StealJS plugin to dynamiclty load language (resouces) packs

steal-lp.js

var getWindowLoader = function(name){
    return `
    module.exports = function(lang){
        return System.import("${name}" + "/" + lang + ".js!" + lang + ".lp")
    }
    `
}

var getNodeLoader = function(name, address, load){
    var fs = require('fs')
    var langs = fs.readdirSync(address).map((f)=> f.split('.')[0])

    load.metadata.deps = langs.map((lang) =>
        name + '/' + lang + '.js!' + lang + '.lp'
    )
    var lpConfig = System.lp || {},
        defaultLang = lpConfig.defaultLang || '',
        fallback = !!lpConfig.langFallback

    langs = langs.map((lang) => '"' + lang + '"').join()

    return `
    module.exports = function(lang){
        var langs = [${langs}]
        var defaultLang = "${defaultLang}"
        if ([langs].indexOf(lang) < 0){
            if (defaultLang && langs.indexOf(defaultLang) < 0){
                if (${fallback} && langs.length){
                    lang = lang[0]
                } else {
                    return Promise.resolve({})
                }
            }
        }
        return System.import("${name}" + "/" + lang + ".js!" + lang + ".lp")
    }
    `
}

var matchLangPlugin = function(address){
    var match = address.match(/([\w\d-]+)\.lp\.js$/i)
    return match && match[1]
}

if (typeof window === 'undefined'){
    var fs = require('fs')
    var oldReadFile = fs.readFile;
    fs.readFile = function(address){

        var lang = matchLangPlugin(address)
        if (lang){
            var args = Array.prototype.slice.call(arguments),
                callback = args[args.length - 1]

            callback(null, `
            export function translate(load) {
            return 'define("' + load.name + '", function(require, exports, module){' +
            '' + load.source + '});'
            }
            export let buildType = '${lang}.lp'
            `)

        } else {
            return oldReadFile.apply(fs, arguments)
        }
    }
}

var oldFetch = System.fetch;

System.fetch = function(load) {
    var lang = matchLangPlugin(load.address)
    if (lang){
        // for browser return empty language module
        return ''
    } else {
        return oldFetch.call(this, load)
    }
}

export function fetch(load) {

    // clean up everything before # and after !
    let name = load.name.replace(/!.*$/, '').replace(/.*#/, '')
    let address = load.address.replace(/^file:/, '').replace(/\\/g, '/')

    if (typeof window === 'undefined'){
        return getNodeLoader(name, address, load)
    } else {
        return getWindowLoader(name, address)
    }
}