Add region parent support

Author: APickledWalrus

src/main/java/org/skriptlang/skriptworldguard/elements/expressions/ExprRegionParent.java

@@ -0,0 +1,71 @@
+package org.skriptlang.skriptworldguard.elements.expressions;
+
+import ch.njol.skript.classes.Changer.ChangeMode;
+import ch.njol.skript.doc.Description;
+import ch.njol.skript.doc.Example;
+import ch.njol.skript.doc.Name;
+import ch.njol.skript.doc.Since;
+import ch.njol.skript.expressions.base.SimplePropertyExpression;
+import com.sk89q.worldguard.protection.regions.ProtectedRegion;
+import com.sk89q.worldguard.protection.regions.ProtectedRegion.CircularInheritanceException;
+import org.bukkit.event.Event;
+import org.jetbrains.annotations.Nullable;
+import org.skriptlang.skript.registration.SyntaxRegistry;
+import org.skriptlang.skriptworldguard.worldguard.WorldGuardRegion;
+
+@Name("Region Parent")
+@Description({
+		"An expression to obtain and change the parent of a region.",
+		"When a region has a parent, it inherits the parents members, owners, and flags (that aren't defined on the child)."
+})
+@Example("""
+	command /setparent <text>:
+		trigger:
+			set the parents of the regions at the player to the region text-argument
+	""")
+@Since("1.0")
+public class ExprRegionParent extends SimplePropertyExpression<WorldGuardRegion, WorldGuardRegion> {
+
+	public static void register(SyntaxRegistry registry) {
+		register(registry, ExprRegionParent.class, WorldGuardRegion.class,
+				"[region] parent[s]", "worldguardregions");
+	}
+
+	@Override
+	public WorldGuardRegion convert(WorldGuardRegion region) {
+		return new WorldGuardRegion(region.world(), region.region().getParent());
+	}
+
+	@Override
+	public Class<?> @Nullable [] acceptChange(ChangeMode mode) {
+		return switch (mode) {
+			case SET, DELETE, RESET -> new Class[]{WorldGuardRegion.class};
+			default -> null;
+		};
+	}
+
+	@Override
+	public void change(Event event, Object @Nullable [] delta, ChangeMode mode) {
+		ProtectedRegion newRegion = delta != null ? ((WorldGuardRegion) delta[0]).region() : null;
+		for (WorldGuardRegion region : getExpr().getArray(event)) {
+			try {
+				region.region().setParent(newRegion);
+			} catch (CircularInheritanceException e) {
+				assert delta != null;
+				error("Circular region inheritance detected. '" + delta[0] + "' has '" +
+						region + "' as an existing parent.");
+			}
+		}
+	}
+
+	@Override
+	protected String getPropertyName() {
+		return "parent";
+	}
+
+	@Override
+	public Class<? extends WorldGuardRegion> getReturnType() {
+		return WorldGuardRegion.class;
+	}
+
+}