#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#include <netinet/in.h>
#include <arpa/inet.h>
#include "md5.h"

static void
usage()
{
    fprintf(stderr, "usage: ipmunge [-s data] templ mask\n");
	exit(2);
}

static int
md5_file(FILE* f, MD5_CTX *ctx)
{
	#define BUF_SIZE 128
	unsigned char buf[BUF_SIZE];
	int r, read = 0;

	while(!feof(f))
	{
		r = fread(buf, 1, BUF_SIZE, f);

		if(ferror(f))
			err(1, "couldn't read input data");

		read += r;
		MD5Update(ctx, buf, r);
	}

	return read;
}

int
main(int argc, char* argv[])
{
	MD5_CTX ctx;
	struct in_addr templ;
	struct in_addr mask;
	struct in_addr result;
	const char* data = NULL;
	int ch, l, i;
	int count = 1;

	memset(&result, 0, sizeof(result));
	memset(&mask, 0, sizeof(mask));
	memset(&templ, 0, sizeof(templ));

	while((ch = getopt(argc, argv, "s:")) != -1)
	{
		switch(ch)
		{
		case 's':
			data = optarg;
			break;
        case '?':
        default:
            usage();
            break;
		}
	}

	argc -= optind;
	argv += optind;

	if(argc != 2)
		usage();

	if(!inet_aton(argv[0], &templ))
		errx(1, "invalid template address: %s", argv[0]);

	if(!inet_aton(argv[1], &mask))
		errx(1, "invalid template mask: %s", argv[1]);

	MD5Init(&ctx);

	if(data)
	{
		l = strlen(data);
		MD5Update(&ctx, data, l);
	}
	else
	{
		l = md5_file(stdin, &ctx);
	}

	if(l > 0)
	{
		unsigned char md[MD5_DIGEST_LENGTH];
		MD5Final(md, &ctx);
		memcpy(&result, md, sizeof(result));
	}

	result.s_addr = result.s_addr & ~mask.s_addr;
	result.s_addr = result.s_addr | (templ.s_addr & mask.s_addr);

	printf("%s\n", inet_ntoa(result));

	return 0;
}