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<?php
/**
* REST API: WP_REST_URL_Details_Controller class
*
* @package WordPress
* @subpackage REST_API
* @since 5.9.0
*/
/**
* Controller which provides REST endpoint for retrieving information
* from a remote site's HTML response.
*
* @since 5.9.0
*
* @see WP_REST_Controller
*/
class WP_REST_URL_Details_Controller extends WP_REST_Controller {
/**
* Constructs the controller.
*
* @since 5.9.0
*/
public function __construct() {
$this->namespace = 'wp-block-editor/v1';
$this->rest_base = 'url-details';
}
/**
* Registers the necessary REST API routes.
*
* @since 5.9.0
*/
public function register_routes() {
register_rest_route(
$this->namespace,
'/' . $this->rest_base,
array(
array(
'methods' => WP_REST_Server::READABLE,
'callback' => array( $this, 'parse_url_details' ),
'args' => array(
'url' => array(
'required' => true,
'description' => __( 'The URL to process.' ),
'validate_callback' => 'wp_http_validate_url',
'sanitize_callback' => 'sanitize_url',
'type' => 'string',
'format' => 'uri',
),
),
'permission_callback' => array( $this, 'permissions_check' ),
'schema' => array( $this, 'get_public_item_schema' ),
),
)
);
}
/**
* Retrieves the item's schema, conforming to JSON Schema.
*
* @since 5.9.0
*
* @return array Item schema data.
*/
public function get_item_schema() {
if ( $this->schema ) {
return $this->add_additional_fields_schema( $this->schema );
}
$this->schema = array(
'$schema' => 'http://json-schema.org/draft-04/schema#',
'title' => 'url-details',
'type' => 'object',
'properties' => array(
'title' => array(
'description' => sprintf(
/* translators: %s: HTML title tag. */
__( 'The contents of the %s element from the URL.' ),
'<title>'
),
'type' => 'string',
'context' => array( 'view', 'edit', 'embed' ),
'readonly' => true,
),
'icon' => array(
'description' => sprintf(
/* translators: %s: HTML link tag. */
__( 'The favicon image link of the %s element from the URL.' ),
'<link rel="icon">'
),
'type' => 'string',
'format' => 'uri',
'context' => array( 'view', 'edit', 'embed' ),
'readonly' => true,
),
'description' => array(
'description' => sprintf(
/* translators: %s: HTML meta tag. */
__( 'The content of the %s element from the URL.' ),
'<meta name="description">'
),
'type' => 'string',
'context' => array( 'view', 'edit', 'embed' ),
'readonly' => true,
),
'image' => array(
'description' => sprintf(
/* translators: 1: HTML meta tag, 2: HTML meta tag. */
__( 'The Open Graph image link of the %1$s or %2$s element from the URL.' ),
'<meta property="og:image">',
'<meta property="og:image:url">'
),
'type' => 'string',
'format' => 'uri',
'context' => array( 'view', 'edit', 'embed' ),
'readonly' => true,
),
),
);
return $this->add_additional_fields_schema( $this->schema );
}
/**
* Retrieves the contents of the title tag from the HTML response.
*
* @since 5.9.0
*
* @param WP_REST_Request $request Full details about the request.
* @return WP_REST_Response|WP_Error The parsed details as a response object. WP_Error if there are errors.
*/
public function parse_url_details( $request ) {
$url = untrailingslashit( $request['url'] );
if ( empty( $url ) ) {
return new WP_Error( 'rest_invalid_url', __( 'Invalid URL' ), array( 'status' => 404 ) );
}
// Transient per URL.
$cache_key = $this->build_cache_key_for_url( $url );
// Attempt to retrieve cached response.
$cached_response = $this->get_cache( $cache_key );
if ( ! empty( $cached_response ) ) {
$remote_url_response = $cached_response;
} else {
$remote_url_response = $this->get_remote_url( $url );
// Exit if we don't have a valid body or it's empty.
if ( is_wp_error( $remote_url_response ) || empty( $remote_url_response ) ) {
return $remote_url_response;
}
// Cache the valid response.
$this->set_cache( $cache_key, $remote_url_response );
}
$html_head = $this->get_document_head( $remote_url_response );
$meta_elements = $this->get_meta_with_content_elements( $html_head );
$data = $this->add_additional_fields_to_object(
array(
'title' => $this->get_title( $html_head ),
'icon' => $this->get_icon( $html_head, $url ),
'description' => $this->get_description( $meta_elements ),
'image' => $this->get_image( $meta_elements, $url ),
),
$request
);
// Wrap the data in a response object.
