#define _DEFAULT_SOURCE
#define _POSIX_C_SOURCE 200809L

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

void create_vfs(void) {
	if (mkdir("/proc", 0755) != 0 && errno != EEXIST) {
		perror("proc");
	}
	if (mkdir("/sys", 0755) != 0 && errno != EEXIST) {
		perror("sys");
	}
	if (mkdir("/dev", 0755) != 0 && errno != EEXIST) {
		perror("dev");
	}
	if (mkdir("/run", 0755) != 0 && errno != EEXIST) {
		perror("run");
	}
}

void mount_vfs(void) {
	if (mount("proc", "/proc", "proc",
			  MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, NULL) != 0 &&
		errno != EBUSY) {
		perror("mount /proc");
	}

	if (mount("sys", "/sys", "sysfs",
			  MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, NULL) != 0 &&
		errno != EBUSY) {
		perror("mount /sys");
	}

	if (mount("dev", "/dev", "devtmpfs", MS_NOSUID | MS_RELATIME, "mode=755") !=
			0 &&
		errno != EBUSY) {
		perror("mount /dev");
	}

	if (mount("run", "/run", "tmpfs", MS_NOSUID | MS_NODEV | MS_RELATIME,
			  "mode=755") != 0 &&
		errno != EBUSY) {
		perror("mount /run");
	}

	mkdir("/dev/pts", 0755);
	mkdir("/dev/shm", 1777);

	if (mount("devpts", "/dev/pts", "devpts",
			  MS_NOSUID | MS_NOEXEC | MS_RELATIME, "gid=5,mode=620") != 0 &&
		errno != EBUSY) {
		perror("mount /dev/pts");
	}

	if (mount("shm", "/dev/shm", "tmpfs", MS_NOSUID | MS_NODEV | MS_RELATIME,
			  "mode=1777") != 0 &&
		errno != EBUSY) {
		perror("mount /dev/shm");
	}
}

void set_hostname(void) {
	char buf[256];
	int fd = open("/etc/hostname", O_RDONLY);

	if (fd < 0) {
		perror("open /etc/hostname");
		return;
	}

	ssize_t bytes_read = read(fd, buf, sizeof(buf) - 1);
	close(fd);

	if (bytes_read > 0) {
		buf[bytes_read] = '\0';
		size_t len = strcspn(buf, "\r\n ");
		buf[len] = '\0';

		if (sethostname(buf, len) != 0) {
			perror("sethostname");
		}
	}
}

int main(void) {
	create_vfs();
	mount_vfs();

	int fd = open("/dev/console", O_RDWR);

	if (fd >= 0) {
		dup2(fd, 0);
		dup2(fd, 1);
		dup2(fd, 2);
		if (fd > 2) {
			close(fd);
		}
	} else {
		perror("console");
	}

	set_hostname();

	return 0;
}