WIP: prototype item teleportation to random dimensions, with safe landing.

src/main/java/moe/nekojimi/dimensionwalker/DimensionwalkerItem.java

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+package moe.nekojimi.dimensionwalker;
+
+import com.mojang.logging.LogUtils;
+import net.minecraft.client.renderer.item.ItemProperties;
+import net.minecraft.core.Registry;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.commands.TeleportCommand;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResultHolder;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.CreativeModeTab;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.NetherPortalBlock;
+import net.minecraftforge.registries.DeferredRegister;
+import net.minecraftforge.registries.ForgeRegistries;
+import net.minecraftforge.registries.RegistryObject;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Collections;
+import java.util.Random;
+import java.util.logging.Logger;
+import java.util.stream.StreamSupport;
+
+public class DimensionwalkerItem extends Item
+{
+    private static DeferredRegister<Level> DIMENSION_REGISTER = DeferredRegister.create(Registry.DIMENSION_REGISTRY, DimensionwalkerMod.MODID);
+
+    private static final org.slf4j.Logger LOGGER = LogUtils.getLogger();
+
+    public DimensionwalkerItem() {
+        super(new Item.Properties().tab(CreativeModeTab.TAB_TOOLS));
+    }
+
+    @Override
+    public @NotNull InteractionResultHolder<ItemStack> use(Level level, @NotNull Player player, @NotNull InteractionHand hand)
+    {
+        if (!level.isClientSide())
+        {
+            MinecraftServer server = level.getServer();
+            if (server != null)
+            {
+                Iterable<ServerLevel> allLevels = server.getAllLevels();
+                List<ServerLevel> levels = new java.util.ArrayList<>(StreamSupport.stream(allLevels.spliterator(), false).toList());
+                levels.remove((ServerLevel) level);
+                ServerLevel destination = levels.get(new Random().nextInt(levels.size()));
+//            server.getPlayerList().getPlayer(player.getUUID()).teleportTo(destination, player.getX(), player.getY(), player.getZ(), player.getYRot(), player.getXRot());
+                ServerPlayer serverPlayer = server.getPlayerList().getPlayer(player.getUUID());
+                if (serverPlayer != null)
+                    serverPlayer.changeDimension(destination, DimensionwalkerTeleporter.instance());
+                else
+                    LOGGER.warn("Can't teleport, serverPlayer == null");
+            }
+            else
+                LOGGER.warn("Can't teleport, server == null");
+        }
+        return super.use(level, player, hand);
+    }
+}

src/main/java/moe/nekojimi/dimensionwalker/DimensionwalkerMod.java

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+package moe.nekojimi.dimensionwalker;
+
+import com.mojang.logging.LogUtils;
+import net.minecraft.client.Minecraft;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent;
+import net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent;
+import net.minecraftforge.event.server.ServerStartingEvent;
+import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
+import net.minecraftforge.registries.DeferredRegister;
+import net.minecraftforge.registries.ForgeRegistries;
+import net.minecraftforge.registries.RegistryObject;
+import org.slf4j.Logger;
+
+// The value here should match an entry in the META-INF/mods.toml file
+@Mod(DimensionwalkerMod.MODID)
+public class DimensionwalkerMod
+{
+    // Define mod id in a common place for everything to reference
+    public static final String MODID = "examplemod";
+    // Directly reference a slf4j logger
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public static final DeferredRegister<Item> ITEMS = DeferredRegister.create(ForgeRegistries.ITEMS, MODID);
+
+    public static final RegistryObject<Item> DIMENSIONWALKER_GLOVE_ITEM = ITEMS.register("dimensionwalker_glove", ()->new DimensionwalkerItem() );
+
+    public DimensionwalkerMod()
+    {
+        IEventBus modEventBus = FMLJavaModLoadingContext.get().getModEventBus();
+
+        // Register the commonSetup method for modloading
+        modEventBus.addListener(this::commonSetup);
+
+        // Register the Deferred Register to the mod event bus so items get registered
+        ITEMS.register(modEventBus);
+
+        // Register ourselves for server and other game events we are interested in
+        MinecraftForge.EVENT_BUS.register(this);
+    }
+
+    private void commonSetup(final FMLCommonSetupEvent event)
+    {
+        // Some common setup code
+        LOGGER.info("HELLO FROM COMMON SETUP");
+        LOGGER.info("DIRT BLOCK >> {}", ForgeRegistries.BLOCKS.getKey(Blocks.DIRT));
+    }
+
+    // You can use SubscribeEvent and let the Event Bus discover methods to call
+    @SubscribeEvent
+    public void onServerStarting(ServerStartingEvent event)
+    {
+        // Do something when the server starts
+        LOGGER.info("HELLO from server starting");
+
+        Iterable<ServerLevel> levels = event.getServer().getAllLevels();
+        levels.forEach(serverLevel ->
+        {
+            LOGGER.info(serverLevel.dimension().toString() + " scale: " + serverLevel.dimensionType().coordinateScale());
+        });
+    }
+
+}

src/main/java/moe/nekojimi/dimensionwalker/DimensionwalkerTeleporter.java

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+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;
+    }
+}

src/main/java/moe/nekojimi/dimensionwalker/Peachy.java

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+package moe.nekojimi.dimensionwalker;
+
+public class Peachy
+{
+    Peachy()
+    {
+        System.out.println("I'm Peachy!");
+    }
+}