Remove shared preferences as a hard dependency

example/pubspec.lock

@@ -50,20 +50,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.2.0"
-  ffi:
-    dependency: transitive
-    description:
-      name: ffi
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.0"
-  file:
-    dependency: transitive
-    description:
-      name: file
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "6.1.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -74,11 +60,6 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  flutter_web_plugins:
-    dependency: transitive
-    description: flutter
-    source: sdk
-    version: "0.0.0"
   http:
     dependency: transitive
     description:
@@ -93,13 +74,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.0"
-  js:
-    dependency: transitive
-    description:
-      name: js
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.6.3"
   matcher:
     dependency: transitive
     description:
@@ -128,97 +102,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
-  path_provider_linux:
-    dependency: transitive
-    description:
-      name: path_provider_linux
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  path_provider_platform_interface:
-    dependency: transitive
-    description:
-      name: path_provider_platform_interface
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.1"
-  path_provider_windows:
-    dependency: transitive
-    description:
-      name: path_provider_windows
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
   pedantic:
     dependency: transitive
     description:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.11.0"
-  platform:
-    dependency: transitive
-    description:
-      name: platform
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "3.0.0"
-  plugin_platform_interface:
-    dependency: transitive
-    description:
-      name: plugin_platform_interface
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  process:
-    dependency: transitive
-    description:
-      name: process
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "4.1.0"
-  shared_preferences:
-    dependency: transitive
-    description:
-      name: shared_preferences
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.3"
-  shared_preferences_linux:
-    dependency: transitive
-    description:
-      name: shared_preferences_linux
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  shared_preferences_macos:
-    dependency: transitive
-    description:
-      name: shared_preferences_macos
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  shared_preferences_platform_interface:
-    dependency: transitive
-    description:
-      name: shared_preferences_platform_interface
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  shared_preferences_web:
-    dependency: transitive
-    description:
-      name: shared_preferences_web
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  shared_preferences_windows:
-    dependency: transitive
-    description:
-      name: shared_preferences_windows
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -280,20 +170,5 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
-  win32:
-    dependency: transitive
-    description:
-      name: win32
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.0"
-  xdg_directories:
-    dependency: transitive
-    description:
-      name: xdg_directories
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.2.0"
 sdks:
   dart: ">=2.12.0 <3.0.0"
-  flutter: ">=1.20.0"

lib/src/mixpanel_analytics.dart

@@ -3,7 +3,7 @@ import 'dart:convert';
 
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart';
-import 'package:shared_preferences/shared_preferences.dart';
+// import 'package:shared_preferences/shared_preferences.dart';
 
 enum MixpanelUpdateOperations {
   $set,
@@ -16,6 +16,40 @@ enum MixpanelUpdateOperations {
   $delete,
 }
 
+abstract class StringCache {
+  Future<String?> getString(String key);
+  Future<bool> setString(String key, String value);
+}
+
+class InMemoryStringCache implements StringCache {
+  final _map = <String, String>{};
+
+  @override
+  Future<String?> getString(String key) => Future.value(_map[key]);
+
+  @override
+  Future<bool> setString(String key, String value) {
+    _map[key] = value;
+    return Future.value(true);
+  }
+}
+
+// class SharedPreferencesStringCache implements StringCache {
+//   SharedPreferences? _prefs;
+//
+//   @override
+//   Future<String?> getString(String key) async {
+//     _prefs ??= await SharedPreferences.getInstance();
+//     return _prefs!.getString(key);
+//   }
+//
+//   @override
+//   Future<bool> setString(String key, String value) async {
+//     _prefs ??= await SharedPreferences.getInstance();
+//     return _prefs!.setString(key, value);
+//   }
+// }
+
 typedef ShaFn = String Function(String value);
 
 class MixpanelAnalytics {
@@ -33,10 +67,7 @@ class MixpanelAnalytics {
   /// Will be zero by default
   Duration _uploadInterval = Duration.zero;
 
-  /// In case we use [MixpanelAnalytics.batch()] we need to provide a storage provider
-  /// This will be used to save the events not sent
-  @visibleForTesting
-  SharedPreferences? prefs;
+  final StringCache _cache;
 
   /// If exists, will be sent in the event, otherwise anonymousId will be used.
   final Stream<String?>? _userId$;
@@ -129,6 +160,7 @@ class MixpanelAnalytics {
   /// [baseApiUrl] Ingestion API URL. If you don't inform it, the US-based url will be used (api.mixpanel.com). https://developer.mixpanel.com/docs/privacy-security#storing-your-data-in-the-european-union
   MixpanelAnalytics({
     required String token,
+    StringCache? cache,
     Stream<String?>? userId$,
     bool shouldAnonymize = false,
     ShaFn shaFn = _defaultShaFn,
@@ -140,6 +172,7 @@ class MixpanelAnalytics {
     String? prefsKey,
     String? baseApiUrl,
   })  : _token = token,
+        _cache = cache ?? InMemoryStringCache(),
         _userId$ = userId$,
         _verbose = verbose,
         _useIp = useIp,
@@ -169,6 +202,7 @@ class MixpanelAnalytics {
   /// [baseApiUrl] Ingestion API URL. If you don't inform it, the US-based url will be used (api.mixpanel.com). https://developer.mixpanel.com/docs/privacy-security#storing-your-data-in-the-european-union
   MixpanelAnalytics.batch({
     required String token,
+    StringCache? cache,
     required Duration uploadInterval,
     Stream<String?>? userId$,
     bool shouldAnonymize = false,
@@ -181,6 +215,7 @@ class MixpanelAnalytics {
     String? prefsKey,
     String? baseApiUrl,
   })  : _token = token,
+        _cache = cache ?? InMemoryStringCache(),
         _userId$ = userId$,
         _verbose = verbose,
         _useIp = useIp,
@@ -269,8 +304,7 @@ class MixpanelAnalytics {
   /// Reads queued events from the storage when we are in batch mode.
   /// We do this in case the app was closed with events pending to be sent.
   Future<void> _restoreQueuedEventsFromStorage() async {
-    prefs ??= await SharedPreferences.getInstance();
-    final encoded = prefs!.getString(_prefsKey);
+    final encoded = await _cache.getString(_prefsKey);
     if (encoded != null) {
       Map<String, dynamic> events = json.decode(encoded);
       _queuedEvents.addAll(events);
@@ -279,10 +313,9 @@ class MixpanelAnalytics {
 
   /// If we are in batch mode we save all events in storage in case the app is closed.
   Future<bool> _saveQueuedEventsToLocalStorage() async {
-    prefs ??= await SharedPreferences.getInstance();
     final encoded = json.encode(_queuedEvents);
     final result =
-        await prefs!.setString(_prefsKey, encoded).catchError((error) {
+        await _cache.setString(_prefsKey, encoded).catchError((error) {
       _onErrorHandler(error, 'Error saving events in storage');
       return false;
     });