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 ");
+}
+
 }