Adds support for exporting a serialized config response from the RC server side SDK. (#2829)

* add serialization method to server side remote config

* update with latest changes

* restructure as a class, add documentation

* more tests for server config

* run apidocs

* Refine api and rerun docs

* add back the newline

* Apply suggestions from review

* Make eTag optional in fetch response

* rerun doc generator

---------

Co-authored-by: Kevin Elko <[email protected]>

Author: kjelko

etc/firebase-admin.remote-config.api.md

@@ -52,6 +52,15 @@ export interface ExplicitParameterValue {
     value: string;
 }
 
+// @public
+export interface FetchResponseData {
+    config?: {
+        [key: string]: string;
+    };
+    eTag?: string;
+    status: number;
+}
+
 // Warning: (ae-forgotten-export) The symbol "App" needs to be exported by the entry point index.d.ts
 //
 // @public
@@ -162,6 +171,13 @@ export interface RemoteConfigCondition {
     tagColor?: TagColor;
 }
 
+// @public
+export class RemoteConfigFetchResponse {
+    constructor(app: App, serverConfig: ServerConfig, requestEtag?: string);
+    // (undocumented)
+    toJSON(): FetchResponseData;
+}
+
 // @public
 export interface RemoteConfigParameter {
     conditionalValues?: {
@@ -205,6 +221,9 @@ export interface RemoteConfigUser {
 
 // @public
 export interface ServerConfig {
+    getAll(): {
+        [key: string]: Value;
+    };
     getBoolean(key: string): boolean;
     getNumber(key: string): number;
     getString(key: string): string;

src/remote-config/index.ts

@@ -31,6 +31,7 @@ export {
   DefaultConfig,
   EvaluationContext,
   ExplicitParameterValue,
+  FetchResponseData,
   GetServerTemplateOptions,
   InAppDefaultValue,
   InitServerTemplateOptions,
@@ -60,7 +61,7 @@ export {
   ValueSource,
   Version,
 } from './remote-config-api';
-export { RemoteConfig } from './remote-config';
+export { RemoteConfig, RemoteConfigFetchResponse } from './remote-config';
 
 /**
  * Gets the {@link RemoteConfig} service for the default app or a given app.

src/remote-config/remote-config-api.ts

@@ -236,7 +236,7 @@ export enum CustomSignalOperator {
   /**
    * Matches a numeric value less than or equal to the target value.
    */
-  NUMERIC_LESS_EQUAL ='NUMERIC_LESS_EQUAL',
+  NUMERIC_LESS_EQUAL = 'NUMERIC_LESS_EQUAL',
 
   /**
    * Matches a numeric value equal to the target value.
@@ -537,7 +537,7 @@ export interface ServerTemplate {
 /**
  * Generic map of developer-defined signals used as evaluation input signals.
  */
-export type UserProvidedSignals = {[key: string]: string|number};
+export type UserProvidedSignals = { [key: string]: string | number };
 
 /**
  * Predefined template evaluation input signals.
@@ -727,6 +727,40 @@ export interface ServerConfig {
    * @returns The value for the given key.
    */
   getValue(key: string): Value;
+
+  /**
+   * Returns all config values.
+   * 
+   * @returns A map of all config keys to their values.
+   */
+  getAll(): { [key: string]: Value }
+}
+
+/**
+ * JSON-serializable representation of evaluated config values. This can be consumed by 
+ * Remote Config web client SDKs.
+ */
+export interface FetchResponseData {
+  /**
+   * The HTTP status, which is useful for differentiating success responses with data from
+   * those without.
+   * 
+   * This use of 200 and 304 response codes is consistent with Remote Config's server 
+   * implementation.
+   */
+  status: number;
+
+  /**
+   * Defines the ETag response header value. Only defined for 200 and 304 responses.
+   * 
+   * This is consistent with Remote Config's server eTag implementation.
+   */
+  eTag?: string;
+
+  /**
+   * Defines the map of parameters returned as "entries" in the fetch response body.
+   */
+  config?: { [key: string]: string };
 }
 
 /**

src/remote-config/remote-config.ts

@@ -15,6 +15,7 @@
  */
 
 import { App } from '../app';
+import * as utils from '../utils/index';
 import * as validator from '../utils/validator';
 import { FirebaseRemoteConfigError, RemoteConfigApiClient } from './remote-config-api-client-internal';
 import { ConditionEvaluator } from './condition-evaluator-internal';
@@ -41,6 +42,7 @@ import {
   GetServerTemplateOptions,
   InitServerTemplateOptions,
   ServerTemplateDataType,
+  FetchResponseData,
 } from './remote-config-api';
 
