maki compiler as a service

index.js

const express = require("express");
const path = require("path");
const fsExtra = require("fs-extra");
const os = require("os");
const app = express();
const port = 3000;
const { exec } = require("child_process");
const Busboy = require("busboy");

const tmpDir = os.tmpdir();
const INTERFACES_PATH = path.join(__dirname, "resources", "lib");
const COMPILERS_DIR = path.join(__dirname, "resources", "compilers");

const TMP_PREFIX = "maki";

function mkTempDir() {
  return new Promise(async (resolve, reject) => {
    fsExtra.mkdtemp(path.join(tmpDir, TMP_PREFIX), async (err, folder) => {
      if (err != null) {
        return reject(err);
      }
      resolve(folder);
    });
  });
}

function readFile(req) {
  return new Promise((resolve, reject) => {
    var busboy = new Busboy({ headers: req.headers });
    busboy.on("file", (fieldname, file, fileName, encoding, mimetype) => {
      file.on("data", buffer => {
        resolve([fileName, buffer]);
      });
      file.on("end", data => {
        // TODO: What happens here?
      });
    });
    req.pipe(busboy);
  });
}

function replaceExt(fileName, ext) {
  return `${path.basename(fileName, path.extname(fileName))}.${ext}`;
}

async function compile(buffer, fileName) {
  const tempDir = await mkTempDir();
  fsExtra.copySync(INTERFACES_PATH, path.join(tempDir, "lib"));
  const sourcePath = path.join(tempDir, fileName);
  fsExtra.writeFileSync(sourcePath, buffer);
  const destPath = replaceExt(sourcePath, "maki");

  return new Promise((resolve, reject) => {
    const options = { cwd: COMPILERS_DIR };
    exec(`mc.exe ${sourcePath}`, options, (err, stdout, stderr) => {
      console.err(stderr);
      console.log(stdout);
      if (err != null) {
        return reject(err);
      }
      const result = fsExtra.readFileSync(destPath);
      resolve(result);
    });
  });
}

app.post("/", async (req, res, next) => {
  const [fileName, buffer] = await readFile(req);
  try {
    const compiled = await compile(buffer, fileName);
    res.send(compiled);
  } catch (e) {
    next(e);
  }
});

app.listen(port, () => console.log(`Example app listening on port ${port}!`));