Paper/src/main/java/org/bukkit/craftbukkit/CraftEquipmentSlot.java

package org.bukkit.craftbukkit;

import net.minecraft.server.EnumItemSlot;
import org.bukkit.inventory.EquipmentSlot;

public class CraftEquipmentSlot {

    private static final EnumItemSlot[] slots = new EnumItemSlot[EquipmentSlot.values().length];
    private static final EquipmentSlot[] enums = new EquipmentSlot[EnumItemSlot.values().length];

    static {
        set(EquipmentSlot.HAND, EnumItemSlot.MAINHAND);
        set(EquipmentSlot.OFF_HAND, EnumItemSlot.OFFHAND);
        set(EquipmentSlot.FEET, EnumItemSlot.FEET);
        set(EquipmentSlot.LEGS, EnumItemSlot.LEGS);
        set(EquipmentSlot.CHEST, EnumItemSlot.CHEST);
        set(EquipmentSlot.HEAD, EnumItemSlot.HEAD);
    }

    private static void set(EquipmentSlot type, EnumItemSlot value) {
        slots[type.ordinal()] = value;
        enums[value.ordinal()] = type;
    }

    public static EquipmentSlot getSlot(EnumItemSlot nms) {
        return enums[nms.ordinal()];
    }

    public static EnumItemSlot getNMS(EquipmentSlot slot) {
        return slots[slot.ordinal()];
    }
}