cleverChallenge.js

/**
 * @author Hamid Zare
 * @email hamid.zare@vanderbilt.edu
 */

// the program would have been much faster and easier to write if the 
// pagination was predictabe, meaning that I could grab the nth page directly
// in that case it would have been possible to fire all the request concurrently
// (after gettig the first response)

// assuming ES6 and Node v6

const axios = require('axios'),
    BASE_URI = 'https://api.clever.com',
    TOKEN = 'DEMO_TOKEN' || process.env.CLEVER_TOKEN;

// grabs all the sections one by one
let grabSections = () => {
    let sections = []; // accumulate :(

    let grabPage = (relativePath) => {
        let url = BASE_URI + (relativePath || '');
        return axios({
            url,
            headers: {
                'Authorization': `Bearer ${TOKEN}`
            }
        })
            .then(response => {
                let {data, links} = response.data;
                // TODO push only the sections.
                sections = sections.concat(data);
                // grab the rest of the data if exists;
                let nextLink = links.find(link => link.rel === 'next');
                if (nextLink){
                    // do this whole process again
                    return grabPage(nextLink.uri);
                }       

                // console.log(response.data);
                // console.log(Object.keys(response.data));
            })
    };

    return grabPage('/v1.2/sections?').then( () => {
        // done grabbing all the pages
        return sections;
    }).catch(err => {
        console.error(err);
        throw err;
    });
};


grabSections()
    .then( sections => {
        let numberOfSections = sections.length;
        // calculate the number of students
        let numberOfStudents = sections
            .map(section => section.data.students.length)
            .reduce( (acc, numStudents) => {
                return acc + numStudents;
            }, 0 );

        let average = numberOfStudents / numberOfSections;
        console.log('#', numberOfStudents, 'students');
        console.log('#', numberOfSections, 'sections');
        console.log('Average per section is:', average, 'or', Math.floor(average));
        return average;
    })
    .catch(console.error);