import 'dart:async'; import 'package:http/http.dart' as http; class ApiManager { String baseUrl; Future ongoingRequest = Future.value(); int consecutiveRateLimitExceeded = 0; Duration rateLimitTimeout = Duration.zero; DateTime? lastRequest; ApiManager(this.baseUrl); Future get(String path) async { Future waitingForRequest = ongoingRequest; Completer completer = Completer(); try { ongoingRequest = completer.future; await waitingForRequest; DateTime? lastRequestLocal = lastRequest; if (consecutiveRateLimitExceeded > 0 && lastRequestLocal != null && DateTime.now().isBefore(lastRequestLocal.add(rateLimitTimeout))) { throw Exception("Too many requests"); } http.Response response = await http.get(Uri.parse(baseUrl + path)); lastRequest = DateTime.now(); if (response.statusCode == 429) { consecutiveRateLimitExceeded++; if (consecutiveRateLimitExceeded == 1) { rateLimitTimeout = const Duration(seconds: 1); } else { rateLimitTimeout *= 2; } String? retryAfter = response.headers["Retry-After"]; if (retryAfter != null) { int? retryAfterSeconds = int.tryParse(retryAfter); if (retryAfterSeconds != null) { Duration retryAfterDuration = Duration(seconds: retryAfterSeconds); if (retryAfterDuration > rateLimitTimeout) { rateLimitTimeout = retryAfterDuration; } } } throw Exception("Too many requests"); } else { consecutiveRateLimitExceeded = 0; } return response; } finally { completer.complete(); } } } class RateLimitStatus { int consecutiveCount = 0; Duration timeout = const Duration(seconds: 1); }