/*
    This file is part of Desu: MapleStory v62 Server Emulator
    Copyright (C) 2014  Zygon <watchmystarz@hotmail.com>

    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 3 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 net.swordie.ms.connection.crypto;

import static net.swordie.ms.connection.crypto.BitTools.multiplyBytes;

/**
 * Artifact from Invictus that improved the old MapleAESOFB by
 * making it easily scaled with session groups while using Apache's 
 * MINA library. Ported over for usage within a Netty setup since it will
 * work exactly the same.
 *
 * @author OdinMS (original author)
 * @author Zygon (ported and modified)
 */
public final class MapleCrypto {

    /**
     * AES cipher used for cryptography.
     *
     * @see AES#encrypt(byte[]) used in this method.
     */
    private AES cipher;
    /**
     * Used for checking the packets being sent and received. These are
     * initialized at the starting part of the program by providing the
     * current version the server is running.
     *
     * @see MapleCrypto#checkPacket(byte[], byte[]) checking packet header using these.
     * @see MapleCrypto#checkPacket(int, byte[]) checking packet header using these.
     * @see MapleCrypto#initialize(short) where the values are initialized.
     */
    private static short gVersion, sVersion, rVersion;
    /**
     * Used for renewing the cryptography seed for sending or receiving 
     * packets.
     *
     */
    public static final int[] SHUFFLE_BYTES = new int[]{0xEC, 0x3F, 0x77, 0xA4, 0x45, 0xD0, 0x71, 0xBF, 0xB7, 0x98, 0x20, 0xFC,
            0x4B, 0xE9, 0xB3, 0xE1, 0x5C, 0x22, 0xF7, 0x0C, 0x44, 0x1B, 0x81, 0xBD, 0x63, 0x8D, 0xD4, 0xC3,
            0xF2, 0x10, 0x19, 0xE0, 0xFB, 0xA1, 0x6E, 0x66, 0xEA, 0xAE, 0xD6, 0xCE, 0x06, 0x18, 0x4E, 0xEB,
            0x78, 0x95, 0xDB, 0xBA, 0xB6, 0x42, 0x7A, 0x2A, 0x83, 0x0B, 0x54, 0x67, 0x6D, 0xE8, 0x65, 0xE7,
            0x2F, 0x07, 0xF3, 0xAA, 0x27, 0x7B, 0x85, 0xB0, 0x26, 0xFD, 0x8B, 0xA9, 0xFA, 0xBE, 0xA8, 0xD7,
            0xCB, 0xCC, 0x92, 0xDA, 0xF9, 0x93, 0x60, 0x2D, 0xDD, 0xD2, 0xA2, 0x9B, 0x39, 0x5F, 0x82, 0x21,
            0x4C, 0x69, 0xF8, 0x31, 0x87, 0xEE, 0x8E, 0xAD, 0x8C, 0x6A, 0xBC, 0xB5, 0x6B, 0x59, 0x13, 0xF1,
            0x04, 0x00, 0xF6, 0x5A, 0x35, 0x79, 0x48, 0x8F, 0x15, 0xCD, 0x97, 0x57, 0x12, 0x3E, 0x37, 0xFF,
            0x9D, 0x4F, 0x51, 0xF5, 0xA3, 0x70, 0xBB, 0x14, 0x75, 0xC2, 0xB8, 0x72, 0xC0, 0xED, 0x7D, 0x68,
            0xC9, 0x2E, 0x0D, 0x62, 0x46, 0x17, 0x11, 0x4D, 0x6C, 0xC4, 0x7E, 0x53, 0xC1, 0x25, 0xC7, 0x9A,
            0x1C, 0x88, 0x58, 0x2C, 0x89, 0xDC, 0x02, 0x64, 0x40, 0x01, 0x5D, 0x38, 0xA5, 0xE2, 0xAF, 0x55,
            0xD5, 0xEF, 0x1A, 0x7C, 0xA7, 0x5B, 0xA6, 0x6F, 0x86, 0x9F, 0x73, 0xE6, 0x0A, 0xDE, 0x2B, 0x99,
            0x4A, 0x47, 0x9C, 0xDF, 0x09, 0x76, 0x9E, 0x30, 0x0E, 0xE4, 0xB2, 0x94, 0xA0, 0x3B, 0x34, 0x1D,
            0x28, 0x0F, 0x36, 0xE3, 0x23, 0xB4, 0x03, 0xD8, 0x90, 0xC8, 0x3C, 0xFE, 0x5E, 0x32, 0x24, 0x50,
            0x1F, 0x3A, 0x43, 0x8A, 0x96, 0x41, 0x74, 0xAC, 0x52, 0x33, 0xF0, 0xD9, 0x29, 0x80, 0xB1, 0x16,
            0xD3, 0xAB, 0x91, 0xB9, 0x84, 0x7F, 0x61, 0x1E, 0xCF, 0xC5, 0xD1, 0x56, 0x3D, 0xCA, 0xF4, 0x05,
            0xC6, 0xE5, 0x08, 0x49};

