Fixed bugs, added serialization for documents state

lib/features/sharing/share_intent_queue.dart

@@ -0,0 +1,36 @@
+import 'dart:collection';
+import 'dart:developer';
+
+import 'package:flutter/widgets.dart';
+import 'package:fluttertoast/fluttertoast.dart';
+import 'package:receive_sharing_intent/receive_sharing_intent.dart';
+import 'package:rxdart/rxdart.dart';
+
+class ShareIntentQueue extends ChangeNotifier {
+  final Queue<SharedMediaFile> _queue = Queue();
+
+  ShareIntentQueue._();
+
+  static final instance = ShareIntentQueue._();
+
+  void add(SharedMediaFile file) {
+    _queue.add(file);
+    notifyListeners();
+  }
+
+  void addAll(Iterable<SharedMediaFile> files) {
+    _queue.addAll(files);
+    notifyListeners();
+  }
+
+  SharedMediaFile? pop() {
+    if (hasUnhandledFiles) {
+      return _queue.removeFirst();
+      // Don't notify listeners, only when new item is added.
+    } else {
+      return null;
+    }
+  }
+
+  bool get hasUnhandledFiles => _queue.isNotEmpty;
+}