import { Injectable } from '@angular/core';
import { MessageService } from './message.service';
import { HttpClient } from '@angular/common/http';
import { UserCreds } from './userCreds'
import jwt_decode  from 'jwt-decode'
import { Observable, interval, Subject, Subscription } from 'rxjs'
import { map, takeWhile } from 'rxjs/operators'
import { authserviceBaseUrl, applicationId } from './config'


interface TokenTuple {
  authToken: string
  refreshToken: string
}

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

  public static Id_AuthToken_Key : string = "id_authtoken";
  public static Id_RefreshToken_Key : string = "id_refreshtoken";

  private _expiryTime =  new Subject<number>()
  private subscription: Subscription

  constructor(private http: HttpClient, private messageService: MessageService) {
  }

  checkAuthenticated(): boolean {
    let result: boolean = false

    const token = localStorage.getItem(TokenService.Id_AuthToken_Key)
    if (token) {
      let expiration = jwt_decode(token)["exp"]
      if ((expiration * 1000) > Date.now()) {
        result = true
      } else {
        this.logout()
      }
    }

    return result
  }

  logout() : void {
    localStorage.removeItem(TokenService.Id_AuthToken_Key)
    localStorage.removeItem(TokenService.Id_RefreshToken_Key)
    this.messageService.add("Token removed from local storage")
  }

  get expiryTime(): Observable<number> {
    return this._expiryTime
  }

  setExpiryTime(token: string) :void {
    let exp = jwt_decode(token)["exp"]
    let iat = jwt_decode(token)["iat"]
    let start = exp - iat
    if (this.subscription && !this.subscription.closed) {
      this.subscription.unsubscribe()
    }
    this.subscription = interval(1000).pipe(map(v => start - v)).pipe(takeWhile(v => v != 0)).subscribe(v => this._expiryTime.next(v))
  }

  async login(login: string, password: string) : Promise<void> {
    this.messageService.add(`TokenService: trying to login and obtain token`)
    const userCreds : UserCreds = {
      "application": applicationId,
      "login": login,
      "password": password
    }
    const tokenTuple: TokenTuple = await this.http.post<TokenTuple>(
      `${authserviceBaseUrl}/refreshable`, 
      userCreds
    ).toPromise()
    localStorage.setItem(TokenService.Id_AuthToken_Key, tokenTuple.authToken)
    localStorage.setItem(TokenService.Id_RefreshToken_Key, tokenTuple.refreshToken)
    this.messageService.add("Token saved")

    this.setExpiryTime(tokenTuple.authToken)
  }

  async refresh() : Promise<void> {
    try {
      this.messageService.add(`TokenService: trying to refresh tokens`)
      const refreshToken = localStorage.getItem(TokenService.Id_RefreshToken_Key)
      const tokenTuple: TokenTuple = await this.http.post<TokenTuple>(
        `${authserviceBaseUrl}/refresh`, 
        refreshToken
      ).toPromise()
      localStorage.setItem(TokenService.Id_AuthToken_Key, tokenTuple.authToken)
      localStorage.setItem(TokenService.Id_RefreshToken_Key, tokenTuple.refreshToken)
      this.messageService.add("Token saved")

      this.setExpiryTime(tokenTuple.authToken)
    } catch (err) {
      this.messageService.add(`error when trying to refresh: ${ JSON.stringify(err, undefined, 4)}`)
      localStorage.removeItem(TokenService.Id_AuthToken_Key)
      localStorage.removeItem(TokenService.Id_RefreshToken_Key)
      this.messageService.add("Token removed from local storage")
    }
  }
}