/*
 * This file is part of LanternServer, licensed under the MIT License (MIT).
 *
 * Copyright (c) LanternPowered <https://www.lanternpowered.org>
 * Copyright (c) SpongePowered <https://www.spongepowered.org>
 * Copyright (c) contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the Software), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
/*
 * Copyright (c) 2011-2014 Glowstone - Tad Hardesty
 * Copyright (c) 2010-2011 Lightstone - Graham Edgecombe
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.lanternpowered.server.network.pipeline;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageCodec;
import org.lanternpowered.server.game.Lantern;

import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;
import java.util.List;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.IvParameterSpec;

public final class MessageEncryptionHandler extends MessageToMessageCodec<ByteBuf, ByteBuf> {

    private final CryptBuf encodeBuf;
    private final CryptBuf decodeBuf;

    public MessageEncryptionHandler(SecretKey sharedSecret) {
        try {
            this.encodeBuf = new CryptBuf(Cipher.ENCRYPT_MODE, sharedSecret);
            this.decodeBuf = new CryptBuf(Cipher.DECRYPT_MODE, sharedSecret);
        } catch (GeneralSecurityException e) {
            // should never happen
            Lantern.getLogger().error("Failed to initialize encrypted channel", e);
            throw new AssertionError("Failed to initialize encrypted channel", e);
        }
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
        this.encodeBuf.crypt(msg, out);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
        this.decodeBuf.crypt(msg, out);
    }

    private static class CryptBuf {

        private final Cipher cipher;

        private CryptBuf(int mode, SecretKey sharedSecret) throws GeneralSecurityException {
            this.cipher = Cipher.getInstance("AES/CFB8/NoPadding");
            this.cipher.init(mode, sharedSecret, new IvParameterSpec(sharedSecret.getEncoded()));
        }

        void crypt(ByteBuf msg, List<Object> out) {
            final ByteBuffer outBuffer = ByteBuffer.allocate(msg.readableBytes());

            try {
                this.cipher.update(msg.nioBuffer(), outBuffer);
            } catch (ShortBufferException e) {
                throw new AssertionError("Encryption buffer was too short", e);
            }

            outBuffer.flip();
            out.add(Unpooled.wrappedBuffer(outBuffer));
        }
    }

}