Applied-Energistics-2/src/main/java/appeng/util/item/FuzzyItemVariantList.java

/*
 * This file is part of Applied Energistics 2.
 * Copyright (c) 2021, TeamAppliedEnergistics, All rights reserved.
 *
 * Applied Energistics 2 is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Applied Energistics 2 is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
 */

package appeng.util.item;

import java.util.Collection;
import java.util.Comparator;
import java.util.Map;

import appeng.util.Platform;
import com.google.common.base.Preconditions;

import gregtech.common.items.MetaTool;
import net.minecraft.item.ItemStack;

import it.unimi.dsi.fastutil.objects.Object2ObjectAVLTreeMap;
import it.unimi.dsi.fastutil.objects.Object2ObjectSortedMap;

import appeng.api.config.FuzzyMode;
import appeng.api.storage.data.IAEItemStack;

/**
 * This variant list is optimized for damageable items, and supports selecting durability ranges with
 * {@link #findFuzzy(IAEItemStack, FuzzyMode)}.
 */
class FuzzyItemVariantList extends ItemVariantList {

    static final SharedStackComparator COMPARATOR = new SharedStackComparator();

    // NOTE: We only use Object as they key here so we can pass our special DamageBounds to the subMap method.
    // We NEVER put any keys in this map that are not AESharedItemStacks.
    private final Object2ObjectSortedMap<Object, IAEItemStack> records = new Object2ObjectAVLTreeMap<>(COMPARATOR);

    @Override
    public Collection<IAEItemStack> findFuzzy(final IAEItemStack filter, final FuzzyMode fuzzy) {
        ItemStack itemStack = filter.getDefinition();

        ItemDamageBound lowerBound = makeLowerBound(itemStack, fuzzy);
        ItemDamageBound upperBound = makeUpperBound(itemStack, fuzzy);
        Preconditions.checkState(lowerBound.itemDamage > upperBound.itemDamage);

        return this.records.subMap(lowerBound, upperBound).values();
    }

    @SuppressWarnings("unchecked")
    @Override
    Map<AESharedItemStack, IAEItemStack> getRecords() {
        // We ensure on our end that we NEVER use anything but AESharedItemStack as the key in this map
        return (Map<AESharedItemStack, IAEItemStack>) (Object) this.records;
    }

    static class ItemDamageBound {
        final int itemDamage;

        public ItemDamageBound(int itemDamage) {
            this.itemDamage = itemDamage;
        }
    }

    /**
     * This comparator creates a strict and total ordering over all {@link AESharedItemStack} of the same item. To
     * support selecting ranges of durability, it is defined for type {@link Object} and also accepts
     * {@link ItemDamageBound} as an argument to compare against.
     */
    static class SharedStackComparator implements Comparator<Object> {
        @Override
        public int compare(Object a, Object b) {
            // Either argument can either be a damage bound or a shared item stack
            // Since we never put damage bounds into the map as keys, only one
            // of the two arguments can possibly be a bound
            ItemDamageBound boundA = null;
            AESharedItemStack stackA = null;
            int itemDamageA;
            if (a instanceof ItemDamageBound) {
                boundA = (ItemDamageBound) a;
                itemDamageA = boundA.itemDamage;
            } else {
                stackA = (AESharedItemStack) a;
                itemDamageA = stackA.getItemDamage();
            }
            ItemDamageBound boundB = null;
            AESharedItemStack stackB = null;
            int itemDamageB;
            if (b instanceof ItemDamageBound) {
                boundB = (ItemDamageBound) b;
                itemDamageB = boundB.itemDamage;
            } else {
                stackB = (AESharedItemStack) b;
                itemDamageB = stackB.getItemDamage();
            }

            // When either argument is a damage bound, we just compare the damage values because it is used
            // only to get a certain damage range out of the map.
            if (boundA != null || boundB != null) {
                return Integer.compare(itemDamageB, itemDamageA);
            }

            ItemStack itemStackA = stackA.getDefinition();
            ItemStack itemStackB = stackB.getDefinition();
            Preconditions.checkState(itemStackA.getCount() == 1, "ItemStack#getCount() has to be 1");
            Preconditions.checkArgument(itemStackB.getCount() == 1, "ItemStack#getCount() has to be 1");

            if (itemStackA == itemStackB) {
                return 0;
            }

            // Damaged items are sorted before undamaged items
            final int damageValue = Integer.compare(itemDamageB, itemDamageA);
            if (damageValue != 0) {
                return damageValue;
            }

            // As a final tie breaker, order by the object identity of the item stack
            // While this will order seemingly at random, we only need the order of
            // damage values to be predictable, while still having to satisfy the
            // complete order requirements of the sorted map
            return Long.compare(System.identityHashCode(itemStackA), System.identityHashCode(itemStackB));
        }
    }

    /**
     * Minecraft reverses the damage values. So anything with a damage of 0 is undamaged and increases the more damaged
     * the item is.
     * <p>
     * Further the used subMap follows [MAX_DAMAGE, MIN_DAMAGE), so to include undamaged items, we have to start with a
     * lower damage value than 0, while it is fine to use {@link ItemStack#getMaxDamage()} for the upper bound.
     */
    private static final int MIN_DAMAGE_VALUE = -1;

    /*
     * Keep in mind that the stack order is from most damaged to least damaged, so this lower bound will actually be a
     * higher number than the upper bound.
     */
    static ItemDamageBound makeLowerBound(final ItemStack stack, final FuzzyMode fuzzy)
    {
        Preconditions.checkState( stack.getItem().isDamageable() || (Platform.isModLoaded( "gregtech" ) && stack.getItem() instanceof MetaTool), "Item#isDamageable() has to be true" );

        int damage;
        if( fuzzy == FuzzyMode.IGNORE_ALL )
        {
            if( stack.getMaxDamage() == 0 )
            {
                damage = stack.getItemDamage();
            }
            else
            {
                damage = stack.getMaxDamage();
            }
        }
        else
        {
            final int breakpoint = fuzzy.calculateBreakPoint( stack.getMaxDamage() );
            damage = stack.getItemDamage() <= breakpoint ? breakpoint : stack.getMaxDamage();
        }

        return new ItemDamageBound( damage );
    }

    /*
     * Keep in mind that the stack order is from most damaged to least damaged, so this upper bound will actually be a
     * lower number than the lower bound. It also is exclusive.
     */
    static ItemDamageBound makeUpperBound(final ItemStack stack, final FuzzyMode fuzzy) {
        Preconditions.checkState(stack.getItem().isDamageable() || (Platform.isModLoaded( "gregtech" ) && stack.getItem() instanceof MetaTool), "Item#isDamageable() has to be true");

        int damage;
        if (fuzzy == FuzzyMode.IGNORE_ALL) {
            damage = MIN_DAMAGE_VALUE;
        } else {
            final int breakpoint = fuzzy.calculateBreakPoint(stack.getMaxDamage());
            damage = stack.getItemDamage() <= breakpoint ? MIN_DAMAGE_VALUE : breakpoint;
        }

        return new ItemDamageBound(damage);
    }

}