Dimensionwalker-Mod/src/main/java/moe/nekojimi/dimensionwalker/DimensionwalkerTeleporter.java

package moe.nekojimi.dimensionwalker;

import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.server.level.ServerLevel;
import net.minecraft.world.entity.Entity;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.border.WorldBorder;
import net.minecraft.world.level.chunk.ChunkAccess;
import net.minecraft.world.level.levelgen.Heightmap;
import net.minecraft.world.level.portal.PortalInfo;
import net.minecraft.world.phys.Vec3;
import net.minecraftforge.common.util.ITeleporter;
import org.apache.http.io.SessionOutputBuffer;
import org.jetbrains.annotations.Nullable;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.function.Function;

public class DimensionwalkerTeleporter implements ITeleporter
{
    private static DimensionwalkerTeleporter INSTANCE = null;

    @Override
    public Entity placeEntity(Entity entity, ServerLevel currentWorld, ServerLevel destWorld, float yaw, Function<Boolean, Entity> repositionEntity)
    {
        return repositionEntity.apply(true);
    }

    @Override
    public @Nullable PortalInfo getPortalInfo(Entity entity, ServerLevel destWorld, Function<ServerLevel, PortalInfo> defaultPortalInfo)
    {
//        return ITeleporter.super.getPortalInfo(entity, destWorld, defaultPortalInfo);

        BlockPos startPos = new BlockPos(entity.getBlockX(), entity.getBlockY(), entity.getBlockZ());
        System.out.println("Current player position: " + startPos);
//        ChunkAccess chunk = destWorld.getChunk(startPos);
//        int maxHeight = startPos.getY();
//        destWorld.get
//        for (Heightmap.Types type : Heightmap.Types.values())
//        {
//            int height = chunk.getHeight(type,startPos.getX(),startPos.getZ());
//            System.out.println("Heightmap type: " + type.name() + ", height: " + height);
//            if (height > maxHeight)
//                maxHeight = height;
//        }
        BlockPos blockPos = findSafePosition(destWorld,startPos);
        if (blockPos == null)
            blockPos = startPos;
        return new PortalInfo(new Vec3((double)blockPos.getX() + 0.5D, (double)blockPos.getY()+1.0D, (double)blockPos.getZ() + 0.5D), entity.getDeltaMovement(), entity.getYRot(), entity.getXRot());
    }

    public @Nullable BlockPos findSafePosition(ServerLevel destWorld, BlockPos startPos)
    {
//        List<BlockPos> candidates = new ArrayList<>();

        WorldBorder worldborder = destWorld.getWorldBorder();
        int worldHeight = Math.min(destWorld.getMaxBuildHeight(), destWorld.getMinBuildHeight() + destWorld.getLogicalHeight()) - 1;

    outer:
        for (BlockPos.MutableBlockPos pos : BlockPos.spiralAround(startPos, 16, Direction.EAST, Direction.SOUTH))
        {
            if (pos == null)
                return null;
            ChunkAccess chunk = destWorld.getChunk(pos);
            int terrainHeight = chunk.getHeight(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,pos.getX(),pos.getZ());
            int freeBlocksAbove = 999;
            int startY = Math.min(worldHeight, terrainHeight);
            System.out.println("Starting search for safe destination at Y=" + startY);
            for (int y = startY; y >= destWorld.getMinBuildHeight(); y--)
            {
                pos.setY(y);

                // check that y is solid
                BlockState blockState = chunk.getBlockState(pos);
                if (blockState.getMaterial().isSolid())
                {
                    if (worldborder.isWithinBounds(pos) && y < worldHeight-3 && freeBlocksAbove >= 2)
                    {
                        System.out.println("Found safe destination! pos: " + pos + " material: " + blockState.getMaterial() + " state: " + blockState);
                        return pos;
//                        candidates.add(pos);
//                        if (candidates.size() >= 16)
//                            break outer;
                    }
                    freeBlocksAbove = 0;
                }
                else if (blockState.getMaterial().isLiquid() || !blockState.isAir())
                {
                    freeBlocksAbove = 0; // liquid blocks aren't free
                }
                else
                {
                    freeBlocksAbove++;
                }
            }
        }
//        if (candidates.size() > 0)
//        {
//            candidates.sort(Comparator.comparingDouble(a -> a.distSqr(startPos)));
//            return candidates.get(0);
//        }

        return null;
    }

    public static ITeleporter instance()
    {
        if (INSTANCE == null)
            INSTANCE = new DimensionwalkerTeleporter();
        return INSTANCE;
    }
}