package cn.x47.handle;


import cn.x47.model.RIPEntry;
import cn.x47.model.RIPPacket;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.socket.DatagramPacket;
import io.netty.handler.codec.MessageToMessageEncoder;

import java.net.InetSocketAddress;
import java.util.List;

/**
 * 编码器
 */
public class RIPPacketEncoder extends MessageToMessageEncoder<RIPPacket> {
    @Override
    protected void encode(ChannelHandlerContext ctx, RIPPacket msg, List<Object> out) throws Exception {
        ByteBuf buf = ctx.alloc().buffer();
        // 编码命令和版本
        buf.writeByte(msg.getCommand());
        buf.writeByte(msg.getVersion());
        buf.writeShort(msg.getUnused()); // unused 字段

        // 编码路由条目
        for (RIPEntry entry : msg.getEntries()) {
            buf.writeShort(entry.getAddressFamily() & 0xFFFF);
            if (msg.getVersion() == 2) {
                buf.writeShort(entry.getRouteTag() & 0xFFFF);
            }
            buf.writeBytes(entry.getIpAddress().getAddress());

            if (msg.getVersion() == 2) {
                buf.writeBytes(entry.getSubnetMask().getAddress());
                buf.writeBytes(entry.getNextHop().getAddress());
            }

            buf.writeInt((int) entry.getMetric() & 0xFFFFFFFF);
        }

        // 根据版本选择目标地址
        InetSocketAddress recipient;
        if (msg.getVersion() == 1) {
            recipient = new InetSocketAddress("255.255.255.255", 520);
        } else {
            recipient = new InetSocketAddress("224.0.0.9", 520);
        }

        out.add(new DatagramPacket(buf, recipient));
    }

}