Open-ILS/src/eg2/src/app/share/util/broadcast.service.ts

   1 /**
   2  * Create and consume BroadcastChannel broadcasts
   3  */
   4 import {Injectable, EventEmitter} from '@angular/core';
   5 import {empty} from 'rxjs';
   6
   7 interface BroadcastSub {
   8     channel: any; // BroadcastChannel
   9     emitter: EventEmitter<any>;
  10 }
  11
  12 @Injectable()
  13 export class BroadcastService {
  14
  15     subscriptions: {[key: string]: BroadcastSub} = {};
  16
  17     noOpEmitter = new EventEmitter<any>();
  18
  19     listen(key: string): EventEmitter<any> {
  20         if (typeof BroadcastChannel === 'undefined') {
  21             return this.noOpEmitter;
  22         }
  23
  24         if (this.subscriptions[key]) {
  25             return this.subscriptions[key].emitter;
  26         }
  27
  28         const emitter = new EventEmitter<any>();
  29         const channel = new BroadcastChannel(key);
  30
  31         channel.onmessage = (e) => {
  32             console.debug('Broadcast received', e.data);
  33             emitter.emit(e.data);
  34         };
  35
  36         this.subscriptions[key] = {
  37             channel: channel,
  38             emitter: emitter
  39         };
  40
  41         return emitter;
  42     }
  43
  44     broadcast(key: string, value: any) {
  45         if (typeof BroadcastChannel === 'undefined') { return; }
  46
  47         if (this.subscriptions[key]) {
  48             this.subscriptions[key].channel.postMessage(value);
  49
  50         } else {
  51
  52             // One time use channel
  53             const channel = new BroadcastChannel(key);
  54             channel.postMessage(value);
  55             channel.close();
  56         }
  57     }
  58
  59     close(key: string) {
  60         if (typeof BroadcastChannel === 'undefined') { return; }
  61
  62         if (this.subscriptions[key]) {
  63             this.subscriptions[key].channel.close();
  64             this.subscriptions[key].emitter.complete();
  65             delete this.subscriptions[key];
  66         }
  67     }
  68 }
  69