Add Roll EnchantmentOffer API

paper-api/src/main/java/io/papermc/paper/InternalAPIBridge.java

@@ -27,6 +27,7 @@
 import org.bukkit.damage.DamageEffect;
 import org.bukkit.damage.DamageSource;
 import org.bukkit.damage.DamageType;
+import org.bukkit.enchantments.EnchantmentOffer;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.LivingEntity;
@@ -127,4 +128,6 @@ default VersionFetcher getVersionFetcher() {
     ComponentFlattener componentFlattener();
 
     <C> PersistentDataKey<C> createPersistentDataKey(Key key, PersistentDataType<?, C> type);
+
+    @Nullable EnchantmentOffer[] rollEnchantmentOffers(ItemStack targetStack, int seed, int bookshelfCount, int offerAmount);
 }

paper-api/src/main/java/org/bukkit/enchantments/EnchantmentOffer.java

@@ -1,18 +1,26 @@
 package org.bukkit.enchantments;
 
 import com.google.common.base.Preconditions;
-import org.jetbrains.annotations.NotNull;
+import io.papermc.paper.InternalAPIBridge;
+import org.bukkit.inventory.ItemStack;
+import java.util.Objects;
+import org.checkerframework.checker.index.qual.Positive;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+import static io.papermc.paper.util.BoundChecker.requirePositive;
 
 /**
  * A class for the available enchantment offers in the enchantment table.
  */
+@NullMarked
 public class EnchantmentOffer {
 
     private Enchantment enchantment;
     private int enchantmentLevel;
     private int cost;
 
-    public EnchantmentOffer(@NotNull Enchantment enchantment, int enchantmentLevel, int cost) {
+    public EnchantmentOffer(final Enchantment enchantment, final int enchantmentLevel, final int cost) {
         this.enchantment = enchantment;
         this.enchantmentLevel = enchantmentLevel;
         this.cost = cost;
@@ -23,17 +31,16 @@ public EnchantmentOffer(@NotNull Enchantment enchantment, int enchantmentLevel,
      *
      * @return type of enchantment
      */
-    @NotNull
     public Enchantment getEnchantment() {
-        return enchantment;
+        return this.enchantment;
     }
 
     /**
      * Sets the type of the enchantment.
      *
      * @param enchantment type of the enchantment
      */
-    public void setEnchantment(@NotNull Enchantment enchantment) {
+    public void setEnchantment(final Enchantment enchantment) {
         Preconditions.checkArgument(enchantment != null, "The enchantment may not be null!");
 
         this.enchantment = enchantment;
@@ -45,16 +52,16 @@ public void setEnchantment(@NotNull Enchantment enchantment) {
      * @return level of the enchantment
      */
     public int getEnchantmentLevel() {
-        return enchantmentLevel;
+        return this.enchantmentLevel;
     }
 
     /**
      * Sets the level of the enchantment.
      *
      * @param enchantmentLevel level of the enchantment
      */
-    public void setEnchantmentLevel(int enchantmentLevel) {
-        Preconditions.checkArgument(enchantmentLevel > 0, "The enchantment level must be greater than 0!");
+    public void setEnchantmentLevel(final @Positive int enchantmentLevel) {
+        requirePositive(enchantmentLevel, "enchantmentLevel");
 
         this.enchantmentLevel = enchantmentLevel;
     }
@@ -66,7 +73,7 @@ public void setEnchantmentLevel(int enchantmentLevel) {
      * @return cost for this enchantment
      */
     public int getCost() {
-        return cost;
+        return this.cost;
     }
 
