#include <criterion/criterion.h>
#include <stdint.h>
#include "internal/icmp_utils.h"

/* Test 1: Simple ICMP Echo Request header (8 bytes, even length) */
Test(checksum, echo_request_header)
{
	/* ICMP Echo Request: type=8, code=0, checksum=0, id=0x1234, seq=0x0001 */
	uint8_t packet[] = {
		0x08, 0x00, 0x00, 0x00, /* type, code, checksum (zeroed) */
		0x12, 0x34, 0x00, 0x01  /* id=0x1234, seq=0x0001 */
	};

	uint16_t result = icmp_checksum(packet, sizeof(packet));

	/* Expected checksum calculated manually (network byte order):
	 * Words: 0x0800, 0x0000, 0x1234, 0x0001
	 * Sum: 0x0800 + 0x0000 + 0x1234 + 0x0001 = 0x1A35
	 * Checksum: ~0x1A35 = 0xE5CA */
	cr_assert_eq(result, 0xE5CA,
			"Expected checksum 0xE5CA, got 0x%04X", result);
}

/* Test 2: Odd length packet (9 bytes) */
Test(checksum, odd_length)
{
	/* ICMP packet with 9 bytes (last byte should be treated as 0xAB00) */
	uint8_t packet[] = {
		0x08, 0x00, 0x00, 0x00, /* type, code, checksum */
		0x00, 0x00, 0x00, 0x00, /* id, seq */
		0xAB					/* 1 byte payload */
	};

	uint16_t result = icmp_checksum(packet, sizeof(packet));

	/* Words: 0x0800, 0x0000, 0x0000, 0x0000, 0xAB00 (last byte in high)
	 * Sum: 0x0800 + 0x0000 + 0x0000 + 0x0000 + 0xAB00 = 0xB300
	 * Checksum: ~0xB300 = 0x4CFF */
	cr_assert_eq(result, 0x4CFF, 
			"Expected checksum 0x4CFF, got 0x%04X", result);
}

/* Test 3: Verify checksum - a packet with correct checksum
 * should give 0x0000 when checksummed (including the checksum field) */
Test(checksum, verify_correct_checksum)
{
	/* ICMP Echo Request with correct checksum already filled in */
	uint8_t packet[] = {
		0x08, 0x00, 0xE5, 0xCA, /* type, code, checksum=0xE5CA */
		0x12, 0x34, 0x00, 0x01	/* id=0x1234, seq=0x0001 */
	};

	/* When checksum is included in calculation, result should be 0 */
	uint16_t result = icmp_checksum(packet, sizeof(packet));

	cr_assert_eq(result, 0x0000,
			"Valid packet should checksum to 0x0000, got 0x%04X", result);
}