text: 
  const services = require('../../constants/services');
  
  const adapters = {
  	'FACEBOOK': require('../../adapters/FacebookAdapter'),
  	'TWITTER': require('../../adapters/TwitterAdapter'),
  	'INSTAGRAM': require('../../adapters/FacebookAdapter'),
  };
  
  module.exports = class ApiService {
  
  	constructor(serviceType) {
  		const AdapterClass = adapters[serviceType];
  
  		if(AdapterClass) {
  			this.adapter = new AdapterClass();
  		} else {
  			throw new Error('Invalid service');
  		}
  	}
  
  	fetchFeed() {
  		return this.adapter.fetchFeed(userId, accessToken)
  			.then(data => this.adapter.normalize(data));
  	}
  
  	authenticate(...args) { return this.adapter.authenticate(...args); }
  	authCallback(...args) { return this.adapter.authCallback(...args); }
  }
  