#include "internal/icmp_packet_internal.h"
#include "internal/icmp_packet.h"
#include <stdint.h>

/* ICMP header size */
#define ICMP_HEADER_SIZE 8

/* Forward declarations */
static int validate_icmp_size(size_t buffer_len, size_t ip_hdr_len);
static const struct icmp_header *get_icmp_header(const void *buffer,
													size_t ip_hdr_len);
static void extract_icmp_fields(const struct icmp_header *hdr, uint8_t *type,
								uint8_t *code);
/* -------------------- */

int
icmp_parse_icmp_payload(const void *buffer, size_t buffer_len,
						size_t ip_hdr_len, uint8_t *type, uint8_t *code,
						const void **payload, size_t *payload_len)
{
	if (validate_icmp_size(buffer_len, ip_hdr_len) != 0)
		return -1;

	const struct icmp_header *hdr = get_icmp_header(buffer, ip_hdr_len);
	extract_icmp_fields(hdr, type, code);
	size_t payload_offset = ip_hdr_len + ICMP_HEADER_SIZE;

	if (buffer_len < payload_offset)
		return -1;

	*payload_len = buffer_len - payload_offset;
	*payload = (const uint8_t *)buffer + payload_offset;
	return 0;
}

static int
validate_icmp_size(size_t buffer_len, size_t ip_hdr_len)
{
	return (buffer_len >= (ip_hdr_len + ICMP_HEADER_SIZE)) ? 0 : -1;
}

static const struct icmp_header *
get_icmp_header(const void *buffer, size_t ip_hdr_len)
{
	return (const struct icmp_header *)((const uint8_t *)buffer + ip_hdr_len);
}

static void
extract_icmp_fields(const struct icmp_header *hdr, uint8_t *type,
					uint8_t *code)
{
	*type = hdr->type;
	*code = hdr->code;
}