ViaLoader/src/main/java/net/raphimc/vialoader/netty/VLLegacyPipeline.java

/*
 * This file is part of ViaLoader - https://github.com/RaphiMC/ViaLoader
 * Copyright (C) 2020-2024 RK_01/RaphiMC and contributors
 *
 * 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.raphimc.vialoader.netty;

import com.viaversion.viaversion.api.connection.UserConnection;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import net.raphimc.viabedrock.api.protocol.BedrockBaseProtocol;
import net.raphimc.viabedrock.netty.BatchLengthCodec;
import net.raphimc.viabedrock.netty.PacketEncapsulationCodec;
import net.raphimc.vialegacy.api.protocol.PreNettyBaseProtocol;
import net.raphimc.vialegacy.netty.PreNettyLengthPrepender;
import net.raphimc.vialegacy.netty.PreNettyLengthRemover;
import net.raphimc.vialoader.netty.viabedrock.DisconnectHandler;
import net.raphimc.vialoader.netty.viabedrock.RakMessageEncapsulationCodec;
import net.raphimc.vialoader.util.VersionEnum;

public abstract class VLLegacyPipeline extends ChannelInboundHandlerAdapter {

    public static final String VIA_DECODER_NAME = "via-decoder";
    public static final String VIA_ENCODER_NAME = "via-encoder";

    public static final String VIALEGACY_PRE_NETTY_LENGTH_PREPENDER_NAME = "vialegacy-pre-netty-length-prepender";
    public static final String VIALEGACY_PRE_NETTY_LENGTH_REMOVER_NAME = "vialegacy-pre-netty-length-remover";

    public static final String VIABEDROCK_DISCONNECT_HANDLER_NAME = "viabedrock-disconnect-handler";
    public static final String VIABEDROCK_FRAME_ENCAPSULATION_HANDLER_NAME = "viabedrock-frame-encapsulation";
    public static final String VIABEDROCK_PACKET_ENCAPSULATION_HANDLER_NAME = "viabedrock-packet-encapsulation";

    protected final UserConnection user;
    protected final VersionEnum version;

    public VLLegacyPipeline(final UserConnection user, final VersionEnum version) {
        this.user = user;
        this.version = version;
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) {
        ctx.pipeline().addBefore(this.packetDecoderName(), VIA_DECODER_NAME, this.createViaDecoder());
        ctx.pipeline().addBefore(this.packetEncoderName(), VIA_ENCODER_NAME, this.createViaEncoder());

        if (this.version.isOlderThanOrEqualTo(VersionEnum.r1_6_4)) {
            this.user.getProtocolInfo().getPipeline().add(PreNettyBaseProtocol.INSTANCE);
            ctx.pipeline().addBefore(this.lengthSplitterName(), VIALEGACY_PRE_NETTY_LENGTH_PREPENDER_NAME, this.createViaLegacyPreNettyLengthPrepender());
            ctx.pipeline().addBefore(this.lengthPrependerName(), VIALEGACY_PRE_NETTY_LENGTH_REMOVER_NAME, this.createViaLegacyPreNettyLengthRemover());
        } else if (this.version.equals(VersionEnum.bedrockLatest)) {
            this.user.getProtocolInfo().getPipeline().add(BedrockBaseProtocol.INSTANCE);
            ctx.pipeline().addBefore(this.lengthSplitterName(), VIABEDROCK_DISCONNECT_HANDLER_NAME, this.createViaBedrockDisconnectHandler());
            ctx.pipeline().addBefore(this.lengthSplitterName(), VIABEDROCK_FRAME_ENCAPSULATION_HANDLER_NAME, this.createViaBedrockFrameEncapsulationHandler());
            this.replaceLengthSplitter(ctx, this.createViaBedrockBatchLengthCodec());
            ctx.pipeline().remove(this.lengthPrependerName());
            ctx.pipeline().addBefore(VIA_DECODER_NAME, VIABEDROCK_PACKET_ENCAPSULATION_HANDLER_NAME, this.createViaBedrockPacketEncapsulationHandler());
        }
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (CompressionReorderEvent.INSTANCE.equals(evt)) {
            final int decoderIndex = ctx.pipeline().names().indexOf(decompressName());
            if (decoderIndex == -1) return;

            if (decoderIndex > ctx.pipeline().names().indexOf(VIA_DECODER_NAME)) {
                final ChannelHandler decoder = ctx.pipeline().get(VIA_DECODER_NAME);
                final ChannelHandler encoder = ctx.pipeline().get(VIA_ENCODER_NAME);

                ctx.pipeline().remove(decoder);
                ctx.pipeline().remove(encoder);

                ctx.pipeline().addAfter(decompressName(), VIA_DECODER_NAME, decoder);
                ctx.pipeline().addAfter(compressName(), VIA_ENCODER_NAME, encoder);
            }
        }

        super.userEventTriggered(ctx, evt);
    }

    protected ChannelHandler createViaDecoder() {
        return new ViaDecoder(this.user);
    }

    protected ChannelHandler createViaEncoder() {
        return new ViaEncoder(this.user);
    }

    protected ChannelHandler createViaLegacyPreNettyLengthPrepender() {
        return new PreNettyLengthPrepender(this.user);
    }

    protected ChannelHandler createViaLegacyPreNettyLengthRemover() {
        return new PreNettyLengthRemover(this.user);
    }

    protected ChannelHandler createViaBedrockDisconnectHandler() {
        return new DisconnectHandler();
    }

    protected ChannelHandler createViaBedrockFrameEncapsulationHandler() {
        return new RakMessageEncapsulationCodec();
    }

    protected ChannelHandler createViaBedrockBatchLengthCodec() {
        return new BatchLengthCodec();
    }

    protected ChannelHandler createViaBedrockPacketEncapsulationHandler() {
        return new PacketEncapsulationCodec();
    }

    protected void replaceLengthSplitter(final ChannelHandlerContext ctx, final ChannelHandler handler) {
        ctx.pipeline().replace(this.lengthSplitterName(), this.lengthSplitterName(), handler);
    }

    protected abstract String decompressName();

    protected abstract String compressName();

    protected abstract String packetDecoderName();

    protected abstract String packetEncoderName();

    protected abstract String lengthSplitterName();

    protected abstract String lengthPrependerName();

}