// Copyright 2016 William Budington

// Copyright 2017 AJ Jordan

// AGPLv3+

'use strict';

const request = require('request'),

unzip = require('unzip');

// (Heavily) modified from code by @Hainish in utils/labeller. Thanks, @Hainish!

// TODO make this return Promises

// TODO test this file

const DAY = 1000 * 60 * 60 * 24,

obj = {data: null};

function retrieveAlexa(cb) {

const alexa = [];

const csvRegex = /^[0-9]+,(.+)/;

request.get('https://s3.amazonaws.com/alexa-static/top-1m.csv.zip')

.on('error', err => {

cb(err);

})

// Dumb ESLint. It's not my fault this person named it like that!?

.pipe(unzip.Parse()) // eslint-disable-line new-cap

.on('entry', entry => {

// TODO this use of readline is super confusing??

const lineReader = require('readline').createInterface({

input: entry

});

lineReader.on('line', line => {

const domain = line.match(csvRegex)[1];

alexa.push(domain);

});

lineReader.on('close', () => {

cb(null, alexa);

});

});

}

module.exports = function getAlexa(log, cb) {

// If the data has already been retrieved, just return it

if (obj.data) {

cb(null, obj);

return;

}

// If it hasn't, invoke the retrieval function and schedule

// refreshes if we don't run into problems

retrieveAlexa((err, data) => {

if (err) {

cb(err, null);

return;

}

log('Retrieved Alexa rankings.');

// We return an object so that setInterval can change the Array

// the `data` property points to

obj.data = data;

setInterval(retrieveAlexa, DAY, (_err, _data) => {

// This is the callback function passed to retrieveAlexa()

if (_err) {

cb(_err, null);

return;

}

obj.data = _data;

log('Refreshed Alexa rankings.');

});

cb(null, obj);

});

};