class-amp-post-meta-box.php

<?php
/**
 * AMP meta box settings.
 *
 * @package AMP
 * @since 0.6
 */

/**
 * Post meta box class.
 *
 * @since 0.6
 */
class AMP_Post_Meta_Box {

	/**
	 * Assets handle.
	 *
	 * @since 0.6
	 * @var string
	 */
	const ASSETS_HANDLE = 'amp-post-meta-box';

	/**
	 * The enabled status post meta value.
	 *
	 * @since 0.6
	 * @var string
	 */
	const ENABLED_STATUS = 'enabled';

	/**
	 * The disabled status post meta value.
	 *
	 * @since 0.6
	 * @var string
	 */
	const DISABLED_STATUS = 'disabled';

	/**
	 * The status post meta key.
	 *
	 * @since 0.6
	 * @var string
	 */
	const STATUS_POST_META_KEY = 'amp_status';

	/**
	 * The field name for the enabled/disabled radio buttons.
	 *
	 * @since 0.6
	 * @var string
	 */
	const STATUS_INPUT_NAME = 'amp_status';

	/**
	 * The nonce name.
	 *
	 * @since 0.6
	 * @var string
	 */
	const NONCE_NAME = 'amp-status-nonce';

	/**
	 * The nonce action.
	 *
	 * @since 0.6
	 * @var string
	 */
	const NONCE_ACTION = 'amp-update-status';

	/**
	 * Initialize.
	 *
	 * @since 0.6
	 */
	public function init() {
		register_meta( 'post', self::STATUS_POST_META_KEY, array(
			'sanitize_callback' => array( $this, 'sanitize_status' ),
			'type'              => 'string',
			'description'       => __( 'AMP status.', 'amp' ),
			'show_in_rest'      => true,
			'single'            => true,
		) );

		add_action( 'admin_enqueue_scripts', array( $this, 'enqueue_admin_assets' ) );
		add_action( 'post_submitbox_misc_actions', array( $this, 'render_status' ) );
		add_action( 'save_post', array( $this, 'save_amp_status' ) );
		add_filter( 'preview_post_link', array( $this, 'preview_post_link' ) );
	}

	/**
	 * Sanitize status.
	 *
	 * @param string $status Status.
	 * @return string Sanitized status. Empty string when invalid.
	 */
	public function sanitize_status( $status ) {
		$status = strtolower( trim( $status ) );
		if ( ! in_array( $status, array( 'enabled', 'disabled' ), true ) ) {
			/*
			 * In lieu of actual validation being available, clear the status entirely
			 * so that the underlying default status will be used instead.
			 * In the future it would be ideal if register_meta() accepted a
			 * validate_callback as well which the REST API could leverage.
			 */
			$status = '';
		}
		return $status;
	}

	/**
	 * Enqueue admin assets.
	 *
	 * @since 0.6
	 */
	public function enqueue_admin_assets() {
		$post     = get_post();
		$screen   = get_current_screen();
		$validate = (
			isset( $screen->base )
			&&
			'post' === $screen->base
			&&
			is_post_type_viewable( $post->post_type )
		);
		if ( ! $validate ) {
			return;
		}

		// Styles.
		wp_enqueue_style(
			self::ASSETS_HANDLE,
			amp_get_asset_url( 'css/amp-post-meta-box.css' ),
			false,
			AMP__VERSION
		);

		// Scripts.
		wp_enqueue_script(
			self::ASSETS_HANDLE,
			amp_get_asset_url( 'js/amp-post-meta-box.js' ),
			array( 'jquery' ),
			AMP__VERSION
		);

		if ( current_theme_supports( 'amp' ) ) {
			$availability   = AMP_Theme_Support::get_template_availability( $post );
			$support_errors = $availability['errors'];
		} else {
			$support_errors = AMP_Post_Type_Support::get_support_errors( $post );
		}

