added WIP 'custom_dimension' to the API

docs/scarpet/api/BlocksAndWorldAccess.md

@@ -730,3 +730,25 @@ All generated structures will retain their properties, like mob spawning, howeve
 itself has certain rules to spawn mobs, like plopping a nether fortress in the overworld will not spawn nether mobs, 
 because nether mobs can spawn only in the nether, but plopped in the nether - will behave like a valid nether fortress.
 
+### `custom_dimension(name, seed?)`
+
+Ensures the dimension with the given `'name'` is available and configured with the given seed. It merely sets the world
+generator settings to the overworld, and the optional custom seed (or using current world seed, if not provided). 
+
+If the dimension with this name already exists, returns `false` and does nothing.
+
+Created dimension with `custom_dimension` only exist till the game restart (same with the datapacks, if removed), but
+all the world data should be saved. If custom dimension is re-created next time the app is loaded it will be using
+the existing world content. This means that it is up to the programmer to make sure the custom dimensions settings
+are stored in app data and restored when app reloads and wants to use previous worlds. Since vanilla game only keeps
+track of world data, not the world settings, if the dimension hasn't been yet configured via `custom_dimension` and
+the app hasn't yet initalized their dimension, the players will be positioned in the overworld at the same coordinates.
+
+List of custom dimensions (to be used in the likes of `/execute in <dim>`) is only send to the clients when joining the 
+game, meaning custom worlds created after a player has joined will not be suggested in vanilla commands, but running
+vanilla commands on them will be successful. Its due to the fact that datapacks with dimensions are always loaded
+with the game and assumed not changing.
+
+`custom_dimension` is experimental and considered a WIP. More customization options besides the seed will be added in
+the future.
+

src/main/java/carpet/fakes/MinecraftServerInterface.java

@@ -1,11 +1,16 @@
 package carpet.fakes;
 
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.registry.RegistryKey;
+import net.minecraft.world.World;
 import net.minecraft.world.level.storage.LevelStorage;
 
+import java.util.Map;
 import java.util.function.BooleanSupplier;
 
 public interface MinecraftServerInterface
 {
     void forceTick(BooleanSupplier sup);
     LevelStorage.Session getCMSession();
+    Map<RegistryKey<World>, ServerWorld> getCMWorlds();
 }

src/main/java/carpet/mixins/MinecraftServer_scarpetMixin.java

@@ -4,8 +4,11 @@ import carpet.CarpetServer;
 import carpet.fakes.MinecraftServerInterface;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.ServerTask;
+import net.minecraft.server.world.ServerWorld;
 import net.minecraft.util.Util;
+import net.minecraft.util.registry.RegistryKey;
 import net.minecraft.util.thread.ReentrantThreadExecutor;
+import net.minecraft.world.World;
 import net.minecraft.world.level.storage.LevelStorage;
 import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
@@ -14,6 +17,7 @@ import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
+import java.util.Map;
 import java.util.function.BooleanSupplier;
 
 import static carpet.script.CarpetEventServer.Event.ENDER_TICK;
@@ -38,6 +42,8 @@ public abstract class MinecraftServer_scarpetMixin extends ReentrantThreadExecut
 
     @Shadow @Final protected LevelStorage.Session session;
 
+    @Shadow @Final private Map<RegistryKey<World>, ServerWorld> worlds;
+
     @Override
     public void forceTick(BooleanSupplier isAhead)
     {
@@ -52,6 +58,12 @@ public abstract class MinecraftServer_scarpetMixin extends ReentrantThreadExecut
         return session;
     }
 
+    @Override
+    public Map<RegistryKey<World>, ServerWorld> getCMWorlds()
+    {
+        return worlds;
+    }
+
     @Inject(method = "tick", at = @At(
             value = "CONSTANT",
             args = "stringValue=tallying"

src/main/java/carpet/script/CarpetExpression.java

@@ -26,6 +26,7 @@ import carpet.script.exception.ExitStatement;
 import carpet.script.exception.ExpressionException;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.utils.ShapeDispatcher;
+import carpet.script.utils.WorldTools;
 import carpet.script.value.BlockValue;
 import carpet.script.value.EntityValue;
 import carpet.script.value.FormattedTextValue;
@@ -1292,6 +1293,33 @@ public class CarpetExpression
             return (_c, _t) -> ret;
         });
 
+        this.expr.addLazyFunction("custom_dimension", -1, (c, t, lv) ->
+        {
+            if (lv.size() == 0) throw new InternalExpressionException("'custom_dimension' requires at least one argument");
+            CarpetContext cc = (CarpetContext)c;
+            String worldKey = lv.get(0).evalValue(c).getString();
+
+            Long seed = null;
+            if (lv.size() > 1)
+            {
+                String seedKey = lv.get(1).evalValue(c).getString();
+                try
+                {
+                    seed = Long.parseLong(seedKey);
+                }
+                catch (NumberFormatException ignored)
+                {
+                    throw new InternalExpressionException("Incorrect number format for seed: " + seedKey);
+                }
+            }
+
+            boolean success = WorldTools.createWorld(cc.s.getMinecraftServer(), worldKey, seed);
+            if (!success) return LazyValue.FALSE;
+            CarpetServer.settingsManager.notifyPlayersCommandsChanged();
+            return LazyValue.TRUE;
+        });
+
+
         this.expr.addLazyFunction("reset_chunk", -1, (c, t, lv) ->
         {
             CarpetContext cc = (CarpetContext)c;

