protohackers/5.ts

import { BufReader } from "https://deno.land/std@0.157.0/io/buffer.ts";
import { copy } from "https://deno.land/std@0.156.0/streams/conversion.ts";

const PORT = 5588;
const PROXY_CHAT_SERVER = "chat.protohackers.com";
const PROXY_CHAT_PORT = 16963;
const TONYS_ADDRESS = "7YWHMfk9JZe0LM0g1ZauHuiSxhI";

const tEnc = new TextEncoder();

console.log(`Starting TCP listener on on 0.0.0.0:${PORT}`);

async function chatSession(conn: Deno.Conn) {
  const proxy = await Deno.connect({
    hostname: PROXY_CHAT_SERVER,
    port: PROXY_CHAT_PORT,
  });

  const closeOnDisconnect = () => {
    console.warn("Disconnected client");
    try {
      proxy.close();
    } catch (err) {
      console.error("Error closing proxy connection:", err);
    }
    try {
      conn.close();
    } catch (err) {
      console.error("Error closing client connection:", err);
    }
  };

  rewriteMessages(conn, proxy).catch((e) => e).finally(closeOnDisconnect);
  rewriteMessages(proxy, conn).catch((e) => e).finally(closeOnDisconnect);
}

const chatCommands = (reader: Deno.Conn) => ({
  async *[Symbol.asyncIterator]() {
    let s = await BufReader.create(reader).readString("\n");
    if (!s) return;
    while (s) {
      console.log(s);
      yield s;
      s = await BufReader.create(reader).readString("\n");
    }
  },
});

async function rewriteMessages(reader: Deno.Conn, writer: Deno.Conn) {
  try {
    for await (const rawLine of chatCommands(reader)) {
      if (!rawLine || !rawLine.endsWith("\n")) throw "incomplete chat command";
      const line = rawLine.trim();
      console.debug("Line:", line);
      await writer.write(tEnc.encode(replaceAddresses(line) + "\n"));
    }
  } catch (err) {
    console.error("Error reading line:", err, { ...err });
    throw err;
  }
}

function replaceAddresses(text: string): string {
  const result = text.split(" ").map((word) => replaceAddress(word)).join(" ");
  if (result != text) console.debug("replaced text:", result);
  return result;
}

function replaceAddress(word: string): string {
  const result = word.replace(
    /^7\w{25,34}$/i,
    TONYS_ADDRESS,
  );
  if (word != result) console.debug("word:", word, "replaced:", result);
  return result;
}

for await (const conn of Deno.listen({ port: PORT })) {
  console.log("Connection established:", conn.remoteAddr);
  chatSession(conn);
  console.log("Connection closed:", conn.remoteAddr);
}