api.ts

import { Injectable } from '@angular/core';
import { Request, Http, RequestMethod, RequestOptions, URLSearchParams, Headers } from '@angular/http';
import { ENV } from '../environment/environment';
import 'rxjs/add/operator/map';

@Injectable()
export class Api {
  url: string = ENV.API_URL;

  constructor(public http: Http) { }

  get(endpoint: string, params?: any, options?: RequestOptions) {
    return this.request(endpoint, RequestMethod.Get, null, params, options);
  }

  post(endpoint: string, body: any, params?: any, options?: RequestOptions) {
    return this.request(endpoint, RequestMethod.Post, body, params, options);
  }

  update(endpoint: string, body: any, params?: any, options?: RequestOptions) {
    return this.request(endpoint, RequestMethod.Put, body, params, options);
  }

  delete(endpoint: string, body: any, params?: any, options?: RequestOptions) {
    return this.request(endpoint, RequestMethod.Delete, body, params, options);
  }

  private request(endpoint: string, method: RequestMethod, body?: any, params?: any, options?: RequestOptions) {
    if (!options) {
      options = new RequestOptions();
    }

    // Request method
    options.method = method;

    // URL.
    options.url = `${this.url}/${endpoint}`;

    if (body) {
      options.body = body;
    }

    // Support easy query params for GET requests
    if (params) {
      let p = new URLSearchParams();
      for (let k in params) {
        p.set(k, params[k]);
      }
      // Set the search field if we have params and don't already have
      // a search field set in options.
      options.search = !options.search && p || options.search;
    }

    // Set headers
    options.headers = this.setHeaders(options);

    let request = new Request(options);

    return this.http.request(request).map(res => res.json());

  }

  private setHeaders(options?: RequestOptions): Headers {
    let headers: Headers;

    if (!options.headers) {
      headers = new Headers();
    }
    else {
      headers = options.headers
    }

    // Set the Content type header if it isn't already set.
    if (!headers.has('Content-type')) {
      headers.set('Content-type','application/vnd.api+json')
    }

    return headers;
  }

}