Code/net/minecraft/world/level/block/DoubleBlockCombiner.java

package net.minecraft.world.level.block;

import java.util.function.BiPredicate;
import java.util.function.Function;
import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.world.level.LevelAccessor;
import net.minecraft.world.level.block.entity.BlockEntity;
import net.minecraft.world.level.block.entity.BlockEntityType;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.block.state.properties.Property;

public class DoubleBlockCombiner {
    public static <S extends BlockEntity> DoubleBlockCombiner.NeighborCombineResult<S> combineWithNeigbour(
        BlockEntityType<S> p_52823_,
        Function<BlockState, DoubleBlockCombiner.BlockType> p_52824_,
        Function<BlockState, Direction> p_52825_,
        Property<Direction> p_366105_,
        BlockState p_52827_,
        LevelAccessor p_52828_,
        BlockPos p_52829_,
        BiPredicate<LevelAccessor, BlockPos> p_52830_
    ) {
        S s = p_52823_.getBlockEntity(p_52828_, p_52829_);
        if (s == null) {
            return DoubleBlockCombiner.Combiner::acceptNone;
        } else if (p_52830_.test(p_52828_, p_52829_)) {
            return DoubleBlockCombiner.Combiner::acceptNone;
        } else {
            DoubleBlockCombiner.BlockType doubleblockcombiner$blocktype = p_52824_.apply(p_52827_);
            boolean flag = doubleblockcombiner$blocktype == DoubleBlockCombiner.BlockType.SINGLE;
            boolean flag1 = doubleblockcombiner$blocktype == DoubleBlockCombiner.BlockType.FIRST;
            if (flag) {
                return new DoubleBlockCombiner.NeighborCombineResult.Single<>(s);
            } else {
                BlockPos blockpos = p_52829_.relative(p_52825_.apply(p_52827_));
                BlockState blockstate = p_52828_.getBlockState(blockpos);
                if (blockstate.is(p_52827_.getBlock())) {
                    DoubleBlockCombiner.BlockType doubleblockcombiner$blocktype1 = p_52824_.apply(blockstate);
                    if (doubleblockcombiner$blocktype1 != DoubleBlockCombiner.BlockType.SINGLE
                        && doubleblockcombiner$blocktype != doubleblockcombiner$blocktype1
                        && blockstate.getValue(p_366105_) == p_52827_.getValue(p_366105_)) {
                        if (p_52830_.test(p_52828_, blockpos)) {
                            return DoubleBlockCombiner.Combiner::acceptNone;
                        }

                        S s1 = p_52823_.getBlockEntity(p_52828_, blockpos);
                        if (s1 != null) {
                            S s2 = flag1 ? s : s1;
                            S s3 = flag1 ? s1 : s;
                            return new DoubleBlockCombiner.NeighborCombineResult.Double<>(s2, s3);
                        }
                    }
                }

                return new DoubleBlockCombiner.NeighborCombineResult.Single<>(s);
            }
        }
    }

    public static enum BlockType {
        SINGLE,
        FIRST,
        SECOND;
    }

    public interface Combiner<S, T> {
        T acceptDouble(S p_52843_, S p_52844_);

        T acceptSingle(S p_52842_);

        T acceptNone();
    }

    public interface NeighborCombineResult<S> {
        <T> T apply(DoubleBlockCombiner.Combiner<? super S, T> p_52845_);

        public static final class Double<S> implements DoubleBlockCombiner.NeighborCombineResult<S> {
            private final S first;
            private final S second;

            public Double(S p_52849_, S p_52850_) {
                this.first = p_52849_;
                this.second = p_52850_;
            }

            @Override
            public <T> T apply(DoubleBlockCombiner.Combiner<? super S, T> p_52852_) {
                return p_52852_.acceptDouble(this.first, this.second);
            }
        }

        public static final class Single<S> implements DoubleBlockCombiner.NeighborCombineResult<S> {
            private final S single;

            public Single(S p_52855_) {
                this.single = p_52855_;
            }

            @Override
            public <T> T apply(DoubleBlockCombiner.Combiner<? super S, T> p_52857_) {
                return p_52857_.acceptSingle(this.single);
            }
        }
    }
}