index.js

const fs = require('fs') // used to get dewey.json data
const path = require('path')

// code path: dogedc => DDC gets class number => lookup class name in dewey.json => convert class name to Doge => execute provided callback

function DDC (num) {
    var validationResult = this.validate(num)

    // no num given or shorthand ddc(cb) usage? assign random num
    if (!num || typeof num === 'function') {
        this.classNumber = this.getRandomClassNum()
    // validate user input
    } else if (validationResult instanceof Error) {
        return validationResult;
    } else {
        this.classNumber = num.padStart(3, '0')
    }
}

// ensure input is 1-3 digits, valid DDC class number
DDC.prototype.validate = function (num) {
    var int = parseInt(num);

    if (int > 999) {
        return new Error('Class number is too high; DDC only goes up to 999.')
    } else if (int < 0) {
        return new Error('Class number is less than 0; DDC stops at 000.')
        // test if input is not all digits
    } else if (!/^\d+$/.test(num)) {
        return new Error('Class is non-numeric; DDC is 000-999.')
    }
};

DDC.prototype.getRandomClassNum = function () {
    // DDC classes go from 000 - 999
    var rando = function () { return Math.floor(Math.random() * 1000).toString() }
        , classNum = rando().padStart(3, '0')
        , unassigned = ['007', '008', '009', '024', '029', '040', '041', '042', '043', '044', '045', '046', '047', '048', '049', '104', '112', '125', '132', '134', '136', '151', '157', '159', '163', '164', '217', '219', '237', '244', '256', '257', '258', '288', '298', '308', '309', '311', '312', '313', '329', '396', '397', '416', '424', '426', '434', '436', '444', '446', '454', '456', '464', '466', '474', '476', '484', '486', '504', '517', '518', '524', '571', '626', '654', '655', '656', '689', '699', '744', '756', '762', '768', '775', '776', '777', '789', '804', '921', '922', '923', '924', '925', '926', '927', '928', '991', '992'];

    while (unassigned.indexOf(classNum) != -1) {
        classNum = rando().padStart(3, '0')
    }

    return classNum;
}

function findClassName (cb, ddc) {
    // load map of Dewey Classes
    fs.readFile(path.join(__dirname, 'data', 'dewey.json'), {
            'encoding': 'utf-8'
        }, function (err, data) {
            var dewey = JSON.parse(data)

            if (err) {
                cb(err, null);
                return;
            } else if (ddc instanceof Error) {
                // DDC returned an error
                // e.g. class number was too high or low
                cb(ddc, null);
                return;
            }

            ddc.className = dewey[ddc.classNumber]
            ddc.dogeClassName = toDoge(ddc.className)
            cb(null, ddc)
    });
}

/**
 * lookup the Doge Decimal Class name for a Dewey number
 * if no param is given, returns a random one
 * @param  {String|Number} num DDC class number
 * @param {Function} cb callback executed once it's all done
 */
function dogedc (num, cb) {
    var ddc = new DDC(num)

    // handle ddc(cb) shorthand
    if (typeof num === 'function') cb = num

    findClassName(cb, ddc)
}

/**
 * Given string, turn it into Dogespeak
 * @param  {String} str boring normal language
 * @return {String}     Such Dogespeak!
 */
function toDoge (str) {
    var flip = () => !!Math.round(Math.random())
        // lowercase, strip semicolons, commas, & stop words
        , clean = (s) => {
            var stops = ['for', 'of', 'the', 'in', '&', 'or']
                , output = s.toLowerCase().replace(/;|,/g,'')

            stops.forEach(function (item) {
                output = output.replace(RegExp(item + ' ', 'g'),'')
            });

            return output;
        }
        // return random item of array
        , rand = array => array[Math.floor(Math.random() * array.length)]
        , arr = clean(str).split(" ")
        , len = arr.length
        , dogeWords = ['Many', 'Much', 'So', 'Such', 'Very']
        , out = arr.map((item) => rand(dogeWords) + ' ' + item + '. ')

    // randomly add "Wow" half of the time
    if (flip()) out.push('Wow.')

    return out.join('').trim()
}

module.exports = dogedc
// expose toDoge function too
// in case someone wants to use it on other strings
module.exports.toDoge = toDoge