Minestom/src/main/java/net/minestom/server/utils/PacketUtils.java

package net.minestom.server.utils;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import net.minestom.server.network.packet.server.ServerPacket;
import net.minestom.server.utils.binary.BinaryWriter;
import org.jetbrains.annotations.NotNull;

/**
 * Class used to write packets.
 */
public final class PacketUtils {

    private PacketUtils() {

    }

    /**
     * Writes a {@link ServerPacket} into a {@link ByteBuf}.
     *
     * @param buf    the recipient of {@code packet}
     * @param packet the packet to write into {@code buf}
     */
    public static void writePacket(@NotNull ByteBuf buf, @NotNull ServerPacket packet) {

        final ByteBuf packetBuffer = getPacketBuffer(packet);

        writePacket(buf, packetBuffer, packet.getId());
    }

    /**
     * Writes a {@link ServerPacket} into a newly created {@link ByteBuf}.
     *
     * @param packet the packet to write
     * @return a {@link ByteBuf} containing {@code packet}
     */
    @NotNull
    public static ByteBuf writePacket(@NotNull ServerPacket packet) {
        final ByteBuf packetBuffer = getPacketBuffer(packet);

        // Add 5 for the packet id and for the packet size
        final int size = packetBuffer.writerIndex() + 5 + 5;
        ByteBuf buffer = Unpooled.buffer(size);

        writePacket(buffer, packetBuffer, packet.getId());

        return buffer;
    }

    /**
     * Writes a packet buffer into {@code buf}.
     *
     * @param buf          the buffer which will receive the packet id/data
     * @param packetBuffer the buffer containing the raw packet data
     * @param packetId     the packet id
     */
    private static void writePacket(@NotNull ByteBuf buf, @NotNull ByteBuf packetBuffer, int packetId) {
        Utils.writeVarIntBuf(buf, packetId);
        buf.writeBytes(packetBuffer);
    }

    /**
     * Gets the buffer representing the raw packet data.
     *
     * @param packet the packet to write
     * @return the {@link ByteBuf} containing the raw packet data
     */
    @NotNull
    private static ByteBuf getPacketBuffer(@NotNull ServerPacket packet) {
        BinaryWriter writer = new BinaryWriter();
        packet.write(writer);

        return writer.getBuffer();
    }

}