Differential D6992 Diff 23833 web/database/utils/WorkerConnectionProxy.js

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web/database/utils/WorkerConnectionProxy.js

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				// @flow

				import type {
				WorkerRequestProxyMessage,
				WorkerResponseMessage,
				WorkerRequestMessage,
				WorkerResponseProxyMessage,
				} from '../../types/worker-types.js';

				type PromiseCallbacks = {
				+resolve: (result: ?WorkerResponseMessage) => void,
				+reject: (error: Error) => void,
				};

				// It's important to have only ONE instance of this object to make it work
				class WorkerConnectionProxy {
				workerPort: MessagePort;
				messageId: number;
				promiseCallbacks: { [index: number]: PromiseCallbacks };
				// This function will be called when worker will send
				// a message with an error but without any app's request
				onError: (error: Error) => void;

				constructor(port: MessagePort, onError: (error: Error) => void) {
				this.workerPort = port;
				this.onError = onError;
				this.workerPort.onmessage = this.handleMessage;
				this.messageId = 1;
				this.promiseCallbacks = {};
				}

				handleMessage: (msg: MessageEvent) => void = (msg: MessageEvent) => {
				const data: WorkerResponseProxyMessage = (msg.data: any);
				const { id, error, message } = data;

				if (!id \|\| !this.promiseCallbacks[id]) {
				if (error) {
				this.onError(error);
				} else if (message) {
				this.onError(new Error(`Unknown error for message: ${message.type}`));
				} else {
				this.onError(new Error('Unknown error'));
				}
				return;
				}

				const callbacks = this.promiseCallbacks[id];
				if (error) {
				callbacks.reject(error);
				} else {
				callbacks.resolve(message);
				}

				delete this.promiseCallbacks[id];
				};

				scheduleOnWorker(
				payload: WorkerRequestMessage,
				): Promise<?WorkerResponseMessage> {
				const msgId = this.messageId++;
				const msg: WorkerRequestProxyMessage = {
				id: msgId,
				message: payload,
				};
				return new Promise((resolve, reject) => {
				this.promiseCallbacks[msgId] = {
				resolve,
				reject,
				};
				this.workerPort.postMessage(msg);
				});
				}
				}

				export default WorkerConnectionProxy;