#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define CAT_USAGE "Usage: cat [-u] [file...]\n"
#define STDIN_ARG "-"
#define BUFFER_SIZE 20480

static void close_file(int fd) {
	if (fd != STDIN_FILENO) {
		close(fd);
	}
}

static bool print_file_content(const char *path) {
	char buffer[BUFFER_SIZE];
	int input = -1;
	ssize_t ret = -1;

	if (strcmp(path, STDIN_ARG) == 0) {
		input = STDIN_FILENO;
	} else {
		if ((input = open(path, O_RDONLY)) == -1) {
			fprintf(stderr,"Can't open file '%s': %s\n", path, strerror(errno));
			return false;
		}
	}

	do {
		ret = read(input, buffer, BUFFER_SIZE);
		if (ret > 0) {
			write(STDOUT_FILENO, buffer, ret);
		}
	} while (ret > 0);

	if (ret == -1) {
		fprintf(stderr, "Failed to read file '%s': %s\n", path, strerror(errno));
	}

	close_file(input);

	return ret == 0;
}

int cat_main(int argc, char *argv[]) {
	int opt = 0;
	bool ret = false;

	while ((opt = getopt(argc, argv, "u")) != -1) {
		if (opt != 'u') {
			perror(CAT_USAGE);
			return EXIT_FAILURE;
		}
	}

	for (int i = optind; i < argc; i++) {
		ret = print_file_content(argv[i]);
		if (!ret) {
			break;
		}
	}

	/* If no argument was provided, we use stdin by default */
	if (argc - optind == 0) {
		ret = print_file_content(STDIN_ARG);
	}

	return ret ? EXIT_SUCCESS : EXIT_FAILURE;
}