SPIGOT-7514, #1289: Add "Enchantment Roll" API to enchant items according to Minecraft mechanics

nms-patches/net/minecraft/world/entity/Entity.patch

@@ -66,6 +66,15 @@
      private static final Logger LOGGER = LogUtils.getLogger();
      public static final String ID_TAG = "id";
      public static final String PASSENGERS_TAG = "Passengers";
+@@ -189,7 +246,7 @@
+     public double zOld;
+     private float maxUpStep;
+     public boolean noPhysics;
+-    protected final RandomSource random;
++    public final RandomSource random;
+     public int tickCount;
+     private int remainingFireTicks;
+     public boolean wasTouchingWater;
 @@ -241,6 +298,25 @@
      public boolean hasVisualFire;
      @Nullable

src/main/java/org/bukkit/craftbukkit/inventory/CraftItemFactory.java

@@ -6,15 +6,21 @@ import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import net.minecraft.commands.arguments.item.ArgumentParserItemStack;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.util.RandomSource;
 import net.minecraft.world.entity.EntityTypes;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemMonsterEgg;
+import net.minecraft.world.item.enchantment.EnchantmentManager;
 import org.bukkit.Color;
 import org.bukkit.Material;
+import org.bukkit.World;
 import org.bukkit.configuration.serialization.ConfigurationSerialization;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.craftbukkit.entity.CraftEntity;
 import org.bukkit.craftbukkit.entity.CraftEntityType;
 import org.bukkit.craftbukkit.util.CraftLegacy;
 import org.bukkit.craftbukkit.util.CraftMagicNumbers;
+import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.inventory.ItemFactory;
 import org.bukkit.inventory.ItemStack;
@@ -23,6 +29,7 @@ import org.bukkit.inventory.meta.ItemMeta;
 public final class CraftItemFactory implements ItemFactory {
     static final Color DEFAULT_LEATHER_COLOR = Color.fromRGB(0xA06540);
     private static final CraftItemFactory instance;
+    private static final RandomSource randomSource = RandomSource.create();
 
     static {
         instance = new CraftItemFactory();
@@ -457,4 +464,36 @@ public final class CraftItemFactory implements ItemFactory {
 
         return CraftMagicNumbers.getMaterial(nmsItem);
     }
+
+    @Override
+    public ItemStack enchantItem(Entity entity, ItemStack itemStack, int level, boolean allowTreasures) {
+        Preconditions.checkArgument(entity != null, "The entity must not be null");
+
+        return enchantItem(((CraftEntity) entity).getHandle().random, itemStack, level, allowTreasures);
+    }
+
+    @Override
+    public ItemStack enchantItem(final World world, final ItemStack itemStack, final int level, final boolean allowTreasures) {
+        Preconditions.checkArgument(world != null, "The world must not be null");
+
+        return enchantItem(((CraftWorld) world).getHandle().random, itemStack, level, allowTreasures);
+    }
+
+    @Override
+    public ItemStack enchantItem(final ItemStack itemStack, final int level, final boolean allowTreasures) {
+        return enchantItem(randomSource, itemStack, level, allowTreasures);
+    }
+
+    private static ItemStack enchantItem(RandomSource source, ItemStack itemStack, int level, boolean allowTreasures) {
+        Preconditions.checkArgument(itemStack != null, "ItemStack must not be null");
+        Preconditions.checkArgument(!itemStack.getType().isAir(), "ItemStack must not be air");
+
+        if (!(itemStack instanceof CraftItemStack)) {
+            itemStack = CraftItemStack.asCraftCopy(itemStack);
+        }
+
+        CraftItemStack craft = (CraftItemStack) itemStack;
+        EnchantmentManager.enchantItem(source, craft.handle, level, allowTreasures);
+        return craft;
+    }
 }