(feat): utility functions for hierarchical post types

src/PostData.php

@@ -6,6 +6,7 @@
 
 use Carbon\CarbonImmutable;
 use Corcel\Model\Post;
+use Illuminate\Support\Collection;
 use ReflectionClass;
 use ReflectionNamedType;
 use RuntimeException;
@@ -102,7 +103,7 @@ private static function dataClass(string $postType): string
 		if (null === $classFQN) {
 			return static::class;
 		}
-		
+
 		if (! class_exists($classFQN)) {
 			throw new RuntimeException(sprintf('The class "%s" does not exist or is not autoloaded.', $classFQN));
 		}
@@ -292,4 +293,53 @@ public function url(): string
 
 		return \get_permalink($this->id) ?: '';
 	}
+
+	public function isTopLevelParent(): bool
+	{
+		return $this->isParent() && ! $this->isChild();
+	}
+
+	public function isParent(): bool
+	{
+		return $this->children()->isNotEmpty();
+	}
+
+	/**
+	 * @param array<string, mixed> $args
+	 *
+	 * @return Collection<int, static>
+	 * */
+	public function children(array $args = []): Collection
+	{
+		if (! is_post_type_hierarchical($this->postType) || ! is_numeric($this->id)) {
+			return collect();
+		}
+		$args = wp_parse_args($args, [
+			'post_parent' => $this->id,
+			'post_type' => $this->postType,
+			'order' => 'ASC',
+			'orderby' => 'menu_order',
+		]);
+		$children = get_children($args);
+
+		return static::collect($children, Collection::class);
+	}
+
+	public function isChild(): bool
+	{
+		return null !== $this->parent();
+	}
+
+	public function parent(): ?PostData
+	{
+		if (! is_post_type_hierarchical($this->postType) || ! is_numeric($this->id)) {
+			return null;
+		}
+		$parent = get_post_parent($this->id);
+		if (null === $parent) {
+			return null;
+		}
+
+		return static::fromPost($parent);
+	}
 }