From d59883d5e16cce2911fb59101887861768cb5762 Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Thu, 6 Oct 2022 12:47:45 -0500
Subject: [PATCH] Problem 4

---
 main.ts | 121 +++++++++-----------------------------------------------
 1 file changed, 19 insertions(+), 102 deletions(-)

diff --git a/main.ts b/main.ts
index 9fa8c7a..e052fbe 100644
--- a/main.ts
+++ b/main.ts
@@ -1,108 +1,25 @@
-import { readLines } from "https://deno.land/std@0.157.0/io/buffer.ts";
-
 const PORT = 5588;
-console.log(`Starting TCP listener on on 0.0.0.0:${PORT}`);
-
-const clients = new Map<Deno.Conn, string>();
+console.log(`Starting UDP listener on port ${PORT}`);
 
+const tDec = new TextDecoder();
 const tEnc = new TextEncoder();
 
-async function chatSession(conn: Deno.Conn) {
-  try {
-    let myNick: string | null = null;
-    await sendPrompt(conn);
-    for await (const line of readLines(conn)) {
-      console.debug("Received line:", line);
-      const message = line.trim();
-      if (myNick == null) {
-        if (isLegalNick(message)) {
-          myNick = message;
-          await join(myNick, conn);
-        } else {
-          console.error("Illegal nick:", message);
-          break;
-        }
-      } else {
-        const conns: Deno.Conn[] = [];
-        for (const themConn of clients.keys()) {
-          if (themConn != conn) conns.push(themConn);
-        }
-        await send(conns, `[${myNick}] ${message}`);
-      }
-    }
-  } finally {
-    if (clients.has(conn)) {
-      try {
-        await disconnect(conn);
-      } catch (err) {
-        console.error("Failed to disconnect:", err);
-      }
-    }
-    try {
-      if (conn.writable) {
-        send(conn, "You are being disconnected...");
-      }
-    } catch (err) {
-      console.error("Failed to send disconnect notice:", err);
-    }
-  }
-  try {
-    conn.close();
-  } catch (err) {
-    console.error("Failed to close connection:", err);
+const reservedData: Record<string, string> = { version: "KeyVal 1.0" };
+const data = new Map<string, string>();
+
+const listener = Deno.listenDatagram({ port: PORT, transport: "udp" });
+
+for await (const [bytes, addr] of listener) {
+  const message = tDec.decode(bytes).trim();
+  console.debug("Datagram Received from:", addr, message);
+  if (message.includes("=")) {
+    const [key, val] = message.split("=", 1);
+    console.debug(`Setting ${key} to ${val}`);
+    if (!(key in reservedData)) data.set(key, val);
+  } else {
+    const value = reservedData[message] || data.get(message) || "";
+    const bytes = tEnc.encode(`${message}=${value}`);
+    console.debug(`Sending ${message}=${value}`);
+    await listener.send(bytes, addr);
   }
 }
-
-async function send(
-  connsArg: Deno.Conn | Array<Deno.Conn>,
-  text: string,
-) {
-  const conns = !Array.isArray(connsArg) ? [connsArg] : connsArg;
-  const messages: Promise<number>[] = [];
-  const bytes = tEnc.encode(text + "\n");
-  conns.forEach((conn) => messages.push(conn.write(bytes)));
-  return await Promise.all(messages);
-}
-
-const broadcast = async (text: string) => await send([...clients.keys()], text);
-
-const LEGAL_NICK_REGEXP = /^[a-z0-9]+$/i;
-const isLegalNick = (nick: string) => {
-  console.debug(
-    `Checking nick: ${nick} (Bytes: ${tEnc.encode(nick)})`,
-  );
-  return LEGAL_NICK_REGEXP.exec(nick) != null;
-};
-
-const sendPrompt = async (conn: Deno.Conn) => {
-  console.debug("Sending prompt...");
-  return await send(conn, "Who you be?");
-};
-
-async function join(myNick: string, conn: Deno.Conn) {
-  const userList: string[] = [];
-  clients.forEach((nick, _) => userList.push(nick));
-  await broadcast(`* ${myNick} joined`);
-  clients.set(conn, myNick);
-  await send(conn, `* users: ${userList.join(", ")}`);
-}
-
-async function disconnect(conn: Deno.Conn) {
-  const myNick = clients.get(conn);
-  clients.delete(conn);
-  await broadcast(`* ${myNick} left`);
-}
-
-for await (const conn of Deno.listen({ port: PORT })) {
-  console.log("Connection established:", conn.remoteAddr);
-  try {
-    chatSession(conn);
-  } catch (e) {
-    console.error(
-      "Exception occurred during chat session:",
-      conn.remoteAddr,
-      e,
-    );
-  }
-  console.log("Connection closed:", conn.remoteAddr);
-}