import {Inject, Injectable, PLATFORM_ID} from '@angular/core';
import {HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpErrorResponse} from '@angular/common/http';
import {fromEvent, Observable, throwError, timer} from 'rxjs';
import {isPlatformBrowser} from '@angular/common';
import {SnackBarService} from '../../snackbar/snack-bar.service';
import {retryWhen, catchError, mapTo, mergeMap} from 'rxjs/operators';

declare var window: any;


@Injectable()
export class HandlerErrorInterceptor implements HttpInterceptor {
  private _onlineChanges$: Observable<any>;

  constructor(
    @Inject(PLATFORM_ID) private _platform: Object,
    private _snackBar: SnackBarService
  ) {
  }

  private genericRetryStrategy = (
    {
      maxRetryAttempts = 3,
      scalingDuration = 1000,
      excludedStatusCodes = []
    }: {
      maxRetryAttempts?: number,
      scalingDuration?: number,
      excludedStatusCodes?: number[]
    } = {}) => (attempts: Observable<any>) => {
    return attempts.pipe(
      mergeMap((error, i) => {
        const retryAttempt = i + 1;
        // if maximum number of retries have been met
        // or response is a status code we don't wish to retry, throw error
        if (
          retryAttempt > maxRetryAttempts ||
          excludedStatusCodes.find(e => e === error.status)
        ) {
          return throwError(error);
        }
        console.log(
          `Attempt ${retryAttempt}: retrying in ${retryAttempt *
          scalingDuration}ms`
        );
        if (navigator.onLine) {
          // retry after 1s, 2s, etc...
          return timer(retryAttempt * scalingDuration);
        } else {
          return this._onlineChanges$;
        }
      })
    );
  }

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (isPlatformBrowser(this._platform)) {
      this._onlineChanges$ = fromEvent(window, 'online').pipe(mapTo(true));
      return next.handle(req)
        .pipe(
          retryWhen(this.genericRetryStrategy({
            scalingDuration: 1000,
            maxRetryAttempts: 5
          })),
          catchError((error: HttpErrorResponse) => {
            let errorMessage;
            if (error instanceof ErrorEvent) {
              errorMessage = `Error client side: ${error.error.message}`;
            } else {
              errorMessage = `Error server side: STATUS: ${error.status} MESSAGE: ${error.message}`;
            }
            this._snackBar.setMessage('Ha ocurrido un error', 'OK', 3000);
            return throwError(errorMessage);
          })
        );
    } else {
      return next.handle(req);
    }
  }
}