// auth.service.ts
import { HttpClient, HttpHeaders, HttpParams } from '@angular/common/http';
import { Injectable, inject } from '@angular/core';
import { FirebaseApp } from '@angular/fire/app';
import { GoogleAuthProvider, UserCredential, createUserWithEmailAndPassword, getAuth, sendEmailVerification, signInWithEmailAndPassword, signInWithPopup } from 'firebase/auth';
import { firstValueFrom } from 'rxjs';
import { environment } from '../../environments/environment';

@Injectable({
  providedIn: 'root',
})
export class AuthService {
  private app = inject(FirebaseApp);
  private auth = getAuth(this.app);
  private http = inject(HttpClient);

  // Registrierung mit Email und Passwort
  async registerWithEmail(email: string, password: string): Promise<UserCredential> {
    const userCredential = await createUserWithEmailAndPassword(this.auth, email, password);

    // E-Mail-Verifizierung senden
    if (userCredential.user) {
      await sendEmailVerification(userCredential.user);
    }

    // Token, RefreshToken und ggf. photoURL speichern
    const token = await userCredential.user.getIdToken();
    localStorage.setItem('authToken', token);
    localStorage.setItem('refreshToken', userCredential.user.refreshToken);
    if (userCredential.user.photoURL) {
      localStorage.setItem('photoURL', userCredential.user.photoURL);
    }

    return userCredential;
  }

  // Login mit Email und Passwort
  loginWithEmail(email: string, password: string): Promise<UserCredential> {
    return signInWithEmailAndPassword(this.auth, email, password).then(async userCredential => {
      if (userCredential.user) {
        const token = await userCredential.user.getIdToken();
        localStorage.setItem('authToken', token);
        localStorage.setItem('refreshToken', userCredential.user.refreshToken);
        if (userCredential.user.photoURL) {
          localStorage.setItem('photoURL', userCredential.user.photoURL);
        }
      }
      return userCredential;
    });
  }

  // Login mit Google
  loginWithGoogle(): Promise<UserCredential> {
    const provider = new GoogleAuthProvider();
    return signInWithPopup(this.auth, provider).then(async userCredential => {
      if (userCredential.user) {
        const token = await userCredential.user.getIdToken();
        localStorage.setItem('authToken', token);
        localStorage.setItem('refreshToken', userCredential.user.refreshToken);
        if (userCredential.user.photoURL) {
          localStorage.setItem('photoURL', userCredential.user.photoURL);
        }
      }
      return userCredential;
    });
  }

  // Logout: Token, RefreshToken und photoURL entfernen
  logout(): Promise<void> {
    localStorage.removeItem('authToken');
    localStorage.removeItem('refreshToken');
    localStorage.removeItem('photoURL');
    return this.auth.signOut();
  }

  // Prüft, ob ein Token noch gültig ist (über die "exp"-Eigenschaft)
  private isTokenValid(token: string): boolean {
    try {
      const payloadBase64 = token.split('.')[1];
      const payloadJson = atob(payloadBase64.replace(/-/g, '+').replace(/_/g, '/'));
      const payload = JSON.parse(payloadJson);
      const exp = payload.exp;
      const now = Math.floor(Date.now() / 1000);
      return exp > now;
    } catch (e) {
      return false;
    }
  }

  // Versucht, mit dem RefreshToken einen neuen Access Token zu erhalten
  async refreshToken(): Promise<string | null> {
    const storedRefreshToken = localStorage.getItem('refreshToken');
    if (!storedRefreshToken) {
      return null;
    }
    const apiKey = environment.firebaseConfig.apiKey; // Stelle sicher, dass dieser Wert in Deiner environment.ts gesetzt ist
    const url = `https://securetoken.googleapis.com/v1/token?key=${apiKey}`;

    const body = new HttpParams().set('grant_type', 'refresh_token').set('refresh_token', storedRefreshToken);

    const headers = new HttpHeaders({ 'Content-Type': 'application/x-www-form-urlencoded' });

    try {
      const response: any = await firstValueFrom(this.http.post(url, body.toString(), { headers }));
      // response enthält z. B. id_token, refresh_token, expires_in etc.
      const newToken = response.id_token;
      const newRefreshToken = response.refresh_token;
      localStorage.setItem('authToken', newToken);
      localStorage.setItem('refreshToken', newRefreshToken);
      return newToken;
    } catch (error) {
      console.error('Error refreshing token:', error);
      return null;
    }
  }

  /**
   * Gibt einen gültigen Token zurück.
   * Falls der gespeicherte Token noch gültig ist, wird er zurückgegeben.
   * Ansonsten wird versucht, einen neuen Token mit dem RefreshToken zu holen.
   * Ist auch das nicht möglich, wird null zurückgegeben.
   */
  async getToken(): Promise<string | null> {
    const token = localStorage.getItem('authToken');
    if (token && this.isTokenValid(token)) {
      return token;
    } else {
      return await this.refreshToken();
    }
  }
}