// Standard C
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// System
#include <unistd.h>

// zlib
#include <zlib.h>

enum { BUFFER_SIZE = 8192 };

static void
usage(void)
{
	(void) fprintf(stderr, "stream [-d] infile outfile\n");
}

static void
error(const char *msg)
{
	perror(msg);
	exit(EXIT_FAILURE);
}

void
do_compress(const char *in_name, const char *out_name, int compress_level)
{
	FILE *in_file = fopen(in_name, "rb");
	if ( in_file == NULL ) {
		error("fopen() on in_file failed");
	}

	char mode[10];
	(void) snprintf(mode, sizeof mode, "wb%d", compress_level);

	gzFile out_file = gzopen(out_name, mode);
	if ( out_file == NULL ) {
		(void) fclose(in_file);
		error("gzopen() on out_file failed");
	}

	unsigned char buffer[BUFFER_SIZE];

	size_t bytes_read = 0;
	while ( (bytes_read = fread(buffer, 1, BUFFER_SIZE, in_file)) != 0 ) {
		gzfwrite(buffer, 1, bytes_read, out_file);
	}

	(void) fclose(in_file);
	gzclose(out_file);
}

void
do_uncompress(const char *in_name, const char *out_name)
{
	gzFile in_file = gzopen(in_name, "rb");
	if ( in_file == NULL ) {
		error("gzopen() on in_file failed");
	}

	FILE *out_file = fopen(out_name, "wb");
	if ( out_file == NULL ) {
		(void) gzclose(in_file);
		error("fopen() on out_file failed");
	}

	unsigned char buffer[BUFFER_SIZE];

	size_t bytes_read = 0;
	while ( (bytes_read = gzfread(buffer, 1, BUFFER_SIZE, in_file)) != 0 ) {
		(void) fwrite(buffer, 1, bytes_read, out_file);
	}

	gzclose(in_file);
	(void) fclose(out_file);
}

int
main(int argc, char *argv[])
{
	enum {
		COMPRESSION_STD  = 5,
		COMPRESSION_BEST = 9
	};

	int decompress     = 0;
	int compress_level = COMPRESSION_STD;

	int opt = 0;
	while ( (opt = getopt(argc, argv, "dl")) != -1 ) {
		switch ( opt ) {
		case 'd':
			decompress = 1;
			break;

		case 'l':
			compress_level = COMPRESSION_BEST;
			break;

		case '?':
		default:
			usage();
			return EXIT_SUCCESS;
		}
	}
	argc -= optind;
	argv += optind;

	if ( argc != 2 ) {
		usage();
		return EXIT_FAILURE;
	}

	if ( !decompress ) {
		do_compress(argv[0], argv[1], compress_level);
	}
	else {
		do_uncompress(argv[0], argv[1]);
	}

	return EXIT_SUCCESS;
}