hmac.ts

import crypto from "node:crypto";

function replaceAll(s: string, search: string, replace: string) {
	return s.split(search).join(replace);
}

/**
 * Builds the canonical Polymarket CLOB HMAC signature
 * @param signer
 * @param key
 * @param secret
 * @param passphrase
 * @returns string
 */
export const buildPolyHmacSignature = (
	secret: string,
	timestamp: number,
	method: string,
	requestPath: string,
	body?: string,
): string => {
	let message = timestamp + method + requestPath;
	if (body !== undefined) {
		message += body;
	}
	const base64Secret = Buffer.from(secret, "base64");
	const hmac = crypto.createHmac("sha256", base64Secret);
	const sig = hmac.update(message).digest("base64");

	// NOTE: Must be url safe base64 encoding, but keep base64 "=" suffix
	// Convert '+' to '-'
	// Convert '/' to '_'
	const sigUrlSafe = replaceAll(replaceAll(sig, "+", "-"), "/", "_");
	return sigUrlSafe;
};