Auth Service Example with FireBase

import { inject, Injectable, signal } from '@angular/core';
import {
  Auth,
  signInWithEmailAndPassword,
  createUserWithEmailAndPassword,
  signOut,
  UserCredential,
  onAuthStateChanged,
  User,
} from '@angular/fire/auth';
import { from, Observable } from 'rxjs';
import { Router } from '@angular/router';

@Injectable({
  providedIn: 'root',
})
export class AuthService {
  private readonly auth = inject(Auth);
  private readonly router = inject(Router);

  user = signal<User | null>(null);
  isLoggedIn: boolean = false;

  constructor() {
    onAuthStateChanged(this.auth, (user) => {
      this.user.set(user);
      this.isLoggedIn = !!user;
      if (user) {
        console.log('Logged in as: ', user.email);
      } else {
        console.log('No user is logged in.');
        this.router.navigate(['/login']);
      }
    });
  }

  getIsLoggedIn(): Promise<boolean> {
    return new Promise((resolve) => {
      onAuthStateChanged(this.auth, (user) => {
        resolve(!!user);
      });
    });
  }

  signIn(email: string, password: string): Observable<UserCredential> {
    return from(signInWithEmailAndPassword(this.auth, email, password));
  }

  signUp(email: string, password: string): Observable<UserCredential> {
    return from(createUserWithEmailAndPassword(this.auth, email, password));
  }

  logOut() {
    return signOut(this.auth);
  }
}