feat: Add Support for Custom Storage Implementation

example/ios/Podfile.lock

@@ -4,7 +4,7 @@ PODS:
   - boost-for-react-native (1.63.0)
   - CocoaAsyncSocket (7.6.5)
   - DoubleConversion (1.1.6)
-  - experiment-react-native-client (1.0.0):
+  - experiment-react-native-client (1.5.2):
     - React-Core
   - FBLazyVector (0.63.4)
   - FBReactNativeSpec (0.63.4):
@@ -443,11 +443,11 @@ EXTERNAL SOURCES:
     :path: "../node_modules/react-native/ReactCommon/yoga"
 
 SPEC CHECKSUMS:
-  amplitude-react-native: 243eb398faa89b4b88998c536c4e9e0bdcbb4d9d
+  amplitude-react-native: 317744313df595a17f8638f6586b58bdfa161bcf
   boost-for-react-native: 39c7adb57c4e60d6c5479dd8623128eb5b3f0f2c
   CocoaAsyncSocket: 065fd1e645c7abab64f7a6a2007a48038fdc6a99
   DoubleConversion: cde416483dac037923206447da6e1454df403714
-  experiment-react-native-client: c2af8630b6209c5d4dcebdcd71ba7ad38abdcc38
+  experiment-react-native-client: 3ad919955ed53e2b3bd4a54341ab244d4fd84eab
   FBLazyVector: 3bb422f41b18121b71783a905c10e58606f7dc3e
   FBReactNativeSpec: f2c97f2529dd79c083355182cc158c9f98f4bd6e
   Flipper: 1bd2db48dcc31e4b167b9a33ec1df01c2ded4893
@@ -457,19 +457,19 @@ SPEC CHECKSUMS:
   Flipper-PeerTalk: 116d8f857dc6ef55c7a5a75ea3ceaafe878aadc9
   Flipper-RSocket: 127954abe8b162fcaf68d2134d34dc2bd7076154
   FlipperKit: 651f50a42eb95c01b3e89a60996dd6aded529eeb
-  Folly: b73c3869541e86821df3c387eb0af5f65addfab4
+  Folly: aeb27d02cdff07ca01f8a8a5a6dd5bcaf6be6f70
   glog: 40a13f7840415b9a77023fbcae0f1e6f43192af3
   libevent: 4049cae6c81cdb3654a443be001fb9bdceff7913
   OpenSSL-Universal: 1aa4f6a6ee7256b83db99ec1ccdaa80d10f9af9b
   RCTRequired: 082f10cd3f905d6c124597fd1c14f6f2655ff65e
   RCTTypeSafety: 8c9c544ecbf20337d069e4ae7fd9a377aadf504b
   React: b0a957a2c44da4113b0c4c9853d8387f8e64e615
   React-callinvoker: c3f44dd3cb195b6aa46621fff95ded79d59043fe
-  React-Core: d3b2a1ac9a2c13c3bcde712d9281fc1c8a5b315b
+  React-Core: aaa6ff028f4e8baa828e5b5cfb6da115bc471cf9
   React-CoreModules: 0581ff36cb797da0943d424f69e7098e43e9be60
-  React-cxxreact: c1480d4fda5720086c90df537ee7d285d4c57ac3
-  React-jsi: a0418934cf48f25b485631deb27c64dc40fb4c31
-  React-jsiexecutor: 93bd528844ad21dc07aab1c67cb10abae6df6949
+  React-cxxreact: af6918793c36186153bc09e981bfff8ba2b41d6a
+  React-jsi: df7455c330f8c1548225004fcc40031d4a7ade47
+  React-jsiexecutor: f42871dfefc3a3ed2a0e62932f750e09b7ae6e19
   React-jsinspector: 58aef7155bc9a9683f5b60b35eccea8722a4f53a
   React-RCTActionSheet: 89a0ca9f4a06c1f93c26067af074ccdce0f40336
   React-RCTAnimation: 1bde3ecc0c104c55df246eda516e0deb03c4e49b
@@ -480,11 +480,11 @@ SPEC CHECKSUMS:
   React-RCTSettings: 60f0691bba2074ef394f95d4c2265ec284e0a46a
   React-RCTText: 5c51df3f08cb9dedc6e790161195d12bac06101c
   React-RCTVibration: ae4f914cfe8de7d4de95ae1ea6cc8f6315d73d9d
-  ReactCommon: 73d79c7039f473b76db6ff7c6b159c478acbbb3b
-  RNCAsyncStorage: 466b9df1a14bccda91da86e0b7d9a345d78e1673
+  ReactCommon: 039a2aabebb7641184ba0cc3974c833b4c48d407
+  RNCAsyncStorage: 8cdcca8a75a7d36c402c02d2f011ff0897e8cb18
   Yoga: 4bd86afe9883422a7c4028c00e34790f560923d6
   YogaKit: f782866e155069a2cca2517aafea43200b01fd5a
 
