fix(analytics): use Android ID and persist UUID fallbacks (#1624)

ui/flutter/lib/util/analytics.dart

@@ -1,8 +1,10 @@
 import 'dart:io';
 
+import 'package:android_id/android_id.dart';
 import 'package:device_info_plus/device_info_plus.dart';
 import 'package:dio/dio.dart';
 import 'package:flutter/foundation.dart';
+import 'package:uuid/uuid.dart';
 
 import 'log_util.dart';
 import 'package_info.dart';
@@ -31,12 +33,23 @@ class Analytics {
 
   String get clientId => _initialized ? _clientId : '';
 
-  Future<void> init({String fallbackClientId = ''}) async {
-    if (_initialized || !AnalyticsConfig.isConfigured) return;
-    _clientId = await _getDeviceId(fallbackClientId);
+  /// Returns a newly generated fallback ID for the caller to persist, if any.
+  Future<String?> init({String fallbackClientId = ''}) async {
+    if (_initialized || !AnalyticsConfig.isConfigured) return null;
+    final deviceId = await _getDeviceId();
+    String? generatedClientId;
+    if (deviceId != null && deviceId.isNotEmpty) {
+      _clientId = deviceId;
+    } else if (fallbackClientId.isNotEmpty) {
+      _clientId = fallbackClientId;
+    } else {
+      _clientId = const Uuid().v4();
+      generatedClientId = _clientId;
+    }
     _sessionId = DateTime.now().millisecondsSinceEpoch ~/ 1000;
     _dio = Dio(BaseOptions(connectTimeout: const Duration(seconds: 10), receiveTimeout: const Duration(seconds: 10)));
     _initialized = true;
+    return generatedClientId;
   }
 
   Future<void> logAppOpen() => logEvent('app_open');
@@ -70,14 +83,14 @@ class Analytics {
     }
   }
 
-  Future<String> _getDeviceId(String fallbackClientId) async {
+  Future<String?> _getDeviceId() async {
+    if (kIsWeb) return null;
+
     String? deviceId;
     try {
       final info = DeviceInfoPlugin();
-      if (kIsWeb) {
-        deviceId = null;
-      } else if (Platform.isAndroid) {
-        deviceId = (await info.androidInfo).id;
+      if (Platform.isAndroid) {
+        deviceId = await const AndroidId().getId();
       } else if (Platform.isIOS) {
         deviceId = (await info.iosInfo).identifierForVendor;
       } else if (Platform.isMacOS) {
@@ -91,14 +104,6 @@ class Analytics {
       logger.w('GA4Analytics: failed to read device id: $error');
     }
 
-    if (deviceId == null || deviceId.isEmpty) {
-      deviceId = fallbackClientId;
-      if (deviceId.isEmpty) {
-        final random = DateTime.now().microsecondsSinceEpoch % 2147483647;
-        final timestamp = DateTime.now().millisecondsSinceEpoch ~/ 1000;
-        deviceId = '$random.$timestamp';
-      }
-    }
     return deviceId;
   }