Kalshi order-book beta

import WebSocket from "ws";
import { createHash, createHmac } from "node:crypto";

const key = process.env.BRAVADO_API_KEY;
const secret = process.env.BRAVADO_API_SECRET;
if (!key || !secret) throw new Error("Set your Market Data key and secret");
const origin = "https://partner-api.bravadotrade.com";
const headers = path => {
  const timestamp = String(Date.now());
  const payload = [timestamp, "GET", path,
    createHash("sha256").update("").digest("hex")].join("\n");
  return {
    "X-BRAVADO-API-KEY": key,
    "X-BRAVADO-TIMESTAMP": timestamp,
    "X-BRAVADO-SIGNATURE": createHmac("sha256", secret).update(payload).digest("hex"),
  };
};
const response = await fetch(`${origin}/stream/capabilities`, {
  headers: headers("/stream/capabilities"), redirect: "error",
  signal: AbortSignal.timeout(8_000),
});
if (!response.ok) throw new Error(`Capabilities refused (${response.status})`);
const capabilities = await response.json();
const kalshi = capabilities.venues?.find(row => row.venue === "kalshi");
if (!kalshi?.implemented || !kalshi.upstream_registered || !kalshi.entitled)
  throw new Error("Kalshi is not available for this organisation right now");

const query = new URLSearchParams({ streams: "book:KXBTC-26OCT3017-B79750" });
const path = `/stream/kalshi/partner?${query}`;
const ws = new WebSocket(`wss://partner-api.bravadotrade.com${path}`, {
  headers: headers(path), handshakeTimeout: 8_000,
  followRedirects: false, rejectUnauthorized: true,
});
ws.on("message", raw => {
  const frame = JSON.parse(raw.toString());
  if (frame.type === "error") { console.error(frame.code); return; }
  if (frame.type === "status") { console.log(frame.state, frame.reason); return; }
  if (frame.channel === "book" && ["snapshot", "delta"].includes(frame.type))
    console.log(frame.asset, frame.seq, frame.bids, frame.asks, frame.quote);
});
ws.on("error", () => console.error("WebSocket connection failed"));
const stop = setTimeout(() => ws.close(), 30_000);
ws.once("close", () => clearTimeout(stop));