Angular Firebase User Service

user.service.ts

import { Injectable } from '@angular/core';
import { User } from '@angular/fire/auth';
import { BehaviorSubject } from 'rxjs';
import { take } from 'rxjs/operators';

import { AppUser } from '../models/user.model';
import { DbService } from './db.service';

@Injectable({
  providedIn: 'root'
})
export class UserService {

  currentUser: BehaviorSubject<AppUser> = new BehaviorSubject(null);

  constructor(
    private db: DbService
  ) { }

  getCurrentUser(): AppUser {
    return this.currentUser.value;
  }

  async updateUserData(user: AppUser): Promise<void> {
    return this.db.updateDocument('users/', user.id, user);
  }

  async getUserData(user: User): Promise<AppUser> {
    if (!user)
      return null;

    const userDetails: AppUser = await this.db.getDocument('users/', user.uid).pipe(take(1)).toPromise() as AppUser;

    if (!!userDetails) {
      return userDetails;
    } else {
      const userData: AppUser = {
        id: user.uid,
        email: user.email,
        displayName: user.displayName,
        photoURL: user.photoURL,
        emailVerified: user.emailVerified
      };
      return this.db.addDocument('users/', userData, user.uid)
        .then(() => userData);
    }
  }
}