class Inventory_Presser_Photo_Numberer {

	/**
	 * Adds hooks
	 *
	 * @return void
	 */
	public function add_hooks() {
		// Check if photos are attached to a vehicle parent.
		add_action( 'add_attachment', array( __CLASS__, 'maybe_number_photo' ), 10, 1 );
		add_action( 'edit_attachment', array( __CLASS__, 'maybe_number_photo' ), 10, 1 );

		/**
		 * Put the sequence number in the title of the post to which photos are
		 * attached in the Media Library table view.
		 */
		add_filter( 'the_title', array( $this, 'add_sequence_number_to_titles' ), 10, 2 );
	}

	/**
	 * Dynamically changes post titles of vehicle attachments in the dashboard
	 * to identify their sequence number.
	 *
	 * @param  string $title The post title.
	 * @param  int    $id The post ID.
	 * @return string
	 */
	public function add_sequence_number_to_titles( $title, $id = null ) {
		// Don't double dip during REST API requests.
		if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
			return $title;
		}

		// What post?
		if ( empty( $id ) ) {
			return $title;
		}

		if ( ! is_admin() ) {
			return $title;
		}

		// Is this the Media Library upload.php?
		if ( ! function_exists( 'get_current_screen' ) ) {
			return $title;
		}
		$screen = get_current_screen();
		if ( empty( $screen->parent_file ) || 'upload.php' !== $screen->parent_file ) {
			// No.
			return $title;
		}

		if ( 'attachment' !== get_post_type( $id ) ) {
			// No.
			return $title;
		}

		$parent = get_post_parent( $id );
		if ( empty( $parent ) || INVP::POST_TYPE !== $parent->post_type ) {
			// No.
			return $title;
		}

		// Get the photo count.
		return sprintf(
			'%s (%s %s %s %s)',
			$title,
			__( 'Photo', 'inventory-presser' ),
			INVP::get_meta( 'photo_number', $id ),
			__( 'of', 'inventory-presser' ),
			invp_get_the_photo_count( $parent->ID )
		);
	}

	/**
	 * Deletes transients that store vehicle photos to help load galleries.
	 *
	 * @param  int $post_id The post ID of a vehicle.
	 * @return void
	 */
	public static function delete_photo_transients( $post_id ) {
		delete_transient( 'invp_get_the_photos_images_' . $post_id );
		delete_transient( 'invp_get_the_photos_image_urls_' . $post_id );
	}

	/**
	 * Filter callback on add_attachment. Decides whether to write meta values
	 * on attachments if they are uploaded to vehicles. If this method
	 * determines the photo sequence number to be 1, the attachment is also set
	 * as the featured image.
	 *
	 * @param  int $post_id Attachment ID.
	 * @return void
	 */
	public static function maybe_number_photo( $post_id ) {
		// Don't double dip during REST API requests.
		if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
			return;
		}

		if ( null === $post_id ) {
			return;
		}

		// Is this new attachment even attached to a post?
		$attachment = get_post( $post_id );
		if ( empty( $attachment->post_parent ) ) {
			// No.
			return;
		}

		// Is this even attached to a vehicle?
		if ( INVP::POST_TYPE !== get_post_type( $attachment->post_parent ) ) {
			// No.
			return;
		}

		// Save the VIN in the photo meta.
		self::save_meta_vin( $post_id, $attachment->post_parent );

		// Save a md5 hash checksum of the attachment in meta.
		self::save_meta_hash( $post_id );

		// Assign and save a sequence number for the photo like 1, 2, 3, etc.
		self::save_meta_photo_number( $post_id, $attachment->post_parent );

		// Delete the transients that hold this vehicle's photos.
		self::delete_photo_transients( $attachment->post_parent );
	}

	/**
	 * Reassigns sequence numbers to all photos attached to a vehicle post.
	 * Useful after multiple attachments or when a photo is deleted.
	 *
	 * @param  int $post_id The post ID of a vehicle.
	 * @return void
	 */
	public static function renumber_photos( $post_id ) {
		// Get all of this vehicle's photos that have numbers.
		$posts = get_children(
			array(
				'meta_key'    => apply_filters( 'invp_prefix_meta_key', 'photo_number' ),
				'orderby'     => 'meta_value_num',
				'post_parent' => $post_id,
				'post_type'   => 'attachment',
			)
		);

		// Get all of this post's attachments with or without numbers.
		$unnumbered_posts = get_children(
			array(
				'post_parent' => $post_id,
				'post_type'   => 'attachment',
			)
		);

		if ( count( $posts ) === count( $unnumbered_posts ) ) {
			return;
		}

		foreach ( $unnumbered_posts as $unnumbered_post ) {
			$have_post_ids = array_column( $posts, 'ID' );
			if ( ! in_array( $unnumbered_post->ID, $have_post_ids, true ) ) {
				$posts[ $unnumbered_post->ID ] = $unnumbered_post;
			}
		}

