import {Injectable} from '@angular/core';
import {LoginService} from '@api';
import {CookieService} from 'ngx-cookie-service';
import {BehaviorSubject, Observable, throwError} from 'rxjs';
import {catchError, tap} from 'rxjs/operators';
import {MatSnackBar} from '@angular/material/snack-bar';
import {JwtHelperService} from '@auth0/angular-jwt';

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  private isAuthenticatedSubject = new BehaviorSubject<boolean>(false);
  public isAuthenticated$ = this.isAuthenticatedSubject.asObservable();

  private userClaimsSubject = new BehaviorSubject<JwtClaims | null>(null);
  public userClaims$ = this.userClaimsSubject.asObservable();

  constructor(
    private loginService: LoginService,
    private cookieService: CookieService,
    private snackBar: MatSnackBar,
    private jwtHelper: JwtHelperService
  ) {
    // Check if user is already logged in on service initialization
    this.checkAuthStatus();
  }

  /**
   * Attempt to login with the provided code
   */
  public login(code: string): Observable<any> {
    return this.loginService.login(code).pipe(
      tap(jwt => {
        this.saveJwt(jwt);
        this.isAuthenticatedSubject.next(true);
      }),
      catchError(error => {
        this.snackBar.open('Login failed', '', {duration: 2000});
        return throwError(() => error);
      })
    );
  }

  /**
   * Log the user out by removing the JWT
   */
  public logout(): void {
    this.cookieService.delete('jwt', '/');
    this.isAuthenticatedSubject.next(false);
    this.userClaimsSubject.next(null);
  }

  /**
   * Check if the user is authenticated
   */
  public checkAuthStatus(): boolean {
    const jwt = this.getJwt();
    if (jwt) {
      try {
        // Check if token is expired
        if (this.jwtHelper.isTokenExpired(jwt)) {
          this.logout();
          return false;
        }

        const claims = this.extractJwtClaims(jwt);
        this.userClaimsSubject.next(claims);
        this.isAuthenticatedSubject.next(true);
        return true;
      } catch (e) {
        this.logout();
      }
    }
    return false;
  }

  /**
   * Get the JWT from cookies
   */
  public getJwt(): string | null {
    return this.cookieService.check('jwt') ? this.cookieService.get('jwt') : null;
  }

  /**
   * Save the JWT to cookies
   */
  private saveJwt(jwt: string): void {
    this.cookieService.set('jwt', jwt, {
      path: '/',
      secure: true,
      sameSite: 'Strict'
    });

    const claims = this.extractJwtClaims(jwt);
    this.userClaimsSubject.next(claims);

  }

  /**
   * Extract claims from JWT
   */
  private extractJwtClaims(jwt: string): JwtClaims {
    return <JwtClaims>this.jwtHelper.decodeToken(jwt);
  }

  /**
   * Get user authorizations from claims
   */
  public getUserAuthorizations(): string[] {
    const claims = this.userClaimsSubject.getValue();
    return claims?.authorizations || [];
  }

  public hasAccess(authorization: string[]): boolean {
    return this.getUserAuthorizations().filter(entry => authorization.includes(entry)).length > 0;
  }
}