frontend/src/app/loading.service.ts

import { HttpErrorResponse } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { MatSnackBar } from '@angular/material/snack-bar';
import { BehaviorSubject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class LoadingService {
  private loadingSubject = new BehaviorSubject<boolean>(false);
  private errorSubject = new BehaviorSubject<boolean>(false);

  public loading$ = this.loadingSubject.asObservable();
  public error$ = this.errorSubject.asObservable();

  constructor(private snackBar: MatSnackBar) {}

  show(): void {
    this.loadingSubject.next(true);
    this.errorSubject.next(false);
  }

  hide(): void {
    this.loadingSubject.next(false);
    this.errorSubject.next(false);
  }

  showError(messageOrError?: string | HttpErrorResponse | any): void {
    this.loadingSubject.next(false);
    this.errorSubject.next(true);

    if (!messageOrError) {
      return;
    }

    const message = this.getErrorMessage(messageOrError);

    const snackBarRef = this.snackBar.open(message, 'Schließen', {
      duration: 0,
      panelClass: ['error-snackbar'],
      horizontalPosition: 'center',
      verticalPosition: 'bottom'
    });

    snackBarRef.afterDismissed().subscribe(() => {
      this.hide();
    });
  }

  private getErrorMessage(error?: string | HttpErrorResponse | any): string {

    if (typeof error === 'string') {
      return error;
    }

    if (error instanceof HttpErrorResponse) {

      if (error.status === 0) {
        return 'Netzwerkfehler: Keine Verbindung zum Server möglich!';
      }

      if (error.status >= 500) {
        return `Serverfehler (${error.status}): ${error.statusText || 'Interner Serverfehler'}`;
      }

      if (error.status >= 400) {
        const errorMessage = error.error?.message || error.error?.error || error.statusText;
        return `Fehler (${error.status}): ${errorMessage}`;
      }

      return `HTTP Fehler (${error.status}): ${error.statusText}`;
    }

    if (error.message) {
      return error.message;
    }

    return 'Ein unbekannter Fehler ist aufgetreten!';
  }
}