     /**
@@ -75,9 +82,42 @@ public int getCost() {
      *
      * @param cost cost for this enchantment
      */
-    public void setCost(int cost) {
-        Preconditions.checkArgument(cost > 0, "The cost must be greater than 0!");
+    public void setCost(final @Positive int cost) {
+        requirePositive(cost, "cost");
 
         this.cost = cost;
     }
+
+    @Override
+    public boolean equals(final @Nullable Object o) {
+        if (o == null || this.getClass() != o.getClass()) {
+            return false;
+        }
+        final EnchantmentOffer that = (EnchantmentOffer) o;
+        return this.getEnchantmentLevel() == that.getEnchantmentLevel() && this.getCost() == that.getCost() && Objects.equals(this.getEnchantment(), that.getEnchantment());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(this.getEnchantment(), this.getEnchantmentLevel(), this.getCost());
+    }
+
+    /**
+     * Rolls a new set of enchantment offers based on a target item stack, a seed and a bookshelf count.
+     *
+     * @param targetStack    the itemstack for which the enchantment offers are rolled.
+     * @param seed           the seed used for random selection of enchantments.
+     *                       Mirrors {@link org.bukkit.inventory.view.EnchantmentView#getEnchantmentSeed()}.
+     * @param bookshelfCount the number of virtual bookshelves to consider when rolling the enchantments.
+     * @param offerAmount    the amount of enchantment offers to roll.
+     * @return an array of enchantment offers with size {@code offerAmount}.
+     */
+    public static @Nullable EnchantmentOffer[] rollEnchantmentOffers(
+        final ItemStack targetStack,
+        final int seed,
+        final int bookshelfCount,
+        final int offerAmount
+    ) {
+        return InternalAPIBridge.get().rollEnchantmentOffers(targetStack, seed, bookshelfCount, offerAmount);
+    }
 }

paper-server/patches/sources/net/minecraft/world/inventory/EnchantmentMenu.java.patch

@@ -64,10 +64,32 @@
                  this.access.execute((level, pos) -> {
                      IdMap<Holder<Enchantment>> holders = level.registryAccess().lookupOrThrow(Registries.ENCHANTMENT).asHolderIdMap();
                      int bookcases = 0;
-@@ -119,6 +_,42 @@
+@@ -97,27 +_,42 @@
                          }
                      }
 
+-                    this.random.setSeed(this.enchantmentSeed.get());
+-
+-                    for (int ixx = 0; ixx < 3; ixx++) {
+-                        this.costs[ixx] = EnchantmentHelper.getEnchantmentCost(this.random, ixx, bookcases, itemStack);
+-                        this.enchantClue[ixx] = -1;
+-                        this.levelClue[ixx] = -1;
+-                        if (this.costs[ixx] < ixx + 1) {
+-                            this.costs[ixx] = 0;
+-                        }
+-                    }
+-
+-                    for (int ix = 0; ix < 3; ix++) {
+-                        if (this.costs[ix] > 0) {
+-                            List<EnchantmentInstance> list = this.getEnchantmentList(level.registryAccess(), itemStack, ix, this.costs[ix]);
+-                            if (!list.isEmpty()) {
+-                                EnchantmentInstance ench = list.get(this.random.nextInt(list.size()));
+-                                this.enchantClue[ix] = holders.getId(ench.enchantment());
+-                                this.levelClue[ix] = ench.level();
+-                            }
+-                        }
+-                    }
++                    fillEnchantmentOffers(this.random, this.enchantmentSeed.get(), bookcases, itemStack, level.registryAccess(), this.costs, this.enchantClue, this.levelClue); // Paper - extracted into net.minecraft.world.inventory.EnchantmentMenu.fillEnchantmentOffers
 +                    // CraftBukkit start
 +                    org.bukkit.inventory.ItemStack craftItemStack = org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitMirror(itemStack);
 +                    org.bukkit.enchantments.EnchantmentOffer[] offers = new org.bukkit.enchantments.EnchantmentOffer[3];
@@ -103,10 +125,46 @@
 +                        }
 +                    }
 +                    // CraftBukkit end
-+
+ 
                      this.broadcastChanges();
                  });
-             } else {
+@@ -131,6 +_,36 @@
+         }
+     }
+
++    // Paper start - extract offer generation
++    // Extracted over modifications in place given nearly every line has diff to account for non-instance fields for
++    // cost, enchantment and level clues.
++    public static void fillEnchantmentOffers(final RandomSource random, final int seed, final int bookcases, final ItemStack itemStack, final RegistryAccess registryAccess, final int[] costs, final int[] enchantClue, final int[] levelClue) {
++        random.setSeed(seed);
++
++        for (int ixx = 0; ixx < costs.length; ixx++) {
++            costs[ixx] = EnchantmentHelper.getEnchantmentCost(random, ixx, bookcases, itemStack);
++            enchantClue[ixx] = -1;
++            levelClue[ixx] = -1;
++            if (costs[ixx] < ixx + 1) {
++                costs[ixx] = 0;
++            }
++        }
++
++        final IdMap<Holder<Enchantment>> holders = registryAccess.lookupOrThrow(Registries.ENCHANTMENT).asHolderIdMap();
++
++        for (int ix = 0; ix < costs.length; ix++) {
++            if (costs[ix] > 0) {
++                List<EnchantmentInstance> list = getEnchantmentList(registryAccess, itemStack, ix, costs[ix], random, seed);
++                if (!list.isEmpty()) {
++                    EnchantmentInstance ench = list.get(random.nextInt(list.size()));
++                    enchantClue[ix] = holders.getId(ench.enchantment());
++                    levelClue[ix] = ench.level();
++                }
++            }
++        }
++    }
++    // Paper end - extract offer generation
++
+     @Override
+     public boolean clickMenuButton(final Player player, final int buttonId) {
+         if (buttonId >= 0 && buttonId < this.costs.length) {
 @@ -148,19 +_,52 @@
              }
 
