$shortlink = '';

	// Return `?p=` link for all public post types.
	if ( ! empty( $post_id ) ) {
		$post_type = get_post_type_object( $post->post_type );

		if ( 'page' === $post->post_type
			&& 'page' === get_option( 'show_on_front' ) && (int) get_option( 'page_on_front' ) === $post->ID
		) {
			$shortlink = home_url( '/' );
		} elseif ( $post_type && $post_type->public ) {
			$shortlink = home_url( '?p=' . $post_id );
		}
	}

	/**
	 * Filters the shortlink for a post.
	 *
	 * @since 3.0.0
	 *
	 * @param string $shortlink   Shortlink URL.
	 * @param int    $id          Post ID, or 0 for the current post.
	 * @param string $context     The context for the link. One of 'post' or 'query',
	 * @param bool   $allow_slugs Whether to allow post slugs in the shortlink. Not used by default.
	 */
	return apply_filters( 'get_shortlink', $shortlink, $id, $context, $allow_slugs );
}

/**
 * Injects rel=shortlink into the head if a shortlink is defined for the current page.
 *
 * Attached to the {@see 'wp_head'} action.
 *
 * @since 3.0.0
 */
function wp_shortlink_wp_head() {
	$shortlink = wp_get_shortlink( 0, 'query' );

	if ( empty( $shortlink ) ) {
		return;
	}

	echo "<link rel='shortlink' href='" . esc_url( $shortlink ) . "' />\n";
}

/**
 * Sends a Link: rel=shortlink header if a shortlink is defined for the current page.
 *
 * Attached to the {@see 'wp'} action.
 *
 * @since 3.0.0
 */
function wp_shortlink_header() {
	if ( headers_sent() ) {
		return;
	}

	$shortlink = wp_get_shortlink( 0, 'query' );

	if ( empty( $shortlink ) ) {
		return;
	}

	header( 'Link: <' . $shortlink . '>; rel=shortlink', false );
}

/**
 * Displays the shortlink for a post.
 *
 * Must be called from inside "The Loop"
 *
 * Call like the_shortlink( __( 'Shortlinkage FTW' ) )
 *
 * @since 3.0.0
 *
 * @param string $text   Optional The link text or HTML to be displayed. Defaults to 'This is the short link.'
 * @param string $title  Optional The tooltip for the link. Must be sanitized. Defaults to the sanitized post title.
 * @param string $before Optional HTML to display before the link. Default empty.
 * @param string $after  Optional HTML to display after the link. Default empty.
 */
function the_shortlink( $text = '', $title = '', $before = '', $after = '' ) {
	$post = get_post();

	if ( empty( $text ) ) {
		$text = __( 'This is the short link.' );
	}

	if ( empty( $title ) ) {
		$title = the_title_attribute( array( 'echo' => false ) );
	}

	$shortlink = wp_get_shortlink( $post->ID );

	if ( ! empty( $shortlink ) ) {
		$link = '<a rel="shortlink" href="' . esc_url( $shortlink ) . '" title="' . $title . '">' . $text . '</a>';

		/**
		 * Filters the short link anchor tag for a post.
		 *
		 * @since 3.0.0
		 *
		 * @param string $link      Shortlink anchor tag.
		 * @param string $shortlink Shortlink URL.
		 * @param string $text      Shortlink's text.
		 * @param string $title     Shortlink's title attribute.
		 */
		$link = apply_filters( 'the_shortlink', $link, $shortlink, $text, $title );
		echo $before, $link, $after;
	}
}

