#!/usr/bin/env node
/** UDP echo RTT. server: node udp-probe.mjs server [port]
 *  client: node udp-probe.mjs client <host> <count> [port] [size] */
import dgram from "node:dgram";

const mode = process.argv[2] || "server";
const port = Number(process.argv[mode === "server" ? 3 : 5] || 9999);

if (mode === "server") {
  const s = dgram.createSocket("udp4");
  s.on("message", (msg, rinfo) => s.send(msg, rinfo.port, rinfo.address));
  s.bind(port, "0.0.0.0", () => console.log(JSON.stringify({ mode: "udp-server", port })));
} else {
  const host = process.argv[3];
  const count = Number(process.argv[4] || 1000);
  const size = Number(process.argv[6] || 128);
  const sock = dgram.createSocket("udp4");
  const payload = Buffer.alloc(size, 7);
  const samples = [];
  let i = 0;
  const sendOne = () => {
    const t0 = process.hrtime.bigint();
    const once = (msg) => {
      sock.off("message", once);
      samples.push(Number(process.hrtime.bigint() - t0) / 1000);
      i += 1;
      if (i >= count) {
        samples.sort((a, b) => a - b);
        const us = (n) => `${(n / 1000).toFixed(3)}ms`;
        const pct = (p) => samples[Math.min(samples.length - 1, Math.floor((p / 100) * samples.length))];
        const sum = samples.reduce((a, b) => a + b, 0);
        console.log(
          JSON.stringify({
            mode: "udp-ping",
            count: samples.length,
            size,
            host,
            min: us(samples[0]),
            avg: us(sum / samples.length),
            p50: us(pct(50)),
            p99: us(pct(99)),
            max: us(samples[samples.length - 1]),
            p50_us: Math.round(pct(50)),
            p99_us: Math.round(pct(99)),
          }),
        );
        sock.close();
      } else sendOne();
    };
    sock.on("message", once);
    sock.send(payload, port, host);
  };
  sendOne();
}