import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { environment } from '@environment';
import { catchError, of as observableOf } from 'rxjs';


@Injectable({ providedIn: 'root' })
export class ServiceWorkerService {
  private alerted: boolean;
  private interval: number|NodeJS.Timeout;
  constructor (
    private http: HttpClient
  ) { }

  async checkForUpdate () {
    // if we are testing or on localhost, don't do this
    if (!environment.production) {
      return;
    }

    const base = document.head.querySelector('base')?.href;

    const result = await this.http.get(base + 'version.json').pipe(
      catchError((e: HttpErrorResponse) => {
        if (e.status === 404) {
          // make sure we aren't adding a new alert every 15 seconds
          this.notifyUpdated('404');
        }

        return observableOf(null);
      }))
      .toPromise();

    if (result !== environment.version) {
      this.notifyUpdated(result as any);
    }
  }

  private notifyUpdated (newVersion: string) {
    if (!this.alerted) {
      this.alerted = true;
      if (this.interval) {
        clearInterval(this.interval as number);
      }
      console.warn('There is a new version of GrantsConnect, the browser will now reload. ');
    }
  }

  startPolling () {
    // if we are testing or on localhost, don't do this
    if (!environment.production) {
      return;
    }
    this.interval = setInterval(() => {
      if (!this.alerted) {
        this.checkForUpdate();
      }
    }, 60000);
  }
}