[skip-ci] [Newsfeed] add a feed items observable

x-pack/plugins/newsfeed/public/lib/api.ts

@@ -3,3 +3,112 @@
  * or more contributor license agreements. Licensed under the Elastic License;
  * you may not use this file except in compliance with the Elastic License.
  */
+
+import * as Rx from 'rxjs';
+import moment from 'moment';
+import { filter, mergeMap, tap } from 'rxjs/operators';
+import { HttpServiceBase } from '../../../../../src/core/public';
+
+interface ApiItem {
+  hash: string;
+  expire_on: Date;
+  title: { [lang: string]: string };
+  description: { [lang: string]: string };
+  link_text: { [lang: string]: string };
+  link_url: { [lang: string]: string };
+
+  badge: null; // not used phase 1
+  image_url: null; // not used phase 1
+  languages: null; // not used phase 1
+  publish_on: null; // not used phase 1
+}
+
+interface NewsfeedItem {
+  title: string;
+  description: string;
+  linkText: string;
+  linkUrl: string;
+}
+
+interface FetchResult {
+  hasNew: boolean;
+  feedItems: NewsfeedItem[];
+}
+
+const DEFAULT_LANGUAGE = 'en'; // TODO: read from settings, default to en
+const NEWSFEED_MAIN_INTERVAL = 120000; // A main interval to check for need to refresh (2min)
+const NEWSFEED_FETCH_INTERVAL = moment.duration(1, 'day'); // how often to actually fetch the API
+const NEWSFEED_LAST_FETCH_STORAGE_KEY = 'xpack.newsfeed.lastfetchtime';
+const NEWSFEED_HASH_SET_STORAGE_KEY = 'xpack.newsfeed.hashes';
+const NEWSFEED_SERVICE_URL = 'https://feeds.elastic.co/kibana/v7.0.0.json'; // FIXME: should be dynamic
+
+function shouldFetch(): boolean {
+  const lastFetch: string | null = localStorage.getItem(NEWSFEED_LAST_FETCH_STORAGE_KEY);
+  if (lastFetch == null) {
+    return true;
+  }
+  const last = moment(lastFetch, 'x'); // parse as unix ms timestamp
+  const now = moment();
+  const duration = moment.duration(now.diff(last));
+
+  return duration > NEWSFEED_FETCH_INTERVAL;
+}
+
+function updateLastFetch() {
+  localStorage.setItem(NEWSFEED_LAST_FETCH_STORAGE_KEY, Date.now().toString());
+}
+
+function updateHashes(items: ApiItem[]): { previous: string[]; current: string[] } {
+  // combine localStorage hashes with new hashes
+  const hashSet: string | null = localStorage.getItem(NEWSFEED_HASH_SET_STORAGE_KEY);
+  let oldHashes: string[] = [];
+  if (hashSet != null) {
+    oldHashes = hashSet.split(',');
+  }
+  const newHashes = items.map(i => i.hash.slice(0, 10));
+  const updatedHashes = [...new Set(oldHashes.concat(newHashes))];
+  localStorage.setItem(NEWSFEED_HASH_SET_STORAGE_KEY, updatedHashes.join(','));
+
+  return { previous: oldHashes, current: updatedHashes };
+}
+
+/*
+ * Creates an Observable to newsfeed items, powered by the main interval
+ * Computes hasNew value from new item hashes saved in localStorage
+ */
+export function getApi(http: HttpServiceBase): Rx.Observable<void | FetchResult> {
+  return Rx.timer(0, NEWSFEED_MAIN_INTERVAL).pipe(
+    filter(() => shouldFetch()),
+    mergeMap(
+      (value: number): Rx.Observable<ApiItem[]> => {
+        return Rx.from(
+          http.fetch(NEWSFEED_SERVICE_URL, { method: 'GET' }).then(({ items }) => items)
+        );
+      }
+    ),
+    filter(items => items.length > 0),
+    tap(() => updateLastFetch()),
+    mergeMap(
+      (items): Rx.Observable<FetchResult> => {
+        // calculate hasNew
+        const { previous, current } = updateHashes(items);
+        const hasNew = current.length > previous.length;
+
+        // model feed items
+        const feedItems: NewsfeedItem[] = items.map(it => {
+          return {
+            title: it.title[DEFAULT_LANGUAGE],
+            description: it.description[DEFAULT_LANGUAGE],
+            linkText: it.link_text[DEFAULT_LANGUAGE],
+            linkUrl: it.link_url[DEFAULT_LANGUAGE],
+          };
+        });
+
+        return Rx.of({
+          hasNew,
+          feedItems,
+        });
+      }
+    )
+  );
+}

x-pack/plugins/newsfeed/public/plugin.tsx

@@ -4,6 +4,8 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
+import * as Rx from 'rxjs';
+import { catchError, takeUntil } from 'rxjs/operators';
 import ReactDOM from 'react-dom';
 import React from 'react';
 import {
@@ -12,12 +14,15 @@ import {
   CoreStart,
   Plugin,
 } from '../../../../src/core/public';
+import { getApi } from './lib/api';
 import { MailNavButton } from './components/spaces_header_nav_button';
 
 export type Setup = void;
 export type Start = void;
 
 export class NewsfeedPublicPlugin implements Plugin<Setup, Start> {
+  private readonly stop$ = new Rx.ReplaySubject(1);
+
   constructor(initializerContext: PluginInitializerContext) {}
 
   public setup(core: CoreSetup): Setup {}
@@ -32,5 +37,22 @@ export class NewsfeedPublicPlugin implements Plugin<Setup, Start> {
       order: 1000,
       mount,
     });
+
+    const { http } = core;
+    const api$ = getApi(http).pipe(
+      takeUntil(this.stop$), // stop the interval when stop method is called
+      catchError(() => {
+        // show a message to try again later?
+        // do not throw error
+        return Rx.of(null);
+      })
+    );
+
+    // TODO: pass to component?
+    api$.subscribe();
+  }
+
+  public stop() {
+    this.stop$.next();
   }
 }