move client from separate repo

client/lib/action-serializer.ts

@@ -0,0 +1,44 @@
+import { Subject, BehaviorSubject, of, Observable, Observer, throwError } from 'rxjs'
+import { concatMap, map, catchError, filter, take } from 'rxjs/operators'
+
+export type Action<T> = {
+  action: () => T,
+  notify: BehaviorSubject<undefined | T>
+}
+
+export class ActionSerializer {
+  private readonly sequentialActions = new Subject<Action<any>>()
+
+  constructor () {
+    this.sequentialActions.pipe(
+      concatMap(({ action, notify }) => fromSync$(action).pipe(
+        catchError(e => of(notify.next({ error: e }))),
+        map(result => notify.next({ result })),
+      )),
+      catchError(e => of(console.error(`Action Serializer Exception`, e))),
+    ).subscribe()
+  }
+
+  run$<T> (action: () => T): Observable<T> {
+    const notify = new BehaviorSubject(undefined) as BehaviorSubject<T | undefined>
+    this.sequentialActions.next({ action, notify })
+    return (notify as BehaviorSubject<T>).pipe(
+      filter(res => res !== undefined),
+      take(1),
+      concatMap((res: any) => res.error ? throwError(res.error) : of(res.result)),
+    )
+  }
+}
+
+function fromSync$<S, T> (action: (s: S) => T, s: S): Observable<T>
+function fromSync$<T> (action: () => T): Observable<T>
+function fromSync$<S, T> (action: (s: S) => T, s?: S): Observable<T> {
+  return new Observable((subscriber: Observer<T>) => {
+    try {
+      subscriber.next(action(s as S))
+      subscriber.complete()
+    } catch (e) {
+      subscriber.error(e)
+    }
+  })
+}