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

// System
#include <unistd.h>

// zlib
#include <zlib.h>

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

unsigned long
get_filesize(FILE *file)
{
	(void) fseek(file, 0, SEEK_END);
	unsigned long size = ftell(file);
	(void) fseek(file, 0, SEEK_SET);
	return size;
}

void
do_compress(FILE *in_file, FILE *out_file, int compress_level)
{
	const unsigned long in_size = get_filesize(in_file);

	(void) fwrite(&in_size, sizeof in_size, 1, out_file);

	unsigned char *in_data = malloc(in_size);
	(void) fread(in_data, 1, in_size, in_file);

	unsigned long  out_size = compressBound(in_size);
	unsigned char *out_data = malloc(out_size);

	const int error = compress2(out_data, &out_size, in_data, in_size, compress_level);

	if ( !error ) {
		(void) fwrite(out_data, 1, out_size, out_file);
	}
	else {
		printf("Error: %d\n", error);
	}

	free(out_data);
	free(in_data);
}

void
do_uncompress(FILE *in_file, FILE *out_file)
{
	const unsigned long in_size = get_filesize(in_file);

	unsigned char *in_data = malloc(in_size);
	(void) fread(in_data, 1, in_size, in_file);

	unsigned long  out_size = *(unsigned long *) in_data;
	unsigned char *out_data = malloc(out_size);

	unsigned long tmp = in_size - sizeof(unsigned long);

	const int error = uncompress2(out_data,
	                              &out_size,
	                              in_data + sizeof(unsigned long),
	                              &tmp);

	if ( !error ) {
		(void) fwrite(out_data, 1, out_size, out_file);
	}
	else {
		printf("Error: %d\n", error);
	}

	free(out_data);
	free(in_data);
}

int
main(int argc, char *argv[])
{
	int decompress     = 0;
	int compress_level = 5;

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

		case 'l':
			compress_level = 9;
			break;

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

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

	FILE *in_file  = fopen(argv[0], "rb");
	FILE *out_file = fopen(argv[1], "wb");

	if ( !decompress ) {
		do_compress(in_file, out_file, compress_level);
	}
	else {
		do_uncompress(in_file, out_file);
	}

	(void) fclose(out_file);
	(void) fclose(in_file);

	return EXIT_SUCCESS;
}