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

int main(int argc, const char* argv[]) {
	const char* file_name = "/root/test_filesystem_link.txt";
	const char* link_name = "/root/link.txt";
	const char* write_msg = "Hello World\n";
	char read_buf[128] = {0};
	int ret;

	// create a file and write message
	int flags = O_WRONLY | O_CREAT| O_TRUNC;
	int mode = 00666;
	int fd = open(file_name, flags, mode);
	if (fd < 0) {
		printf("ERROR: failed to open a file for write\n");
		return -1;
	}
	int len = write(fd, write_msg, strlen(write_msg));
	if (len <= 0) {
		printf("ERROR: failed to write to the file\n");
		return -1;
	}
	close(fd);

	// link
	ret = link(file_name, link_name);
	if(ret < 0) {
		printf("ERROR: failed to link the file\n");
		return -1;
	}

	// read the link file
	fd = open(link_name, O_RDONLY, 00666);
	if (fd < 0) {
		printf("ERROR: failed to open the file for read\n");
		return -1;
	}
	len = read(fd, read_buf, sizeof(read_buf));
	if (len != strlen(write_msg)) {
		printf("ERROR: failed to read to the file\n");
		return -1;
	}
	ret = strcmp(write_msg, read_buf);
	if (ret != 0) {
		printf("ERROR: the message read from the file is not as it was written\n");
		return -1;
	}

	// unlink
	ret = unlink(link_name);
	if(ret < 0) {
		printf("ERROR: failed to link the file\n");
		return -1;
	}

	// stat
	struct stat stat_buf;
	ret = stat(link_name, &stat_buf);
	if(!(ret < 0 && errno == ENOENT)) {
		printf("ERROR: stat on \"%s\" should return ENOENT", link_name);
		return -1;
	}

	// rename
	ret = rename(file_name, link_name);
	if(ret < 0) {
		printf("ERROR: failed to rename the file");
		return -1;
	}

	// stat
	ret = stat(file_name, &stat_buf);
	if(!(ret < 0 && errno == ENOENT)) {
		printf("ERROR: stat on \"%s\" should return ENOENT", file_name);
		return -1;
	}
	ret = stat(link_name, &stat_buf);
	if(ret < 0) {
		printf("ERROR: failed to stat the file");
		return -1;
	}

    printf("link, unlink, rename test successful\n");
    return 0;
}