Improve event service (#15353)

Signed-off-by: AllForNothing <sshijun@vmware.com>

src/portal/src/app/services/event-service/event.service.spec.ts

@@ -1,5 +1,6 @@
 import { TestBed } from '@angular/core/testing';
 import { EventService } from "./event.service";
+import { Subscription } from "rxjs";
 
 
 describe('EventServiceService', () => {
@@ -13,4 +14,18 @@ describe('EventServiceService', () => {
   it('should be created', () => {
     expect(service).toBeTruthy();
   });
+
+
+  it('able to subscribe', () => {
+    let result: string;
+    const sub1 = service.subscribe('testEvent', data => {
+      result = data;
+    });
+    expect(sub1 ).toBeTruthy();
+    expect((sub1 instanceof Subscription)).toEqual(true);
+    service.publish('testEvent', 'resultString');
+    sub1.unsubscribe();
+    expect(result).toEqual('resultString');
+
+  });
 });

src/portal/src/app/services/event-service/event.service.ts

@@ -1,54 +1,73 @@
 import { Injectable } from '@angular/core';
-import { from, Subject } from "rxjs";
+import { Subscription } from "rxjs";
 
 @Injectable({
   providedIn: "root"
 })
 export class EventService {
 
-  private listeners = {};
-  private eventsSubject = new Subject();
-  private events = from(this.eventsSubject);
-
-  constructor() {
-    this.events.subscribe(
-      ({name, args}) => {
-        if (this.listeners[name]) {
-          for (let listener of this.listeners[name]) {
-            listener(...args);
-          }
-        }
-      });
-  }
-  subscribe(name: string, listener): any {
-    if (!this.listeners[name]) {
-      this.listeners[name] = [];
+  private _channels: any = [];
+  /**
+   * Subscribe to an event topic. Events that get posted to that topic will trigger the provided handler.
+   *
+   * @param {string} topic the topic to subscribe to
+   * @param {function} handler the event handler
+   * @return A Subscription to unsubscribe
+   */
+  subscribe(topic: string, handler: Function): Subscription {
+    if (!this._channels[topic]) {
+      this._channels[topic] = [];
     }
-    this.listeners[name].push(listener);
-    return {
-      unsubscribe: () => {
-        this.doUnsubscribe(name, listener);
-      }
-    };
-  }
-  doUnsubscribe(name, listener) {
-    this.listeners[name] = this.listeners[name].filter((v) => {
-      return v !== listener;
+    this._channels[topic].push(handler);
+    return new Subscription(() => {
+      this.unsubscribe(topic, handler);
     });
   }
-  unsubscribe(name, listener?) {
-    if (this.listeners[name]) {
-      if (!listener) {
-        this.listeners[name] = [];
-      } else {
-        this.doUnsubscribe(name, listener);
-      }
+
+  /**
+   * Unsubscribe from the given topic. Your handler will no longer receive events published to this topic.
+   *
+   * @param {string} topic the topic to unsubscribe from
+   * @param {function} handler the event handler
+   *
+   */
+  private unsubscribe(topic: string, handler: Function = null) {
+    let t = this._channels[topic];
+    if (!t) {
+      // Wasn't found, wasn't removed
+      return;
     }
+    if (!handler) {
+      // Remove all handlers for this topic
+      delete this._channels[topic];
+      return;
+    }
+    // We need to find and remove a specific handler
+    let i = t.indexOf(handler);
+    if (i < 0) {
+      // Wasn't found, wasn't removed
+      return;
+    }
+    t.splice(i, 1);
+    // If the channel is empty now, remove it from the channel map
+    if (!t.length) {
+      delete this._channels[topic];
+    }
+    return;
   }
-  publish(name, ...args) {
-    this.eventsSubject.next({
-      name,
-      args
+
+  /**
+   * Publish an event to the given topic.
+   * @param topic
+   * @param data
+   */
+  publish(topic: string, data?: any) {
+    const t = this._channels[topic];
+    if (!t) {
+      return;
+    }
+    t.forEach((handler: any) => {
+      handler(data);
     });
   }
 }