#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           = 0,
  OWD_MSG_PING          = 1,
  OWD_MSG_PONG          = 2,
  OWD_MSG_SYNC_REQUEST  = 3,
  OWD_MSG_SYNC_RESPONSE = 4,
};

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;
  uint32_t tid;
};

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,
  uint32_t tid)
{
  hdr->magic = htonl(OWD_MAGIC);
  hdr->version = OWD_VERSION;
  hdr->msg_type = msg_type;
  hdr->length = htons(length);
  hdr->tid = htonl(tid);
}

static inline int owd_hdr_validate(struct owdhdr *hdr, ssize_t len) {
  if (len < sizeof(struct owdhdr))
    return 1;
  if (hdr->magic != ntohl(OWD_MAGIC))
    return 1;
  if (hdr->version != OWD_VERSION)
    return 1;
  return 0;
}