feat: use interface for events

packages/client/README.md

@@ -298,7 +298,7 @@ class MyProvider implements Provider {
   }
 
   status?: ProviderStatus | undefined;
-  events?: OpenFeatureEventEmitter | undefined;
+  events?: OpenFeatureEventEmitter | undefined; // implement with "new OpenFeatureEventEmitter()", and use "emit()" to emit events
 
   initialize?(context?: EvaluationContext | undefined): Promise<void> {
     // code to initialize your provider

packages/server/README.md

@@ -302,7 +302,7 @@ class MyProvider implements Provider {
   }
 
   status?: ProviderStatus | undefined;
-  events?: OpenFeatureEventEmitter | undefined;
+  events?: OpenFeatureEventEmitter | undefined; // implement with "new OpenFeatureEventEmitter()", and use "emit()" to emit events
 
   initialize?(context?: EvaluationContext | undefined): Promise<void> {
     // code to initialize your provider

packages/shared/src/events/event-emitter.ts

@@ -0,0 +1,22 @@
+import { ManageLogger } from '../logger';
+import { EventContext, EventHandler } from './eventing';
+import { AnyProviderEvent } from './events';
+
+/**
+ * Event emitter to be optionally implemented by providers.
+ * Implemented by @see OpenFeatureEventEmitter.
+ */
+export interface ProviderEventEmitter<E extends AnyProviderEvent, AdditionalContext extends Record<string, unknown> = Record<string, unknown>>
+  extends ManageLogger<ProviderEventEmitter<E, AdditionalContext>>
+{
+  // here we use E, to restrict the events a provider can manually emit (PROVIDER_CONTEXT_CHANGED is emitted by the SDK)
+  emit(eventType: E, context?: EventContext): void;
+
+  addHandler(eventType: AnyProviderEvent, handler: EventHandler): void;
+
+  removeHandler(eventType: AnyProviderEvent, handler: EventHandler): void;
+
+  removeAllHandlers(eventType?: AnyProviderEvent): void ;
+
+  getHandlers(eventType: AnyProviderEvent): EventHandler[];
+}

packages/shared/src/events/generic-event-emitter.ts

@@ -1,4 +1,5 @@
 import { Logger, ManageLogger, SafeLogger } from '../logger';
+import { ProviderEventEmitter } from './event-emitter';
 import { EventContext, EventDetails, EventHandler } from './eventing';
 import { AllProviderEvents, AnyProviderEvent } from './events';
 
@@ -7,7 +8,7 @@ import { AllProviderEvents, AnyProviderEvent } from './events';
  * in the event details.
  */
 export abstract class GenericEventEmitter<E extends AnyProviderEvent, AdditionalContext extends Record<string, unknown> = Record<string, unknown>>
-  implements ManageLogger<GenericEventEmitter<E, AdditionalContext>>
+  implements ProviderEventEmitter<E>, ManageLogger<GenericEventEmitter<E, AdditionalContext>>
 {
   protected abstract readonly eventEmitter: PlatformEventEmitter;
 

packages/shared/src/events/index.ts

@@ -1,4 +1,6 @@
+export * from './event-emitter';
 export * from './event-utils';
 export * from './eventing';
 export * from './events';
 export * from './generic-event-emitter';
+

packages/shared/src/provider/provider.ts

@@ -1,5 +1,5 @@
 import { EvaluationContext } from '../evaluation';
-import { AnyProviderEvent, GenericEventEmitter } from '../events';
+import { AnyProviderEvent, ProviderEventEmitter } from '../events';
 import { Metadata, Paradigm } from '../types';
 
 /**
@@ -57,7 +57,7 @@ export interface CommonProvider {
    * An event emitter for ProviderEvents.
    * @see ProviderEvents
    */
-  events?: GenericEventEmitter<AnyProviderEvent>;
+  events?: ProviderEventEmitter<AnyProviderEvent>;
 
   /**
    * A function used to shut down the provider.