#include <stdint.h>
#include <unity.h>

#define SENT_TIME_1_MS 1000
#define NOW_TIME_1_MS 1500
#define RTT_POSITIVE_EXPECTED 500

#define SENT_TIME_2_MS 2000
#define NOW_TIME_2_MS 2000
#define RTT_ZERO_EXPECTED 0

#define SENT_TIME_3_MS 3000
#define NOW_TIME_3_MS 2500
#define RTT_NEGATIVE_EXPECTED (-500)

/*
 * calculate_rtt - calculate round-trip time
 * @sent_ms: time when message was sent (ms)
 * @now_ms: current time (ms)
 *
 * Return: RTT in milliseconds (now_ms - sent_ms)
 */
static int32_t calculate_rtt(int32_t sent_ms, int32_t now_ms)
{
	return now_ms - sent_ms;
}

static void test_rtt_positive_difference(void)
{
	TEST_ASSERT_EQUAL_INT32(RTT_POSITIVE_EXPECTED,
	                        calculate_rtt(SENT_TIME_1_MS, NOW_TIME_1_MS));
}

static void test_rtt_zero_difference(void)
{
	TEST_ASSERT_EQUAL_INT32(RTT_ZERO_EXPECTED,
	                        calculate_rtt(SENT_TIME_2_MS, NOW_TIME_2_MS));
}

static void test_rtt_negative_difference(void)
{
	TEST_ASSERT_EQUAL_INT32(RTT_NEGATIVE_EXPECTED,
	                        calculate_rtt(SENT_TIME_3_MS, NOW_TIME_3_MS));
}

int app_main(void)
{
	UNITY_BEGIN();

	RUN_TEST(test_rtt_positive_difference);
	RUN_TEST(test_rtt_zero_difference);
	RUN_TEST(test_rtt_negative_difference);

	return UNITY_END();
}