Unicopia/src/main/java/com/minelittlepony/unicopia/item/EnchantableItem.java

package com.minelittlepony.unicopia.item;

import java.util.function.Predicate;

import org.jetbrains.annotations.Nullable;

import com.minelittlepony.unicopia.Affinity;
import com.minelittlepony.unicopia.ability.magic.spell.Spell;
import com.minelittlepony.unicopia.ability.magic.spell.effect.CustomisedSpellType;
import com.minelittlepony.unicopia.ability.magic.spell.effect.SpellType;
import com.minelittlepony.unicopia.ability.magic.spell.trait.SpellTraits;

import net.minecraft.entity.player.PlayerEntity;
import net.minecraft.item.ItemConvertible;
import net.minecraft.item.ItemStack;
import net.minecraft.util.Hand;
import net.minecraft.util.Identifier;
import net.minecraft.util.TypedActionResult;

public interface EnchantableItem extends ItemConvertible {

    default ItemStack getDefaultStack(SpellType<?> spell) {
        return enchant(asItem().getDefaultStack(), spell);
    }

    default CustomisedSpellType<?> getSpellEffect(ItemStack stack) {
        return EnchantableItem.getSpellKey(stack).withTraits(SpellTraits.of(stack));
    }

    static TypedActionResult<CustomisedSpellType<?>> consumeSpell(ItemStack stack, PlayerEntity player, @Nullable Predicate<CustomisedSpellType<?>> filter) {

        if (!isEnchanted(stack)) {
            return TypedActionResult.pass(null);
        }

        SpellType<Spell> key = EnchantableItem.getSpellKey(stack);

        if (key.isEmpty()) {
            return TypedActionResult.fail(null);
        }

        CustomisedSpellType<?> result = key.withTraits(SpellTraits.of(stack));

        if (filter != null && !filter.test(result)) {
            return TypedActionResult.fail(null);
        }

        if (!player.world.isClient) {
            player.swingHand(player.getStackInHand(Hand.OFF_HAND) == stack ? Hand.OFF_HAND : Hand.MAIN_HAND);

            if (stack.getCount() == 1) {
                unenchant(stack);
            } else {
                player.giveItemStack(unenchant(stack.split(1)));
            }
        }

        return TypedActionResult.consume(result);
    }

    static boolean isEnchanted(ItemStack stack) {
        return !stack.isEmpty() && stack.hasNbt() && stack.getNbt().contains("spell");
    }

    static ItemStack enchant(ItemStack stack, SpellType<?> type) {
        return enchant(stack, type, type.getAffinity());
    }

    static ItemStack enchant(ItemStack stack, SpellType<?> type, Affinity affinity) {
        if (type.isEmpty()) {
            return unenchant(stack);
        }
        stack.getOrCreateNbt().putString("spell", type.getId().toString());
        return type.getTraits().applyTo(stack);
    }

    static ItemStack unenchant(ItemStack stack) {
        stack.removeSubNbt("spell");
        stack.removeSubNbt("spell_traits");
        return stack;
    }

    static <T extends Spell> SpellType<T> getSpellKey(ItemStack stack) {
        return SpellType.getKey(isEnchanted(stack) ? new Identifier(stack.getNbt().getString("spell")) : SpellType.EMPTY_ID);
    }
}