gistfile1.js

'use strict';

var fs      = require('fs'),
    path    = require('path'),
    Promise = require('es6-promise').Promise,
    zlib    = require('zlib');

module.exports = filesizes;

// -----------------------------------------------------------------------------

function filesizes(dirPath, callback) {
    getModules(dirPath).then(function (modules) {
        return Promise.all(modules.map(function (module) {
            var filePath = path.join(dirPath, module + '-min.css');
            return readModule(filePath).then(getSize);
        })).then(function (sizes) {
            return sizes.reduce(function (map, size, i) {
                map[modules[i]] = size;
                return map;
            }, {});
        });
    }).then(function (moduleSizes) {
        callback(null, moduleSizes);
    }, function (err) {
        callback(err);
    });
}

function getModules(dirPath) {
    return new Promise(function (resolve, reject) {
        fs.readdir(dirPath, function (err, files) {
            if (err) { return reject(err); }

            resolve(files.filter(function (file) {
                return (/\-min\.css$/).test(file);
            }).map(function (file) {
                return file.replace(/\-min\.css$/, '');
            }));
        });
    });
}

function readModule(filePath) {
    return new Promise(function (resolve, reject) {
        fs.readFile(filePath, function (err, file) {
            if (err) { return reject(err); }
            resolve(file);
        });
    });
}

function getSize(file) {
    return new Promise(function (resolve, reject) {
        zlib.gzip(file, function (err, compressed) {
            if (err) { return reject(err); }
            resolve(compressed.length);
        });
    });
}