Price alert webhooks

{
  "id": "evt_3f0c6a52-6a2e-4b8e-9c1d-2f4b7e9a1c03_level_cross:492841",
  "type": "price.level_cross",
  "created_at": "2026-10-23T14:02:11.482113Z",
  "data": {
    "alert_id": "3f0c6a52-6a2e-4b8e-9c1d-2f4b7e9a1c03",
    "kind": "level_cross",
    "symbol": "XAU-USD-SPOT",
    "direction": "above",
    "price": "4203.1",
    "level": "4200",
    "observed_at": "2026-10-23T14:02:11.482113+00:00"
  }
}

{
  "id": "evt_8a1d52c4-0b7e-4f55-a3d9-61e2c7b8f410_percent_move:492855",
  "type": "price.percent_move",
  "created_at": "2026-10-23T09:15:40.120934Z",
  "data": {
    "alert_id": "8a1d52c4-0b7e-4f55-a3d9-61e2c7b8f410",
    "kind": "percent_move",
    "symbol": "XAU-USD-SPOT",
    "direction": "either",
    "price": "4168.8",
    "percent": "2",
    "window": "24h",
    "reference_price": "4083.05",
    "observed_at": "2026-10-23T09:15:40.120934+00:00"
  }
}

{
  "id": "evt_c92e0f7b-31a4-4d6a-8e57-a05b3d1c92e8_close:2026-10-22",
  "type": "price.daily_close",
  "created_at": "2026-10-22T23:59:59Z",
  "data": {
    "alert_id": "c92e0f7b-31a4-4d6a-8e57-a05b3d1c92e8",
    "kind": "daily_close",
    "symbol": "XAG-USD-SPOT",
    "direction": "either",
    "date": "2026-10-22",
    "close": "48.62"
  }
}

{
  "id": "evt_test_1792143012345",
  "type": "webhook.test",
  "created_at": "2026-10-23T09:30:12.345000Z",
  "data": {
    "alert_id": "3f0c6a52-6a2e-4b8e-9c1d-2f4b7e9a1c03"
  }
}

import { createHmac, timingSafeEqual } from "node:crypto";
import { createServer } from "node:http";

const TOLERANCE_SECONDS = 300;

// rawBody: the request body exactly as received (a Buffer), before any JSON parsing.
function verifyWebhook(rawBody, header, secret, now = Math.floor(Date.now() / 1000)) {
  const fields = {};
  for (const part of String(header ?? "").split(",")) {
    const i = part.indexOf("=");
    if (i > 0) fields[part.slice(0, i).trim()] = part.slice(i + 1).trim();
  }
  const t = Number(fields.t);
  if (!Number.isInteger(t) || Math.abs(now - t) > TOLERANCE_SECONDS) return false;
  const expected = createHmac("sha256", secret).update(t + ".").update(rawBody).digest();
  const given = Buffer.from(fields.v1 ?? "", "hex");
  return given.length === expected.length && timingSafeEqual(given, expected);
}

const seen = new Set(); // use your database in production

createServer((req, res) => {
  const chunks = [];
  req.on("data", (chunk) => chunks.push(chunk));
  req.on("end", () => {
    const rawBody = Buffer.concat(chunks);
    const header = req.headers["webhook-signature"];
    if (!verifyWebhook(rawBody, header, process.env.WEBHOOK_SECRET)) {
      res.writeHead(400).end();
      return;
    }
    const event = JSON.parse(rawBody);
    if (!seen.has(event.id)) {
      seen.add(event.id);
      // Hand the event to a queue or background job here, then answer quickly.
      console.log(event.type, event.data);
    }
    res.writeHead(204).end();
  });
}).listen(Number(process.env.PORT ?? 3000));

import hashlib
import hmac
import time

TOLERANCE_SECONDS = 300


def verify_webhook(raw_body: bytes, header: str, secret: str, now: int | None = None) -> bool:
    """raw_body is the request body exactly as received, before any JSON parsing."""
    fields = dict(p.strip().split("=", 1) for p in (header or "").split(",") if "=" in p)
    try:
        t = int(fields["t"])
    except (KeyError, ValueError):
        return False
    now = int(time.time()) if now is None else now
    if abs(now - t) > TOLERANCE_SECONDS:
        return False
    signed = f"{t}.".encode() + raw_body
    expected = hmac.new(secret.encode(), signed, hashlib.sha256).hexdigest()
    return hmac.compare_digest(fields.get("v1", "").encode(), expected.encode())


# Flask:  verify_webhook(request.get_data(), request.headers.get("Webhook-Signature", ""), secret)
# Django: verify_webhook(request.body, request.headers.get("Webhook-Signature", ""), secret)