		wp_add_inline_script( self::ASSETS_HANDLE, sprintf( 'ampPostMetaBox.boot( %s );',
			wp_json_encode( array(
				'previewLink'     => esc_url_raw( add_query_arg( amp_get_slug(), '', get_preview_post_link( $post ) ) ),
				'canonical'       => amp_is_canonical(),
				'enabled'         => empty( $support_errors ),
				'canSupport'      => 0 === count( array_diff( $support_errors, array( 'post-status-disabled' ) ) ),
				'statusInputName' => self::STATUS_INPUT_NAME,
				'l10n'            => array(
					'ampPreviewBtnLabel' => __( 'Preview changes in AMP (opens in new window)', 'amp' ),
				),
			) )
		) );
	}

	/**
	 * Render AMP status.
	 *
	 * @since 0.6
	 * @param WP_Post $post Post.
	 */
	public function render_status( $post ) {
		$verify = (
			isset( $post->ID )
			&&
			is_post_type_viewable( $post->post_type )
			&&
			current_user_can( 'edit_post', $post->ID )
		);

		if ( true !== $verify ) {
			return;
		}

		/*
		 * When theme support is present then theme templates can be served in AMP and we check first if the template is available.
		 * Checking for template availability will include a check for get_support_errors. Otherwise, if theme support is not present
		 * then we just check get_support_errors.
		 */
		if ( current_theme_supports( 'amp' ) ) {
			$availability = AMP_Theme_Support::get_template_availability( $post );
			$status       = $availability['supported'] ? self::ENABLED_STATUS : self::DISABLED_STATUS;
			$errors       = array_diff( $availability['errors'], array( 'post-status-disabled' ) ); // Subtract the status which the metabox will allow to be toggled.
			if ( true === $availability['immutable'] ) {
				$errors[] = 'status_immutable';
			}
		} else {
			$errors = AMP_Post_Type_Support::get_support_errors( $post );
			$status = empty( $errors ) ? self::ENABLED_STATUS : self::DISABLED_STATUS;
			$errors = array_diff( $errors, array( 'post-status-disabled' ) ); // Subtract the status which the metabox will allow to be toggled.
		}

		$labels = array(
			'enabled'  => __( 'Enabled', 'amp' ),
			'disabled' => __( 'Disabled', 'amp' ),
		);

		// The preceding variables are used inside the following amp-status.php template.
		include AMP__DIR__ . '/templates/admin/amp-status.php';
	}

	/**
	 * Save AMP Status.
	 *
	 * @since 0.6
	 * @param int $post_id The Post ID.
	 */
	public function save_amp_status( $post_id ) {
		$verify = (
			isset( $_POST[ self::NONCE_NAME ] )
			&&
			isset( $_POST[ self::STATUS_INPUT_NAME ] )
			&&
			wp_verify_nonce( sanitize_key( wp_unslash( $_POST[ self::NONCE_NAME ] ) ), self::NONCE_ACTION )
			&&
			current_user_can( 'edit_post', $post_id )
			&&
			! wp_is_post_revision( $post_id )
			&&
			! wp_is_post_autosave( $post_id )
		);

		if ( true === $verify ) {
			update_post_meta(
				$post_id,
				self::STATUS_POST_META_KEY,
				$_POST[ self::STATUS_INPUT_NAME ] // Note: The sanitize_callback has been supplied in the register_meta() call above.
			);
		}
	}

	/**
	 * Modify post preview link.
	 *
	 * Add the AMP query var is the amp-preview flag is set.
	 *
	 * @since 0.6
	 *
	 * @param string $link The post preview link.
	 * @return string Preview URL.
	 */
	public function preview_post_link( $link ) {
		$is_amp = (
			isset( $_POST['amp-preview'] ) // WPCS: CSRF ok.
			&&
			'do-preview' === sanitize_key( wp_unslash( $_POST['amp-preview'] ) ) // WPCS: CSRF ok.
		);

		if ( $is_amp ) {
			$link = add_query_arg( amp_get_slug(), true, $link );
		}

		return $link;
	}

}