class Post_Thumbnail implements \ArrayAccess, \Serializable {
	/**
	 * An array of the site image sizes, including the `full` one.
	 *
	 * @since 4.9.14
	 *
	 * @var array
	 */
	protected $image_sizes;

	/**
	 * The post ID this images collection is for.
	 *
	 * @since 4.9.14
	 *
	 * @var int
	 */
	protected $post_id;

	/**
	 * The post thumbnail data.
	 *
	 * @since 4.9.14
	 *
	 * @var array
	 */
	protected $data;

	/**
	 * Post_Images constructor.
	 *
	 * @param int $post_id The post ID.
	 */
	public function __construct( $post_id ) {
		$this->post_id = $post_id;
	}

	/**
	 * {@inheritDoc}
	 */
	public function __get( $property ) {
		return $this->offsetGet( $property );
	}

	/**
	 * {@inheritDoc}
	 */
	public function __set( $property, $value ) {
		$this->offsetSet( $property, $value );
	}

	/**
	 * {@inheritDoc}
	 */
	public function __isset( $property ) {
		return $this->offsetExists( $property );
	}

	/**
	 * Fetches and returns the image sizes registered on the site, if any.
	 *
	 * @since 4.9.14
	 *
	 * @return array An array of the registered image sizes.
	 */
	public function get_image_sizes() {
		if ( null !== $this->image_sizes ) {
			return $this->image_sizes;
		}

		$image_sizes = array_merge( [ 'full' ], get_intermediate_image_sizes() );

		/**
		 * Filters the image sizes the `Tribe\Utils\Post_Thumbnail` class will manage and fetch data for.
		 *
		 * @since 4.9.14
		 *
		 * @param array $image_sizes All the available image sizes; this includes the default and the intermediate ones.
		 */
		$this->image_sizes = apply_filters( 'tribe_post_thumbnail_image_sizes', $image_sizes );

		return $this->image_sizes;
	}

	/**
	 * Returns the data about the post thumbnail, if any.
	 *
	 * @since 4.9.14
	 *
	 * @return array An array of objects containing the post thumbnail data.
	 */
	public function fetch_data() {
		if ( null !== $this->data ) {
			return $this->data;
		}

		$post_id     = $this->post_id;
		$image_sizes = $this->get_image_sizes();

		$thumbnail_id = get_post_thumbnail_id( $post_id );

		if ( empty( $thumbnail_id ) ) {
			return [];
		}

		$thumbnail_data = array_combine(
			$image_sizes,
			array_map(
				static function ( $size ) use ( $thumbnail_id ) {
					$size_data = wp_get_attachment_image_src( $thumbnail_id, $size );

					if ( false === $size_data ) {
						return (object) [
							'url'             => '',
							'width'           => '',
							'height'          => '',
							'is_intermediate' => false,
						];
					}

					return (object) [
						'url'             => Arr::get( $size_data, 0, '' ),
						'width'           => Arr::get( $size_data, 1, '' ),
						'heigth'          => Arr::get( $size_data, 2, '' ),
						'is_intermediate' => (bool) Arr::get( $size_data, 3, false ),
					];
				},
				$image_sizes
			)
		);

		$srcset                   = wp_get_attachment_image_srcset( $thumbnail_id );
		$thumbnail_data['srcset'] = ! empty( $srcset ) ? $srcset : false;

		/**
		 * Filters the post thumbnail data and information that will be returned for a specific post.
		 *
		 * Note that the thumbnail data will be cast to an object after this filtering.
		 *
		 * @since 4.9.14
		 *
		 * @param array $thumbnail_data The thumbnail data for the post.
		 * @param int   $post_id        The ID of the post the data is for.
		 */
		$thumbnail_data = apply_filters( 'tribe_post_thumbnail_data', $thumbnail_data, $post_id );

		return $thumbnail_data;
	}

	/**
	 * {@inheritDoc}
	 */
	public function offsetExists( $offset ) {
		$this->data = $this->fetch_data();

		return isset( $this->data[ $offset ] );
	}

	/**
	 * {@inheritDoc}
	 */
	public function offsetGet( $offset ) {
		$this->data = $this->fetch_data();

		return isset( $this->data[ $offset ] )
			? $this->data[ $offset ]
			: null;
	}

	/**
	 * {@inheritDoc}
	 */
	public function offsetSet( $offset, $value ) {
		$this->data = $this->fetch_data();

		$this->data[ $offset ] = $value;
	}

	/**
	 * {@inheritDoc}
	 */
	public function offsetUnset( $offset ) {
		$this->data = $this->fetch_data();

		unset( $this->data[ $offset ] );
	}

	/**
	 * Returns an array representation of the post thumbnail data.
	 *
	 * @since 4.9.14
	 *
	 *
	 * @return array An array representation of the post thumbnail data.
	 */
	public function to_array() {
		$this->data = $this->fetch_data();

		return json_decode( json_encode( $this->data ), true );
	}

	/**
	 * {@inheritDoc}
	 */
	public function serialize() {
		$data            = $this->fetch_data();
		$data['post_id'] = $this->post_id;

		return serialize( $data );
	}

	/**
	 * {@inheritDoc}
	 */
	public function unserialize( $serialized ) {
		$data          = unserialize( $serialized );
		$this->post_id = $data['post_id'];
		unset( $data['post_id'] );
		$this->data = $data;
	}
}