Add ability to enchant an item at a specific level.

src/main/java/ch/njol/skript/effects/EffEnchant.java

@@ -4,40 +4,56 @@
 import ch.njol.skript.aliases.ItemType;
 import ch.njol.skript.classes.Changer.ChangeMode;
 import ch.njol.skript.classes.Changer.ChangerUtils;
-import ch.njol.skript.doc.Description;
-import ch.njol.skript.doc.Examples;
-import ch.njol.skript.doc.Name;
-import ch.njol.skript.doc.Since;
+import ch.njol.skript.doc.*;
 import ch.njol.skript.lang.Effect;
 import ch.njol.skript.lang.Expression;
 import ch.njol.skript.lang.SkriptParser.ParseResult;
 import ch.njol.skript.util.EnchantmentType;
+import ch.njol.skript.util.Patterns;
 import ch.njol.util.Kleenean;
+import org.bukkit.Bukkit;
 import org.bukkit.event.Event;
+import org.bukkit.inventory.ItemFactory;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.function.Function;
 
-/**
- * @author Peter Güttinger
- */
 @Name("Enchant/Disenchant")
-@Description("Enchant or disenchant an existing item.")
-@Examples({"enchant the player's tool with sharpness 5",
-		"disenchant the player's tool"})
-@Since("2.0")
+@Description("Enchant or disenchant an existing item. Enchanting at a specific level will act as if an enchanting table " +
+	"was used, and will apply the enchantments randomly chosen at that level. Treasure enchantments, like mending, can " +
+	"optionally be allowed. Note that enchanting a book at a specific level will turn it into an enchanted book, rather " +
+	"than a book with enchantments.")
+@Example("enchant the player's tool with sharpness 5")
+@Example("enchant the player's tool at level 30 ")
+@Example("disenchant the player's tool")
+@Since("2.0, INSERT VERSION (at level)")
 public class EffEnchant extends Effect {
+
+	private enum Operation {
+		ENCHANT,
+		ENCHANT_AT_LEVEL,
+		DISENCHANT
+	}
+
+	private static final Patterns<Operation> patterns;
+
 	static {
-		Skript.registerEffect(EffEnchant.class,
-				"enchant %~itemtypes% with %enchantmenttypes%",
-				"disenchant %~itemtypes%");
+		 patterns = new Patterns<>(new Object[][]{
+				{"enchant %~itemtypes% with %enchantmenttypes%", Operation.ENCHANT},
+				{"[naturally|randomly] enchant %~itemtypes% at level %number%[treasure:[,] allowing treasure enchant[ment]s]",
+						Operation.ENCHANT_AT_LEVEL},
+				{"disenchant %~itemtypes%", Operation.DISENCHANT}
+			});
+		Skript.registerEffect(EffEnchant.class, patterns.getPatterns());
 	}
-
-	@SuppressWarnings("null")
+
 	private Expression<ItemType> items;
-	@Nullable
 	private Expression<EnchantmentType> enchantments;
+	private Expression<Number> level;
+	private boolean treasure;
+	private Operation operation;
 
 	@Override
 	@SuppressWarnings("unchecked")
@@ -47,36 +63,63 @@ public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelaye
 			Skript.error(items + " cannot be changed, thus it cannot be (dis)enchanted");
 			return false;
 		}
-		if (matchedPattern == 0)
+		if (matchedPattern == 0) {
 			enchantments = (Expression<EnchantmentType>) exprs[1];
+		} else if (matchedPattern == 1) {
+			level = (Expression<Number>) exprs[1];
+			treasure = parseResult.hasTag("treasure");
+		}
+		operation = patterns.getInfo(matchedPattern);
 		return true;
 	}
 
 	@Override
 	protected void execute(Event event) {
 		Function<ItemType, ItemType> changeFunction;
 
-		if (enchantments != null) {
-			EnchantmentType[] types = enchantments.getArray(event);
-			if (types.length == 0)
-				return;
-			changeFunction = item -> {
-				item.addEnchantments(types);
-				return item;
-			};
-		} else {
-			changeFunction = item -> {
+		switch (operation) {
+			case ENCHANT -> {
+				EnchantmentType[] types = enchantments.getArray(event);
+				if (types.length == 0)
+					return;
+				changeFunction = item -> {
+					item.addEnchantments(types);
+					return item;
+				};
+			}
+			case ENCHANT_AT_LEVEL -> {
+				ItemFactory factory = Bukkit.getItemFactory();
+				Number levelValue = level.getSingle(event);
+				if (levelValue == null || levelValue.intValue() < 0) {
+					return;
+				}
+				changeFunction = item -> {
+					ItemStack itemstack = item.getRandom();
+					if (itemstack == null) {
+						return item;
+					}
+					itemstack = factory.enchantWithLevels(itemstack, levelValue.intValue(), treasure, ThreadLocalRandom.current());
+					return new ItemType(itemstack);
+				};
+			}
+			case DISENCHANT -> changeFunction = item -> {
 				item.clearEnchantments();
 				return item;
 			};
+			default -> throw new IllegalStateException("Unexpected operation: " + operation);
 		}
 
 		this.items.changeInPlace(event, changeFunction);
 	}
 
 	@Override
 	public String toString(@Nullable Event event, boolean debug) {
-		return enchantments == null ? "disenchant " + items.toString(event, debug) : "enchant " + items.toString(event, debug) + " with " + enchantments;
+		return switch (operation) {
+			case ENCHANT -> "enchant " + items.toString(event, debug) + " with " + enchantments.toString(event, debug);
+			case ENCHANT_AT_LEVEL -> "enchant " + items.toString(event, debug) + " at level " + level.toString(event, debug)
+					+ (treasure ? " allowing treasure enchantments" : "");
+			case DISENCHANT -> "disenchant " + items.toString(event, debug);
+		};
 	}
 
 }