Add optional enrichContext for SyncContext

Signed-off-by: marcozabel <[email protected]>

Author: marcozabel

libs/providers/flagd/src/lib/SyncMetadataHook.ts

@@ -1,13 +1,15 @@
 import {Hook} from "@openfeature/web-sdk";
+import { EvaluationContext } from "@openfeature/server-sdk";
+import { BeforeHookContext, HookHints } from "@openfeature/core";
 
 export class SyncMetadataHook implements Hook<any> {
-  contextSupplier: () => { [key: string]: any } | null;
+  enrichedContext: () => EvaluationContext;
 
-  constructor(getContext: () => { [key: string]: any } | null) {
-    this.contextSupplier = getContext;
+  constructor(enrichedContext: () => EvaluationContext) {
+    this.enrichedContext = enrichedContext
   }
 
-  public before(): any {
-    return this.contextSupplier();
+  public before(hookContext: BeforeHookContext, hookHints?: HookHints): EvaluationContext {
+    return this.enrichedContext.apply(this);
   }
 }

libs/providers/flagd/src/lib/configuration.ts

@@ -1,4 +1,5 @@
 import { DEFAULT_MAX_CACHE_SIZE } from './constants';
+import { EvaluationContext } from "@openfeature/core";
 
 export type CacheOption = 'lru' | 'disabled';
 export type ResolverType = 'rpc' | 'in-process';
@@ -83,20 +84,36 @@ export interface Config {
   defaultAuthority?: string;
 }
 
-export type FlagdProviderOptions = Partial<Config>;
+interface FlagdConfig extends Config {
 
-const DEFAULT_CONFIG: Omit<Config, 'port' | 'resolverType'> = {
+  /**
+   * Function providing an EvaluationContext to mix into every evaluation.
+   * The syncContext from the SyncFlagsResponse
+   * (https://buf.build/open-feature/flagd/docs/main:flagd.sync.v1#flagd.sync.v1.SyncFlagsResponse),
+   * represented as a {@link dev.openfeature.sdk.Structure}, is passed as an argument.
+   *
+   * This function runs every time the provider (re)connects, and its result is cached and used in every evaluation.
+   * By default, the entire sync response (converted to a Structure) is used.
+   */
+  contextEnricher: (syncContext: {[key: string]: string} | null) => EvaluationContext
+
+}
+
+export type FlagdProviderOptions = Partial<FlagdConfig>;
+
+const DEFAULT_CONFIG: Omit<FlagdConfig, 'port' | 'resolverType'> = {
   deadlineMs: 500,
   host: 'localhost',
   tls: false,
   selector: '',
   cache: 'lru',
   maxCacheSize: DEFAULT_MAX_CACHE_SIZE,
+  contextEnricher: (syncContext: {[key: string]: string} | null) => syncContext as EvaluationContext
 };
 
-const DEFAULT_RPC_CONFIG: Config = { ...DEFAULT_CONFIG, resolverType: 'rpc', port: 8013 };
+const DEFAULT_RPC_CONFIG: FlagdConfig = { ...DEFAULT_CONFIG, resolverType: 'rpc', port: 8013 };
 
-const DEFAULT_IN_PROCESS_CONFIG: Config = { ...DEFAULT_CONFIG, resolverType: 'in-process', port: 8015 };
+const DEFAULT_IN_PROCESS_CONFIG: FlagdConfig = { ...DEFAULT_CONFIG, resolverType: 'in-process', port: 8015 };
 
 enum ENV_VAR {
   FLAGD_HOST = 'FLAGD_HOST',
@@ -167,7 +184,7 @@ const getEnvVarConfig = (): Partial<Config> => {
   };
 };
 
-export function getConfig(options: FlagdProviderOptions = {}) {
+export function getConfig(options: FlagdProviderOptions = {}): FlagdConfig {
   const envVarConfig = getEnvVarConfig();
   const defaultConfig =
     options.resolverType == 'in-process' || envVarConfig.resolverType == 'in-process'

libs/providers/flagd/src/lib/flagd-provider.ts

@@ -13,7 +13,7 @@ export class FlagdProvider implements Provider {
     name: 'flagd',
   };
 
-  readonly hooks: Hook[] = [];
+  readonly hooks?: Hook[];
   readonly runsOn = 'server';
   readonly events = new OpenFeatureEventEmitter();
   private syncContext: { [key: string]: string } | null = null;
@@ -39,7 +39,7 @@ export class FlagdProvider implements Provider {
         this._service = new InProcessService(config, this.setSyncContext, undefined, logger);
 
         if (config?.offlineFlagSourcePath === undefined) {
-          this.hooks.push(new SyncMetadataHook(this.getSyncContext));
+          this.hooks = [new SyncMetadataHook(() => config.contextEnricher(this.getSyncContext()))];
         }
       } else {
         this._service = new GRPCService(config, undefined, logger);