#pragma once

#include <cstdint>
#include <stdexcept>
#include <vector>

#include "secsgem/hsms/header.hpp"

namespace secsgem::hsms {

class FrameError : public std::runtime_error {
 public:
  using std::runtime_error::runtime_error;
};

// One HSMS message: a header plus an optional SECS-II body (control messages
// have no body). On the wire it is prefixed by a 4-byte big-endian length that
// counts the header (10) plus the body.
struct Frame {
  Header header;
  std::vector<uint8_t> body;

  Frame() = default;
  explicit Frame(Header h, std::vector<uint8_t> b = {})
      : header(h), body(std::move(b)) {}

  // Full wire bytes including the 4-byte length prefix.
  std::vector<uint8_t> encode() const;

  // Decode a message from its payload (header + body, i.e. the bytes that
  // follow the length prefix). `len` must be >= 10.
  static Frame decode(const uint8_t* payload, std::size_t len);
};

// HSMS message length prefix is 4 bytes; payload must be at least the 10-byte
// header.
inline constexpr std::size_t kLengthPrefixSize = 4;
inline constexpr std::size_t kHeaderSize = 10;

}  // namespace secsgem::hsms