HOSN-app/app/src/providers/twitter-api/twitter-api.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { Storage } from '@ionic/storage';
import CryptoJS from 'crypto-js';


@Injectable()
export class TwitterApiProvider {
  consumer_key: string = 'UxZkbKotkr8Uc6seupnaZ1kDE';
  consumer_secret: string = 'fEAas8iugR60FOEXsFG0iajq6oyfIIXRBVMlTgWxBd1stWIKHq';
  access_token_key: string;
  access_token_secret: string;
  client;

  constructor(public http: HttpClient, private storage: Storage) {
    console.log('Hello TwitterApiProvider Provider');

    Promise.all([this.storage.get('accessTokenKey'), this.storage.get('accessTokenSecret')]).then(values => {
      this.access_token_key = values[0];
      this.access_token_secret = values[1];
      this.initApi();
    });
  }


  initApi() {

  }

  private buildHeaders(): HttpHeaders {
    let oauth_consumer_key = this.consumer_key;
    let oauth_nonce = this.getNonce();
    let oauth_signature = this.getSignature('get', 'https://api.twitter.com/1.1/statuses/home_timeline.json', '');
    let oauth_signature_method = 'HMAC-SHA1';
    let oauth_timestamp = Math.floor(Date.now() / 1000).toString();
    let oauth_token = this.access_token_key;
    let oauth_version = '1.0';

    let authToken = `OAuth oauth_consumer_key="${oauth_consumer_key}", oauth_nonce="${oauth_nonce}", oauth_signature="${oauth_signature}", oauth_signature_method="${oauth_signature_method}", oauth_timestamp="${oauth_timestamp}", oauth_token="${oauth_token}", oauth_version="${oauth_version}"`;
    console.log(authToken);

    return new HttpHeaders({
      'Authorization': authToken
    });
  }

  private getNonce(numChars = 32): string {
    var st = "0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz";
    var l = st.length;
    var result = "";

    for (var i = 0; i < numChars; i++) {
      var randomIndex = Math.floor(Math.random() * l);
      result = result + st.charAt(randomIndex);
    }
    return result;
  }

  private getSignature(method: string, url: string, parameterString: string): string {
    let shaKey = encodeURIComponent(this.consumer_secret) + "&" + encodeURIComponent(this.access_token_secret);
    let signatureBaseString = `${method.toUpperCase()}&${encodeURIComponent(url)}&${encodeURIComponent(parameterString)}`;
    let signature = CryptoJS.HmacSHA1(signatureBaseString, shaKey);
    return CryptoJS.enc.Base64.stringify(signature);
  }

  fetchHomeFeed() {
    return this.http.get('https://api.twitter.com/1.1/statuses/home_timeline.json', { headers: this.buildHeaders() });
  }
}