import { Injectable } from '@angular/core'
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpResponse, HttpErrorResponse } from '@angular/common/http'

import { Observable } from 'rxjs'
import { LoadingMaskService } from './loading-mask.service'
import { tap } from 'rxjs/operators'
import { LOADING_MASK_HEADER } from './config'

@Injectable()
export class LoadingMaskInterceptor implements HttpInterceptor {
  constructor(
    private service: LoadingMaskService
  ) { }

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (req.headers.has(LOADING_MASK_HEADER)) {
      // TODO use custom header as custom metadata, maybe deprecated in the future
      // refer to https://github.com/angular/angular/issues/18155
      const groupName = req.headers.get(LOADING_MASK_HEADER)

      if (!!groupName) {
        // req = req.clone({
        //   headers: req.headers.delete(LOADING_MASK_HEADER)
        // })

        this.service.showGroup(groupName)

        return next.handle(req).pipe(
          tap(event => {
            if (event instanceof HttpResponse) {
              // TODO hide mask here
              this.service.hideGroup(groupName)
            }
          }, error => {
            if (error instanceof HttpErrorResponse) {
              // TODO hide mask with error here
              this.service.hideGroupError(groupName, error)
            }
          })
        )
      } else {
        return next.handle(req)
      }
    } else {
      return next.handle(req)
    }
  }
}