datasource.js

//to make the GraphQL wrapper of the REST API, we need to work with the RESTDataSource class
const { RESTDataSource } = require('apollo-datasource-rest')

class ITunesSearchAPI extends RESTDataSource {
  constructor() {
    super()
    //this is the base url for our API call, if you had more than one async query 
    //below this base would be the point where the queries diverge
    this.baseURL = 'https://itunes.apple.com/search'
  }
  
  //this is our main fetch call for our iTunes query
  async getITunesSearchResult({ term }) {
    //use template literals so you can change the search term with each query - 
    //our client side application will provide the search term
    const response = await this.get(`?term=${term}`)
    console.log("Raw repsonse: " + response)
    return this.iTunesSearchResultReducer(JSON.parse(response), term)
  }
  
  // our async call will pass data to this reducer, which will return the data 
  //mapped to our GraphQL schema
  iTunesSearchResultReducer(response, term) {
    console.log("Result count: " + response.resultCount)
    return response.results.map(res => ({
      id: "123",
      kind: res.kind,
      trackId: res.trackId,
      trackName: res.trackName,
      artistId: res.artistId,
      artistName: res.artistName
    }));
  }
}

module.exports = ITunesSearchAPI