import { JsonParseStream } from "https://deno.land/std@0.157.0/encoding/json/stream.ts";
import { TextLineStream } from "https://deno.land/std@0.156.0/streams/delimiter.ts";

const PORT = 5588;
const tEnc = new TextEncoder();

console.log(`Listening on port ${PORT}`);
for await (const conn of Deno.listen({ port: PORT })) {
  processRequestStream(conn);
}

async function processRequestStream(conn: Deno.Conn) {
  console.log("Connection established:", conn.remoteAddr);
  try {
    for await (const request of requests(conn)) {
      console.debug("Request:", request);
      if (
        request == null || typeof request != "object" ||
        !("method" in request) || !("number" in request)
      ) {
        throw "Invalid request";
      }
      if (
        request.method == "isPrime" &&
        typeof request.number == "number"
      ) {
        const response = {
          method: "isPrime",
          prime: isPrime(request.number),
        };
        console.debug("Response:", response);
        conn.write(tEnc.encode(JSON.stringify(response) + "\n"));
      } else {
        console.debug("Request malformed");
        conn.write(tEnc.encode("Malformed!\n"));
      }
    }
  } catch (e) {
    console.error(conn.remoteAddr, e);
  } finally {
    console.log("Connection closed:", conn.remoteAddr);
    try {
      conn.close();
    } catch (_err) {
      // connection already closed
    }
  }
}

function isPrime(n: number) {
  if (!Number.isInteger(n)) return false;
  for (let i = 2, s = Math.sqrt(n); i <= s; i++) if (n % i === 0) return false;
  return n > 1;
}

function requests(conn: Deno.Conn) {
  try {
    const readable = conn.readable
      .pipeThrough(new TextDecoderStream())
      .pipeThrough(new TextLineStream())
      .pipeThrough(new JsonParseStream());

    return {
      async *[Symbol.asyncIterator]() {
        for await (const data of readable) {
          yield data;
        }
      },
    };
  } catch (err) {
    console.error(err);
  }
}