    /**
     * Constructor for MapleAES. Creates the cipher that will be
     * used for the cryptography segment as well as the lock used for the
     * same segment.
     */
    public MapleCrypto() {
        cipher = new AES();
        // key changes later on in version
        // ---------------------------
        // KEYZ HERE (Locale 8 Version 196 Subversion 2 unk 0)
        //---------------------------
        // 29 B3 88 20
        // F6 BF 02 48
        // 18 5B 76 10
        // 5E DA 0F 87
        // CA 5E CD 9F
        // 5A 0C F5 29
        // 40 D5 9C 7E
        // 61 2F 30 28
        //---------------------------
        // Version 198.1
        //---------------------------
        // 29 23 BE 84
        // E1 6C D6 AE
        // 52 90 49 F1
        // F1 BB E9 EB
        // B3 A6 DB 3C
        // 87 0C 3E 99
        // 24 5E 0D 1C
        // 06 B7 47 DE
        cipher.setKey(new byte[]{
                (byte) 0x29, 0x00, 0x00, 0x00,
                (byte) 0xE1, 0x00, 0x00, 0x00,
                (byte) 0x52, 0x00, 0x00, 0x00,
                (byte) 0xF1, 0x00, 0x00, 0x00,
                (byte) 0xB3, 0x00, 0x00, 0x00,
                (byte) 0x87, 0x00, 0x00, 0x00,
                (byte) 0x24, 0x00, 0x00, 0x00,
                (byte) 0x06, 0x00, 0x00, 0x00
        });
    }

    /**
     * Initializes the send and receive version values for packet
     * checking using the current version.
     *
     * @param v the current version this service is running.
     */
    public static void initialize(short v) {
        gVersion = v;
        sVersion = (short) ((((0xFFFF - v) >>> 8) & 0xFF) | (((0xFFFF - v) << 8) & 0xFF00));
        rVersion = (short) (((v >>> 8) & 0xFF) | ((v << 8) & 0xFF00));
    }

    public static void encInit(int seqSnd, byte[] delta, boolean decrypt) {
        for (int i = 0; i < delta.length; i++) {
            if (decrypt) {
                delta[i] -= (byte) seqSnd;
            } else {
                delta[i] += (byte) seqSnd;
            }
        }
    }

    /**
     * Cryptography segment of MapleAESOFB.
     *
     * @param delta the input data to be put into stage for finalized encryption
     * or to be finally decryption.
     * @param gamma the input seed for this cryptography stage. This value is
     * renewed after each encryption by the corresponding encoder or decoder.
     *
     * @return the bytes having been converted to a stage for encryption or
     * being fully decrypted.
     */
    public byte[] crypt(byte[] delta, byte[] gamma) {
        int a = delta.length;
        int b = 0x5B0;
        int c = 0;
        while (a > 0) {
            byte[] d = multiplyBytes(gamma, 4, 4);
            if (a < b) {
                b = a;
            }
            for (int e = c; e < (c + b); e++) {
                if ((e - c) % d.length == 0) {
                    try {
                        cipher.encrypt(d);
                    } catch (Exception ex) {
                        ex.printStackTrace(); // may eventually want to remove this
                    }
                }
                delta[e] ^= d[(e - c) % d.length];
            }
            c += b;
            a -= b;
            b = 0x5B4;
        }
        return delta;
    }

    /**
     * Creates a header for the new packet to be sent to the opposite
     * end of the session (Server to Channel for this engine). Contains
     * information about the net.swordie.ms.connection.packet: whether or not it is valid and the actual
     * length of the net.swordie.ms.connection.packet.
     *
     * @param delta the input packet length before adding the header.
     * @param gamma the input sending seed before changing it.
     *
     * @return the header to be sent with this net.swordie.ms.connection.packet.
     */
    public static byte[] getHeader(int delta, byte[] gamma) {
        int a = (gamma[3]) & 0xFF;
        a |= (gamma[2] << 8) & 0xFF00;
        a ^= sVersion;
        int b = ((delta << 8) & 0xFF00) | (delta >>> 8);
        int c = a ^ b;
        byte[] ret = new byte[4];
        ret[0] = (byte) ((a >>> 8) & 0xFF);
        ret[1] = (byte) (a & 0xFF);
        ret[2] = (byte) ((c >>> 8) & 0xFF);
        ret[3] = (byte) (c & 0xFF);
        return ret;
    }

    public static byte[] getHeader(int delta, byte[] gamma, short v) {
        int a = (gamma[3]) & 0xFF;
        a |= (gamma[2] << 8) & 0xFF00;
        a ^= sVersion;
        int b = ((delta << 8) & 0xFF00) | (delta >>> 8);
        int c = a ^ b;
        byte[] ret = new byte[4];
        ret[0] = (byte) ((a >>> 8) & 0xFF);
        ret[1] = (byte) (a & 0xFF);
        ret[2] = (byte) ((c >>> 8) & 0xFF);
        ret[3] = (byte) (c & 0xFF);
        return ret;
    }

