OpenSlides/client/src/app/core/ui-services/count-users.service.ts

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import { Injectable } from '@angular/core';
import { Observable, Subject } from 'rxjs';
import { NotifyService } from '../core-services/notify.service';
import { OperatorService } from '../core-services/operator.service';
interface CountUserRequest {
token: string;
}
interface CountUserResponse extends CountUserRequest {
userId: number;
}
const REQUEST_NAME = 'count-user-request';
const RESPONSE_NAME = 'count-user-response';
/**
* Provides functionality to count users with notify.
* Sends requests to all active instances, which (hopefully) respond to this message.
* Here, the answers will be collected and aggegated.
*/
@Injectable({
providedIn: 'root'
})
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export class CountUsersService {
private activeCounts: { [token: string]: Subject<number> } = {};
private currentUserId: number;
/**
* Sets up all listeners
*
* @param notifyService
* @param operator
*/
public constructor(private notifyService: NotifyService, operator: OperatorService) {
// Listen for requests to send an answer.
this.notifyService.getMessageObservable<CountUserRequest>(REQUEST_NAME).subscribe(request => {
if (request.content.token) {
this.notifyService.sendToChannels(
RESPONSE_NAME,
{
token: request.content.token,
userId: this.currentUserId
},
request.senderChannelName
);
}
});
// Listen for responses and distribute them through `activeCounts`
this.notifyService.getMessageObservable<CountUserResponse>(RESPONSE_NAME).subscribe(response => {
if (response.content.userId && response.content.token && this.activeCounts[response.content.token]) {
this.activeCounts[response.content.token].next(response.content.userId);
}
});
// Look for the current user.
operator.getUserObservable().subscribe(user => (this.currentUserId = user ? user.id : null));
}
/**
* @returns a generated track token to keep track of the counting.
*/
private generateTrackToken(): string {
let token = '';
const characters = '0123456789abcdef';
for (let i = 0; i < 32; i++) {
token += characters.charAt(Math.floor(Math.random() * characters.length));
}
return token;
}
/**
* Starts the counting process
*
* @returns a tuple: the first entry is a token, which can be used to stop the
* counting with `stopCounting`. The second entry is an observable, where all user
* ids will be published.
*/
public countUsers(): [string, Observable<number>] {
const trackToken = this.generateTrackToken();
const subject = new Subject<number>();
this.activeCounts[trackToken] = subject;
this.notifyService.sendToAllUsers<CountUserRequest>(REQUEST_NAME, {
token: trackToken
});
return [trackToken, this.activeCounts[trackToken].asObservable()];
}
/**
* Stops an active counting by the provided token
*
* @param token The count to stop
*/
public stopCounting(trackToken: string): void {
if (this.activeCounts[trackToken]) {
this.activeCounts[trackToken].complete();
delete this.activeCounts[trackToken];
}
}
}