/*
 * clock-malfunction-imitation.c
 *
 * The imitations include:
 * - time change
 * - clock overflow
 * - clock hang
 * - clock reverse
 * - exponential growth of time
 *
 * Author: Intel A80486DX2-66
 * License: Unlicense
 */

#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

#define EXIT_IN 2U
#define SECOND_PRECISION 1L
#define TIME_BEFORE_ACCIDENT 2UL

#define TEST_LABEL(s) do {                                                    \
    printf("Test: %s\n", s);                                                  \
    fflush(stdout);                                                           \
} while (0)

#define CLOCK_FUN_BEGIN                                                       \
    static unsigned ticks_before_accident = TIME_BEFORE_ACCIDENT;             \
    time_t y

#define CLOCK_FUN_END                                                         \
    if (x != NULL)                                                            \
        *x = y;                                                               \
                                                                              \
    return y

time_t clock_change_time(time_t* x);
time_t clock_exponential_growth(time_t* x);
time_t clock_hang(time_t* x);
time_t clock_overflow(time_t* x);
time_t clock_reverse(time_t* x);
void time_flow_test(time_t (*time_function)(time_t*));

time_t clock_change_time(time_t* x) {
	CLOCK_FUN_BEGIN;

	time(&y);

	if (ticks_before_accident == 0) {
		y = 0;

		size_t max = sizeof(time_t) / sizeof(int),
		       intmax_plus_1 = (size_t) INT_MAX + 1;

		for (size_t i = 0; i < max; i++)
			y |= rand() % intmax_plus_1;
	} else
		ticks_before_accident--;

	CLOCK_FUN_END;
}

time_t clock_exponential_growth(time_t* x) {
	CLOCK_FUN_BEGIN;

	static time_t counter = 1;

	time(&y);

	if (ticks_before_accident == 0) {
		y += counter++;
		counter *= counter;
	} else
		ticks_before_accident--;

	CLOCK_FUN_END;
}

time_t clock_hang(time_t* x) {
	CLOCK_FUN_BEGIN;

	static time_t last_time;

	if (ticks_before_accident == 0)
		y = last_time;
	else {
		time(&y);
		last_time = y;
		ticks_before_accident--;
	}

	CLOCK_FUN_END;
}

time_t clock_overflow(time_t* x) {
	CLOCK_FUN_BEGIN;

	time(&y);

	if (ticks_before_accident == 0)
		y = LONG_MAX - y;
	else
		ticks_before_accident--;

	CLOCK_FUN_END;
}

time_t clock_reverse(time_t* x) {
	CLOCK_FUN_BEGIN;

	static time_t counter = 1, old_time;

	if (ticks_before_accident == 0)
		y = old_time - counter++;
	else {
		time(&y);
		old_time = y;
		ticks_before_accident--;
	}

	CLOCK_FUN_END;
}

void time_flow_test(time_t (*time_function)(time_t*)) {
	time_t current_time, previous_time;
	double time_diff;

	// Get the current time
	time(&current_time);
	previous_time = current_time;
	bool first_time_passed = false;
	unsigned i = 0;

	for (;;) {
		// Get the current time
		time_function(&current_time);

		// Calculate the time difference in seconds
		time_diff = difftime(current_time, previous_time);
		if (!first_time_passed) {
			time_diff = (double) SECOND_PRECISION;
			first_time_passed = true;
		}
		printf("time difference: %f", time_diff);
		fflush(stdout);

		// Check if the time difference is not normal
		if (time_diff != (double) SECOND_PRECISION) {
			printf(" -> Abnormal time flow detected!");
			fflush(stdout);
			if (++i >= EXIT_IN) {
				puts("\nAborting");
				fflush(stdout);
				break;
			}
		}
		putchar('\n');
		fflush(stdout);

		// Update the previous time
		previous_time = current_time;

		usleep(SECOND_PRECISION * 1000000L);

		first_time_passed = true;
	}

	putchar('\n');
	fflush(stdout);
}

int main(void) {
	srand(time(NULL));

	TEST_LABEL("clock_change_time");
	                                        time_flow_test(&clock_change_time);

	TEST_LABEL("clock_exponential_growth");
	                                 time_flow_test(&clock_exponential_growth);

	TEST_LABEL("clock_hang");
	                                               time_flow_test(&clock_hang);

	TEST_LABEL("clock_overflow");
	                                           time_flow_test(&clock_overflow);

	TEST_LABEL("clock_reverse");
	                                            time_flow_test(&clock_reverse);

	return 0;
}