#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#include <sys/stat.h>

int main(int argc, char *argv[]) {

	int cur, flag_append, flag_force;
	int fd_from, fd_to, mode;
	char buf[1];

	flag_append = 0;
	flag_force  = 0;

	while((cur = getopt(argc, argv, "af")) != -1) {
		switch(cur) {

			case 'a':
				flag_append = 1;
				break;

			case 'f':
				flag_force = 1;
				break;

			default:
				printf("invalid argument\n");
				return 1;
		}
	}

	if(argc - optind != 2) {

		printf("invalid number of args\n");
		return 1;

	} else if(flag_append && flag_force) {

		printf("cannot simultaneously specify overwrite and append\n");
		return 1;
	}

	if(access(argv[optind + 1], F_OK) != -1 && !flag_append && !flag_force) {

		printf("destination file already exists, pass -f to overwrite\n");
		return 1;
	}

	if(flag_force)       mode = O_TRUNC;
	else if(flag_append) mode = O_APPEND;
	else                 mode = O_CREAT;

	fd_from = open(argv[optind], O_RDONLY);
	fd_to   = open(argv[optind + 1], mode | O_WRONLY, S_IRWXU);

	if(fd_from == -1) {

		printf("could not open source file\n");
		return 1;

	} else if(fd_to == -1 && !flag_force && !flag_append) {

		printf("could not create new destination file\n");
		return 1;

	} else if(fd_to == -1) {

	}

	while(read(fd_from, buf, 1) == 1)
		write(fd_to, buf, 1);

	close(fd_from);
	close(fd_to);

	return 0;
}