hmac js

const ec = new TextEncoder();
const algorithm = { name: "HMAC", hash: "SHA-256" };

//  generates a signature for the given data using the given key
async function generateHmacKey(secret) {
  const { subtle } = globalThis.crypto;
  return subtle.importKey(
    "raw",
    typeof secret === "string" ? ec.encode(secret) : secret,
    algorithm,
    false,
    ["sign"]
  );
}

async function hash(key, data) {
  const { subtle } = globalThis.crypto;
  return subtle.sign(algorithm, await generateHmacKey(key), ec.encode(data));
}

function arrayBufferToHexString(arrayBuffer) {
  const byteArray = new Uint8Array(arrayBuffer);
  let hexString = "";
  for (let i = 0; i < byteArray.length; i++) {
    hexString += byteArray[i].toString(16).padStart(2, "0");
  }
  return hexString;
}

const nonce = generateNonce();
const date = new Date();
const apiSecret = "DEYt52UW00siPrqeaTIaSKL8o7cMhUil";
const requestData = {
  method: "GET",
  uri: "/example",
  xDate: ISO8601DateFormat(date),
  nonce: generateNonce(),
  requestBody: '{"data": "test"}',
};

async function createAuthorizeToken(secret, data) {
  const signature = await hash(secret, data);
  const hexSignature = arrayBufferToHexString(signature);
  return hexSignature;
}

// Construct the signing string
const signingString = `${requestData.method}\n${requestData.uri}\n${requestData.timestamp}\n${requestData.nonce}\n${requestData.requestBody}`;

async function performAPICall() {
  const signature = await createAuthorizeToken(apiSecret, signingString);
    const headers = {
        Authorization: `${apiSecret}:${signature}`,
        "Content-Type": "application/json",
        "X-Date": requestData.xDate,
        "X-Nonce": requestData.nonce,
    }

    // xhr request
    const xhr = new XMLHttpRequest();

    xhr.open(requestData.method, `https://api.sandbox.gemini.com${requestData.uri}`, true);

    xhr.setRequestHeader("Authorization", headers.Authorization);
    xhr.setRequestHeader("Content-Type", headers["Content-Type"]);
    xhr.setRequestHeader("X-Date", headers["X-Date"]);
    xhr.setRequestHeader("X-Nonce", headers["X-Nonce"]);
    xhr.send(requestData.requestBody);

    xhr.onreadystatechange = function () {
        if (xhr.readyState === 4) {
            console.log(xhr.status);
            console.log(xhr.responseText);
        }
    }
}

performAPICall();

// Authorization Header Format
// Authorization:${apiSecret}:${signature}
//Content-Type: application/json
// X-Date: ${date}
// X-Nonce: ${nonce}

function generateNonce() {
  const timestamp = Date.now(); // in milliseconds
  const randomDigits = Math.floor(Math.random() * 1000);
  const nonce = `${timestamp}${randomDigits}`;
  return nonce;
}



function ISO8601DateFormat(date) {
  const year = date.getFullYear();
  const month = String(date.getMonth() + 1).padStart(2, "0"); // Months are 0-based, so add 1 and pad with 0 if necessary
  const day = String(date.getDate()).padStart(2, "0");
  const hours = String(date.getHours()).padStart(2, "0");
  const minutes = String(date.getMinutes()).padStart(2, "0");
  const seconds = String(date.getSeconds()).padStart(2, "0");
  return `${year}${month}${day}T${hours}${minutes}${seconds}Z`;
}

console.log(ISO8601DateFormat(date));