src/main/java/carpet/script/utils/WorldTools.java

@@ -1,15 +1,36 @@
 package carpet.script.utils;
 
 import carpet.fakes.MinecraftServerInterface;
+import com.google.common.collect.ImmutableList;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldGenerationProgressListener;
 import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.Util;
 import net.minecraft.util.math.ChunkPos;
+import net.minecraft.util.registry.Registry;
+import net.minecraft.util.registry.RegistryKey;
+import net.minecraft.util.registry.SimpleRegistry;
+import net.minecraft.world.World;
+import net.minecraft.world.biome.source.BiomeAccess;
+import net.minecraft.world.border.WorldBorderListener;
 import net.minecraft.world.chunk.ChunkStatus;
+import net.minecraft.world.dimension.DimensionOptions;
+import net.minecraft.world.dimension.DimensionType;
+import net.minecraft.world.gen.GeneratorOptions;
+import net.minecraft.world.gen.Spawner;
+import net.minecraft.world.gen.chunk.ChunkGenerator;
+import net.minecraft.world.level.ServerWorldProperties;
+import net.minecraft.world.level.UnmodifiableLevelProperties;
 import net.minecraft.world.storage.RegionFile;
 
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.List;
 import java.util.Map;
+import java.util.Random;
+import java.util.Set;
 
 public class WorldTools
 {
@@ -43,4 +64,68 @@ public class WorldTools
         catch (IOException ignored) { }
         return true;
     }
+
+    public static boolean createWorld(MinecraftServer server, String worldKey, Long seed)
+    {
+        Identifier worldId = new Identifier(worldKey);
+        ServerWorld overWorld = server.getOverworld();
+
+        Set<RegistryKey<World>> worldKeys = server.getWorldRegistryKeys();
+        for (RegistryKey<World> worldRegistryKey : worldKeys)
+        {
+            if (worldRegistryKey.getValue().equals(worldId))
+            {
+                // world with this id already exists
+                return false;
+            }
+        }
+        ServerWorldProperties serverWorldProperties = server.getSaveProperties().getMainWorldProperties();
+        GeneratorOptions generatorOptions = server.getSaveProperties().getGeneratorOptions();
+        boolean bl = generatorOptions.isDebugWorld();
+        long l = generatorOptions.getSeed();
+        long m = BiomeAccess.hashSeed(l);
+        List<Spawner> list = ImmutableList.of();
+        SimpleRegistry<DimensionOptions> simpleRegistry = generatorOptions.getDimensions();
+        DimensionOptions dimensionOptions = simpleRegistry.get(DimensionOptions.OVERWORLD);
+        ChunkGenerator chunkGenerator2;
+        DimensionType dimensionType2;
+        if (dimensionOptions == null) {
+            dimensionType2 = (DimensionType)server.getRegistryManager().getDimensionTypes().getOrThrow(DimensionType.OVERWORLD_REGISTRY_KEY);
+            chunkGenerator2 = GeneratorOptions.createOverworldGenerator(server.getRegistryManager().get(Registry.BIOME_KEY), server.getRegistryManager().get(Registry.NOISE_SETTINGS_WORLDGEN), (new Random()).nextLong());
+        } else {
+            dimensionType2 = dimensionOptions.getDimensionType();
+            chunkGenerator2 = dimensionOptions.getChunkGenerator();
+        }
+
+        RegistryKey<World> customWorld = RegistryKey.of(Registry.DIMENSION, worldId);
+
+        chunkGenerator2 = GeneratorOptions.createOverworldGenerator(server.getRegistryManager().get(Registry.BIOME_KEY), server.getRegistryManager().get(Registry.NOISE_SETTINGS_WORLDGEN), (seed==null)?l:seed);
+
+        ServerWorld serverWorld = new ServerWorld(
+                server,
+                Util.getMainWorkerExecutor(),
+                ((MinecraftServerInterface) server).getCMSession(),
+                new UnmodifiableLevelProperties(server.getSaveProperties(), serverWorldProperties),
+                customWorld,
+                dimensionType2,
+                NOOP_LISTENER,
+                chunkGenerator2,
+                bl,
+                (seed==null)?l:seed,
+                list,
+                false);
+        overWorld.getWorldBorder().addListener(new WorldBorderListener.WorldBorderSyncer(serverWorld.getWorldBorder()));
+        ((MinecraftServerInterface) server).getCMWorlds().put(customWorld, serverWorld);
+        return true;
+    }
+
+
+    private static class NoopWorldGenerationProgressListener implements WorldGenerationProgressListener
+    {
+        @Override public void start(ChunkPos spawnPos) { }
+        @Override public void setChunkStatus(ChunkPos pos, ChunkStatus status) { }
+        @Override public void stop() { }
+    }
+
+    private static final WorldGenerationProgressListener NOOP_LISTENER = new NoopWorldGenerationProgressListener();
 }