#pragma once

#include <stdint.h>
#include <arpa/inet.h>

#define OWD_MAGIC 0x4f574454
#define OWD_VERSION 1

#define OWD_DECL_DATA_END char _data_end[0]
#define OWD_DATA_LEN(HDR) (offsetof(__typeof__(HDR), _data_end))

enum owd_msg_type {
  OWD_MSG_ERR,
  OWD_MSG_SYNC_REQUEST,
  OWD_MSG_SYNC_RESPONSE,
};

enum owd_error_code {
  OWD_ERR_BAD_HEADER,
  OWD_ERR_BAD_TYPE,
};

struct owd_timestamp {
  uint32_t ts_upper;
  uint32_t ts_lower;
};

struct owdhdr {
  uint32_t magic;
  uint8_t version;
  uint8_t msg_type;
  uint16_t length;
};

struct owd_msg_err {
  struct owdhdr hdr;
  uint8_t err;
  OWD_DECL_DATA_END;
};

struct owd_msg_sync_response {
  struct owdhdr hdr;
  struct owd_timestamp ts;
  OWD_DECL_DATA_END;
};

static inline void owd_hdr_populate(struct owdhdr *hdr, uint8_t msg_type, uint16_t length) {
  hdr->magic = htonl(OWD_MAGIC);
  hdr->version = OWD_VERSION;
  hdr->msg_type = msg_type;
  hdr->length = htons(length);
}