minecraft-src/net/minecraft/world/item/trading/MerchantOffer.java

package net.minecraft.world.item.trading;

import com.mojang.serialization.Codec;
import com.mojang.serialization.codecs.RecordCodecBuilder;
import java.util.Optional;
import net.minecraft.network.RegistryFriendlyByteBuf;
import net.minecraft.network.codec.StreamCodec;
import net.minecraft.util.Mth;
import net.minecraft.world.item.ItemStack;

public class MerchantOffer {
	public static final Codec<MerchantOffer> CODEC = RecordCodecBuilder.create(
		instance -> instance.group(
				ItemCost.CODEC.fieldOf("buy").forGetter(merchantOffer -> merchantOffer.baseCostA),
				ItemCost.CODEC.lenientOptionalFieldOf("buyB").forGetter(merchantOffer -> merchantOffer.costB),
				ItemStack.CODEC.fieldOf("sell").forGetter(merchantOffer -> merchantOffer.result),
				Codec.INT.lenientOptionalFieldOf("uses", 0).forGetter(merchantOffer -> merchantOffer.uses),
				Codec.INT.lenientOptionalFieldOf("maxUses", 4).forGetter(merchantOffer -> merchantOffer.maxUses),
				Codec.BOOL.lenientOptionalFieldOf("rewardExp", true).forGetter(merchantOffer -> merchantOffer.rewardExp),
				Codec.INT.lenientOptionalFieldOf("specialPrice", 0).forGetter(merchantOffer -> merchantOffer.specialPriceDiff),
				Codec.INT.lenientOptionalFieldOf("demand", 0).forGetter(merchantOffer -> merchantOffer.demand),
				Codec.FLOAT.lenientOptionalFieldOf("priceMultiplier", 0.0F).forGetter(merchantOffer -> merchantOffer.priceMultiplier),
				Codec.INT.lenientOptionalFieldOf("xp", 1).forGetter(merchantOffer -> merchantOffer.xp)
			)
			.apply(instance, MerchantOffer::new)
	);
	public static final StreamCodec<RegistryFriendlyByteBuf, MerchantOffer> STREAM_CODEC = StreamCodec.of(
		MerchantOffer::writeToStream, MerchantOffer::createFromStream
	);
	/**
	 * The first input for this offer.
	 */
	private final ItemCost baseCostA;
	/**
	 * The second input for this offer.
	 */
	private final Optional<ItemCost> costB;
	/**
	 * The output of this offer.
	 */
	private final ItemStack result;
	private int uses;
	private final int maxUses;
	private final boolean rewardExp;
	private int specialPriceDiff;
	private int demand;
	private final float priceMultiplier;
	private final int xp;

	private MerchantOffer(
		ItemCost baseCostA,
		Optional<ItemCost> costB,
		ItemStack result,
		int uses,
		int maxUses,
		boolean rewardExp,
		int specialPriceDiff,
		int demand,
		float priceMultiplier,
		int xp
	) {
		this.baseCostA = baseCostA;
		this.costB = costB;
		this.result = result;
		this.uses = uses;
		this.maxUses = maxUses;
		this.rewardExp = rewardExp;
		this.specialPriceDiff = specialPriceDiff;
		this.demand = demand;
		this.priceMultiplier = priceMultiplier;
		this.xp = xp;
	}

	public MerchantOffer(ItemCost baseCostA, ItemStack result, int maxUses, int xp, float priceMultiplier) {
		this(baseCostA, Optional.empty(), result, maxUses, xp, priceMultiplier);
	}

	public MerchantOffer(ItemCost baseCostA, Optional<ItemCost> costB, ItemStack result, int maxUses, int xp, float priceMultiplier) {
		this(baseCostA, costB, result, 0, maxUses, xp, priceMultiplier);
	}

	public MerchantOffer(ItemCost baseCostA, Optional<ItemCost> costB, ItemStack result, int uses, int maxUses, int xp, float priceMultiplier) {
		this(baseCostA, costB, result, uses, maxUses, xp, priceMultiplier, 0);
	}

	public MerchantOffer(ItemCost baseCostA, Optional<ItemCost> costB, ItemStack result, int uses, int maxUses, int xp, float priceMultiplier, int demand) {
		this(baseCostA, costB, result, uses, maxUses, true, 0, demand, priceMultiplier, xp);
	}

	private MerchantOffer(MerchantOffer other) {
		this(
			other.baseCostA,
			other.costB,
			other.result.copy(),
			other.uses,
			other.maxUses,
			other.rewardExp,
			other.specialPriceDiff,
			other.demand,
			other.priceMultiplier,
			other.xp
		);
	}

	public ItemStack getBaseCostA() {
		return this.baseCostA.itemStack();
	}

	public ItemStack getCostA() {
		return this.baseCostA.itemStack().copyWithCount(this.getModifiedCostCount(this.baseCostA));
	}

