feat: Process experiment metadata in RC fetch response

Author: Athira M

packages/remote-config/src/client/rest_client.ts

@@ -18,7 +18,8 @@
 import {
   CustomSignals,
   FetchResponse,
-  FirebaseRemoteConfigObject
+  FirebaseRemoteConfigObject,
+  FirebaseExperimentDescription
 } from '../public_types';
 import {
   RemoteConfigFetchClient,
@@ -140,6 +141,7 @@ export class RestClient implements RemoteConfigFetchClient {
 
     let config: FirebaseRemoteConfigObject | undefined;
     let state: string | undefined;
+    let experiments: FirebaseExperimentDescription[] | undefined;
 
     // JSON parsing throws SyntaxError if the response body isn't a JSON string.
     // Requesting application/json and checking for a 200 ensures there's JSON data.
@@ -154,6 +156,7 @@ export class RestClient implements RemoteConfigFetchClient {
       }
       config = responseBody['entries'];
       state = responseBody['state'];
+      experiments = responseBody['experimentDescriptions'];
     }
 
     // Normalizes based on legacy state.
@@ -176,6 +179,6 @@ export class RestClient implements RemoteConfigFetchClient {
       });
     }
 
-    return { status, eTag: responseEtag, config };
+    return { status, eTag: responseEtag, config, experiments };
   }
 }

packages/remote-config/src/public_types.ts

@@ -57,6 +57,32 @@ export interface FirebaseRemoteConfigObject {
   [key: string]: string;
 }
 
+/**
+ * Defines experiment and variant attached to a config parameter.
+ */
+export interface FirebaseExperimentDescription {
+  // A string of max length 22 characters and of format: _exp_<experiment_id>
+  experimentId: string;
+
+  // The variant of the experiment assigned to the app instance.
+  variantId: string;
+
+  // When the experiment was started.
+  experimentStartTime: string;
+
+  // How long the experiment can remain in STANDBY state. Valid range from 1 ms
+  // to 6 months.
+  triggerTimeoutMillis: string;
+
+  // How long the experiment can remain in ON state. Valid range from 1 ms to 6
+  // months.
+  timeToLiveMillis: string;
+
+  // A repeated of Remote Config parameter keys that this experiment is
+  // affecting the value of.
+  affectedParameterKeys?: string[];
+}
+
 /**
  * Defines a successful response (200 or 304).
  *
@@ -90,8 +116,12 @@ export interface FetchResponse {
    */
   config?: FirebaseRemoteConfigObject;
 
-  // Note: we're not extracting experiment metadata until
-  // ABT and Analytics have Web SDKs.
+  /**
+   * A/B Test and Rollout experiment metadata.
+   * 
+   * <p>Only defined for 200 responses.
+   */
+  experiments?: FirebaseExperimentDescription[];
 }
 
 /**