Parent.ts

import { Injectable, Inject } from '@angular/core';
import { Headers, Http } from '@angular/http';

// Need to import interfaces dependencies
// Bug TypeScript https://github.com/Microsoft/TypeScript/issues/5938
import { Observable } from 'rxjs/Observable';
import { RequestOptionsArgs } from '@angular/http/src/interfaces';
import { Response } from '@angular/http/src/static_response';

import { WpApiLoader } from './Loaders';
import { stripTrailingSlash } from './utils';

import { AuthSession } from './AuthSession';
import { IParent } from './interfaces';


@Injectable()
export class WpApiParent implements IParent {

  constructor(
    public wpApiLoader: WpApiLoader,
    public http: Http
  ) { }

  protected getToken(): string {
    let sessionCredentials = AuthSession.getSession();
    return sessionCredentials ? sessionCredentials.token : null;
  }

  protected hasToken(): boolean {
    return this.getToken() ? true : false;
  }

  protected getWebServiceUrl(postfix: string): string {
    return this.wpApiLoader.getWebServiceUrl(postfix);
  }

  protected getDefaultOptions(
    options: RequestOptionsArgs = { headers: new Headers() }
  ): RequestOptionsArgs {
    if (!options.headers) {
      options.headers = new Headers();
    }
    if (!options.headers.has('Authorization') && this.hasToken()) {
      options.headers.append('Authorization', `Bearer ${this.getToken()}`);
    }
    return options;
  }

  httpGet(url: string, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.get(this.getWebServiceUrl(url), options);
  }
  httpHead(url: string, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.head(this.getWebServiceUrl(url), options);
  }
  httpDelete(url: string, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.delete(this.getWebServiceUrl(url), options);
  }
  httpPost(url: string, body = {}, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.post(this.getWebServiceUrl(url), body, options);
  }
  httpPut(url: string, body = {}, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.put(this.getWebServiceUrl(url), body, options);
  }
  httpPatch(url: string, body = {}, options = {}) {
    options = this.getDefaultOptions(options);
    return this.http.patch(this.getWebServiceUrl(url), body, options);
  }
}