/*******************************************************************************
 * Copyright (C) 2013 JMaNGOS <http://jmangos.org/>
 * 
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package org.jmangos.auth.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;

import org.jmangos.commons.model.AccountInfo;
import org.jmangos.commons.network.model.NettyNetworkChannel;
import org.jmangos.commons.utils.BigNumber;

/**
 * The Class AccountUtils.
 */
public class AccountUtils {

    /** The Constant N. */
    public static final BigNumber N = new BigNumber(
            "894B645E89E1535BBDAD5B8B290650530801B18EBFBF5E8FAB3C82872A3E9BB7");

    /** The Constant g. */
    public static final BigNumber g = new BigNumber("7");

    /** The Constant k. */
    public static final BigNumber k = new BigNumber("3");

    /**
     * Sets the vs fields.
     * 
     * @param Ir
     *        the ir
     * @return the hash map
     */
    public static HashMap<String, BigNumber> calculateVSFields(final String Ir) {

        final BigNumber I = new BigNumber(Ir);
        final HashMap<String, BigNumber> res = new HashMap<String, BigNumber>();
        final byte[] hash = I.asByteArray(20);

        final int length = hash.length;
        for (int i = 0; i < (length / 2); i++) {
            final byte j = hash[i];
            hash[i] = hash[length - 1 - i];
            hash[length - 1 - i] = j;
        }
        // System.out.println("passhash:"+new BigInteger(1,
        // hash).toString(16).toUpperCase());
        final BigNumber s = new BigNumber();
        s.setRand(32);
        // System.out.println("s: " + s.asHexStr());

        MessageDigest sha = null;
        try {
            sha = MessageDigest.getInstance("SHA-1");
        } catch (final NoSuchAlgorithmException e) {
            e.printStackTrace();
            return null;
        }
        sha.update(s.asByteArray(32));
        sha.update(hash);
        final BigNumber x = new BigNumber();
        x.setBinary(sha.digest());
        // System.out.println("x: " + x.asHexStr());
        final BigNumber verifier = g.modPow(x, N);
        // System.out.println("v: " + verifier.asHexStr());
        res.put("v", verifier);
        res.put("s", s);
        return res;
    }

    /**
     * Gets the b.
     * 
     * @param v
     *        the v
     * @param con
     *        the con
     * @return the b
     */
    public static BigNumber getB(final BigNumber v, final NettyNetworkChannel con) {

        final BigNumber b = new BigNumber();
        b.setRand(19);
        ((AccountInfo) con.getChanneledObject()).setB(b);
        final BigNumber gmod = g.modPow(b, N);
        return ((v.multiply(k)).add(gmod)).mod(N);

    }
}