SkriptParser refactor, add ParsingConstraints

src/main/java/ch/njol/skript/lang/DefaultExpressionUtils.java

@@ -3,14 +3,16 @@
 import ch.njol.skript.classes.ClassInfo;
 import ch.njol.skript.lang.SkriptParser.ExprInfo;
 import ch.njol.util.StringUtils;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.List;
 
 /**
  * Utility class for {@link DefaultExpression}.
  */
-final class DefaultExpressionUtils {
+@ApiStatus.Internal
+public final class DefaultExpressionUtils {
 
 	/**
 	 * Check if {@code expr} is valid with the settings from {@code exprInfo}.
@@ -20,7 +22,8 @@ final class DefaultExpressionUtils {
 	 * @param index The index of the {@link ClassInfo} in {@code exprInfo} used to grab {@code expr}.
 	 * @return {@link DefaultExpressionError} if it's not valid, otherwise {@code null}.
 	 */
-	static @Nullable DefaultExpressionError isValid(DefaultExpression<?> expr, ExprInfo exprInfo, int index) {
+	@ApiStatus.Internal
+	public static @Nullable DefaultExpressionError isValid(DefaultExpression<?> expr, ExprInfo exprInfo, int index) {
 		if (expr == null) {
 			return DefaultExpressionError.NOT_FOUND;
 		} else if (!(expr instanceof Literal<?>) && (exprInfo.flagMask & SkriptParser.PARSE_EXPRESSIONS) == 0) {
@@ -35,7 +38,8 @@ final class DefaultExpressionUtils {
 		return null;
 	}
 
-	enum DefaultExpressionError {
+	@ApiStatus.Internal
+	public enum DefaultExpressionError {
 		/**
 		 * Error type for when a {@link DefaultExpression} can not be found for a {@link Class}.
 		 */
@@ -132,6 +136,7 @@ public String getError(List<String> codeNames, String pattern) {
 		 * @param pattern The pattern to include in the error message.
 		 * @return error message.
 		 */
+		@ApiStatus.Internal
 		public abstract String getError(List<String> codeNames, String pattern);
 
 		/**

src/main/java/ch/njol/skript/lang/EventRestrictedSyntax.java

@@ -1,8 +1,14 @@
 package ch.njol.skript.lang;
 
+import ch.njol.skript.Skript;
 import ch.njol.util.Kleenean;
+import ch.njol.util.StringUtils;
 import ch.njol.util.coll.CollectionUtils;
 import org.bukkit.event.Event;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * A syntax element that restricts the events it can be used in.
@@ -23,4 +29,25 @@ public interface EventRestrictedSyntax {
 	 */
 	Class<? extends Event>[] supportedEvents();
 
+	/**
+	 * Creates a readable list of the user-facing names of the given event classes.
+	 * @param supportedEvents The classes of the events to list.
+	 * @return A string containing the names of the events as a list: {@code "the on death event, the on explosion event, or the on player join event"}.
+	 */
+	static @NotNull String supportedEventsNames(Class<? extends Event>[] supportedEvents) {
+		List<String> names = new ArrayList<>();
+
+		for (SkriptEventInfo<?> eventInfo : Skript.getEvents()) {
+			for (Class<? extends Event> eventClass : supportedEvents) {
+				for (Class<? extends Event> event : eventInfo.events) {
+					if (event.isAssignableFrom(eventClass)) {
+						names.add("the %s event".formatted(eventInfo.getName().toLowerCase()));
+					}
+				}
+			}
+		}
+
+		return StringUtils.join(names, ", ", " or ");
+	}
+
 }