Fetch things in bulk for the homepage

2 files changed, 30 insertions, 0 deletions

diff --git a/client/src/app/helpers/index.ts b/client/src/app/helpers/index.ts
index cc61255ba..beff749ec 100644
--- a/client/src/app/helpers/index.ts
+++ b/client/src/app/helpers/index.ts
@@ -1,5 +1,6 @@
 export * from './locales'
 export * from './constants'
 export * from './i18n-utils'
+export * from './rxjs'
 export * from './utils'
 export * from './zone'
diff --git a/client/src/app/helpers/rxjs.ts b/client/src/app/helpers/rxjs.ts
new file mode 100644
index 000000000..eb051f868
--- /dev/null
+++ b/client/src/app/helpers/rxjs.ts
@@ -0,0 +1,29 @@
+import { uniq } from 'lodash-es'
+import { asyncScheduler, Observable } from 'rxjs'
+import { bufferTime, distinctUntilChanged, filter, map, observeOn, share, switchMap } from 'rxjs/operators'
+import { NgZone } from '@angular/core'
+import { enterZone, leaveZone } from './zone'
+
+function buildBulkObservable <T extends number | string, R> (options: {
+  ngZone: NgZone
+  notifierObservable: Observable<T>
+  time: number
+  bulkGet: (params: T[]) => Observable<R>
+}) {
+  const { ngZone, notifierObservable, time, bulkGet } = options
+
+  return notifierObservable.pipe(
+    distinctUntilChanged(),
+    // We leave Angular zone so Protractor does not get stuck
+    bufferTime(time, leaveZone(ngZone, asyncScheduler)),
+    filter(params => params.length !== 0),
+    map(params => uniq(params)),
+    observeOn(enterZone(ngZone, asyncScheduler)),
+    switchMap(params => bulkGet(params)),
+    share()
+  )
+}
+
+export {
+  buildBulkObservable
+}