#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>

#if 1
#define PREFIX		"________________________________________________________________________________________________________________________________________________________________________________________________"
#else
#define PREFIX		"________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________"
#endif

#define PRINT_STEP	1000

#define N_FILES		65536
#define DEFAULT_PATH	"."

static unsigned long n_files = N_FILES;
static char *path = DEFAULT_PATH;
static unsigned long n_loops = -1;

static bool *map;

static bool dir = false;
static bool lnk = false;

static char *file_name(unsigned long i)
{
	static char fn[8192];
	snprintf(fn, sizeof(fn), "%s/" PREFIX "%ld", path, i);
	return fn;
}

static char link_file[8192];

static void test_flip(void)
{
	int r;
	unsigned long i = random() % n_files;
	if (map[i]) {
		if (!dir)
			r = unlink(file_name(i));
		else
			r = rmdir(file_name(i));
		if (r) fprintf(stderr, "\nfile %lu can't be unlinked: %s\n", i, strerror(errno)), exit(1);
		map[i] = false;
	} else {
		if (lnk) {
			r = link(link_file, file_name(i));
			if (r < 0) fprintf(stderr, "\nfile %lu can't be linked: %s\n", i, strerror(errno)), exit(1);
		} else if (!dir) {
			r = open(file_name(i), O_RDONLY | O_CREAT | O_EXCL, 0644);
			if (r < 0) fprintf(stderr, "\nfile %lu can't be created: %s\n", i, strerror(errno)), exit(1);
			r = close(r);
			if (r) fprintf(stderr, "\nfile %lu can't be closed: %s\n", i, strerror(errno)), exit(1);
		} else {
			r = mkdir(file_name(i), 0755);
			if (r < 0) fprintf(stderr, "\nfile %lu can't be created: %s\n", i, strerror(errno)), exit(1);
		}
		map[i] = true;
	}
}

static void test_access(void)
{
	int r;
	unsigned long i = random() % n_files;
	r = open(file_name(i), O_RDONLY);
	if (!map[i]) {
		if (r >= 0) fprintf(stderr, "\nfile %lu was incorrectly opened\n", i), exit(1);
		if (errno != ENOENT) fprintf(stderr, "\nnon-existing file %lu can't be open: %s\n", i, strerror(errno)), exit(1);
	} else {
		if (r < 0) fprintf(stderr, "\nfile %lu can't be open: %s\n", i, strerror(errno)), exit(1);
		r = close(r);
		if (r) fprintf(stderr, "\nfile %lu can't be closed: %s\n", i, strerror(errno)), exit(1);
	}
}

int main(int argc, char *argv[])
{
	unsigned long i;
	if (argc >= 2)
		path = argv[1];
	if (argc >= 3)
		n_files = strtoul(argv[2], NULL, 10);
	if (argc >= 4)
		n_loops = strtol(argv[3], NULL, 10);
	if (argc >= 5) {
		if (!strcmp(argv[4], "dir"))
			dir = true;
		if (!strcmp(argv[4], "link"))
			lnk = true;
	}

	if (!n_files) fprintf(stderr, "\nzero files\n"), exit(1);

	map = calloc(n_files, sizeof(bool));
	if (!map) perror("calloc"), exit(1);

	for (i = 0; i < n_files; i++) {
		if (!(i % PRINT_STEP))
			fprintf(stderr, "deleting: %lu\r", i);
		unlink(file_name(i));
		rmdir(file_name(i));
	}
	fprintf(stderr, "\n");

	if (argc >= 4 && !strcmp(argv[3], "d"))
		return 0;

	if (lnk) {
		int r = open(strcpy(link_file, file_name(i)), O_RDONLY | O_CREAT, 0644);
		if (r < 0) fprintf(stderr, "\nfile can't be created: %s\n", strerror(errno)), exit(1);
		r = close(r);
		if (r) fprintf(stderr, "\nfile can't be closed: %s\n", strerror(errno)), exit(1);
	}

	i = 0;
	while (i < n_loops) {
		test_flip();
		test_access();
		if (!(i % PRINT_STEP))
			fprintf(stderr, "%lu\r", i);
		i++;
	}

	return 0;
}