoded);
      final type = (map['event']?.toString().isNotEmpty == true)
          ? map['event'].toString()
          : eventType;
      final cardId = map['card_id']?.toString();
      final payload = map['data'];

      CarteBulle? card;
      if (type == 'response.added' && payload is Map) {
        final nested = payload['card'];
        if (nested is Map) {
          card = CarteBulle.fromJson(Map<String, dynamic>.from(nested));
        }
      } else if ((type == 'card.created' || type == 'card.updated') &&
          payload is Map) {
        card = CarteBulle.fromJson(Map<String, dynamic>.from(payload));
      }

      onEvent(
        CardsStreamEvent(
          type: type,
          cardId: cardId ?? card?.id,
          card: card,
        ),
      );
    } catch (_) {
      // Événement mal formé : ignorer.
    }
  }

  void _scheduleRetry() {
    if (_stopRequested) return;
    _retryTimer?.cancel();
    final delaySec = (1 << _attempt.clamp(0, 4)).clamp(1, 30);
    _attempt++;
    _retryTimer = Timer(Duration(seconds: delaySec), () {
      if (_stopRequested) return;
      if (_hadConnection) {
        // Resync REST après coupure pour ne pas manquer d'événements.
        onReconnectSync?.call();
      }
      unawaited(_connect());
    });
  }
}