protohackers/4.ts

const PORT = 5588;
console.log(`Starting UDP listener on port ${PORT}`);

const tDec = new TextDecoder();
const tEnc = new TextEncoder();

const reservedData: Record<string, string> = { version: "KeyVal 1.0" };
const data = new Map<string, string>();

const listener = Deno.listenDatagram({
  hostname: "::",
  port: PORT,
  transport: "udp",
});

for await (const [bytes, addr] of listener) {
  const message = tDec.decode(bytes);
  if (message.includes("=")) {
    const [key, ...val] = message.split("=");
    console.debug(`Setting '${key}' to '${val}'`);
    if (!(key in reservedData)) data.set(key, val.join("="));
  } else {
    const value = reservedData[message] || data.get(message) || "";
    const bytes = tEnc.encode(`${message}=${value}`);
    console.debug(`Sending '${message}=${value}'`);
    await listener.send(bytes, addr);
  }
}