escProxy/index.js

import net from "node:net";
import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import dotenv from "dotenv";
import { parse, renderTokens, serialize } from "./parser.js";

dotenv.config();

const __dirname = path.dirname(fileURLToPath(import.meta.url));

const num = (v, d) => (v === undefined || v === "" ? d : Number(v));
const str = (v, d) => (v === undefined || v === "" ? d : v);
const bool = (v, d) =>
  v === undefined || v === "" ? d : v.toLowerCase() === "true" || v === "1";

// Parse CUT_PREFIX (hex, space-separated) into a byte array.
function parseCutPrefix(v, d) {
  if (v === undefined || v === "") return d;
  return v
    .trim()
    .split(/\s+/)
    .map((h) => parseInt(h, 16));
}

const config = {
  listenHost: str(process.env.LISTEN_HOST, "0.0.0.0"),
  listenPort: num(process.env.LISTEN_PORT, 9100),
  targetHost: str(process.env.TARGET_HOST, "10.10.10.24"),
  targetPort: num(process.env.TARGET_PORT, 9100),
  logDir: str(process.env.LOG_DIR, "./logs"),
  forward: bool(process.env.FORWARD, true),
  cutPrefix: parseCutPrefix(process.env.CUT_PREFIX, [0x1d, 0x56]),
  keepAfterCut: bool(process.env.KEEP_AFTER_CUT, true),
};

const logDir = path.resolve(__dirname, config.logDir);
fs.mkdirSync(logDir, { recursive: true });

let seq = 0;

function timestamp() {
  // ISO timestamp without colons (filesystem friendly), with ms.
  return new Date().toISOString().replace(/[:.]/g, "-");
}

function logJob(buffer) {
  if (!buffer || buffer.length === 0) return;
  const id = `${timestamp()}-${String(++seq).padStart(4, "0")}`;
  const parsedPath = path.join(logDir, `job-${id}.log`);

  // Only the parsed, lossless token stream is logged.
  let parsedLines = "";
  try {
    const events = parse(buffer);
    parsedLines = renderTokens(events);
    // Sanity: the parser must be lossless (rebuild == original).
    const rebuilt = serialize(events);
    if (!rebuilt.equals(buffer)) {
      throw new Error("parser round-trip mismatch");
    }
  } catch (err) {
    parsedLines = `[parse error] ${err.message}\n${buffer.toString("latin1")}`;
  }
  fs.writeFileSync(parsedPath, parsedLines);

  console.log(`[log] job ${id} (${buffer.length} bytes) -> ${parsedPath}`);
}

// Find the end offset (exclusive) of the first complete cut command in `buf`.
// Returns -1 if no complete cut sequence is present yet.
// A cut is: cutPrefix (0x1D 0x56) followed by 1 mode byte.
function findCutEnd(buf, cutPrefix) {
  const n = cutPrefix.length;
  let i = 0;
  while (i <= buf.length - (n + 1)) {
    let match = true;
    for (let k = 0; k < n; k++) {
      if (buf[i + k] !== cutPrefix[k]) {
        match = false;
        break;
      }
    }
    if (match) {
      // cut + mode byte => end is i + n + 1
      return i + n + 1;
    }
    i++;
  }
  return -1;
}

// Streams received bytes to the target printer (unless forwarding is disabled).
function connectTarget() {
  if (!config.forward) return null;
  const target = net.createConnection(
    { host: config.targetHost, port: config.targetPort },
    () => console.log(`[target] connected to ${config.targetHost}:${config.targetPort}`)
  );
  target.on("error", (err) => {
    console.error(`[target] error: ${err.message}`);
    target.destroy();
  });
  target.on("close", () => console.log("[target] connection closed"));
  return target;
}

const server = net.createServer((clientSocket) => {
  const clientAddr = `${clientSocket.remoteAddress}:${clientSocket.remotePort}`;
  console.log(`[client] connected ${clientAddr}`);

  let buffer = Buffer.alloc(0);
  const target = connectTarget();

  clientSocket.on("data", (chunk) => {
    // Forward raw bytes straight to the printer (if forwarding is enabled).
    if (target && target.writable) target.write(chunk);

    buffer = Buffer.concat([buffer, chunk]);

    // Finalize any complete jobs delimited by a cut command.
    let cutEnd = findCutEnd(buffer, config.cutPrefix);
    while (cutEnd !== -1) {
      const job = buffer.subarray(0, cutEnd);
      logJob(job);
      if (config.keepAfterCut) {
        buffer = buffer.subarray(cutEnd);
        cutEnd = findCutEnd(buffer, config.cutPrefix);
      } else {
        buffer = Buffer.alloc(0);
        break;
      }
    }
  });

  const finalize = () => {
    // Connection drop: any remaining bytes form the last job.
    if (buffer.length > 0) {
      logJob(buffer);
      buffer = Buffer.alloc(0);
    }
    if (target) target.end();
  };

  clientSocket.on("end", () => {
    console.log(`[client] end ${clientAddr}`);
    finalize();
  });

  clientSocket.on("close", () => {
    console.log(`[client] closed ${clientAddr}`);
    finalize();
  });

  clientSocket.on("error", (err) => {
    console.error(`[client] error ${clientAddr}: ${err.message}`);
    finalize();
  });
});

server.listen(config.listenPort, config.listenHost, () => {
  console.log(
    `[server] listening on ${config.listenHost}:${config.listenPort}, ` +
      (config.forward
        ? `forwarding to ${config.targetHost}:${config.targetPort}, `
        : `forwarding DISABLED (receive + log only), `) +
      `logging to ${logDir}`
  );
});