import { Injectable } from '@angular/core';
import { HttpClient, HttpParams } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/defer';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/share';
import 'rxjs/add/operator/publishReplay';
import 'rxjs/add/operator/take';

// TODO: This should be pulled out as a part of Flexible Questionnaire Library
@Injectable()
export class QueryService {
  private pendingRequests: object = {};
  private cachedResponses: object = {};
  cachedSrvUrl;

  constructor(private http: HttpClient) { }

  query(url, search?) {
    return this.http
      .get(url, { params: search })
      .catch(err => Observable.throw(err));
  }

  queryCache(url) {
    if (this.cachedResponses[url]) {
    } else if (this.pendingRequests[url]) {
      return this.pendingRequests[url];
    } else {
      this.pendingRequests[url] = this.query(url)
        .map(res => {
          this.pendingRequests[url] = null;
          this.cachedResponses[url] = res;
          return this.cachedResponses[url];
        })
        .share();
      return this.pendingRequests[url];
    }
  }
}