'use strict';

const got = require('got');
const uniqueRandomArray = require('unique-random-array');

const randomCache = {};

function formatResult(getRandomImage) {
    const imageData = getRandomImage();
    if (!imageData) {
        return;
    }
    return `http://imgur.com/${imageData.hash}${imageData.ext.replace(/\?.*/, '')}`;
}

function storeResults(images, subreddit) {
    const getRandomImage = uniqueRandomArray(images);

    randomCache[subreddit] = getRandomImage;
    return getRandomImage;
}

module.exports = function (subreddit) {
    subreddit = (typeof subreddit === 'string' && subreddit.length !== 0) ? subreddit : 'puppies';

    if (randomCache[subreddit]) {
        return Promise.resolve(formatResult(randomCache[subreddit]));
    }

    return got(`https://imgur.com/r/${subreddit}/hot.json`, {json: true})
        .then(response => storeResults(response.body.data, subreddit))
        .then(getRandomImage => formatResult(getRandomImage));
};