Code/net/minecraft/world/level/lighting/BlockLightEngine.java

package net.minecraft.world.level.lighting;

import com.google.common.annotations.VisibleForTesting;
import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.core.SectionPos;
import net.minecraft.world.level.ChunkPos;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.chunk.LightChunk;
import net.minecraft.world.level.chunk.LightChunkGetter;

public final class BlockLightEngine extends LightEngine<BlockLightSectionStorage.BlockDataLayerStorageMap, BlockLightSectionStorage> {
    private final BlockPos.MutableBlockPos mutablePos = new BlockPos.MutableBlockPos();

    public BlockLightEngine(LightChunkGetter p_75492_) {
        this(p_75492_, new BlockLightSectionStorage(p_75492_));
    }

    @VisibleForTesting
    public BlockLightEngine(LightChunkGetter p_278252_, BlockLightSectionStorage p_278255_) {
        super(p_278252_, p_278255_);
    }

    @Override
    protected void checkNode(long p_285169_) {
        long i = SectionPos.blockToSection(p_285169_);
        if (this.storage.storingLightForSection(i)) {
            BlockState blockstate = this.getState(this.mutablePos.set(p_285169_));
            int j = this.getEmission(p_285169_, blockstate);
            int k = this.storage.getStoredLevel(p_285169_);
            if (j < k) {
                this.storage.setStoredLevel(p_285169_, 0);
                this.enqueueDecrease(p_285169_, LightEngine.QueueEntry.decreaseAllDirections(k));
            } else {
                this.enqueueDecrease(p_285169_, PULL_LIGHT_IN_ENTRY);
            }

            if (j > 0) {
                this.enqueueIncrease(p_285169_, LightEngine.QueueEntry.increaseLightFromEmission(j, isEmptyShape(blockstate)));
            }
        }
    }

    @Override
    protected void propagateIncrease(long p_285500_, long p_285410_, int p_285492_) {
        BlockState blockstate = null;

        for (Direction direction : PROPAGATION_DIRECTIONS) {
            if (LightEngine.QueueEntry.shouldPropagateInDirection(p_285410_, direction)) {
                long i = BlockPos.offset(p_285500_, direction);
                if (this.storage.storingLightForSection(SectionPos.blockToSection(i))) {
                    int j = this.storage.getStoredLevel(i);
                    int k = p_285492_ - 1;
                    if (k > j) {
                        this.mutablePos.set(i);
                        BlockState blockstate1 = this.getState(this.mutablePos);
                        int l = p_285492_ - this.getOpacity(blockstate1);
                        if (l > j) {
                            if (blockstate == null) {
                                blockstate = LightEngine.QueueEntry.isFromEmptyShape(p_285410_)
                                    ? Blocks.AIR.defaultBlockState()
                                    : this.getState(this.mutablePos.set(p_285500_));
                            }

                            if (!this.shapeOccludes(blockstate, blockstate1, direction)) {
                                this.storage.setStoredLevel(i, l);
                                if (l > 1) {
                                    this.enqueueIncrease(i, LightEngine.QueueEntry.increaseSkipOneDirection(l, isEmptyShape(blockstate1), direction.getOpposite()));
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    @Override
    protected void propagateDecrease(long p_285435_, long p_285230_) {
        int i = LightEngine.QueueEntry.getFromLevel(p_285230_);

        for (Direction direction : PROPAGATION_DIRECTIONS) {
            if (LightEngine.QueueEntry.shouldPropagateInDirection(p_285230_, direction)) {
                long j = BlockPos.offset(p_285435_, direction);
                if (this.storage.storingLightForSection(SectionPos.blockToSection(j))) {
                    int k = this.storage.getStoredLevel(j);
                    if (k != 0) {
                        if (k <= i - 1) {
                            BlockState blockstate = this.getState(this.mutablePos.set(j));
                            int l = this.getEmission(j, blockstate);
                            this.storage.setStoredLevel(j, 0);
                            if (l < k) {
                                this.enqueueDecrease(j, LightEngine.QueueEntry.decreaseSkipOneDirection(k, direction.getOpposite()));
                            }

                            if (l > 0) {
                                this.enqueueIncrease(j, LightEngine.QueueEntry.increaseLightFromEmission(l, isEmptyShape(blockstate)));
                            }
                        } else {
                            this.enqueueIncrease(j, LightEngine.QueueEntry.increaseOnlyOneDirection(k, false, direction.getOpposite()));
                        }
                    }
                }
            }
        }
    }

    private int getEmission(long p_285243_, BlockState p_284973_) {
        int i = p_284973_.getLightEmission();
        return i > 0 && this.storage.lightOnInSection(SectionPos.blockToSection(p_285243_)) ? i : 0;
    }

    @Override
    public void propagateLightSources(ChunkPos p_285274_) {
        this.setLightEnabled(p_285274_, true);
        LightChunk lightchunk = this.chunkSource.getChunkForLighting(p_285274_.x, p_285274_.z);
        if (lightchunk != null) {
            lightchunk.findBlockLightSources((p_360638_, p_360639_) -> {
                int i = p_360639_.getLightEmission();
                this.enqueueIncrease(p_360638_.asLong(), LightEngine.QueueEntry.increaseLightFromEmission(i, isEmptyShape(p_360639_)));
            });
        }
    }
}