Code/net/minecraft/server/packs/CompositePackResources.java

package net.minecraft.server.packs;

import com.google.common.collect.Lists;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.server.packs.metadata.MetadataSectionType;
import net.minecraft.server.packs.resources.IoSupplier;

public class CompositePackResources implements PackResources {
    private final PackResources primaryPackResources;
    private final List<PackResources> packResourcesStack;

    public CompositePackResources(PackResources p_301152_, List<PackResources> p_299588_) {
        this.primaryPackResources = p_301152_;
        List<PackResources> list = new ArrayList<>(p_299588_.size() + 1);
        list.addAll(Lists.reverse(p_299588_));
        list.add(p_301152_);
        this.packResourcesStack = List.copyOf(list);
    }

    @Nullable
    @Override
    public IoSupplier<InputStream> getRootResource(String... p_299314_) {
        return this.primaryPackResources.getRootResource(p_299314_);
    }

    @Nullable
    @Override
    public IoSupplier<InputStream> getResource(PackType p_299283_, ResourceLocation p_299837_) {
        for (PackResources packresources : this.packResourcesStack) {
            IoSupplier<InputStream> iosupplier = packresources.getResource(p_299283_, p_299837_);
            if (iosupplier != null) {
                return iosupplier;
            }
        }

        return null;
    }

    @Override
    public void listResources(PackType p_299029_, String p_300961_, String p_297881_, PackResources.ResourceOutput p_298322_) {
        Map<ResourceLocation, IoSupplier<InputStream>> map = new HashMap<>();

        for (PackResources packresources : this.packResourcesStack) {
            packresources.listResources(p_299029_, p_300961_, p_297881_, map::putIfAbsent);
        }

        map.forEach(p_298322_);
    }

    @Override
    public Set<String> getNamespaces(PackType p_299362_) {
        Set<String> set = new HashSet<>();

        for (PackResources packresources : this.packResourcesStack) {
            set.addAll(packresources.getNamespaces(p_299362_));
        }

        return set;
    }

    @Nullable
    @Override
    public <T> T getMetadataSection(MetadataSectionType<T> p_378152_) throws IOException {
        return this.primaryPackResources.getMetadataSection(p_378152_);
    }

    @Override
    public PackLocationInfo location() {
        return this.primaryPackResources.location();
    }

    @Override
    public void close() {
        this.packResourcesStack.forEach(PackResources::close);
    }
}