		$photo_count = count( $posts );
		if ( 0 === $photo_count ) {
			return;
		}

		$n = 1;
		foreach ( $posts as $child_post_id => $post ) {
			self::save_meta_photo_number( $child_post_id, $post_id, $n );
			if ( 1 === $n ) {
				// This is photo number 1, it should be the featured image.
				set_post_thumbnail( $post_id, $child_post_id );
			}
			++$n;
		}
		self::delete_photo_transients( $post_id );
	}

	/**
	 * Saves an MD5 hash checksum of the attachment file bytes in the attachment
	 * post meta. This 32 character string can be used for file comparisons
	 * while not taxing the server as much as other methods.
	 *
	 * @param  int $post_id The post ID of the attachment.
	 * @return void
	 */
	public static function save_meta_hash( $post_id ) {
		// Save a md5 hash checksum of the attachment in meta.
		$file_path = get_attached_file( $post_id );
		if ( false === $file_path ) {
			return;
		}
		update_post_meta(
			$post_id,
			apply_filters( 'invp_prefix_meta_key', 'hash' ),
			hash_file( 'md5', $file_path )
		);
	}

	/**
	 * Saves a sequence number like 1, 2, or 99 in attachment post meta. This
	 * number dictates the order in which the photos will be disabled in sliders
	 * and galleries.
	 *
	 * @param  int $post_id         The post ID of the attachment.
	 * @param  int $parent_post_id  The post ID of the vehicle to which $post_id is a child.
	 * @param  int $sequence_number The sequence number to save. Do not provide to append.
	 * @return void
	 */
	public static function save_meta_photo_number( $post_id, $parent_post_id, $sequence_number = null ) {
		if ( null === $sequence_number ) {
			// Does this photo already have a sequence number?
			if ( ! empty( INVP::get_meta( 'photo_number', $post_id ) ) ) {
				// Yes.
				return;
			}

			// Is the number in the slug?
			// photo-5-of-19-of-vinsgsdkdkdkgf.
			$number = 0;
			if ( ! empty( $_POST['slug'] ) && preg_match( '/photo\-([0-9]+)\-of\-[0-9]+\-of\-.*/', sanitize_text_field( wp_unslash( $_POST['slug'] ) ), $matches ) ) {
				$number = intval( $matches[1] );
			} else {
				/**
				 * This hook fires after the attachment(s) are added, so the
				 * vehicle may have 1 photo that is numbered, and the 3 that
				 * were just added have the vehicle as a parent but do not have
				 * number meta values. This request is for one of the 3, they
				 * are all happening simultaneously.
				 */
				global $wpdb;
				$numbered_count = (int) $wpdb->get_var(
					$wpdb->prepare(
						"SELECT		COUNT( `{$wpdb->prefix}posts`.`ID` )

FROM		`{$wpdb->prefix}postmeta`
			LEFT JOIN `{$wpdb->prefix}posts` ON `{$wpdb->prefix}posts`.`ID` = `{$wpdb->prefix}postmeta`.`post_id`

WHERE		`{$wpdb->prefix}posts`.`post_parent` = %d
			AND `post_type` = 'attachment'
			AND `meta_key` = %s",
						$parent_post_id,
						apply_filters( 'invp_prefix_meta_key', 'photo_number' )
					)
				);

				// How many unnumbered photos does this vehicle have?
				$unnumbered_count = invp_get_the_photo_count( $parent_post_id ) - $numbered_count;
				if ( 1 < $unnumbered_count ) {
					/**
					 * Abort. There are a couple unnumbered photos running this
					 * method simultaneously. Let the photos remain unnumbered
					 * until the user presses the Save Draft or Update button in
					 * the editor.
					 */
					return;
				}

				$number = 1 + $numbered_count;

				if ( 1 === $number ) {
					// This is photo number 1, it should be the featured image.
					set_post_thumbnail( $parent_post_id, $post_id );
				}
			}
		} else {
			$number = $sequence_number;
		}

		// Save the photo number in the photo's meta.
		if ( 0 !== $number ) {
			update_post_meta( $post_id, apply_filters( 'invp_prefix_meta_key', 'photo_number' ), $number );
		}
	}

	/**
	 * Saves the vehicle VIN in attachment meta when an attachment is uploaded
	 * to a vehicle post.
	 *
	 * @param  int $post_id The post ID of the attachment.
	 * @param  int $parent_post_id The post ID of the vehicle to which $post_id is a child.
	 * @return void
	 */
	public static function save_meta_vin( $post_id, $parent_post_id ) {
		$vin = invp_get_the_VIN( $parent_post_id );
		if ( empty( $vin ) ) {
			return;
		}
		update_post_meta( $post_id, apply_filters( 'invp_prefix_meta_key', 'vin' ), $vin );
	}
}