/*
 * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
 * Copyright (C) 2016-2021 ViaVersion 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 com.viaversion.viaversion.velocity.handlers;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import io.netty.handler.codec.MessageToMessageDecoder;
import com.viaversion.viaversion.api.data.UserConnection;
import com.viaversion.viaversion.exception.CancelCodecException;
import com.viaversion.viaversion.exception.CancelDecoderException;
import com.viaversion.viaversion.util.PipelineUtil;

import java.lang.reflect.InvocationTargetException;
import java.util.List;

@ChannelHandler.Sharable
public class VelocityDecodeHandler extends MessageToMessageDecoder<ByteBuf> {
    private final UserConnection info;
    private boolean handledCompression;
    private boolean skipDoubleTransform;

    public VelocityDecodeHandler(UserConnection info) {
        this.info = info;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf bytebuf, List<Object> out) throws Exception {
        if (skipDoubleTransform) {
            skipDoubleTransform = false;
            out.add(bytebuf.retain());
            return;
        }

        if (!info.checkIncomingPacket()) throw CancelDecoderException.generate(null);
        if (!info.shouldTransformPacket()) {
            out.add(bytebuf.retain());
            return;
        }

        ByteBuf transformedBuf = ctx.alloc().buffer().writeBytes(bytebuf);
        try {
            boolean needsCompress = handleCompressionOrder(ctx, transformedBuf);

            info.transformIncoming(transformedBuf, CancelDecoderException::generate);

            if (needsCompress) {
                recompress(ctx, transformedBuf);
                skipDoubleTransform = true;
            }
            out.add(transformedBuf.retain());
        } finally {
            transformedBuf.release();
        }
    }

    private boolean handleCompressionOrder(ChannelHandlerContext ctx, ByteBuf buf) throws InvocationTargetException {
        if (handledCompression) return false;

        int decoderIndex = ctx.pipeline().names().indexOf("compression-decoder");
        if (decoderIndex == -1) return false;
        handledCompression = true;
        if (decoderIndex > ctx.pipeline().names().indexOf("via-decoder")) {
            // Need to decompress this packet due to bad order
            ByteBuf decompressed = (ByteBuf) PipelineUtil.callDecode((MessageToMessageDecoder<?>) ctx.pipeline().get("compression-decoder"), ctx, buf).get(0);
            try {
                buf.clear().writeBytes(decompressed);
            } finally {
                decompressed.release();
            }
            ChannelHandler encoder = ctx.pipeline().get("via-encoder");
            ChannelHandler decoder = ctx.pipeline().get("via-decoder");
            ctx.pipeline().remove(encoder);
            ctx.pipeline().remove(decoder);
            ctx.pipeline().addAfter("compression-encoder", "via-encoder", encoder);
            ctx.pipeline().addAfter("compression-decoder", "via-decoder", decoder);
            return true;
        }
        return false;
    }

    private void recompress(ChannelHandlerContext ctx, ByteBuf buf) throws Exception {
        ByteBuf compressed = ctx.alloc().buffer();
        try {
            PipelineUtil.callEncode((MessageToByteEncoder<?>) ctx.pipeline().get("compression-encoder"), ctx, buf, compressed);
            buf.clear().writeBytes(compressed);
        } finally {
            compressed.release();
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        if (cause instanceof CancelCodecException) return;
        super.exceptionCaught(ctx, cause);
    }
}
