Implement authentication feature with role-based access control and login dialog

src/app/auth.service.ts

@@ -0,0 +1,63 @@
+import { Injectable, signal } from '@angular/core';
+import { Router } from '@angular/router';
+
+export type UserRole = 'admin' | 'employee';
+
+export interface User {
+  role: UserRole;
+  displayName: string;
+}
+
+
+@Injectable({
+  providedIn: 'root',
+})
+export class AuthService {
+  private readonly SESSION_KEY = 'userRole';
+
+  private readonly USERS: Record<UserRole, { password: string; displayName: string }> = {
+    admin: { password: 'admin123', displayName: 'Admin' },
+    employee: { password: 'employee123', displayName: 'Mitarbeiter' },
+  };
+
+  user = signal<User | null>(this.loadUserFromSession());
+
+  constructor(private router: Router) {}
+
+  private loadUserFromSession(): User | null {
+    const stored = sessionStorage.getItem(this.SESSION_KEY);
+    return stored ? JSON.parse(stored) as User : null;
+  }
+
+  login(role: UserRole, password: string): boolean {
+    const user = this.USERS[role];
+    if (!user) {
+      return false
+    };
+
+    if (password === user.password) {
+      const userObj: User = { role, displayName: user.displayName };
+      sessionStorage.setItem(this.SESSION_KEY, JSON.stringify(userObj));
+      this.user.set(userObj);
+      return true;
+    }
+    return false;
+  }
+
+  logout() {
+    sessionStorage.removeItem(this.SESSION_KEY);
+    this.user.set(null);
+    this.router.navigate(['/']);
+  }
+
+  getUserDataByRole(role: UserRole): User | null {
+    const userDef = this.USERS[role];
+    return userDef ? { role, displayName: userDef.displayName } : null;
+  }
+
+  isLoggedIn(role?: UserRole): boolean {
+    const current = this.user();
+    if (!current) return false;
+    return role ? current.role === role : true;
+  }
+}