added initial draft of inbox

lib/core/model/error_message.dart

@@ -4,12 +4,14 @@ class ErrorMessage implements Exception {
   final StackTrace? stackTrace;
   final int? httpStatusCode;
 
-  const ErrorMessage(this.code,
-      {this.details, this.stackTrace, this.httpStatusCode});
+  const ErrorMessage(
+    this.code, {
+    this.details,
+    this.stackTrace,
+    this.httpStatusCode,
+  });
 
-  factory ErrorMessage.unknown() {
-    return const ErrorMessage(ErrorCode.unknown);
-  }
+  const ErrorMessage.unknown() : this(ErrorCode.unknown);
 
   @override
   String toString() {

lib/core/model/paperless_statistics.dart

@@ -0,0 +1,15 @@
+import 'package:paperless_mobile/core/type/types.dart';
+
+class PaperlessStatistics {
+  final int documentsTotal;
+  final int documentsInInbox;
+
+  PaperlessStatistics({
+    required this.documentsTotal,
+    required this.documentsInInbox,
+  });
+
+  PaperlessStatistics.fromJson(JSON json)
+      : documentsTotal = json['documents_total'],
+        documentsInInbox = json['documents_inbox'];
+}

lib/core/service/paperless_statistics_service.dart

@@ -0,0 +1,29 @@
+import 'dart:convert';
+
+import 'package:http/http.dart';
+import 'package:injectable/injectable.dart';
+import 'package:paperless_mobile/core/model/error_message.dart';
+import 'package:paperless_mobile/core/model/paperless_statistics.dart';
+import 'package:paperless_mobile/core/type/types.dart';
+
+abstract class PaperlessStatisticsService {
+  Future<PaperlessStatistics> getStatistics();
+}
+
+@Injectable(as: PaperlessStatisticsService)
+class PaperlessStatisticsServiceImpl extends PaperlessStatisticsService {
+  final BaseClient client;
+
+  PaperlessStatisticsServiceImpl(@Named('timeoutClient') this.client);
+
+  @override
+  Future<PaperlessStatistics> getStatistics() async {
+    final response = await client.get(Uri.parse('/api/statistics/'));
+    if (response.statusCode == 200) {
+      return PaperlessStatistics.fromJson(
+        jsonDecode(utf8.decode(response.bodyBytes)) as JSON,
+      );
+    }
+    throw const ErrorMessage.unknown();
+  }
+}