add connection monitoring

client/lib/patch-db.ts

@@ -1,4 +1,4 @@
-import { merge, Observable, of } from 'rxjs'
+import { Observable } from 'rxjs'
 import { concatMap, finalize, map, tap } from 'rxjs/operators'
 import { Source } from './source/source'
 import { Store } from './store'
@@ -7,6 +7,7 @@ export { Operation } from 'fast-json-patch'
 
 export class PatchDB<T extends object> {
   store: Store<T>
+  connectionStatus$ = this.source.connectionStatus$
 
   constructor (
     private readonly source: Source<T>,
@@ -21,7 +22,7 @@ export class PatchDB<T extends object> {
     const sequence$ = this.store.watchAll$().pipe(map(cache => cache.sequence))
     // nested concatMaps, as it is written, ensure sync is not run for update2 until handleSyncResult is complete for update1.
     // flat concatMaps would allow many syncs to run while handleSyncResult was hanging. We can consider such an idea if performance requires it.
-    return merge(this.source.watch$(sequence$)).pipe(
+    return this.source.watch$(sequence$).pipe(
       tap(update => console.log('PATCHDB - source updated:', update)),
       concatMap(update => this.store.update$(update)),
       finalize(() => {

client/lib/source/poll-source.ts

@@ -1,6 +1,6 @@
 import { BehaviorSubject, concat, from, Observable, of } from 'rxjs'
 import { catchError, concatMap, delay, skip, switchMap, take, tap } from 'rxjs/operators'
-import { Http, Update } from '../types'
+import { ConnectionStatus, Http, Update } from '../types'
 import { Source } from './source'
 
 export type PollConfig = {
@@ -8,6 +8,7 @@ export type PollConfig = {
 }
 
 export class PollSource<T> implements Source<T> {
+  connectionStatus$ = new BehaviorSubject(ConnectionStatus.Initializing)
 
   constructor (
     private readonly pollConfig: PollConfig,
@@ -15,26 +16,22 @@ export class PollSource<T> implements Source<T> {
   ) { }
 
   watch$ (sequence$: Observable<number>): Observable<Update<T>> {
-    console.log('POLL_SOURCE - watch$()')
-
     const polling$ = new BehaviorSubject('')
 
     const updates$ = of('').pipe(
       concatMap(_ => sequence$),
       take(1),
-      tap(_ => console.log('making request')),
       concatMap(seq => this.http.getRevisions(seq)),
+      tap(_ => this.connectionStatus$.next(ConnectionStatus.Connected)),
       catchError(e => {
         console.error(e)
+        this.connectionStatus$.next(ConnectionStatus.Disconnected)
         return of([])
       }),
-      tap(_ => console.log('request complete')),
     )
 
     const delay$ = of([]).pipe(
-      tap(_ => console.log('starting cooldown')),
       delay(this.pollConfig.cooldown),
-      tap(_ => console.log('cooldown finished')),
       tap(_ => polling$.next('')),
       skip(1),
     )

client/lib/source/source.ts

@@ -1,6 +1,7 @@
-import { Observable } from 'rxjs'
+import { BehaviorSubject, Observable } from 'rxjs'
-import { Update } from '../types'
+import { ConnectionStatus, Update } from '../types'
 
 export interface Source<T> {
+  connectionStatus$: BehaviorSubject<ConnectionStatus>
   watch$ (sequence$?: Observable<number>): Observable<Update<T>>
 }

client/lib/source/ws-source.ts

@@ -1,34 +1,40 @@
-import { Observable } from 'rxjs'
+import { BehaviorSubject, Observable } from 'rxjs'
 import { webSocket, WebSocketSubject, WebSocketSubjectConfig } from 'rxjs/webSocket'
-import { Update } from '../types'
+import { ConnectionStatus, Update } from '../types'
 import { Source } from './source'
 
 export class WebsocketSource<T> implements Source<T> {
-  private websocket$: WebSocketSubject<Update<T>>
+  connectionStatus$ = new BehaviorSubject(ConnectionStatus.Initializing)
+  private websocket$: WebSocketSubject<Update<T>> | undefined
 
   constructor (
-    readonly url: string,
+    private readonly url: string,
   ) {
+  }
+
+  watch$ (): Observable<Update<T>> {
     const fullConfig: WebSocketSubjectConfig<Update<T>> = {
-      url,
+      url: this.url,
       openObserver: {
         next: () => {
           console.log('WebSocket connection open')
-          this.websocket$.next('open message' as any)
+          this.connectionStatus$.next(ConnectionStatus.Connected)
+          this.websocket$!.next('open message' as any)
         },
       },
       closeObserver: {
         next: () => {
+          this.connectionStatus$.next(ConnectionStatus.Disconnected)
           console.log('WebSocket connection closed')
-          // @TODO re-open websocket on retry loop
         },
       },
       closingObserver: {
-        next: () => console.log('Websocket subscription cancelled, websocket closing'),
+        next: () => {
+          console.log('Websocket subscription cancelled, websocket closing')
+        },
       },
     }
     this.websocket$ = webSocket(fullConfig)
+    return this.websocket$
   }
-
-  watch$ (): Observable<Update<T>> { return this.websocket$.asObservable() }
 }

client/lib/types.ts

@@ -27,3 +27,9 @@ export interface DBCache<T>{
   sequence: number,
   data: T | { }
 }
+
+export enum ConnectionStatus {
+  Initializing = 'initializing',
+  Connected = 'connected',
+  Disconnected = 'disconnected',
+}