server.js

const http = require("http");
const https = require("https");
const { URL } = require("url");

const gm = require("gm").subClass({
  imageMagick: true,
});

const bucketName = process.env.BUCKET_NAME || "assets.cytoid.io";

function requestURLForPath(url) {
  let path = url.pathname;
  if (path.startsWith("/")) {
    path = path.substr(1);
  }
  return `https://assets.cytoid.io/` + path;
}

function requestListener(req, res) {
  res.setHeader("X-Powered-By", "cytoid");
  if (req.method !== "GET") {
    res.writeHead(405);
    res.end("Method not allowed");
  }
  const url = new URL(req.url, "https://images.cytoid.io");
  const request = https.get(
    requestURLForPath(url),
    {
      headers: {
        "user-agent": "cytoid-img-resizer",
      },
    },
    (response) => {
      if (response.statusCode === 200) {
        // Image exists.
        const contentType = response.headers["content-type"];
        res.setHeader("content-type", contentType);
        if (!contentType.startsWith("image/")) {
          res.writeHead(response.statusCode);
          response.pipe(res);
          return;
        }

        // Copy headers
        for (const headerName of [
          "expires",
          "etag",
          "content-disposition",
          "date",
          "vary",
        ]) {
          const header = response.headers[headerName];
          if (header) res.setHeader(headerName, header);
        }
        res.setHeader("cache-control", "max-age=3153600,public");

        let height = url.searchParams.get("h");
        if (height) height = parseInt(height) || null;
        let width = url.searchParams.get("w");
        if (width) width = parseInt(width) || null;

        res.writeHead(response.statusCode);

        if (height && width) {
          gm(response)
            .resize(width, height, "^")
            .gravity("Center")
            .crop(width, height)
            .stream()
            .pipe(res);
        } else if (height || width) {
          gm(response).resize(width, height).stream().pipe(res);
        } else {
          response.pipe(res);
        }
      } else {
        // Error
        for (const headerName of [
          "content-type",
          "expires",
          "etag",
          "content-disposition",
          "date",
          "vary",
        ]) {
          const header = response.headers[headerName];
          if (header) res.setHeader(headerName, header);
        }
        res.writeHead(response.statusCode);
        response.pipe(res);
      }
    }
  );
}

const port = process.env.PORT || 8040;
const server = http.createServer(requestListener);
server.listen(port, "0.0.0.0", () => {
  console.log("Server listening on " + port);
});