/**
 * Retrieves the avatar URL.
 *
 * @since 4.2.0
 *
 * @param mixed $id_or_email The avatar to retrieve a URL for. Accepts a user ID, Gravatar MD5 hash,
 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
 * @param array $args {
 *     Optional. Arguments to use instead of the default arguments.
 *
 *     @type int    $size           Height and width of the avatar in pixels. Default 96.
 *     @type string $default        URL for the default image or a default type. Accepts:
 *                                  - '404' (return a 404 instead of a default image)
 *                                  - 'retro' (a 8-bit arcade-style pixelated face)
 *                                  - 'robohash' (a robot)
 *                                  - 'monsterid' (a monster)
 *                                  - 'wavatar' (a cartoon face)
 *                                  - 'identicon' (the "quilt", a geometric pattern)
 *                                  - 'mystery', 'mm', or 'mysteryman' (The Oyster Man)
 *                                  - 'blank' (transparent GIF)
 *                                  - 'gravatar_default' (the Gravatar logo)
 *                                  Default is the value of the 'avatar_default' option,
 *                                  with a fallback of 'mystery'.
 *     @type bool   $force_default  Whether to always show the default image, never the Gravatar.
 *                                  Default false.
 *     @type string $rating         What rating to display avatars up to. Accepts:
 *                                  - 'G' (suitable for all audiences)
 *                                  - 'PG' (possibly offensive, usually for audiences 13 and above)
 *                                  - 'R' (intended for adult audiences above 17)
 *                                  - 'X' (even more mature than above)
 *                                  Default is the value of the 'avatar_rating' option.
 *     @type string $scheme         URL scheme to use. See set_url_scheme() for accepted values.
 *                                  Default null.
 *     @type array  $processed_args When the function returns, the value will be the processed/sanitized $args
 *                                  plus a "found_avatar" guess. Pass as a reference. Default null.
 * }
 * @return string|false The URL of the avatar on success, false on failure.
 */
function get_avatar_url( $id_or_email, $args = null ) {
	$args = get_avatar_data( $id_or_email, $args );
	return $args['url'];
}

/**
 * Check if this comment type allows avatars to be retrieved.
 *
 * @since 5.1.0
 *
 * @param string $comment_type Comment type to check.
 * @return bool Whether the comment type is allowed for retrieving avatars.
 */
function is_avatar_comment_type( $comment_type ) {
	/**
	 * Filters the list of allowed comment types for retrieving avatars.
	 *
	 * @since 3.0.0
	 *
	 * @param array $types An array of content types. Default only contains 'comment'.
	 */
	$allowed_comment_types = apply_filters( 'get_avatar_comment_types', array( 'comment' ) );

	return in_array( $comment_type, (array) $allowed_comment_types, true );
}

/**
 * Retrieves default data about the avatar.
 *
 * @since 4.2.0
 * @since 6.7.0 Gravatar URLs always use HTTPS.
 *
 * @param mixed $id_or_email The avatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
 * @param array $args {
 *     Optional. Arguments to use instead of the default arguments.
 *
 *     @type int    $size           Height and width of the avatar in pixels. Default 96.
 *     @type int    $height         Display height of the avatar in pixels. Defaults to $size.
 *     @type int    $width          Display width of the avatar in pixels. Defaults to $size.
 *     @type string $default        URL for the default image or a default type. Accepts:
 *                                  - '404' (return a 404 instead of a default image)
 *                                  - 'retro' (a 8-bit arcade-style pixelated face)
 *                                  - 'robohash' (a robot)
 *                                  - 'monsterid' (a monster)
 *                                  - 'wavatar' (a cartoon face)
 *                                  - 'identicon' (the "quilt", a geometric pattern)
 *                                  - 'mystery', 'mm', or 'mysteryman' (The Oyster Man)
 *                                  - 'blank' (transparent GIF)
 *                                  - 'gravatar_default' (the Gravatar logo)
 *                                  Default is the value of the 'avatar_default' option,
 *                                  with a fallback of 'mystery'.
 *     @type bool   $force_default  Whether to always show the default image, never the Gravatar.
 *                                  Default false.
 *     @type string $rating         What rating to display avatars up to. Accepts:
 *                                  - 'G' (suitable for all audiences)
 *                                  - 'PG' (possibly offensive, usually for audiences 13 and above)
 *                                  - 'R' (intended for adult audiences above 17)
 *                                  - 'X' (even more mature than above)
 *                                  Default is the value of the 'avatar_rating' option.
 *     @type string $scheme         URL scheme to use. See set_url_scheme() for accepted values.
 *                                  For Gravatars this setting is ignored and HTTPS is used to avoid
 *                                  unnecessary redirects. The setting is retained for systems using
 *                                  the {@see 'pre_get_avatar_data'} filter to customize avatars.
 *                                  Default null.
 *     @type array  $processed_args When the function returns, the value will be the processed/sanitized $args
 *                                  plus a "found_avatar" guess. Pass as a reference. Default null.
 *     @type string $extra_attr     HTML attributes to insert in the IMG element. Is not sanitized.
 *                                  Default empty.
 * }
 * @return array {
 *     Along with the arguments passed in `$args`, this will contain a couple of extra arguments.
 *
 *     @type bool         $found_avatar True if an avatar was found for this user,
 *                                      false or not set if none was found.
 *     @type string|false $url          The URL of the avatar that was found, or false.
 * }
 */
function get_avatar_data( $id_or_email, $args = null ) {
	$args = wp_parse_args(
		$args,
		array(
			'size'           => 96,
			'height'         => null,
			'width'          => null,
			'default'        => get_option( 'avatar_default', 'mystery' ),
			'force_default'  => false,
			'rating'         => get_option( 'avatar_rating' ),
			'scheme'         => null,
			'processed_args' => null, // If used, should be a reference.
			'extra_attr'     => '',
		)
	);