 /**
@@ -298,7 +300,7 @@ class RemoteConfigTemplateImpl implements RemoteConfigTemplate {
  */
 class ServerTemplateImpl implements ServerTemplate {
   private cache: ServerTemplateData;
-  private stringifiedDefaultConfig: {[key: string]: string} = {};
+  private stringifiedDefaultConfig: { [key: string]: string } = {};
 
   constructor(
     private readonly apiClient: RemoteConfigApiClient,
@@ -425,7 +427,7 @@ class ServerTemplateImpl implements ServerTemplate {
 class ServerConfigImpl implements ServerConfig {
   constructor(
     private readonly configValues: { [key: string]: Value },
-  ){}
+  ) { }
   getBoolean(key: string): boolean {
     return this.getValue(key).asBoolean();
   }
@@ -438,6 +440,9 @@ class ServerConfigImpl implements ServerConfig {
   getValue(key: string): Value {
     return this.configValues[key] || new ValueImpl('static');
   }
+  getAll(): { [key: string]: Value } {
+    return { ...this.configValues };
+  }
 }
 
 /**
@@ -613,3 +618,62 @@ class VersionImpl implements Version {
     return validator.isNonEmptyString(timestamp) && (new Date(timestamp)).getTime() > 0;
   }
 }
+
+const HTTP_NOT_MODIFIED = 304;
+const HTTP_OK = 200;
+
+/**
+ * Represents a fetch response that can be used to interact with RC's client SDK.
+ */
+export class RemoteConfigFetchResponse {
+  private response: FetchResponseData;
+
+  /**
+   * @param app - The app for this RemoteConfig service.
+   * @param serverConfig - The server config for which to generate a fetch response.
+   * @param requestEtag - A request eTag with which to compare the current response.
+   */
+  constructor(app: App, serverConfig: ServerConfig, requestEtag?: string) {
+    const config: { [key: string]: string } = {};
+    for (const [param, value] of Object.entries(serverConfig.getAll())) {
+      config[param] = value.asString();
+    }
+
+    const currentEtag = this.processEtag(config, app);
+
+    if (currentEtag === requestEtag) {
+      this.response = {
+        status: HTTP_NOT_MODIFIED,
+        eTag: currentEtag,
+      };
+    } else {
+      this.response = {
+        status: HTTP_OK,
+        eTag: currentEtag,
+        config,
+      }
+    }
+  }
+
+  /** 
+   * @returns JSON representation of the fetch response that can be consumed
+   * by the RC client SDK.
+   */
+  public toJSON(): FetchResponseData {
+    return this.response;
+  }
+
+  private processEtag(config: { [key: string]: string }, app: App): string {
+    const configJson = JSON.stringify(config);
+    let hash = 0;
+    // Mimics Java's `String.hashCode()` which is used in RC's servers.
+    for (let i = 0; i < configJson.length; i++) {
+      const char = configJson.charCodeAt(i);
+      hash = (hash << 5) - hash + char;
+      hash |= 0;
+    }
+    const projectId = utils.getExplicitProjectId(app);
+    const parts = ['etag', projectId, 'firebase-server', 'fetch', hash];
+    return parts.filter(a => !!a).join('-');
+  }
+}