    /**
     * Gets the length of the packet given the received header.
     *
     * @param delta the packet header to be used to find the packet length.
     *
     * @return the length of the received net.swordie.ms.connection.packet.
     */
    public static int getLength(int delta) {
        int a = ((delta >>> 16) ^ (delta & 0xFFFF));
        a = ((a << 8) & 0xFF00) | ((a >>> 8) & 0xFF);
        return a;
    }

    /**
     * Checks the packet to make sure it is valid and that the session
     * between the net.swordie.ms.client and server is secure and legitimate.
     *
     * @param delta the packet header from the received packet (4 bytes in length).
     * @param gamma the current receive seed.
     *
     * @return whether or not the packet is valid (consequently, if not valid,
     * the session is terminated usually).
     */
    public static boolean checkPacket(byte[] delta, byte[] gamma) {
//        System.out.println("Delta[0] = " + delta[0] + " \t- " + Integer.toBinaryString(delta[0] & 0xFF));
//        System.out.println("Gamme[2] = " + gamma[2] + " \t- " + Integer.toBinaryString(gamma[2] & 0xFF));
//        System.out.println("Delta[1] = " + delta[1] + " \t- " + Integer.toBinaryString(delta[1] & 0xFF));
//        System.out.println("Gamme[3] = " + gamma[3] + " \t- " + Integer.toBinaryString(gamma[3] & 0xFF));
//        System.out.println("Delta[0] ^ gamma[2] = " + Integer.toBinaryString((delta[0] ^ gamma[2]) & 0xFF));
//        System.out.println("Delta[1] ^ gamma[3] = " + Integer.toBinaryString((delta[1] ^ gamma[3]) & 0xFF));
        return ((((delta[0] ^ gamma[2]) & 0xFF) == ((rVersion >>> 8) & 0xFF))
                && (((delta[1] ^ gamma[3]) & 0xFF) == (rVersion & 0xFF)));
    }

    /**
     * @see MapleCrypto#checkPacket(byte[], byte[]) same thing as this method,
     * except that we convert the integer packet header (4 bytes combined)
     * into an array of the first 2 bytes of the integer packet header.
     * @param delta foreign header.
     * @param gamma current receive seed.
     */
    public static boolean checkPacket(int delta, byte[] gamma) {
        byte[] a = new byte[2];
        a[0] = (byte) ((delta >>> 24) & 0xFF);
        a[1] = (byte) ((delta >>> 16) & 0xFF);
        return checkPacket(a, gamma);
    }

    /**
     * Shuffles the seed (or IV) used for this cryptography stage.
     * Almost always called when this cryptography stage is finished since
     * rolling the seed is important to keeping a valid session.
     *
     * @param delta the old seed or IV to be changed into the new one.
     *
     * @return the new seed or IV to be used for this stage of cryptography
     * for the next packet sent or received.
     */
    public static byte[] getNewIv(byte[] delta) {
        byte[] ret = delta;
        int[] nIv = {0xF2, 0x53, 0x50, 0xC6};
        for (int i = 0; i < 4; i++) {
            int a = (ret[i] & 0xFF);
            int b = SHUFFLE_BYTES[a];
            nIv[0] += SHUFFLE_BYTES[nIv[1]] - a;
            nIv[1] -= nIv[2] ^ b;
            nIv[2] ^= SHUFFLE_BYTES[nIv[3]] + a;
            nIv[3] -= nIv[0] - b;
            int c = nIv[0] & 0xFF;
            c |= (nIv[1] << 8) & 0xFF00;
            c |= (nIv[2] << 16) & 0xFF0000;
            c |= (nIv[3] << 24) & 0xFF000000;
            int d = (c << 3) | (c >>> 0x1D);
            nIv[0] = (d & 0xFF);
            nIv[1] = ((d >>> 8) & 0xFF);
            nIv[2] = ((d >>> 16) & 0xFF);
            nIv[3] = ((d >>> 24) & 0xFF);
        }
        for (int i = 0; i < 4; i++) {
            ret[i] = (byte) nIv[i];
        }
        return ret;
    }
}
