const activeTask = { task, resolver, method, cancelTask }

this.activeTasks.push(activeTask)

// active tasks receive cancel signal and shut down gracefully

async function cancelTask() {

await runner.stop()

await runner.waitForTerminated()

resolver.reject(new Error('Cancelled'))

}

private _state: RunnerState = RunnerState.IDLE

private _operationLock: DeferPromise<void> | null = null

private _terminatePromise: DeferPromise<void> = createDefer()

private _eventEmitter: EventEmitter<{

message: [WorkerResponse]

return this._state === RunnerState.STOPPED

}

public waitForTerminated(): Promise<void> {

return this._terminatePromise

}

public get isStarted(): boolean {

return this._state === RunnerState.STARTED

}

}),

{

eventNames: ['onCancel'],

post: request => this.postMessage(request),

post: (request) => {

if (this._state !== RunnerState.STOPPING && this._state !== RunnerState.STOPPED) {

this.postMessage(request)

}

},

on: callback => this._eventEmitter.on('rpc', callback),

timeout: -1,

},

finally {

this._operationLock.resolve()

this._operationLock = null

this._terminatePromise.resolve()

}

}