// firmware/src/hmac.h
#pragma once
#include <stdint.h>

#ifdef NATIVE_TEST
#include <string>
using HString = std::string;
#else
#include <Arduino.h>
using HString = String;
#endif

// Returns lowercase hex-encoded HMAC-SHA256 signature.
// Message signed: device_id + ":" + timestamp_str + ":" + hex(sha256(body))
HString hmac_sign(const HString& secret_hex, const HString& device_id,
                  uint32_t timestamp, const HString& body);