	private int getModifiedCostCount(ItemCost itemCost) {
		int i = itemCost.count();
		int j = Math.max(0, Mth.floor(i * this.demand * this.priceMultiplier));
		return Mth.clamp(i + j + this.specialPriceDiff, 1, itemCost.itemStack().getMaxStackSize());
	}

	public ItemStack getCostB() {
		return (ItemStack)this.costB.map(ItemCost::itemStack).orElse(ItemStack.EMPTY);
	}

	public ItemCost getItemCostA() {
		return this.baseCostA;
	}

	public Optional<ItemCost> getItemCostB() {
		return this.costB;
	}

	public ItemStack getResult() {
		return this.result;
	}

	/**
	 * Calculates the demand with following formula: demand = demand + uses - maxUses - uses
	 */
	public void updateDemand() {
		this.demand = this.demand + this.uses - (this.maxUses - this.uses);
	}

	public ItemStack assemble() {
		return this.result.copy();
	}

	public int getUses() {
		return this.uses;
	}

	public void resetUses() {
		this.uses = 0;
	}

	public int getMaxUses() {
		return this.maxUses;
	}

	public void increaseUses() {
		this.uses++;
	}

	public int getDemand() {
		return this.demand;
	}

	public void addToSpecialPriceDiff(int add) {
		this.specialPriceDiff += add;
	}

	public void resetSpecialPriceDiff() {
		this.specialPriceDiff = 0;
	}

	public int getSpecialPriceDiff() {
		return this.specialPriceDiff;
	}

	public void setSpecialPriceDiff(int price) {
		this.specialPriceDiff = price;
	}

	public float getPriceMultiplier() {
		return this.priceMultiplier;
	}

	public int getXp() {
		return this.xp;
	}

	public boolean isOutOfStock() {
		return this.uses >= this.maxUses;
	}

	public void setToOutOfStock() {
		this.uses = this.maxUses;
	}

	public boolean needsRestock() {
		return this.uses > 0;
	}

	public boolean shouldRewardExp() {
		return this.rewardExp;
	}

	public boolean satisfiedBy(ItemStack playerOfferA, ItemStack playerOfferB) {
		if (!this.baseCostA.test(playerOfferA) || playerOfferA.getCount() < this.getModifiedCostCount(this.baseCostA)) {
			return false;
		} else {
			return !this.costB.isPresent()
				? playerOfferB.isEmpty()
				: ((ItemCost)this.costB.get()).test(playerOfferB) && playerOfferB.getCount() >= ((ItemCost)this.costB.get()).count();
		}
	}

	public boolean take(ItemStack playerOfferA, ItemStack playerOfferB) {
		if (!this.satisfiedBy(playerOfferA, playerOfferB)) {
			return false;
		} else {
			playerOfferA.shrink(this.getCostA().getCount());
			if (!this.getCostB().isEmpty()) {
				playerOfferB.shrink(this.getCostB().getCount());
			}

			return true;
		}
	}

	public MerchantOffer copy() {
		return new MerchantOffer(this);
	}

	private static void writeToStream(RegistryFriendlyByteBuf buffer, MerchantOffer offer) {
		ItemCost.STREAM_CODEC.encode(buffer, offer.getItemCostA());
		ItemStack.STREAM_CODEC.encode(buffer, offer.getResult());
		ItemCost.OPTIONAL_STREAM_CODEC.encode(buffer, offer.getItemCostB());
		buffer.writeBoolean(offer.isOutOfStock());
		buffer.writeInt(offer.getUses());
		buffer.writeInt(offer.getMaxUses());
		buffer.writeInt(offer.getXp());
		buffer.writeInt(offer.getSpecialPriceDiff());
		buffer.writeFloat(offer.getPriceMultiplier());
		buffer.writeInt(offer.getDemand());
	}

	public static MerchantOffer createFromStream(RegistryFriendlyByteBuf buffer) {
		ItemCost itemCost = ItemCost.STREAM_CODEC.decode(buffer);
		ItemStack itemStack = ItemStack.STREAM_CODEC.decode(buffer);
		Optional<ItemCost> optional = ItemCost.OPTIONAL_STREAM_CODEC.decode(buffer);
		boolean bl = buffer.readBoolean();
		int i = buffer.readInt();
		int j = buffer.readInt();
		int k = buffer.readInt();
		int l = buffer.readInt();
		float f = buffer.readFloat();
		int m = buffer.readInt();
		MerchantOffer merchantOffer = new MerchantOffer(itemCost, optional, itemStack, i, j, k, f, m);
		if (bl) {
			merchantOffer.setToOutOfStock();
		}

		merchantOffer.setSpecialPriceDiff(l);
		return merchantOffer;
	}
}