feat: add flush() method, resolves #106

packages/core/src/genericHIDDevice.ts

@@ -8,5 +8,8 @@ export interface HIDDevice {
 
 	write(data: number[]): void
 
+	/** Returns a promise which settles when all writes has completed */
+	flush(): Promise<void>
+
 	close(): Promise<void>
 }

packages/core/src/xkeys.ts

@@ -647,6 +647,12 @@ export class XKeys extends EventEmitter {
 	public writeData(message: HIDMessage): void {
 		this._write(message)
 	}
+	/**
+	 * Returns a Promise that settles when all writes have been completed
+	 */
+	public async flush(): Promise<void> {
+		await this.device.flush()
+	}
 
 	/** (Internal function) Called when there has been detected that the device has been disconnected */
 	public async _handleDeviceDisconnected(): Promise<void> {

packages/node/src/__tests__/xkeys.spec.ts

@@ -137,4 +137,95 @@ describe('Unit tests', () => {
 
 		expect(onError).toHaveBeenCalledTimes(0)
 	})
+	test('flush()', async () => {
+		const hidDevice = {
+			vendorId: XKeys.vendorId,
+			productId: 1029,
+			interface: 0,
+			path: 'mockPath',
+		} as HID.Device
+
+		const mockWriteStart = jest.fn()
+		const mockWriteEnd = jest.fn()
+		HIDMock.setMockWriteHandler(async (hid, message) => {
+			mockWriteStart()
+			await sleep(10)
+			mockWriteEnd()
+			handleXkeysMessages(hid, message)
+		})
+
+		const myXkeysPanel = await setupXkeysPanel(hidDevice)
+
+		const errorListener = jest.fn(console.error)
+		myXkeysPanel.on('error', errorListener)
+
+		mockWriteStart.mockClear()
+		mockWriteEnd.mockClear()
+
+		myXkeysPanel.toggleAllBacklights()
+
+		expect(mockWriteStart).toBeCalledTimes(1)
+		expect(mockWriteEnd).toBeCalledTimes(0) // Should not have been called yet
+
+		// cleanup:
+		await myXkeysPanel.flush() // waits for all writes to finish
+
+		expect(mockWriteEnd).toBeCalledTimes(1)
+
+		await myXkeysPanel.close() // close the device.
+		myXkeysPanel.off('error', errorListener)
+
+		expect(errorListener).toHaveBeenCalledTimes(0)
+	})
+	test('flush() with error', async () => {
+		const hidDevice = {
+			vendorId: XKeys.vendorId,
+			productId: 1029,
+			interface: 0,
+			path: 'mockPath',
+		} as HID.Device
+
+		const mockWriteStart = jest.fn()
+		const mockWriteEnd = jest.fn()
+		HIDMock.setMockWriteHandler(async (hid, message) => {
+			mockWriteStart()
+			await sleep(10)
+			mockWriteEnd()
+			// console.log('message', message)
+
+			if (message[0] === 0 && message[1] === 184) {
+				// toggleAllBacklights
+				throw new Error('Mock error')
+			}
+
+			handleXkeysMessages(hid, message)
+		})
+
+		const myXkeysPanel = await setupXkeysPanel(hidDevice)
+
+		const errorListener = jest.fn((e) => {
+			if (`${e}`.includes('Mock error')) return // ignore
+			console.error(e)
+		})
+		myXkeysPanel.on('error', errorListener)
+
+		mockWriteStart.mockClear()
+		mockWriteEnd.mockClear()
+
+		myXkeysPanel.toggleAllBacklights()
+
+		expect(mockWriteStart).toBeCalledTimes(1)
+		expect(errorListener).toBeCalledTimes(0) // Should not have been called yet
+
+		// cleanup:
+		await myXkeysPanel.flush() // waits for all writes to finish
+
+		expect(errorListener).toBeCalledTimes(1)
+		errorListener.mockClear()
+
+		await myXkeysPanel.close() // close the device.
+		myXkeysPanel.off('error', errorListener)
+
+		expect(errorListener).toHaveBeenCalledTimes(0)
+	})
 })

packages/node/src/node-hid-wrapper.ts

@@ -41,6 +41,9 @@ export class NodeHIDDevice extends EventEmitter implements HIDDevice {
 		this.device.removeListener('error', this._handleError)
 		this.device.removeListener('data', this._handleData)
 	}
+	public async flush(): Promise<void> {
+		await this.writeQueue.onIdle()
+	}
 
 	private _handleData = (data: Buffer) => {
 		this.emit('data', data)

packages/webhid/src/web-hid-wrapper.ts

@@ -30,6 +30,9 @@ export class WebHIDDevice extends EventEmitter implements CoreHIDDevice {
 				this.emit('error', err)
 			})
 	}
+	public async flush(): Promise<void> {
+		await this.reportQueue.onIdle()
+	}
 
 	public async close(): Promise<void> {
 		await this.device.close()