package org.redrune.network.world.codec.io;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import org.redrune.cache.crypto.ISAACCipher;
import org.redrune.network.NetworkConstants;
import org.redrune.network.NetworkSession;
import org.redrune.network.world.WorldSession;
import org.redrune.network.world.packet.Packet;
import org.redrune.network.world.packet.Packet.PacketType;
import org.redrune.utility.rs.NetworkUtils;

import java.util.List;

/**
 * Decodes a received packet.
 *
 * @author Tyluur <itstyluur@gmail.com>
 * @author Emperor
 * @since 7/19/17
 */
public class RSPacketDecoder extends ByteToMessageDecoder {

    /**
     * Constructs a new {@code RS2GameDecoder} {@code Object}.
     *
     * @param session
     *      The networkSession.
     */
    public RSPacketDecoder(NetworkSession session) {
        session.getChannel().attr(NetworkConstants.SESSION_KEY).setIfAbsent(session);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        while (in.readableBytes() > 0 && session.getChannel().isActive()) {
            // the session
            WorldSession session = (WorldSession) ctx.channel().attr(NetworkConstants.SESSION_KEY).get();

            // the cipher
            final ISAACCipher cipher = session.getInCipher();

            // the opcode of the packet
            int opcode = (in.readByte() - cipher.take()) & 0xFF;

            if (opcode < 0 || opcode >= NetworkUtils.PACKET_SIZES.length) {
                System.err.println("packet_opcode [" + opcode + "] out of bounds");
                in.discardReadBytes();
                return;
            }
            int length = NetworkUtils.PACKET_SIZES[opcode];
            System.err.println("received_packet [opcode=" + opcode + ", length=" + length + "]");
            switch (length) {
                case -1:
                    length = in.readByte() & 0xFF;
                    break;
                case -2:
                    length = in.readShort() & 0xFFFF;
                    break;
                case -3:
                    length = in.readInt();
                    break;
                case -4:
                    length = in.readableBytes();
                    System.err.println("unknown_packet_size [opcode=" + opcode + ", length=" + length + ", guessedLength=" + in.readableBytes() + "]");
                    break;
            }
            byte[] payload = new byte[length];
            in.readBytes(payload);
            out.add(new Packet(opcode, PacketType.STANDARD, Unpooled.wrappedBuffer(payload)));
        }
    }

}