@@ -167,6 +225,30 @@
                      currency.consume(enchantmentCost, player);
                      if (currency.isEmpty()) {
                          this.enchantSlots.setItem(1, ItemStack.EMPTY);
+@@ -185,15 +_,20 @@
+     }
+
+     private List<EnchantmentInstance> getEnchantmentList(final RegistryAccess access, final ItemStack itemStack, final int slot, final int enchantmentCost) {
+-        this.random.setSeed(this.enchantmentSeed.get() + slot);
++        // Paper start - make static and public
++        return getEnchantmentList(access, itemStack, slot, enchantmentCost, this.random, this.enchantmentSeed.get());
++    }
++    public static List<EnchantmentInstance> getEnchantmentList(final RegistryAccess access, final ItemStack itemStack, final int slot, final int enchantmentCost, final RandomSource random, final int seed) {
++        random.setSeed(seed + slot);
++        // Paper end - make static and public
+         Optional<HolderSet.Named<Enchantment>> tag = access.lookupOrThrow(Registries.ENCHANTMENT).get(EnchantmentTags.IN_ENCHANTING_TABLE);
+         if (tag.isEmpty()) {
+             return List.of();
+         }
+
+-        List<EnchantmentInstance> list = EnchantmentHelper.selectEnchantment(this.random, itemStack, enchantmentCost, tag.get().stream());
++        List<EnchantmentInstance> list = EnchantmentHelper.selectEnchantment(random, itemStack, enchantmentCost, tag.get().stream()); // Paper - make static and public
+         if (itemStack.is(Items.BOOK) && list.size() > 1) {
+-            list.remove(this.random.nextInt(list.size()));
++            list.remove(random.nextInt(list.size())); // Paper - make static and public
+         }
+
+         return list;
 @@ -204,6 +_,12 @@
          return goldStack.isEmpty() ? 0 : goldStack.getCount();
      }