$response = rest_ensure_response( $data );
/**
* Filters the URL data for the response.
*
* @since 5.9.0
*
* @param WP_REST_Response $response The response object.
* @param string $url The requested URL.
* @param WP_REST_Request $request Request object.
* @param string $remote_url_response HTTP response body from the remote URL.
*/
return apply_filters( 'rest_prepare_url_details', $response, $url, $request, $remote_url_response );
}
/**
* Checks whether a given request has permission to read remote URLs.
*
* @since 5.9.0
*
* @return true|WP_Error True if the request has permission, else WP_Error.
*/
public function permissions_check() {
if ( current_user_can( 'edit_posts' ) ) {
return true;
}
foreach ( get_post_types( array( 'show_in_rest' => true ), 'objects' ) as $post_type ) {
if ( current_user_can( $post_type->cap->edit_posts ) ) {
return true;
}
}
return new WP_Error(
'rest_cannot_view_url_details',
__( 'Sorry, you are not allowed to process remote URLs.' ),
array( 'status' => rest_authorization_required_code() )
);
}
/**
* Retrieves the document title from a remote URL.
*
* @since 5.9.0
*
* @param string $url The website URL whose HTML to access.
* @return string|WP_Error The HTTP response from the remote URL on success.
* WP_Error if no response or no content.
*/
private function get_remote_url( $url ) {
/*
* Provide a modified UA string to workaround web properties which block WordPress "Pingbacks".
* Why? The UA string used for pingback requests contains `WordPress/` which is very similar
* to that used as the default UA string by the WP HTTP API. Therefore requests from this
* REST endpoint are being unintentionally blocked as they are misidentified as pingback requests.
* By slightly modifying the UA string, but still retaining the "WordPress" identification (via "WP")
* we are able to work around this issue.
* Example UA string: `WP-URLDetails/5.9-alpha-51389 (+http://localhost:8888)`.
*/
$modified_user_agent = 'WP-URLDetails/' . get_bloginfo( 'version' ) . ' (+' . get_bloginfo( 'url' ) . ')';
$args = array(
'limit_response_size' => 150 * KB_IN_BYTES,
'user-agent' => $modified_user_agent,
);
/**
* Filters the HTTP request args for URL data retrieval.
*
* Can be used to adjust response size limit and other WP_Http::request() args.
*
* @since 5.9.0
*
* @param array $args Arguments used for the HTTP request.
* @param string $url The attempted URL.
*/
$args = apply_filters( 'rest_url_details_http_request_args', $args, $url );
$response = wp_safe_remote_get( $url, $args );
if ( WP_Http::OK !== wp_remote_retrieve_response_code( $response ) ) {
// Not saving the error response to cache since the error might be temporary.
return new WP_Error(
'no_response',
__( 'URL not found. Response returned a non-200 status code for this URL.' ),
array( 'status' => WP_Http::NOT_FOUND )
);
}
$remote_body = wp_remote_retrieve_body( $response );
if ( empty( $remote_body ) ) {
return new WP_Error(
'no_content',
__( 'Unable to retrieve body from response at this URL.' ),
array( 'status' => WP_Http::NOT_FOUND )
);
}
return $remote_body;
}
/**
* Parses the title tag contents from the provided HTML.
*
* @since 5.9.0
*
* @param string $html The HTML from the remote website at URL.
* @return string The title tag contents on success. Empty string if not found.
*/
private function get_title( $html ) {
$pattern = '#<title[^>]*>(.*?)<\s*/\s*title>#is';
preg_match( $pattern, $html, $match_title );
if ( empty( $match_title[1] ) || ! is_string( $match_title[1] ) ) {
return '';
}
$title = trim( $match_title[1] );
return $this->prepare_metadata_for_output( $title );
}
/**
* Parses the site icon from the provided HTML.
*
* @since 5.9.0
*
* @param string $html The HTML from the remote website at URL.
* @param string $url The target website URL.
* @return string The icon URI on success. Empty string if not found.
*/
private function get_icon( $html, $url ) {
// Grab the icon's link element.
$pattern = '#<link\s[^>]*rel=(?:[\"\']??)\s*(?:icon|shortcut icon|icon shortcut)\s*(?:[\"\']??)[^>]*\/?>#isU';
preg_match( $pattern, $html, $element );
if ( empty( $element[0] ) || ! is_string( $element[0] ) ) {
return '';
}
$element = trim( $element[0] );
// Get the icon's href value.