	if ( is_numeric( $args['size'] ) ) {
		$args['size'] = absint( $args['size'] );
		if ( ! $args['size'] ) {
			$args['size'] = 96;
		}
	} else {
		$args['size'] = 96;
	}

	if ( is_numeric( $args['height'] ) ) {
		$args['height'] = absint( $args['height'] );
		if ( ! $args['height'] ) {
			$args['height'] = $args['size'];
		}
	} else {
		$args['height'] = $args['size'];
	}

	if ( is_numeric( $args['width'] ) ) {
		$args['width'] = absint( $args['width'] );
		if ( ! $args['width'] ) {
			$args['width'] = $args['size'];
		}
	} else {
		$args['width'] = $args['size'];
	}

	if ( empty( $args['default'] ) ) {
		$args['default'] = get_option( 'avatar_default', 'mystery' );
	}

	switch ( $args['default'] ) {
		case 'mm':
		case 'mystery':
		case 'mysteryman':
			$args['default'] = 'mm';
			break;
		case 'gravatar_default':
			$args['default'] = false;
			break;
	}

	$args['force_default'] = (bool) $args['force_default'];

	$args['rating'] = strtolower( $args['rating'] );

	$args['found_avatar'] = false;

	/**
	 * Filters whether to retrieve the avatar URL early.
	 *
	 * Passing a non-null value in the 'url' member of the return array will
	 * effectively short circuit get_avatar_data(), passing the value through
	 * the {@see 'get_avatar_data'} filter and returning early.
	 *
	 * @since 4.2.0
	 *
	 * @param array $args        Arguments passed to get_avatar_data(), after processing.
	 * @param mixed $id_or_email The avatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
	 */
	$args = apply_filters( 'pre_get_avatar_data', $args, $id_or_email );

	if ( isset( $args['url'] ) ) {
		/** This filter is documented in wp-includes/link-template.php */
		return apply_filters( 'get_avatar_data', $args, $id_or_email );
	}

	$email_hash = '';
	$user       = false;
	$email      = false;

	if ( is_object( $id_or_email ) && isset( $id_or_email->comment_ID ) ) {
		$id_or_email = get_comment( $id_or_email );
	}

	// Process the user identifier.
	if ( is_numeric( $id_or_email ) ) {
		$user = get_user_by( 'id', absint( $id_or_email ) );
	} elseif ( is_string( $id_or_email ) ) {
		if ( str_contains( $id_or_email, '@md5.gravatar.com' ) ) {
			// MD5 hash.
			list( $email_hash ) = explode( '@', $id_or_email );
		} else {
			// Email address.
			$email = $id_or_email;
		}
	} elseif ( $id_or_email instanceof WP_User ) {
		// User object.
		$user = $id_or_email;
	} elseif ( $id_or_email instanceof WP_Post ) {
		// Post object.
		$user = get_user_by( 'id', (int) $id_or_email->post_author );
	} elseif ( $id_or_email instanceof WP_Comment ) {
		if ( ! is_avatar_comment_type( get_comment_type( $id_or_email ) ) ) {
			$args['url'] = false;
			/** This filter is documented in wp-includes/link-template.php */
			return apply_filters( 'get_avatar_data', $args, $id_or_email );
		}

		if ( ! empty( $id_or_email->user_id ) ) {
			$user = get_user_by( 'id', (int) $id_or_email->user_id );
		}
		if ( ( ! $user || is_wp_error( $user ) ) && ! empty( $id_or_email->comment_author_email ) ) {
			$email = $id_or_email->comment_author_email;
		}
	}

	if ( ! $email_hash ) {
		if ( $user ) {
			$email = $user->user_email;
		}

		if ( $email ) {
			$email_hash = md5( strtolower( trim( $email ) ) );
		}
	}

	if ( $email_hash ) {
		$args['found_avatar'] = true;
	}

	$url_args = array(
		's' => $args['size'],
		'd' => $args['default'],
		'f' => $args['force_default'] ? 'y' : false,
		'r' => $args['rating'],
	);

	/*
	 * Gravatars are always served over HTTPS.
	 *
	 * The Gravatar website redirects HTTP requests to HTTPS URLs so always
	 * use the HTTPS scheme to avoid unnecessary redirects.
	 */
	$url = 'https://secure.gravatar.com/avatar/' . $email_hash;

