import { EventEmitter } from "events" ; import { IEvent , TransformedEvent , IEventTransformer , IEventProvider } from "@fluidframework/common-definitions" ; export type EventEmitterEventType = EventEmitter extends { on ( event , listener ) ; } ? E : never ; export type TypedEventTransform < TThis , TEvent > = TransformedEvent < TThis , "newListener" | "removeListener" , Parameters < ( event : string , listener : ( ... args : any [ ] ) => void ) => void > > & IEventTransformer < TThis , TEvent & IEvent > & TransformedEvent < TThis , EventEmitterEventType , any [ ] > ; /**
 * Event Emitter helper class the supports emitting typed events
 */ export class TypedEventEmitter < TEvent > extends EventEmitter implements IEventProvider < TEvent & IEvent > { constructor ( ) { super ( ) ; this . addListener = super . addListener . bind ( this ) as TypedEventTransform < this , TEvent > ; this . on = super . on . bind ( this ) as TypedEventTransform < this , TEvent > ; this . once = super . once . bind ( this ) as TypedEventTransform < this , TEvent > ; this . prependListener = super . prependListener . bind ( this ) as TypedEventTransform < this , TEvent > ; this . prependOnceListener = super . prependOnceListener . bind ( this ) as TypedEventTransform < this , TEvent > ; this . removeListener = super . removeListener . bind ( this ) as TypedEventTransform < this , TEvent > ; this . off = super . off . bind ( this ) as TypedEventTransform < this , TEvent > ; } readonly addListener : TypedEventTransform < this , TEvent > ; readonly on : TypedEventTransform < this , TEvent > ; readonly once : TypedEventTransform < this , TEvent > ; readonly prependListener : TypedEventTransform < this , TEvent > ; readonly prependOnceListener : TypedEventTransform < this , TEvent > ; readonly removeListener : TypedEventTransform < this , TEvent > ; readonly off : TypedEventTransform < this , TEvent > ; }