import { Injectable, Inject } from '@angular/core';
import { HttpClient, HttpHeaders, HttpErrorResponse } from '@angular/common/http';

import { Observable } from 'rxjs/Observable';

import { Location } from '@angular/common';

import 'rxjs/add/operator/do';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/timeout';
import 'rxjs/add/observable/throw';

import { ErrorResponse } from './error-response';

@Injectable()
export class RESTService {
  private readonly httpHeaders: HttpHeaders;

  constructor(
    @Inject('REST_BASE_URL') private _baseURL: string,
    @Inject(HttpClient) private _httpClient: HttpClient,
  ) {
    this.httpHeaders = new HttpHeaders()
      .set('Content-Type', 'application/json');
  }

  public get httpClient(): HttpClient {
    return this._httpClient;
  }

  public get<T>(entry: string, params?: {[param: string]: string | string[]}): Observable<T> {
    const headers: HttpHeaders = this.httpHeaders;

    return this._httpClient
      .get(Location.joinWithSlash(this._baseURL, entry), {
        headers: headers,
        params: params,
        responseType: 'json',
      })
      .map((response: string) => <T>JSON.parse(response))
      .catch((error: HttpErrorResponse) => Observable.throw(ErrorResponse.restError(error)));
  }

  public post<T>(entry: string, body: any | null, params?: {[param: string]: string | string[]}): Observable<T> {
    const headers: HttpHeaders = this.httpHeaders;

    return this._httpClient
      .post(Location.joinWithSlash(this._baseURL, entry), body, {
        headers: headers,
        params: params,
        responseType: 'json',
      })
      .map((response: string) => <T>JSON.parse(response))
      .catch((error: HttpErrorResponse) => Observable.throw(ErrorResponse.restError(error)));
  }

}