paper-server/src/main/java/io/papermc/paper/PaperServerInternalAPIBridge.java

@@ -22,16 +22,21 @@
 import io.papermc.paper.world.damagesource.FallLocationType;
 import io.papermc.paper.world.damagesource.PaperCombatEntryWrapper;
 import io.papermc.paper.world.damagesource.PaperCombatTrackerWrapper;
+import java.util.Random;
+import java.util.function.Predicate;
 import java.io.IOException;
 import java.util.Objects;
 import java.util.Set;
 import java.util.function.BooleanSupplier;
 import java.util.function.Function;
-import java.util.function.Predicate;
 import net.kyori.adventure.key.Key;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.flattener.ComponentFlattener;
 import net.minecraft.Optionull;
+import net.minecraft.core.Holder;
+import net.minecraft.core.IdMap;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.util.RandomSource;
 import net.minecraft.commands.Commands;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.nbt.CompoundTag;
@@ -42,36 +47,42 @@
 import net.minecraft.world.entity.ai.attributes.DefaultAttributes;
 import net.minecraft.world.entity.ai.village.poi.PoiManager;
 import net.minecraft.world.entity.decoration.Mannequin;
+import net.minecraft.world.inventory.EnchantmentMenu;
+import net.minecraft.world.item.enchantment.Enchantment;
+import org.bukkit.block.Biome;
+import org.bukkit.craftbukkit.CraftRegistry;
 import org.bukkit.GameRule;
 import org.bukkit.NamespacedKey;
 import org.bukkit.Statistic;
 import org.bukkit.attribute.Attributable;
-import org.bukkit.block.Biome;
 import org.bukkit.command.CommandSender;
 import org.bukkit.craftbukkit.CraftGameRule;
 import org.bukkit.craftbukkit.CraftStatistic;
 import org.bukkit.craftbukkit.block.CraftBiome;
 import org.bukkit.craftbukkit.command.VanillaCommandWrapper;
 import org.bukkit.craftbukkit.damage.CraftDamageEffect;
 import org.bukkit.craftbukkit.damage.CraftDamageSource;
+import org.bukkit.craftbukkit.enchantments.CraftEnchantment;
+import org.bukkit.craftbukkit.entity.CraftLivingEntity;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.util.RandomSourceWrapper;
+import org.bukkit.damage.DamageEffect;
+import org.bukkit.damage.DamageSource;
+import org.bukkit.enchantments.EnchantmentOffer;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.inventory.ItemStack;
 import org.bukkit.craftbukkit.damage.CraftDamageSourceBuilder;
 import org.bukkit.craftbukkit.entity.CraftEntity;
 import org.bukkit.craftbukkit.entity.CraftEntityType;
-import org.bukkit.craftbukkit.entity.CraftLivingEntity;
 import org.bukkit.craftbukkit.entity.CraftMannequin;
-import org.bukkit.craftbukkit.inventory.CraftItemStack;
 import org.bukkit.craftbukkit.util.CraftMagicNumbers;
 import org.bukkit.craftbukkit.util.CraftNamespacedKey;
 import org.bukkit.craftbukkit.util.CraftSpawnCategory;
-import org.bukkit.damage.DamageEffect;
-import org.bukkit.damage.DamageSource;
 import org.bukkit.damage.DamageType;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
-import org.bukkit.entity.LivingEntity;
 import org.bukkit.entity.Pose;
 import org.bukkit.entity.SpawnCategory;
-import org.bukkit.inventory.ItemStack;
 import org.bukkit.persistence.PersistentDataType;
 import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.java.JavaPlugin;
@@ -269,4 +280,29 @@ public <C> PersistentDataKey<C> createPersistentDataKey(final Key key, final Per
             : new NamespacedKey(key.namespace(), key.value());
         return new PaperPersistentDataKey<>(namespacedKey, type);
     }
+
+    @Override
+    public @Nullable EnchantmentOffer[] rollEnchantmentOffers(final ItemStack targetStack, final int seed, final int bookshelfCount, final int offerAmount) {
+        final int[] costs = new int[offerAmount];
+        final int[] enchantClue = new int[offerAmount];
+        final int[] levelClue = new int[offerAmount];
+
+        final RandomSource randomSource = new RandomSourceWrapper(new Random());
+        EnchantmentMenu.fillEnchantmentOffers(randomSource, seed, bookshelfCount, CraftItemStack.unwrap(targetStack), CraftRegistry.getMinecraftRegistry(), costs, enchantClue, levelClue);
+
+        final IdMap<Holder<Enchantment>> holderIdMap = CraftRegistry.getMinecraftRegistry()
+            .lookupOrThrow(Registries.ENCHANTMENT)
+            .asHolderIdMap();
+
+        final @Nullable EnchantmentOffer[] offers = new EnchantmentOffer[offerAmount];
+        for (int i = 0; i < costs.length; i++) {
+            if (enchantClue[i] < 0) {
+                continue;
+            }
+
+            offers[i] = new EnchantmentOffer(CraftEnchantment.minecraftHolderToBukkit(holderIdMap.byId(enchantClue[i])), levelClue[i], costs[i]);
+        }
+
+        return offers;
+    }
 }