/* $Id$ */
/*
   Copyright (C) 2008 - 2010 by Thomas Baumhauer <thomas.baumhauer@NOSPAMgmail.com>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License version 2
   or at your option any later version.
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY.

   See the COPYING file for more details.
*/

#include <iostream>
#include <string>

#include "md5.hpp"
#include "hash.hpp"

namespace util {

const std::string itoa64 = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" ;
const std::string hash_prefix = "$H$";

unsigned char* md5(const std::string& input) {
	MD5 md5_worker;
	md5_worker.update((unsigned char*) input.c_str(), input.size());
	md5_worker.finalize();
	return md5_worker.raw_digest();
}

int get_iteration_count(const std::string& hash) {
	return itoa64.find_first_of(hash[3]);
}

std::string get_salt(const std::string& hash) {
	return hash.substr(4,8);
}

bool is_valid_hash(const std::string& hash) {
	if(hash.size() != 34) return false;
	if(hash.substr(0,3) != hash_prefix) return false;

	const int iteration_count = get_iteration_count(hash);
	if(iteration_count < 7 || iteration_count > 30) return false;

	return true;
}

std::string encode_hash(unsigned char* input) {
	std::string encoded_hash;

	unsigned int i = 0;
	do {
		unsigned value = input[i++];
		encoded_hash.append(itoa64.substr(value & 0x3f,1));
		if(i < 16)
			value |= (int)input[i] << 8;
		encoded_hash.append(itoa64.substr((value >> 6) & 0x3f,1));
		if(i++ >= 16)
			break;
		if(i < 16)
			value |= (int)input[i] << 16;
		encoded_hash.append(itoa64.substr((value >> 12) & 0x3f,1));
		if(i++ >= 16)
			break;
		encoded_hash.append(itoa64.substr((value >> 18) & 0x3f,1));
	} while (i < 16);

	return encoded_hash;
}

std::string create_hash(const std::string& password, const std::string& salt, int iteration_count) {
	iteration_count = 1 << iteration_count;

	unsigned char* output = md5(salt + password);
	do {
		output = md5(std::string((char *) output, (char *) output + 16).append(password));
	} while(--iteration_count);

	return encode_hash(output);
}

bool password_matches_hash(const std::string& password, const std::string& hash) {
	return hash.substr(12,34) == create_hash(password, get_salt(hash), get_iteration_count(hash));
}

} // namespace util