import { Injectable, inject, signal } from '@angular/core';
import { LiveAnnouncer } from '@angular/cdk/a11y';

export interface Toast { id: number; text: string; kind: 'ok' | 'error'; }

/** Short messages in the corner; also read out by screen readers. */
@Injectable({ providedIn: 'root' })
export class ToastService {
  private announcer = inject(LiveAnnouncer);
  private next = 1;
  readonly toasts = signal<Toast[]>([]);

  ok(text: string): void { this.show(text, 'ok', 4000); }
  error(text: string): void { this.show(text, 'error', 8000); }

  dismiss(id: number): void { this.toasts.update(list => list.filter(t => t.id !== id)); }

  private show(text: string, kind: Toast['kind'], ms: number): void {
    const id = this.next++;
    this.toasts.update(list => [...list.slice(-3), { id, text, kind }]);
    this.announcer.announce(text, kind === 'error' ? 'assertive' : 'polite');
    setTimeout(() => this.dismiss(id), ms);
  }
}