server.js

const http = require("http");
const fs = require("fs");
const sudo = require("sudo-js");
const formidable = require("formidable");
const util = require("util");
const exec = util.promisify(require("child_process").exec);

const password = "pwd";

var NumberOfFiles = 0;
var FilesReceived = 0;

sudo.setPassword(password);

// Reading the file that has to be displayed
fs.readFile("./index.html", function(err, data) {
  if (err) {
    throw err;
  }
  htmlFile = data;
});

fs.readFile("./favicon.ico", function(err, data) {
  if (err) {
    throw err;
  }
  favicon = data;
});

fs.readFile("./styles.css", function(err, data) {
  if (err) {
    throw err;
  }
  cssFile = data;
});

fs.readFile("./upload.js", function(err, data) {
  if (err) {
    throw err;
  }
  javascriptFile = data;
});

// Server creation
var server = http.createServer(function(req, res) {
  // GET methode -> User wants something (html, css, etc..)
  if (req.method === "GET") {
    // Serves different pages depending on what whants the client
    switch (req.url) {
      case "/upload.js":
        res.writeHead(200, { "Content-Type": "application/js" });
        res.write(javascriptFile);
        res.end();
        break;
      case "/styles.css":
        res.writeHead(200, { "Content-Type": "text/css" });
        res.write(cssFile);
        res.end();
        break;
      case "/favicon.ico":
        res.writeHead(200, { "Content-Type": "image/x-icon" });
        res.write(favicon);
        res.end();
        break;
      case "/":
        res.writeHead(200, { "Content-Type": "text/html" });
        res.write(htmlFile);
        res.end();
        break;
      default:
        break;
    }
    // POST METHOD when user want to send something
  } else if (req.method === "POST") {
    if (req.url === "/replugStorage") {
      console.log("Unmounting USB to upload new files..");
      UnmoutUSB();
      console.log("Mounting USB back..");
      MountUSB();
      res.writeHead(200, { "content-type": "application/json" });
      res.end(JSON.stringify({ message: "success" }));
    }
    // CHECK IF USER WANTS TO UPLOAD
    else if (req.url === "/upload") {
      if (req.headers["numberoffiles"]) {
        NumberOfFiles = req.headers["numberoffiles"];
        console.log("Unmounting USB to upload new files..");
        UnmoutUSB();
      } else {
        var form = new formidable.IncomingForm();

        form.parse(req, function(err, fields, files) {
          if (err) throw err;

          try {
            console.log("Uploading " + files["files[]"].name);

            fs.readFile(files["files[]"].path, function(err, data) {
              if (err) throw err;

              var fileName = files["files[]"].name;
              var directory = "/mnt/usb_share/";
              //var directory = '';

              fs.writeFile(directory + fileName, data, function(err) {
                if (err) throw err;
                console.log("File " + fileName + " was successfully saved.");
                console.log("Compressing image..");
                compressImage(directory + fileName)
              });
            });
            FilesReceived++;
            if (FilesReceived == NumberOfFiles) {
              console.log("Mounting USB back..");
              MountUSB();
              FilesReceived = 0;
              NumberOfFiles = 0;
            }
            res.writeHead(200, { "content-type": "application/json" });
            res.end(JSON.stringify({ message: "success" }));
          } catch (error) {
            console.log(error);
          }
        });
      }
    }
  }
});
server.listen(8081);

console.log("Server running at http://localhost:8081/");

function MountUSB() {
  // Bash command to remount the USB
  var command = [
    "modprobe",
    "g_mass_storage",
    "file=/pisusb.bin",
    "stall=0",
    "ro=1"
  ];
  sudo.exec(command, function(err, pid, result) {
    console.log(result);
  });
}

function UnmoutUSB() {
  // Bash command to unmount the USB
  var command = ["modprobe", "-r", "g_mass_storage"];
  sudo.exec(command, function(err, pid, result) {
    console.log(result);
  });
}

async function compressImage(filePath){
  var command = "convert " + filePath + " -quality 30% " + filePath;
  const { stdout, stderr } = await exec(command);
  console.log('stdout:', stdout);
  console.log('stderr:', stderr);
}