import { Injectable } from '@angular/core';
import { Subject, Subscription } from 'rxjs';

export interface Notification {
    msg: string;
    type: NotificationType;
}

export enum NotificationType {
    Information = 'info',
    Error = 'error',
}

export type NotificationCallback = (notification: Notification) => void;

@Injectable({ providedIn: 'root' })
export class NotificationService {
    private readonly bus: Subject<Notification> = new Subject();
    private readonly subscribers: Map<string, Subscription> = new Map<string, Subscription>();

    subscribe(subscriberId: string, callback: NotificationCallback): void {
        this.subscribers.set(
            subscriberId,
            this.bus.subscribe({
                next: callback
            })
        );
    }

    publish(msg: string, type: NotificationType = NotificationType.Information) {
        this.bus.next({ msg, type });
    }

    unsubscribe(subscriberId: string) {
        this.subscribers.get(subscriberId)?.unsubscribe();
    }
}