Added observable for web worker communication

src/assets/javascripts/config/index.ts

@@ -29,6 +29,7 @@
  */
 export interface Config {
   base: string                         /* Base URL */
+  search: string                       /* Web worker URL */
 }
 
 /* ----------------------------------------------------------------------------

src/assets/javascripts/ui/worker/index.ts

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2016-2019 Martin Donath <martin.donath@squidfunk.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+import { Observable, fromEvent } from "rxjs"
+import {
+  pluck,
+  shareReplay,
+  switchMap,
+  take,
+  tap,
+  throttle
+} from "rxjs/operators"
+
+/* ----------------------------------------------------------------------------
+ * Types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Worker message
+ */
+export interface WorkerMessage {
+  type: unknown                        /* Message type */
+  data: unknown                        /* Message data */
+}
+
+/* ----------------------------------------------------------------------------
+ * Function types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Options
+ *
+ * @template T - Worker message type
+ */
+interface Options<T extends WorkerMessage> {
+  message$: Observable<T>              /* Message observable */
+}
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Watch a web worker
+ *
+ * This function returns an observable that will send all values emitted by the
+ * message observable to the web worker. Web worker communication is expected
+ * to be bidirectional (request-response) and synchronous. Messages that are
+ * emitted during a pending request are throttled, the last one is emitted.
+ *
+ * @param worker - Web worker
+ *
+ * @return Worker message observable
+ */
+export function watchWorker<T extends WorkerMessage>(
+  worker: Worker, { message$ }: Options<T>
+): Observable<T> {
+
+  /* Receive messages from web worker */
+  const worker$ = fromEvent(worker, "message")
+    .pipe(
+      pluck<Event, T>("data")
+    )
+
+  /* Send request and wait for response */
+  return message$
+    .pipe(
+      throttle(() => worker$, { leading: true, trailing: true }),
+      tap(message => worker.postMessage(message)),
+      switchMap(() => worker$
+        .pipe(
+          take(1)
+        )
+      ),
+      shareReplay(1)
+    )
+}