	$url = add_query_arg(
		rawurlencode_deep( array_filter( $url_args ) ),
		$url
	);

	/**
	 * Filters the avatar URL.
	 *
	 * @since 4.2.0
	 *
	 * @param string $url         The URL of the avatar.
	 * @param mixed  $id_or_email The avatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                            user email, WP_User object, WP_Post object, or WP_Comment object.
	 * @param array  $args        Arguments passed to get_avatar_data(), after processing.
	 */
	$args['url'] = apply_filters( 'get_avatar_url', $url, $id_or_email, $args );

	/**
	 * Filters the avatar data.
	 *
	 * @since 4.2.0
	 *
	 * @param array $args        Arguments passed to get_avatar_data(), after processing.
	 * @param mixed $id_or_email The avatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
	 */
	return apply_filters( 'get_avatar_data', $args, $id_or_email );
}

/**
 * Retrieves the URL of a file in the theme.
 *
 * Searches in the stylesheet directory before the template directory so themes
 * which inherit from a parent theme can just override one file.
 *
 * @since 4.7.0
 *
 * @param string $file Optional. File to search for in the stylesheet directory.
 * @return string The URL of the file.
 */
function get_theme_file_uri( $file = '' ) {
	$file = ltrim( $file, '/' );

	$stylesheet_directory = get_stylesheet_directory();

	if ( empty( $file ) ) {
		$url = get_stylesheet_directory_uri();
	} elseif ( get_template_directory() !== $stylesheet_directory && file_exists( $stylesheet_directory . '/' . $file ) ) {
		$url = get_stylesheet_directory_uri() . '/' . $file;
	} else {
		$url = get_template_directory_uri() . '/' . $file;
	}

	/**
	 * Filters the URL to a file in the theme.
	 *
	 * @since 4.7.0
	 *
	 * @param string $url  The file URL.
	 * @param string $file The requested file to search for.
	 */
	return apply_filters( 'theme_file_uri', $url, $file );
}

/**
 * Retrieves the URL of a file in the parent theme.
 *
 * @since 4.7.0
 *
 * @param string $file Optional. File to return the URL for in the template directory.
 * @return string The URL of the file.
 */
function get_parent_theme_file_uri( $file = '' ) {
	$file = ltrim( $file, '/' );

	if ( empty( $file ) ) {
		$url = get_template_directory_uri();
	} else {
		$url = get_template_directory_uri() . '/' . $file;
	}

	/**
	 * Filters the URL to a file in the parent theme.
	 *
	 * @since 4.7.0
	 *
	 * @param string $url  The file URL.
	 * @param string $file The requested file to search for.
	 */
	return apply_filters( 'parent_theme_file_uri', $url, $file );
}

/**
 * Retrieves the path of a file in the theme.
 *
 * Searches in the stylesheet directory before the template directory so themes
 * which inherit from a parent theme can just override one file.
 *
 * @since 4.7.0
 *
 * @param string $file Optional. File to search for in the stylesheet directory.
 * @return string The path of the file.
 */
function get_theme_file_path( $file = '' ) {
	$file = ltrim( $file, '/' );

	$stylesheet_directory = get_stylesheet_directory();
	$template_directory   = get_template_directory();

	if ( empty( $file ) ) {
		$path = $stylesheet_directory;
	} elseif ( $stylesheet_directory !== $template_directory && file_exists( $stylesheet_directory . '/' . $file ) ) {
		$path = $stylesheet_directory . '/' . $file;
	} else {
		$path = $template_directory . '/' . $file;
	}

	/**
	 * Filters the path to a file in the theme.
	 *
	 * @since 4.7.0
	 *
	 * @param string $path The file path.
	 * @param string $file The requested file to search for.
	 */
	return apply_filters( 'theme_file_path', $path, $file );
}

/**
 * Retrieves the path of a file in the parent theme.
 *
 * @since 4.7.0
 *
 * @param string $file Optional. File to return the path for in the template directory.
 * @return string The path of the file.
 */
function get_parent_theme_file_path( $file = '' ) {
	$file = ltrim( $file, '/' );

	if ( empty( $file ) ) {
		$path = get_template_directory();
	} else {
		$path = get_template_directory() . '/' . $file;
	}

	/**
	 * Filters the path to a file in the parent theme.
	 *
	 * @since 4.7.0
	 *
	 * @param string $path The file path.
	 * @param string $file The requested file to search for.
	 */
	return apply_filters( 'parent_theme_file_path', $path, $file );
}

