README.md

Instructions

Simple running above file via node will show the name of organisation with address and rounded distance from Centre London in KMs.

node findNearestOffices.js

By deafult, it fetches offices within 100km of Centre London, but it is configurable. For eg, to find offices within 500km of Centre London, pass it as env variable like,

OFFSET_DISTANCE=500 && node findNearestOffices.js

findNearestOffices.js

'use strict'

const https = require('https');

const milesToKm = 1.609344; // in Kms
const londonCoords = [51.515419, -0.141099];
const API_URL = 'https://success.spidergap.com/partners.json?inf_contact_key=e1630715cd03ec4f60b3b9267d9d79586f50da9776b71adcafe8af8556562912';
const offsetDist = process.env.OFFSET_DISTANCE || 100;

/**
 * @desc Find distance between two locations in Kms
 * @param {*} Object
 */
const getDistance = (source, target) => {
    const {
        lat1, long1
    } = source;
    const {
        lat2, long2
    } = target
	const radlat1 = Math.PI * lat1/180
	const radlat2 = Math.PI * lat2/180
	const theta = long1-long2
	const radtheta = Math.PI * theta/180
	let dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	if (dist > 1) {
		dist = 1;
	}
	dist = Math.acos(dist)
	dist = dist * 180/Math.PI
	dist = dist * 60 * 1.1515
	dist = dist * milesToKm
	return dist
}

/**
 * @desc Service for fetching data from Spidergap dataset
 */
const getSpiderGapData = () => new Promise((resolve, reject) => {
    console.log('Fetching data for SpiderGap Sample Dataset');
    https.get(API_URL, (res) => {
        let data = '';
        res.on('data', (chunk) => {
          data += chunk
        });
        res.on('end', (chunk) => {
          return resolve(JSON.parse(data));
        });
      }).on('error', (e) => {
        console.error(e);
        return reject(e);
      });
});

/**
 * 
 * @param {Number} offset - Number of kms within source 
 * @param {*} done - Callback, returns list of sorted office name with address
 */
const fetchOfficesByDistance = async (offset, done) => {
    try {
        const dataset = await getSpiderGapData();
        const result = [];        
        dataset.map((partner) => {
            const {
                offices
            } = partner;
            offices.map((office) => {
                const targetCoords = office.coordinates
                    .split(',')
                    .map(x => parseFloat(x));
                const distance = getDistance(
                    { lat1: londonCoords[0], long1: londonCoords[1] }, 
                    { lat2: targetCoords[0], long2: targetCoords[1] }
                );
                if (distance < offset) {
                    result.push({
                        name: partner.organization,
                        address: office.location, 
                        distance
                    })
                }
            });
        });
        return done(result.sort(x => x.name));
    } catch (error) {
        throw new Error(error)
    }
};

fetchOfficesByDistance(offsetDist, (listOfOffices) => {
    console.log(`List of offices within ${offsetDist} kms are: \n`);
    listOfOffices.forEach(office => console.log(`${office.name}, ${office.address} ${Math.floor(office.distance)} KMs\n`));
});