feat: add methods for Post featured media Attachments (#4)

In this PR we add methods for setting and getting featured media attachments for posts.

Reviewed-on: https://codeberg.org/vlw/wp/pulls/4

src/Posts/Post.php

@@ -107,6 +107,29 @@
 			return Term::from_post($this);
 		}
 
+		/**
+		 * Get, set, or unset featured media for this Post
+		 *
+		 * @param Attachment|false|null $attachment Pass Attachment to set featured media, false to unset, and null (or nothing) to get featured media
+		 * @return Attachment|null Returns an Attachment if featured media is set. Null if no featured media is set
+		 */
+		public function featured_media(Attachment|false|null $featured_media = null): ?Attachment {
+			// Remove featured media from this Post
+			if ($featured_media === false) {
+				Attachment::remove_post_featured_media($this);
+				return null;
+			}
+
+			// Set Attachment as the featured media for this Post
+			if ($featured_media instanceof Attachment) {
+				$featured_media->set_post_featured($this);
+
+				return $featured_media;
+			}
+
+			return Attachment::from_post_featured($this);
+		}
+
 		public int $post_author {
 			get                    => $this->get(Posts::POST_AUTHOR->value);
 			set (int $post_author) => $this->set(Posts::POST_AUTHOR->value, $post_author);

src/Posts/Type/Attachment.php

@@ -3,14 +3,64 @@
 	namespace vlw\WP\Posts\Type;
 
 	use vlw\WP\Posts\Post;
+	use vlw\WP\Posts\PostMeta;
 	use function vlw\WP\Support\slugify;
 
 	require_once dirname(__DIR__, 1) . "/Post.php";
+	require_once dirname(__DIR__, 1) . "/PostMeta.php";
 	require_once dirname(__DIR__, 2) . "/Support/Slugify.php";
 
 	class Attachment {
+		private const META_KEY_THUMBNAIL_ID   = "_thumbnail_id";
+		private const META_KEY_FEATURED_MEDIA = "_featured_media";
+
 		private readonly Post $post;
 
+		/**
+		 * Return featured media for a Post if it exists
+		 *
+		 * @param Post $post
+		 * @param bool $thumbnail Thumbnail is the same as the featured meta. Default to true
+		 * @return Attachment|null
+		 */
+		public static function from_post_featured(Post $post, bool $thumbnail = true): ?Attachment {
+			// Check the thumbnail for an attachment ID. This operation is slightly less demanding than unserialize
+			if ($thumbnail) {
+				$post_meta = PostMeta::get_post_meta($post, self::META_KEY_THUMBNAIL_ID);
+
+				if ($post_meta) {
+					return new static($post_meta->id);
+				}
+			}
+
+			$post_meta = PostMeta::get_post_meta($post, self::META_KEY_FEATURED_MEDIA);
+
+			// Bail out, the target Post does not have any featured media
+			if (!$post_meta) {
+				return null;
+			}
+
+			// New instance from post ID in featured media serialized object
+			return new static((int) unserialize($post_meta->meta_value)[0]);
+		}
+
+		/**
+		 * Remove featured media from a Post
+		 *
+		 * @param Post $post
+		 * @return void
+		 */
+		public static function remove_post_featured_media(Post $post): void {
+			foreach ([
+				PostMeta::get_post_meta($post, self::META_KEY_THUMBNAIL_ID),
+				PostMeta::get_post_meta($post, self::META_KEY_FEATURED_MEDIA)
+			] as $post_meta) {
+				if ($post_meta) {
+					$post_meta->delete();
+				}
+			}
+		}
+
 		/**
 		 * Create a new post
 		 *
@@ -20,8 +70,10 @@
 		 */
 		public static function new(string $title, string $url): static {
 			$post = Post::new($title);
+
 			$post->post_title = slugify($title);
 			$post->guid = $url;
+			$post->post_type = "attachment";
 
 			return new static($post->id);
 		}
@@ -30,7 +82,20 @@
 			$this->post = new Post($id);
 		}
 
-		public function get_attachment(): string {
+		/**
-			return file_get_contents($this->post->guid);
+		 * Make this Attachment the featured media of a Post
+		 *
+		 * @param Post $post
+		 * @return object
+		 */
+		public function set_post_featured(Post $post): object {
+			return (object) [
+				"thumbnail"      => PostMeta::new($post, self::META_KEY_THUMBNAIL_ID, $this->id),
+				"featured_media" => PostMeta::new($post, self::META_KEY_FEATURED_MEDIA, "a:1:{i:0;s:3:\"{$this->id}\";}")
+			];
+		}
+
+		public string|false $content {
+			get => file_get_contents($this->post->guid);
 		}
 	}