const http = require("http");
const fs = require("fs");
const path = require("path");
const util = require("util");

const PORT = process.argv[2] || 8080;
const __cwd = process.cwd();
const _access = util.promisify(fs.access);
const _readdir = util.promisify(fs.readdir);

const reqListener = async (req, res) => {
    console.log(req.url);
    const fp = path.join(__cwd, req.url);
    try {
        // If file does not exist we skill to catch block.
        await _access(fp, fs.constants.F_OK);
        // If path is a directory, we show directory listing.
        // TODO: The only exception is the root directory, in which
        // index.html will be tried first before falling back
        // to directory list.
        if (fs.statSync(fp).isDirectory()) {
            let files = await _readdir(fp);
            let d_listing = "<pre>";
            d_listing += `<a href="../">../</a>\n`;
            files.forEach(file => {
                try {
                    fs.statSync(path.join(fp, file)).isDirectory()
                        ? d_listing += `<a href="${file}/">${file}/</a>`
                        : d_listing += `<a href="${file}">${file}</a>`;
                } catch (e) {
                    console.error(e.message);
                    d_listing += `<a href="${file}">${file}</a>`;
                }
                d_listing += "\n";
            });
            d_listing += "</pre>";
            res.writeHead(200, {
                "Content-Type": "text/html"
            });
            return res.end(d_listing);
        } else {
            const readable = fs.createReadStream(fp);
            res.writeHead(200, {
                "Content-Length": fs.statSync(fp).size,
            });
            readable.pipe(res);
        }
    } catch (e) {
        console.log(e);
        res.writeHead(404);
        res.end(":(");
    }
};

const server = http.createServer(reqListener);
server.listen(PORT, () => {
    console.log(`Serving on http://localhost:${PORT}`);
});