chore: clean up, cancel-poll hook

packages/client/hmi-client/src/api/api.ts

@@ -55,33 +55,40 @@ const NOOP = () => {};
 export enum PollerState {
 	Done = 'done',
 	Failed = 'failed',
-	ExceedThreshold = 'ExceedThreshold'
+	ExceedThreshold = 'ExceedThreshold',
+	Cancelled = 'Cancelled'
 }
 
-// FIXME: need to refine based on actual needs
 interface PollResponse<T> {
 	error: any;
 	progress: any;
 	data: T;
 }
 
+type PollerCallback<T> = (...args: any[]) => Promise<PollResponse<T>>;
+
 interface PollerResult<T> {
 	state: PollerState;
 	data: T | null;
 }
+
 export class Poller<T> {
 	pollingInterval = 2000;
 
 	pollingThreshold = 10;
 
 	keepGoing = false;
 
-	poll: Function = NOOP;
+	poll: PollerCallback<T> | null;
 
 	progressAction: Function = NOOP;
 
 	numPolls = 0;
 
+	constructor() {
+		this.poll = null;
+	}
+
 	setInterval(v: number) {
 		this.pollingInterval = v;
 		return this;
@@ -113,10 +120,15 @@ export class Poller<T> {
 
 		let response: PollResponse<T> | null = null;
 
+		if (!this.poll) throw new Error('Poll callback undefined');
+
 		while (this.numPolls < this.pollingThreshold) {
 			this.numPolls++;
 			if (!this.keepGoing) {
-				break;
+				return {
+					state: PollerState.Cancelled,
+					data: null
+				};
 			}
 
 			try {

packages/client/hmi-client/tests/unit/api/api.spec.ts

@@ -49,4 +49,27 @@ describe('API utilities test', () => {
 		const result = await poller.start();
 		expect(result.state).eq('ExceedThreshold');
 	});
+
+	it('polling can be cancelled', async () => {
+		let c = 0;
+		const poller = new Poller<number[]>()
+			.setInterval(1000)
+			.setThreshold(10)
+			.setPollAction(async () => {
+				c++;
+				if (c <= 99) {
+					return { data: null, error: null };
+				}
+				return { data: [1, 2, 3], error: null };
+			});
+
+		// Cancel between 2nd and 3rd iteration
+		setTimeout(() => {
+			poller.stop();
+		}, 2500);
+		const result = await poller.start();
+		expect(result.state).eq('Cancelled');
+		expect(c).gt(1);
+		expect(c).lt(4);
+	});
 });