 PODFILE CHECKSUM: be8ac95a530dede03d7b3bef7b71d1e8fb613dfc
 
-COCOAPODS: 1.11.3
+COCOAPODS: 1.16.2

src/experimentClient.ts

@@ -132,7 +132,7 @@ export class ExperimentClient implements Client {
       httpClient,
     );
     // Storage & Caching
-    const storage = new LocalStorage();
+    const storage = this.config.storage || new LocalStorage();
     this.variants = getVariantStorage(
       this.apiKey,
       this.config.instanceName,

src/storage/cache.ts

@@ -3,8 +3,6 @@ import { EvaluationFlag } from '@amplitude/experiment-core';
 import { Storage } from '../types/storage';
 import { Variant } from '../types/variant';
 
-import { LocalStorage } from './local-storage';
-
 export const getVariantStorage = (
   deploymentKey: string,
   instanceName: string,
@@ -22,7 +20,7 @@ export const getVariantStorage = (
 export const getFlagStorage = (
   deploymentKey: string,
   instanceName: string,
-  storage: Storage = new LocalStorage(),
+  storage: Storage,
 ): LoadStoreCache<EvaluationFlag> => {
   const truncatedDeployment = deploymentKey.substring(deploymentKey.length - 6);
   const namespace = `amp-exp-${instanceName}-${truncatedDeployment}-flags`;
@@ -75,7 +73,7 @@ export class LoadStoreCache<V> {
     const rawValues = await this.storage.get(this.namespace);
     let jsonValues: Record<string, unknown>;
     try {
-      jsonValues = JSON.parse(rawValues) || {};
+      jsonValues = rawValues ? JSON.parse(rawValues) : {};
     } catch {
       // Do nothing
       return;
@@ -104,7 +102,7 @@ export class LoadStoreCache<V> {
   }
 
   public async store(values: Record<string, V> = this.cache): Promise<void> {
-    await this.storage.put(this.namespace, JSON.stringify(values));
+    await this.storage.set(this.namespace, JSON.stringify(values));
   }
 }
 

src/storage/local-storage.ts

@@ -3,11 +3,12 @@ import AsyncStorage from '@react-native-async-storage/async-storage';
 import { Storage } from '../types/storage';
 
 export class LocalStorage implements Storage {
-  async get(key: string): Promise<string> {
+  async get(key: string): Promise<string | null> {
     return await AsyncStorage.getItem(key);
   }
 
-  async put(key: string, value: string): Promise<void> {
+  async set(key: string, value: string): Promise<void> {
+    // TTL is ignored in the default implementation
     await AsyncStorage.setItem(key, value);
     return;
   }

src/types/config.ts

@@ -2,6 +2,7 @@ import { FetchHttpClient } from '../transport/http';
 
 import { ExposureTrackingProvider } from './exposure';
 import { Source } from './source';
+import { Storage } from './storage';
 import { HttpClient } from './transport';
 import { ExperimentUserProvider } from './user';
 import { Variant, Variants } from './variant';
@@ -131,6 +132,12 @@ export interface ExperimentConfig {
    * (Advanced) Use your own http client.
    */
   httpClient?: HttpClient;
+
+  /**
+   * Custom storage implementation. By default, AsyncStorage is used.
+   * Implement the Storage interface to use a different storage mechanism.
+   */
+  storage?: Storage;
 }
 
 /**
@@ -156,6 +163,7 @@ export interface ExperimentConfig {
  | **userProvider**    | `null` |
  | **analyticsProvider**    | `null` |
  | **exposureTrackingProvider**    | `null` |
+ | **storage**    | `null` (defaults to AsyncStorage) |
 
  *
  * @category Configuration
@@ -179,4 +187,5 @@ export const Defaults: ExperimentConfig = {
   userProvider: null,
   exposureTrackingProvider: null,
   httpClient: FetchHttpClient,
+  storage: null,
 };

src/types/storage.ts

@@ -1,5 +1,5 @@
 export interface Storage {
-  get(key: string): Promise<string>;
-  put(key: string, value: string): Promise<void>;
+  get(key: string): Promise<string | null>;
+  set(key: string, value: string, ttl?: number): Promise<void>;
   delete(key: string): Promise<void>;
 }