#include <pwd.h>
#include <grp.h>
#include <stdio.h>
#include <errno.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
unsigned int r_flag;

int (*chown_func)(const char *pathname, uid_t owner, gid_t group);
int (*stat_func)(const char *restrict pathname, struct stat *restrict statbuf);
long gid;
long uid;

int get_stat(const char *path, struct stat *stat_path) {
	if (stat_func(path, stat_path)) {
		fprintf(stderr, "chown: unable to stat %s: %s\n", path, strerror(errno));
		return 1;
	}

	return 0;
}

char *make_path(const char *src, const char *dst) {
	size_t len = strlen(src) + strlen(dst) + 2;
	char *full_path = malloc(len + 1);
	if (full_path == NULL) {
		fprintf(stderr, "chown: malloc() returned NULL\n");
		return NULL;
	}

	snprintf(full_path, len, "%s/%s", src, dst);
	return full_path;
}

int change(const char *file) {
	struct stat old_file;
	if (get_stat(file, &old_file))
		return 1;

	if (chown_func(file, uid, gid) == 0) {
		struct stat new_file;
		if (get_stat(file, &new_file))
			return 1;

		if (old_file.st_gid != new_file.st_gid || old_file.st_uid != new_file.st_uid)
			return 0;

		fprintf(stderr, "chown: %s unchanged\n", file);
	}

	else
		fprintf(stderr, "chown: unable to chown %s: %s\n", file, strerror(errno));

	return 1;
}

int cntree(const char *dst) {
	int ret = change(dst);


	struct stat stat_path;
	if (get_stat(dst, &stat_path))
		return 1;

	if (!S_ISDIR(stat_path.st_mode) || !r_flag)
		return ret;

	DIR *dir = opendir(dst);
	if (dir == NULL) {
		fprintf(stderr, "chown: %s: Can`t open directory\n", dst);
		return 1;
	}

	struct dirent *ep;
	while ((ep = readdir(dir)) != NULL) {
		if (!strcmp(ep->d_name, ".") || !strcmp(ep->d_name, ".."))
			continue;

		char *full_path = make_path(dst, ep->d_name);
		if (full_path == NULL)
			continue;

		if (cntree(full_path))
			ret = 1;

		free(full_path);
	}

	closedir(dir);
	return ret;
}

void get_owner(const char *arg) {
	char *group = strchr(arg, ':');

	unsigned int g_flag = 1;
	unsigned int u_flag = 1;
	if (group == arg)
		u_flag = 0;

	else if (!group)
		g_flag = 0;

	if (g_flag) {
		group[0] = '\0';
		group++;

		struct group *grp = getgrnam(group);
		if (!grp) {
			fprintf(stderr, "chown: invalid group: %s\n", group);
			exit(1);
		}

		gid = grp->gr_gid;
	}

	if (u_flag) {
		struct passwd *pwd = getpwnam(arg);
		if (!pwd) {
			fprintf(stderr, "chown: invalid user: %s\n", arg);
			exit(1);
		}

		uid = pwd->pw_gid;
	}
}

int main(const int argc, char **argv) {
	chown_func = lchown;
	stat_func = stat;

	int i;
	for (i = 1; i < argc; i++) {
		if (argv[i][0] != '-')
			break;

		else if (!strcmp(argv[i], "-r"))
			r_flag = 1;

		else if (!strcmp(argv[i], "-H")) {
			chown_func = chown;
			stat_func = stat;
		}

		else if (!strcmp(argv[i], "--help")) {
			printf("chown [-H (if a command line argument is a symbolic link)] [-r (recursive)] [owner]:[group] [file file2...]\n");
			return 0;
		}
	}

	if (argc - i == 0) {
		fprintf(stderr, "chown: missing operand\n");
		return 1;
	}

	gid = -1;
	uid = -1;
	get_owner(argv[i++]);

	if (argc - i == 0) {
		fprintf(stderr, "chown: missing operand\n");
		return 1;
	}

	int ret = 0;
	for (; i < argc; i++)
		if (cntree(argv[i]))
			ret = 1;

	return ret;
}