/**
 * Retrieves the URL to the privacy policy page.
 *
 * @since 4.9.6
 *
 * @return string The URL to the privacy policy page. Empty string if it doesn't exist.
 */
function get_privacy_policy_url() {
	$url            = '';
	$policy_page_id = (int) get_option( 'wp_page_for_privacy_policy' );

	if ( ! empty( $policy_page_id ) && get_post_status( $policy_page_id ) === 'publish' ) {
		$url = (string) get_permalink( $policy_page_id );
	}

	/**
	 * Filters the URL of the privacy policy page.
	 *
	 * @since 4.9.6
	 *
	 * @param string $url            The URL to the privacy policy page. Empty string
	 *                               if it doesn't exist.
	 * @param int    $policy_page_id The ID of privacy policy page.
	 */
	return apply_filters( 'privacy_policy_url', $url, $policy_page_id );
}

/**
 * Displays the privacy policy link with formatting, when applicable.
 *
 * @since 4.9.6
 *
 * @param string $before Optional. Display before privacy policy link. Default empty.
 * @param string $after  Optional. Display after privacy policy link. Default empty.
 */
function the_privacy_policy_link( $before = '', $after = '' ) {
	echo get_the_privacy_policy_link( $before, $after );
}

/**
 * Returns the privacy policy link with formatting, when applicable.
 *
 * @since 4.9.6
 * @since 6.2.0 Added 'privacy-policy' rel attribute.
 *
 * @param string $before Optional. Display before privacy policy link. Default empty.
 * @param string $after  Optional. Display after privacy policy link. Default empty.
 * @return string Markup for the link and surrounding elements. Empty string if it
 *                doesn't exist.
 */
function get_the_privacy_policy_link( $before = '', $after = '' ) {
	$link               = '';
	$privacy_policy_url = get_privacy_policy_url();
	$policy_page_id     = (int) get_option( 'wp_page_for_privacy_policy' );
	$page_title         = ( $policy_page_id ) ? get_the_title( $policy_page_id ) : '';

	if ( $privacy_policy_url && $page_title ) {
		$link = sprintf(
			'<a class="privacy-policy-link" href="%s" rel="privacy-policy">%s</a>',
			esc_url( $privacy_policy_url ),
			esc_html( $page_title )
		);
	}

	/**
	 * Filters the privacy policy link.
	 *
	 * @since 4.9.6
	 *
	 * @param string $link               The privacy policy link. Empty string if it
	 *                                   doesn't exist.
	 * @param string $privacy_policy_url The URL of the privacy policy. Empty string
	 *                                   if it doesn't exist.
	 */
	$link = apply_filters( 'the_privacy_policy_link', $link, $privacy_policy_url );

	if ( $link ) {
		return $before . $link . $after;
	}

	return '';
}

/**
 * Returns an array of URL hosts which are considered to be internal hosts.
 *
 * By default the list of internal hosts is comprised of the host name of
 * the site's home_url() (as parsed by wp_parse_url()).
 *
 * This list is used when determining if a specified URL is a link to a page on
 * the site itself or a link offsite (to an external host). This is used, for
 * example, when determining if the "nofollow" attribute should be applied to a
 * link.
 *
 * @see wp_is_internal_link
 *
 * @since 6.2.0
 *
 * @return string[] An array of URL hosts.
 */
function wp_internal_hosts() {
	static $internal_hosts;

	if ( empty( $internal_hosts ) ) {
		/**
		 * Filters the array of URL hosts which are considered internal.
		 *
		 * @since 6.2.0
		 *
		 * @param string[] $internal_hosts An array of internal URL hostnames.
		 */
		$internal_hosts = apply_filters(
			'wp_internal_hosts',
			array(
				wp_parse_url( home_url(), PHP_URL_HOST ),
			)
		);
		$internal_hosts = array_unique(
			array_map( 'strtolower', (array) $internal_hosts )
		);
	}

	return $internal_hosts;
}

/**
 * Determines whether or not the specified URL is of a host included in the internal hosts list.
 *
 * @see wp_internal_hosts()
 *
 * @since 6.2.0
 *
 * @param string $link The URL to test.
 * @return bool Returns true for internal URLs and false for all other URLs.
 */
function wp_is_internal_link( $link ) {
	$link = strtolower( $link );
	if ( in_array( wp_parse_url( $link, PHP_URL_SCHEME ), wp_allowed_protocols(), true ) ) {
		return in_array( wp_parse_url( $link, PHP_URL_HOST ), wp_internal_hosts(), true );
	}
	return false;
}