test/unit/remote-config/remote-config.spec.ts

@@ -26,6 +26,7 @@ import {
   RemoteConfigCondition,
   TagColor,
   ListVersionsResult,
+  RemoteConfigFetchResponse,
 } from '../../../src/remote-config/index';
 import { FirebaseApp } from '../../../src/app/firebase-app';
 import * as mocks from '../../resources/mocks';
@@ -1001,14 +1002,14 @@ describe('RemoteConfig', () => {
       describe('should throw error if there are any JSON or tempalte parsing errors', () => {
         const INVALID_PARAMETERS: any[] = [null, '', 'abc', 1, true, []];
         const INVALID_CONDITIONS: any[] = [null, '', 'abc', 1, true, {}];
-  
+
         let sourceTemplate = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE);
         const jsonString = '{invalidJson: null}';
         it('should throw if template is an invalid JSON', () => {
           expect(() => remoteConfig.initServerTemplate({ template: jsonString }))
             .to.throw(/Failed to parse the JSON string: ([\D\w]*)\./);
         });
-  
+
         INVALID_PARAMETERS.forEach((invalidParameter) => {
           sourceTemplate.parameters = invalidParameter;
           const jsonString = JSON.stringify(sourceTemplate);
@@ -1017,7 +1018,7 @@ describe('RemoteConfig', () => {
               .to.throw('Remote Config parameters must be a non-null object');
           });
         });
-  
+
         sourceTemplate = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE);
         INVALID_CONDITIONS.forEach((invalidConditions) => {
           sourceTemplate.conditions = invalidConditions;
@@ -1292,20 +1293,53 @@ describe('RemoteConfig', () => {
   // Note the static source is set in the getValue() method, but the other sources
   // are set in the evaluate() method, so these tests span a couple layers.
   describe('ServerConfig', () => {
+    describe('getAll', () => {
+      it('should return all values', () => {
+        const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
+        templateData.parameters = {
+          dog_type: {
+            defaultValue: {
+              value: 'pug'
+            }
+          },
+          dog_type_enabled: {
+            defaultValue: {
+              value: 'true'
+            }
+          },
+          dog_age: {
+            defaultValue: {
+              value: '22'
+            }
+          },
+          dog_use_inapp_default: {
+            defaultValue: {
+              useInAppDefault: true
+            }
+          },
+        };
+        const template = remoteConfig.initServerTemplate({ template: templateData });
+        const config = template.evaluate().getAll();
+        expect(Object.keys(config)).deep.equal(['dog_type', 'dog_type_enabled', 'dog_age']);
+        expect(config['dog_type'].asString()).to.equal('pug');
+        expect(config['dog_type_enabled'].asBoolean()).to.equal(true);
+        expect(config['dog_age'].asNumber()).to.equal(22);
+      });
+    });
+
     describe('getValue', () => {
       it('should return static when default and remote are not defined', () => {
         const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
         // Omits remote parameter values.
         templateData.parameters = {
-        };
-        // Omits in-app default values.
+        }
         const template = remoteConfig.initServerTemplate({ template: templateData });
         const config = template.evaluate();
         const value = config.getValue('dog_type');
         expect(value.asString()).to.equal('');
         expect(value.getSource()).to.equal('static');
       });
-  
+
       it('should return default value when it is defined', () => {
         const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
         // Omits remote parameter values.
@@ -1323,7 +1357,7 @@ describe('RemoteConfig', () => {
         expect(value.asString()).to.equal('shiba');
         expect(value.getSource()).to.equal('default');
       });
-  
+
       it('should return remote value when it is defined', () => {
         const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
         // Defines remote parameter values.
@@ -1391,6 +1425,65 @@ describe('RemoteConfig', () => {
     });
   });
 
+  describe('RemoteConfigFetchResponse', () => {
+    it('should return a 200 response when supplied with no etag', () => {
+      const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
+      // Defines remote parameter values.
+      templateData.parameters = {
+        dog_type: {
+          defaultValue: {
+            value: 'beagle'
+          }
+        }
+      };
+      const template = remoteConfig.initServerTemplate({ template: templateData });
+      const fetchResponse = new RemoteConfigFetchResponse(mockApp, template.evaluate());
+      expect(fetchResponse.toJSON()).deep.equals({
+        status: 200,
+        eTag: 'etag-project_id-firebase-server-fetch--2039110429',
+        config: { 'dog_type': 'beagle' }
+      });
+    });
+
+    it('should return a 200 response when supplied with a stale etag', () => {
+      const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
+      // Defines remote parameter values.
+      templateData.parameters = {
+        dog_type: {
+          defaultValue: {
+            value: 'beagle'
+          }
+        }
+      };
+      const template = remoteConfig.initServerTemplate({ template: templateData });
+      const fetchResponse = new RemoteConfigFetchResponse(mockApp, template.evaluate(), 'fake-etag');
+      expect(fetchResponse.toJSON()).deep.equals({
+        status: 200,
+        eTag: 'etag-project_id-firebase-server-fetch--2039110429',
+        config: { 'dog_type': 'beagle' }
+      });
+    });
+
+    it('should return a 304 repsonse with matching etag', () => {
+      const templateData = deepCopy(SERVER_REMOTE_CONFIG_RESPONSE) as ServerTemplateData;
+      // Defines remote parameter values.
+      templateData.parameters = {
+        dog_type: {
+          defaultValue: {
+            value: 'beagle'
+          }
+        }
+      };
+      const template = remoteConfig.initServerTemplate({ template: templateData });
+      const fetchResponse = new RemoteConfigFetchResponse(
+        mockApp, template.evaluate(), 'etag-project_id-firebase-server-fetch--2039110429');
+      expect(fetchResponse.toJSON()).deep.equals({
+        status: 304,
+        eTag: 'etag-project_id-firebase-server-fetch--2039110429'
+      });
+    });
+  });
+
   function runInvalidResponseTests(rcOperation: () => Promise<RemoteConfigTemplate>,
     operationName: any): void {
     it('should propagate API errors', () => {