#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/mman.h>
#include <sys/stat.h>

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, "cp: malloc() returned NULL\n");
		return NULL;
	}

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

int write_buffer(int mode, int ifd, int ofd, const char *dst) {
	off_t len = lseek(ifd, 0, SEEK_END);
	if (len < 0)
		return 1;

	else if (len == 0) {
		int fd = open(dst, O_CREAT | O_RDONLY, mode);
		if (fd < 0)
			return 1;

		close(fd);
		return 0;
	}

	if (ftruncate(ofd, len) < 0)
		return 1;

	void *buf_in = mmap(NULL, len, PROT_READ, MAP_SHARED, ifd, 0);
	if (buf_in == MAP_FAILED)
		return 1;

	void *buf_out = mmap(NULL, len, PROT_WRITE, MAP_SHARED, ofd, 0);
	if (buf_out == MAP_FAILED)
		return 1;

	memcpy(buf_out, buf_in, len);

	if (munmap(buf_in, len) || munmap(buf_out, len))
		return 1;

	return 0;

}

int copy(int mode, const char *src, const char *dst) {
	int ifd = open(src, O_RDONLY);
	if (ifd < 0)
		return 1;

	int ofd = open(dst, O_CREAT | O_TRUNC | O_RDWR, mode);
	if (ofd < 0) {
		close(ifd);
		return 1;
	}

	if (write_buffer(mode, ifd, ofd, dst))
		fprintf(stderr, "cp: (%s %s) %s\n", src, dst, strerror(errno));

	close(ifd);
	close(ofd);
	return 0;
}

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

	return 0;
}

int cptree(const char *src, const char *dst) {
	struct stat stat_path;
	if (get_stat(src, &stat_path))
		return 1;

	if (S_ISDIR(stat_path.st_mode) == 0) {
		if (copy(stat_path.st_mode, src, dst)) {
			fprintf(stderr, "cp: %s: copy() failed (%s)\n", src, strerror(errno));
			return 1;
		}

		return 0;
	}

	else if (mkdir(dst, 0777) < 0)
		fprintf(stderr, "cp: %s\n", strerror(errno));

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

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

		char *src_path = make_path(src, ep->d_name);
		if (src_path == NULL)
			continue;

		char *dst_path = make_path(dst, ep->d_name);
		if (dst_path == NULL) {
			free(src_path);
			continue;
		}

		cptree(src_path, dst_path);

		free(src_path);
		free(dst_path);
	}

	closedir(dir);
	return 0;
}

int main(const int argc, char **argv) {

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

		else if (!strcmp(argv[i], "--help")) {
			printf("cp [Src] [Dst]\n");
			return 0;
		}
	}

	int ret = 0;
	if (argc - i == 2)
		ret = cptree(argv[i], argv[argc - 1]);

	else {
		for (; i < argc - 1; i++) {
			char *new_path = make_path(argv[argc - 1], basename(argv[i]));
			if (new_path == NULL)
				return 1;

			if (cptree(argv[i], new_path))
				ret = 1;

			free(new_path);
		}
	}

	return ret;
}