move client from separate repo

client/lib/source/ws-source.ts

@@ -0,0 +1,28 @@
+import { Observable } from 'rxjs'
+import { webSocket, WebSocketSubject, WebSocketSubjectConfig } from 'rxjs/webSocket'
+import { UpdateReal } from '../sequence-store'
+import { Source } from './source'
+
+export class WebsocketSource<T> implements Source<T> {
+  private websocket$: WebSocketSubject<UpdateReal<T>>
+
+  constructor (
+    readonly url: string,
+  ) {
+    const fullConfig: WebSocketSubjectConfig<UpdateReal<T>> = {
+      url,
+      openObserver: {
+        next: () => console.log('WebSocket connection open'),
+      },
+      closeObserver: {
+        next: () => console.log('WebSocket connection closed'),
+      },
+      closingObserver: {
+        next: () => console.log('Websocket subscription cancelled, websocket closing'),
+      },
+    }
+    this.websocket$ = webSocket(fullConfig)
+  }
+
+  watch$ (): Observable<UpdateReal<T>> { return this.websocket$.asObservable() }
+}