feat(time): Add Interval class (#5792)

Creates our own version of an Interval, similar to how we have our own
Timeout

---

<!--- REMINDER: Ensure that your PR meets the guidelines in
CONTRIBUTING.md -->

License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Signed-off-by: nkomonen-amazon <[email protected]>

Author: nkomonen-amazon

packages/core/src/shared/utilities/timeoutUtils.ts

@@ -184,6 +184,34 @@ export class Timeout {
     }
 }
 
+export class Interval {
+    private _setCompleted: (() => void) | undefined
+    private _nextCompletion: Promise<void>
+    private ref: NodeJS.Timer | number | undefined
+
+    constructor(intervalMillis: number, onCompletion: () => Promise<void>) {
+        this._nextCompletion = new Promise<void>((resolve) => {
+            this._setCompleted = () => resolve()
+        })
+        this.ref = globals.clock.setInterval(async () => {
+            await onCompletion()
+            this._setCompleted!()
+            this._nextCompletion = new Promise<void>((resolve) => {
+                this._setCompleted = () => resolve()
+            })
+        }, intervalMillis)
+    }
+
+    /** Allows to wait for the next interval to finish running */
+    public async nextCompletion() {
+        await this._nextCompletion
+    }
+
+    public dispose() {
+        globals.clock.clearInterval(this.ref)
+    }
+}
+
 interface WaitUntilOptions {
     /** Timeout in ms (default: 5000) */
     readonly timeout?: number

packages/core/src/test/shared/utilities/timeoutUtils.test.ts

@@ -8,22 +8,29 @@ import * as FakeTimers from '@sinonjs/fake-timers'
 import * as timeoutUtils from '../../../shared/utilities/timeoutUtils'
 import { installFakeClock, tickPromise } from '../../../test/testUtil'
 import { sleep } from '../../../shared/utilities/timeoutUtils'
+import { SinonStub, SinonSandbox, createSandbox } from 'sinon'
 
 // We export this describe() so it can be used in the web tests as well
 export const timeoutUtilsDescribe = describe('timeoutUtils', async function () {
     let clock: FakeTimers.InstalledClock
+    let sandbox: SinonSandbox
 
     before(function () {
         clock = installFakeClock()
     })
 
+    beforeEach(function () {
+        sandbox = createSandbox()
+    })
+
     after(function () {
         clock.uninstall()
     })
 
     afterEach(function () {
         clock.reset()
         this.timer?.dispose()
+        sandbox.restore()
     })
 
     describe('Timeout', async function () {
@@ -192,6 +199,53 @@ export const timeoutUtilsDescribe = describe('timeoutUtils', async function () {
         })
     })
 
+    describe('Interval', async function () {
+        let interval: timeoutUtils.Interval
+        let onCompletionStub: SinonStub
+
+        beforeEach(async function () {
+            onCompletionStub = sandbox.stub()
+            interval = new timeoutUtils.Interval(1000, onCompletionStub)
+        })
+
+        afterEach(async function () {
+            interval?.dispose()
+        })
+
+        it('Executes the callback on an interval', async function () {
+            await clock.tickAsync(999)
+            assert.strictEqual(onCompletionStub.callCount, 0)
+            await clock.tickAsync(1)
+            assert.strictEqual(onCompletionStub.callCount, 1)
+
+            await clock.tickAsync(500)
+            assert.strictEqual(onCompletionStub.callCount, 1)
+            await clock.tickAsync(500)
+            assert.strictEqual(onCompletionStub.callCount, 2)
+
+            await clock.tickAsync(1000)
+            assert.strictEqual(onCompletionStub.callCount, 3)
+        })
+
+        it('allows to wait for next completion', async function () {
+            clock.uninstall()
+
+            let curr = 'Did Not Change'
+
+            const realInterval = new timeoutUtils.Interval(50, async () => {
+                await sleep(50)
+                curr = 'Did Change'
+            })
+
+            const withoutWait = curr
+            await realInterval.nextCompletion()
+            const withWait = curr
+
+            assert.strictEqual(withoutWait, 'Did Not Change')
+            assert.strictEqual(withWait, 'Did Change')
+        })
+    })
+
     describe('waitUntil', async function () {
         const testSettings = {
             callCounter: 0,