Server that causes animations for curl

curl-animations.js

/**
 * The command to see the animation:
 * curl localhost:3000
 *
 * @see https://github.com/alexeyraspopov/picocolors/blob/main/picocolors.js
 * @see https://github.com/sindresorhus/ansi-escapes/blob/main/index.js
 * @see https://github.com/sindresorhus/cli-spinners
 */
import { Readable } from "node:stream";
import { fastify } from "fastify";

//#region Terminal colors / ANSI
const ESC = "\u001B[";
const CURSOR_PREV_LINE = ESC + "F";

const RESET = "\x1b[0m";
const [BLACK_START, BLACK_END] = ["\x1b[30m", "\x1b[39m"];
const [BG_CYAN_START, BG_CYAN_END] = ["\x1b[46m", "\x1b[49m"];
const COLOR_START = BG_CYAN_START + BLACK_START;
const COLOR_END = BLACK_END + BG_CYAN_END;

/** {@link https://github.com/sindresorhus/cli-spinners} */
const SPINNER = [
  "⢀⠀",
  "⡀⠀",
  "⠄⠀",
  "⢂⠀",
  "⡂⠀",
  "⠅⠀",
  "⢃⠀",
  "⡃⠀",
  "⠍⠀",
  "⢋⠀",
  "⡋⠀",
  "⠍⠁",
  "⢋⠁",
  "⡋⠁",
  "⠍⠉",
  "⠋⠉",
  "⠋⠉",
  "⠉⠙",
  "⠉⠙",
  "⠉⠩",
  "⠈⢙",
  "⠈⡙",
  "⢈⠩",
  "⡀⢙",
  "⠄⡙",
  "⢂⠩",
  "⡂⢘",
  "⠅⡘",
  "⢃⠨",
  "⡃⢐",
  "⠍⡐",
  "⢋⠠",
  "⡋⢀",
  "⠍⡁",
  "⢋⠁",
  "⡋⠁",
  "⠍⠉",
  "⠋⠉",
  "⠋⠉",
  "⠉⠙",
  "⠉⠙",
  "⠉⠩",
  "⠈⢙",
  "⠈⡙",
  "⠈⠩",
  "⠀⢙",
  "⠀⡙",
  "⠀⠩",
  "⠀⢘",
  "⠀⡘",
  "⠀⠨",
  "⠀⢐",
  "⠀⡐",
  "⠀⠠",
  "⠀⢀",
  "⠀⡀",
];
//#endregion

process.on("unhandledRejection", function (err) {
  throw err;
});
process.on("SIGINT", handleExit);
process.on("SIGTERM", handleExit);

function handleExit() {
  if (server != null) {
    server.close();
  }
}

function delay(ms = 80) {
  return new Promise((r) => setTimeout(r, ms));
}

async function animate(stream) {
  stream.push("\n");

  for (let i = 0; i < SPINNER.length; i++) {
    stream.push(CURSOR_PREV_LINE);
    stream.push(RESET);
    stream.push(SPINNER[i]);
    stream.push(" ");

    const text = "Animating";
    for (const [index, ch] of [...text].entries()) {
      const j = i % text.length;

      if (index === j) stream.push(COLOR_START);
      stream.push(ch);
      if (index === j) stream.push(COLOR_END);
    }

    if (((i / 3) | 0) % 2 === 0) {
      stream.push("…");
    } else {
      stream.push(" ");
    }
    stream.push("\n");
    await delay();
  }

  stream.push(CURSOR_PREV_LINE);
  stream.push("The end!         \n\n");
  stream.push(null);
}

const server = fastify({
  requestTimeout: Number.MAX_SAFE_INTEGER,
  logger: {
    level: "debug",
  },
});

server.get("/", (__request, reply) => {
  const stream = new Readable({
    read() {},
  });

  reply.send(stream);
  animate(stream);

  return reply;
});

server.setNotFoundHandler((__request, reply) => {
  reply.status(404);
  reply.send();
});

server.listen({ port: 3000, host: "localhost" }, (error) => {
  if (error) throw error;

  server.log.debug(server.printRoutes());
});