Stream Order Book Depth

import "dotenv/config";
import WebSocket from "ws";

const DFLOW_TRADE_API_WS_URL =
  process.env.DFLOW_TRADE_API_WS_URL ?? "wss://dev-quote-api.dflow.net";
const DFLOW_API_KEY = process.env.DFLOW_API_KEY; // optional; not needed for dev

const SOL_MINT = "So11111111111111111111111111111111111111112";
const USDC_MINT = "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v";

const ws = new WebSocket(
  `${DFLOW_TRADE_API_WS_URL}/book-stream`,
  DFLOW_API_KEY ? { headers: { "x-api-key": DFLOW_API_KEY } } : undefined
);

ws.on("open", () => {
  ws.send(
    JSON.stringify({ op: "subscribe", base_mint: SOL_MINT, quote_mint: USDC_MINT })
  );
});

ws.on("message", (data) => {
  const frame = JSON.parse(data.toString());
  for (const book of frame.updates ?? []) {
    if (book.e) {
      console.log(`${book.sb} / ${book.sq}: ${book.e}`);
      continue;
    }
    console.log(`\nslot ${frame.u}  mid ${book.mid}  tick ${book.tick}`);
    console.log("asks (low to high):");
    for (const level of [...book.a].reverse()) {
      console.log(`  ${level.price}\t${level.cumulative_size_human}`);
    }
    console.log("bids (high to low):");
    for (const level of book.b) {
      console.log(`  ${level.price}\t${level.cumulative_size_human}`);
    }
  }
});

ws.on("error", (err) => console.error("WebSocket error:", err));
ws.on("close", () => console.log("Connection closed"));

// demo only: stop after the first updates
setTimeout(() => ws.close(), 6000);