src/game/java/net/minecraft/resources/RegistryFixedCodec.java

package net.minecraft.resources;

import com.mojang.datafixers.util.Pair;
import com.mojang.serialization.Codec;
import com.mojang.serialization.DataResult;
import com.mojang.serialization.DynamicOps;
import com.mojang.serialization.Lifecycle;
import java.util.Optional;
import net.minecraft.core.Holder;
import net.minecraft.core.HolderGetter;
import net.minecraft.core.HolderOwner;
import net.minecraft.core.Registry;

public final class RegistryFixedCodec<E> implements Codec<Holder<E>> {
    private final ResourceKey<? extends Registry<E>> registryKey;

    public static <E> RegistryFixedCodec<E> create(ResourceKey<? extends Registry<E>> p_206741_) {
        return new RegistryFixedCodec<>(p_206741_);
    }

    private RegistryFixedCodec(ResourceKey<? extends Registry<E>> p_206723_) {
        this.registryKey = p_206723_;
    }

    public <T> DataResult<T> encode(Holder<E> p_206729_, DynamicOps<T> p_206730_, T p_206731_) {
        if (p_206730_ instanceof RegistryOps<?> registryops) {
            Optional<HolderOwner<E>> optional = registryops.owner(this.registryKey);
            if (optional.isPresent()) {
                if (!p_206729_.canSerializeIn(optional.get())) {
                    return DataResult.error(() -> "Element " + p_206729_ + " is not valid in current registry set");
                }

                return p_206729_.unwrap()
                    .map(
                        p_206727_ -> ResourceLocation.CODEC.encode(p_206727_.location(), p_206730_, p_206731_),
                        p_274804_ -> DataResult.error(() -> "Elements from registry " + this.registryKey + " can't be serialized to a value")
                    );
            }
        }

        return DataResult.error(() -> "Can't access registry " + this.registryKey);
    }

    @Override
    public <T> DataResult<Pair<Holder<E>, T>> decode(DynamicOps<T> p_206743_, T p_206744_) {
        if (p_206743_ instanceof RegistryOps<?> registryops) {
            Optional<HolderGetter<E>> optional = registryops.getter(this.registryKey);
            if (optional.isPresent()) {
                return ResourceLocation.CODEC
                    .decode(p_206743_, p_206744_)
                    .flatMap(
                        p_326174_ -> {
                            ResourceLocation resourcelocation = p_326174_.getFirst();
                            return optional.get()
                                .get(ResourceKey.create(this.registryKey, resourcelocation))
                                .map(DataResult::success)
                                .orElseGet(() -> DataResult.error(() -> "Failed to get element " + resourcelocation))
                                .<Pair<Holder<E>, T>>map(p_256041_ -> Pair.of(p_256041_, (T)p_326174_.getSecond()))
                                .setLifecycle(Lifecycle.stable());
                        }
                    );
            }
        }

        return DataResult.error(() -> "Can't access registry " + this.registryKey);
    }

    @Override
    public String toString() {
        return "RegistryFixedCodec[" + this.registryKey + "]";
    }
}