Code/net/minecraft/server/WorldLoader.java

package net.minecraft.server;

import com.mojang.datafixers.util.Pair;
import com.mojang.logging.LogUtils;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.stream.Stream;
import net.minecraft.commands.Commands;
import net.minecraft.core.HolderLookup;
import net.minecraft.core.LayeredRegistryAccess;
import net.minecraft.core.Registry;
import net.minecraft.core.RegistryAccess;
import net.minecraft.resources.RegistryDataLoader;
import net.minecraft.server.packs.PackResources;
import net.minecraft.server.packs.PackType;
import net.minecraft.server.packs.repository.PackRepository;
import net.minecraft.server.packs.resources.CloseableResourceManager;
import net.minecraft.server.packs.resources.MultiPackResourceManager;
import net.minecraft.server.packs.resources.ResourceManager;
import net.minecraft.tags.TagLoader;
import net.minecraft.world.level.WorldDataConfiguration;
import org.slf4j.Logger;

public class WorldLoader {
    private static final Logger LOGGER = LogUtils.getLogger();

    public static <D, R> CompletableFuture<R> load(
        WorldLoader.InitConfig p_214363_,
        WorldLoader.WorldDataSupplier<D> p_214364_,
        WorldLoader.ResultFactory<D, R> p_214365_,
        Executor p_214366_,
        Executor p_214367_
    ) {
        try {
            Pair<WorldDataConfiguration, CloseableResourceManager> pair = p_214363_.packConfig.createResourceManager();
            CloseableResourceManager closeableresourcemanager = pair.getSecond();
            LayeredRegistryAccess<RegistryLayer> layeredregistryaccess = RegistryLayer.createRegistryAccess();
            List<Registry.PendingTags<?>> list = TagLoader.loadTagsForExistingRegistries(closeableresourcemanager, layeredregistryaccess.getLayer(RegistryLayer.STATIC));
            RegistryAccess.Frozen registryaccess$frozen = layeredregistryaccess.getAccessForLoading(RegistryLayer.WORLDGEN);
            List<HolderLookup.RegistryLookup<?>> list1 = TagLoader.buildUpdatedLookups(registryaccess$frozen, list);
            RegistryAccess.Frozen registryaccess$frozen1 = RegistryDataLoader.load(closeableresourcemanager, list1, RegistryDataLoader.WORLDGEN_REGISTRIES);
            List<HolderLookup.RegistryLookup<?>> list2 = Stream.concat(list1.stream(), registryaccess$frozen1.listRegistries()).toList();
            RegistryAccess.Frozen registryaccess$frozen2 = RegistryDataLoader.load(closeableresourcemanager, list2, RegistryDataLoader.DIMENSION_REGISTRIES);
            WorldDataConfiguration worlddataconfiguration = pair.getFirst();
            HolderLookup.Provider holderlookup$provider = HolderLookup.Provider.create(list2.stream());
            WorldLoader.DataLoadOutput<D> dataloadoutput = p_214364_.get(
                new WorldLoader.DataLoadContext(closeableresourcemanager, worlddataconfiguration, holderlookup$provider, registryaccess$frozen2)
            );
            LayeredRegistryAccess<RegistryLayer> layeredregistryaccess1 = layeredregistryaccess.replaceFrom(
                RegistryLayer.WORLDGEN, registryaccess$frozen1, dataloadoutput.finalDimensions
            );
            return ReloadableServerResources.loadResources(
                    closeableresourcemanager,
                    layeredregistryaccess1,
                    list,
                    worlddataconfiguration.enabledFeatures(),
                    p_214363_.commandSelection(),
                    p_214363_.functionCompilationLevel(),
                    p_214366_,
                    p_214367_
                )
                .whenComplete((p_214370_, p_214371_) -> {
                    if (p_214371_ != null) {
                        closeableresourcemanager.close();
                    }
                })
                .thenApplyAsync(p_358549_ -> {
                    p_358549_.updateStaticRegistryTags();
                    return p_214365_.create(closeableresourcemanager, p_358549_, layeredregistryaccess1, dataloadoutput.cookie);
                }, p_214367_);
        } catch (Exception exception) {
            return CompletableFuture.failedFuture(exception);
        }
    }

    public record DataLoadContext(ResourceManager resources, WorldDataConfiguration dataConfiguration, HolderLookup.Provider datapackWorldgen, RegistryAccess.Frozen datapackDimensions) {
    }

    public record DataLoadOutput<D>(D cookie, RegistryAccess.Frozen finalDimensions) {
    }

    public record InitConfig(WorldLoader.PackConfig packConfig, Commands.CommandSelection commandSelection, int functionCompilationLevel) {
    }

    public record PackConfig(PackRepository packRepository, WorldDataConfiguration initialDataConfig, boolean safeMode, boolean initMode) {
        public Pair<WorldDataConfiguration, CloseableResourceManager> createResourceManager() {
            WorldDataConfiguration worlddataconfiguration = MinecraftServer.configurePackRepository(this.packRepository, this.initialDataConfig, this.initMode, this.safeMode);
            List<PackResources> list = this.packRepository.openAllSelected();
            CloseableResourceManager closeableresourcemanager = new MultiPackResourceManager(PackType.SERVER_DATA, list);
            return Pair.of(worlddataconfiguration, closeableresourcemanager);
        }
    }

    @FunctionalInterface
    public interface ResultFactory<D, R> {
        R create(CloseableResourceManager p_214408_, ReloadableServerResources p_214409_, LayeredRegistryAccess<RegistryLayer> p_248844_, D p_214411_);
    }

    @FunctionalInterface
    public interface WorldDataSupplier<D> {
        WorldLoader.DataLoadOutput<D> get(WorldLoader.DataLoadContext p_251042_);
    }
}