first working version

lib/services/osm_block_service.dart

@@ -0,0 +1,55 @@
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+import '../state/settings_state.dart';
+import 'http_client.dart';
+
+/// Service for checking whether the current user has an active OSM DWG block.
+///
+/// See: https://wiki.openstreetmap.org/wiki/API_v0.6#List_active_blocks:_GET_/api/0.6/user/blocks/active
+class OSMBlockService {
+  final http.Client _client;
+
+  OSMBlockService({http.Client? client}) : _client = client ?? UserAgentClient();
+
+  /// Returns whether the user currently has an active block.
+  ///
+  /// Returns null if not logged in, in simulate mode, or on any error
+  /// (including no network connection) - callers should treat null as
+  /// "unknown, assume unchanged" rather than "not blocked".
+  Future<bool?> checkActiveBlock({
+    required String? accessToken,
+    required UploadMode uploadMode,
+  }) async {
+    if (uploadMode == UploadMode.simulate) return null;
+    if (accessToken == null || accessToken.isEmpty) return null;
+
+    try {
+      final apiHost = _getApiHost(uploadMode);
+      final response = await _client.get(
+        Uri.parse('$apiHost/api/0.6/user/blocks/active.json'),
+        headers: {'Authorization': 'Bearer $accessToken'},
+      );
+
+      if (response.statusCode != 200) return null;
+
+      final data = jsonDecode(response.body);
+      final userBlocks = data['user_blocks'];
+      if (userBlocks is! List) return null;
+
+      return userBlocks.isNotEmpty;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  String _getApiHost(UploadMode uploadMode) {
+    switch (uploadMode) {
+      case UploadMode.production:
+        return 'https://api.openstreetmap.org';
+      case UploadMode.sandbox:
+        return 'https://api06.dev.openstreetmap.org';
+      case UploadMode.simulate:
+        return 'https://api.openstreetmap.org';
+    }
+  }
+}