#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

struct test_case {

	clockid_t clock;
	timer_t timer_id;
	int flags;
	struct itimerspec end;
	int error;
	int result_ms;

	// is the result shall be altered by setting the system clock?
	int is_altered;

};

static struct test_case tests[] = {
	{ .clock = CLOCK_REALTIME, .flags = TIMER_ABSTIME, .is_altered = 1 },
	{ .clock = CLOCK_MONOTONIC, .flags = TIMER_ABSTIME},
	{ .clock = CLOCK_REALTIME},
	{ .clock = CLOCK_MONOTONIC}
};

static const int num_tests = sizeof(tests)/sizeof(tests[0]);

void shift_time(int t)
{
	int error = 0;

	struct timespec tp;
	error |= clock_gettime(CLOCK_REALTIME, &tp);
	if (!error) {
		tp.tv_sec += t;
		error |= clock_settime(CLOCK_REALTIME, &tp);
	}
	if (error) {
		printf("Couldn't set the system clock.\n"
		       "(Please try again with the necessary administrative rights.)\n");
		exit(1);
	}
}

int main()
{

	// Alter the system clock
	// (will be set back to the correct value later)
	shift_time(-2);
	
	// Setup
	for(int i=0; i < num_tests; ++i) {

		struct sigevent evt = { .sigev_notify = SIGEV_NONE };
		
		tests[i].error |= timer_create(tests[i].clock, &evt, &tests[i].timer_id);

		if (tests[i].flags & TIMER_ABSTIME) {
			tests[i].error |= clock_gettime(tests[i].clock, &tests[i].end.it_value);
		}

		tests[i].end.it_value.tv_sec += 5;
		tests[i].error |= timer_settime(tests[i].timer_id, tests[i].flags, &tests[i].end, NULL);
	}

	sleep(1);

	// Shift time forward
	// (correcting the system time as a result)
	shift_time(2);

	// get remaining times
	for(int i=0; i < num_tests; ++i) {
		struct itimerspec remaining;
		tests[i].error |= timer_gettime(tests[i].timer_id, &remaining);
		tests[i].result_ms = remaining.it_value.tv_sec*1000;
		tests[i].result_ms += (remaining.it_value.tv_nsec+500*1000)/(1000*1000);
	}

	// Report results
	int overall_ok = 1;
	for(int i=0; i < num_tests; ++i) {
		if (tests[i].clock == CLOCK_REALTIME) { printf("CLOCK_REALTIME,  "); }
		if (tests[i].clock == CLOCK_MONOTONIC) { printf("CLOCK_MONOTONIC, "); }
		if (tests[i].flags & TIMER_ABSTIME) {
			printf("absolute: ");
		}
		else {
			printf("relative: ");
		}
		if (tests[i].error) {
			overall_ok = 0;
			puts("ERROR");
			continue;
		}
		printf("%d ms, ", tests[i].result_ms);

		int expected_ms = tests[i].is_altered ? 2000 : 4000;
		if (abs(tests[i].result_ms - expected_ms) < 500) {
			puts("OK");
		}
		else {
			puts("Failed");
			overall_ok = 0;
		}
	}

	printf("\nResult: %s\n", overall_ok ? "OK" : "Failed");
	return 0;
}