Code/net/minecraft/world/level/block/piston/PistonStructureResolver.java

package net.minecraft.world.level.block.piston;

import com.google.common.collect.Lists;
import java.util.List;
import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.world.level.Level;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.material.PushReaction;

public class PistonStructureResolver {
    public static final int MAX_PUSH_DEPTH = 12;
    private final Level level;
    private final BlockPos pistonPos;
    private final boolean extending;
    private final BlockPos startPos;
    private final Direction pushDirection;
    private final List<BlockPos> toPush = Lists.newArrayList();
    private final List<BlockPos> toDestroy = Lists.newArrayList();
    private final Direction pistonDirection;

    public PistonStructureResolver(Level p_60418_, BlockPos p_60419_, Direction p_60420_, boolean p_60421_) {
        this.level = p_60418_;
        this.pistonPos = p_60419_;
        this.pistonDirection = p_60420_;
        this.extending = p_60421_;
        if (p_60421_) {
            this.pushDirection = p_60420_;
            this.startPos = p_60419_.relative(p_60420_);
        } else {
            this.pushDirection = p_60420_.getOpposite();
            this.startPos = p_60419_.relative(p_60420_, 2);
        }
    }

    public boolean resolve() {
        this.toPush.clear();
        this.toDestroy.clear();
        BlockState blockstate = this.level.getBlockState(this.startPos);
        if (!PistonBaseBlock.isPushable(blockstate, this.level, this.startPos, this.pushDirection, false, this.pistonDirection)) {
            if (this.extending && blockstate.getPistonPushReaction() == PushReaction.DESTROY) {
                this.toDestroy.add(this.startPos);
                return true;
            } else {
                return false;
            }
        } else if (!this.addBlockLine(this.startPos, this.pushDirection)) {
            return false;
        } else {
            for (int i = 0; i < this.toPush.size(); i++) {
                BlockPos blockpos = this.toPush.get(i);
                if (isSticky(this.level.getBlockState(blockpos)) && !this.addBranchingBlocks(blockpos)) {
                    return false;
                }
            }

            return true;
        }
    }

    private static boolean isSticky(BlockState p_155938_) {
        return p_155938_.is(Blocks.SLIME_BLOCK) || p_155938_.is(Blocks.HONEY_BLOCK);
    }

    private static boolean canStickToEachOther(BlockState p_155940_, BlockState p_155941_) {
        if (p_155940_.is(Blocks.HONEY_BLOCK) && p_155941_.is(Blocks.SLIME_BLOCK)) {
            return false;
        } else {
            return p_155940_.is(Blocks.SLIME_BLOCK) && p_155941_.is(Blocks.HONEY_BLOCK) ? false : isSticky(p_155940_) || isSticky(p_155941_);
        }
    }

    private boolean addBlockLine(BlockPos p_60434_, Direction p_60435_) {
        BlockState blockstate = this.level.getBlockState(p_60434_);
        if (blockstate.isAir()) {
            return true;
        } else if (!PistonBaseBlock.isPushable(blockstate, this.level, p_60434_, this.pushDirection, false, p_60435_)) {
            return true;
        } else if (p_60434_.equals(this.pistonPos)) {
            return true;
        } else if (this.toPush.contains(p_60434_)) {
            return true;
        } else {
            int i = 1;
            if (i + this.toPush.size() > 12) {
                return false;
            } else {
                while (isSticky(blockstate)) {
                    BlockPos blockpos = p_60434_.relative(this.pushDirection.getOpposite(), i);
                    BlockState blockstate1 = blockstate;
                    blockstate = this.level.getBlockState(blockpos);
                    if (blockstate.isAir()
                        || !canStickToEachOther(blockstate1, blockstate)
                        || !PistonBaseBlock.isPushable(blockstate, this.level, blockpos, this.pushDirection, false, this.pushDirection.getOpposite())
                        || blockpos.equals(this.pistonPos)) {
                        break;
                    }

                    if (++i + this.toPush.size() > 12) {
                        return false;
                    }
                }

                int l = 0;

                for (int i1 = i - 1; i1 >= 0; i1--) {
                    this.toPush.add(p_60434_.relative(this.pushDirection.getOpposite(), i1));
                    l++;
                }

                int j1 = 1;

                while (true) {
                    BlockPos blockpos1 = p_60434_.relative(this.pushDirection, j1);
                    int j = this.toPush.indexOf(blockpos1);
                    if (j > -1) {
                        this.reorderListAtCollision(l, j);

                        for (int k = 0; k <= j + l; k++) {
                            BlockPos blockpos2 = this.toPush.get(k);
                            if (isSticky(this.level.getBlockState(blockpos2)) && !this.addBranchingBlocks(blockpos2)) {
                                return false;
                            }
                        }

                        return true;
                    }

                    blockstate = this.level.getBlockState(blockpos1);
                    if (blockstate.isAir()) {
                        return true;
                    }

                    if (!PistonBaseBlock.isPushable(blockstate, this.level, blockpos1, this.pushDirection, true, this.pushDirection) || blockpos1.equals(this.pistonPos)) {
                        return false;
                    }

                    if (blockstate.getPistonPushReaction() == PushReaction.DESTROY) {
                        this.toDestroy.add(blockpos1);
                        return true;
                    }

                    if (this.toPush.size() >= 12) {
                        return false;
                    }

                    this.toPush.add(blockpos1);
                    l++;
                    j1++;
                }
            }
        }
    }

    private void reorderListAtCollision(int p_60424_, int p_60425_) {
        List<BlockPos> list = Lists.newArrayList();
        List<BlockPos> list1 = Lists.newArrayList();
        List<BlockPos> list2 = Lists.newArrayList();
        list.addAll(this.toPush.subList(0, p_60425_));
        list1.addAll(this.toPush.subList(this.toPush.size() - p_60424_, this.toPush.size()));
        list2.addAll(this.toPush.subList(p_60425_, this.toPush.size() - p_60424_));
        this.toPush.clear();
        this.toPush.addAll(list);
        this.toPush.addAll(list1);
        this.toPush.addAll(list2);
    }

    private boolean addBranchingBlocks(BlockPos p_60432_) {
        BlockState blockstate = this.level.getBlockState(p_60432_);

        for (Direction direction : Direction.values()) {
            if (direction.getAxis() != this.pushDirection.getAxis()) {
                BlockPos blockpos = p_60432_.relative(direction);
                BlockState blockstate1 = this.level.getBlockState(blockpos);
                if (canStickToEachOther(blockstate1, blockstate) && !this.addBlockLine(blockpos, direction)) {
                    return false;
                }
            }
        }

        return true;
    }

    public Direction getPushDirection() {
        return this.pushDirection;
    }

    public List<BlockPos> getToPush() {
        return this.toPush;
    }

    public List<BlockPos> getToDestroy() {
        return this.toDestroy;
    }
}