#pragma once

#include <cstdint>
#include <optional>
#include <string>
#include <vector>

#include "secsgem/secs2/item.hpp"

namespace secsgem::secs2 {

// A logical SECS-II message: stream/function, the W-bit (reply expected), and
// an optional root data item as the body. The transport (HSMS) header carries
// stream/function/W on the wire; the body bytes are the encoded root item.
struct Message {
  uint8_t stream = 0;
  uint8_t function = 0;
  bool reply_expected = false;  // W-bit
  std::optional<Item> body;

  Message() = default;
  Message(uint8_t s, uint8_t f, bool w, std::optional<Item> b = std::nullopt)
      : stream(s), function(f), reply_expected(w), body(std::move(b)) {}

  // Encode the body item to bytes (empty if there is no body).
  std::vector<uint8_t> encode_body() const;

  // Build a Message from stream/function/W and raw body bytes (empty -> no body).
  static Message from_body(uint8_t stream, uint8_t function, bool reply_expected,
                           const std::vector<uint8_t>& body_bytes);

  // e.g.  S1F2 W
  //         <L [2] <A "MDLN"> <A "1.0"> >
  std::string sml() const;
};

}  // namespace secsgem::secs2