ikeeppromises.js

(([http, fs]) => fs.readdir([__dirname, 'public'].join('/'))
    .then(names => names.map(name => fs.readFile([__dirname, 'public', name].join('/'))
        .then(contents => [name, contents])))
    .then(promises => Promise.all(promises))
    .then(pairs => [new Map(), pairs])
    .then(([assets, pairs]) => [assets, pairs.map(pair => assets.set(...pair))].shift())
    .then(assets => [
        assets,
        [...assets.keys()]
            .map(name =>
                console.warn(`${['public', name].join('/')} has been loaded into memory.`))
    ].shift())
    .then(assets =>
        http.createServer(
            (request, response) => (([response, url]) =>
                (name =>
                    (async (dict, key) =>
                        new Promise((resolve, reject) =>
                            dict.has(key) ? resolve(dict.get(key)) : reject(key))
                    )(assets, name)
                        .then(data => [name, data])
                        .catch(k => (x => {throw x})(['404.html', assets.get('404.html')]))
                )(url == '/' ? 'index.html' : url.substring(1))
                    .then(([name, data]) => ({ assetName: name, status: 200, reply: data }))
                    .catch(([name, data]) => ({ assetName: name, status: 404, reply: data }))
                    .then(({ assetName, status, reply }) =>
                    ({
                        assetName: assetName,
                        status: status,
                        contentType:
                            [...Object.entries({
                                'application/json': ['json'],
                                'text/html': ['html'],
                                'text/css': ['css'],
                                'application/javascript': ['js'],
                                'image/jpeg': ['jpeg', 'jpg']
                            })
                                .filter(([header, extensions]) => extensions.includes(assetName.split('.').pop()))
                                .map(([k, v]) => k)
                                , 'text/plain'].shift(),
                        reply: reply,
                    }))
                    .then(package => [
                        package,
                        package.contentType == 'text/plain' ? console.warn(`Undefined content type for .${extension}!`) : undefined
                    ].shift())
                    .then(({ assetName, status, contentType, reply }) => [
                        response.setHeader('Content-Type', contentType),
                        response.writeHead(status),
                        response.end(reply),
                    ]))
                    ([response, request.url])
        ).listen(
            process.env.PORT || 3000,
            'localhost',
            () => console.log(`Server is running on http://localhost:${process.env.PORT || 3000}`)
        )))(['http', 'fs']
            .map(name => [name, require(name)])
            .map(([name, mod]) =>
                name == 'fs' ? mod.promises : mod));