$pattern = '#href=([\"\']??)([^\" >]*?)\\1[^>]*#isU';
preg_match( $pattern, $element, $icon );
if ( empty( $icon[2] ) || ! is_string( $icon[2] ) ) {
return '';
}
$icon = trim( $icon[2] );
// If the icon is a data URL, return it.
$parsed_icon = parse_url( $icon );
if ( isset( $parsed_icon['scheme'] ) && 'data' === $parsed_icon['scheme'] ) {
return $icon;
}
// Attempt to convert relative URLs to absolute.
if ( ! is_string( $url ) || '' === $url ) {
return $icon;
}
$parsed_url = parse_url( $url );
if ( isset( $parsed_url['scheme'] ) && isset( $parsed_url['host'] ) ) {
$root_url = $parsed_url['scheme'] . '://' . $parsed_url['host'] . '/';
$icon = WP_Http::make_absolute_url( $icon, $root_url );
}
return $icon;
}
/**
* Parses the meta description from the provided HTML.
*
* @since 5.9.0
*
* @param array $meta_elements {
* A multidimensional indexed array on success, else empty array.
*
* @type string[] $0 Meta elements with a content attribute.
* @type string[] $1 Content attribute's opening quotation mark.
* @type string[] $2 Content attribute's value for each meta element.
* }
* @return string The meta description contents on success. Empty string if not found.
*/
private function get_description( $meta_elements ) {
// Bail out if there are no meta elements.
if ( empty( $meta_elements[0] ) ) {
return '';
}
$description = $this->get_metadata_from_meta_element(
$meta_elements,
'name',
'(?:description|og:description)'
);
// Bail out if description not found.
if ( '' === $description ) {
return '';
}
return $this->prepare_metadata_for_output( $description );
}
/**
* Parses the Open Graph (OG) Image from the provided HTML.
*
* See: https://ogp.me/.
*
* @since 5.9.0
*
* @param array $meta_elements {
* A multidimensional indexed array on success, else empty array.
*
* @type string[] $0 Meta elements with a content attribute.
* @type string[] $1 Content attribute's opening quotation mark.
* @type string[] $2 Content attribute's value for each meta element.
* }
* @param string $url The target website URL.
* @return string The OG image on success. Empty string if not found.
*/
private function get_image( $meta_elements, $url ) {
$image = $this->get_metadata_from_meta_element(
$meta_elements,
'property',
'(?:og:image|og:image:url)'
);
// Bail out if image not found.
if ( '' === $image ) {
return '';
}
// Attempt to convert relative URLs to absolute.
$parsed_url = parse_url( $url );
if ( isset( $parsed_url['scheme'] ) && isset( $parsed_url['host'] ) ) {
$root_url = $parsed_url['scheme'] . '://' . $parsed_url['host'] . '/';
$image = WP_Http::make_absolute_url( $image, $root_url );
}
return $image;
}
/**
* Prepares the metadata by:
* - stripping all HTML tags and tag entities.
* - converting non-tag entities into characters.
*
* @since 5.9.0
*
* @param string $metadata The metadata content to prepare.
* @return string The prepared metadata.
*/
private function prepare_metadata_for_output( $metadata ) {
$metadata = html_entity_decode( $metadata, ENT_QUOTES, get_bloginfo( 'charset' ) );
$metadata = wp_strip_all_tags( $metadata );
return $metadata;
}
/**
* Utility function to build cache key for a given URL.
*
* @since 5.9.0
*
* @param string $url The URL for which to build a cache key.
* @return string The cache key.
*/
private function build_cache_key_for_url( $url ) {
return 'g_url_details_response_' . md5( $url );
}
/**
* Utility function to retrieve a value from the cache at a given key.
*
* @since 5.9.0
*
* @param string $key The cache key.
* @return mixed The value from the cache.
*/
private function get_cache( $key ) {
return get_site_transient( $key );
}
/**
* Utility function to cache a given data set at a given cache key.
*
* @since 5.9.0
*
* @param string $key The cache key under which to store the value.
* @param string $data The data to be stored at the given cache key.
* @return bool True when transient set. False if not set.
*/
private function set_cache( $key, $data = '' ) {
$ttl = HOUR_IN_SECONDS;
/**
* Filters the cache expiration.
*
* Can be used to adjust the time until expiration in seconds for the cache
* of the data retrieved for the given URL.
*
* @since 5.9.0
*
* @param int $ttl The time until cache expiration in seconds.
*/
$cache_expiration = apply_filters( 'rest_url_details_cache_expiration', $ttl );
return set_site_transient( $key, $data, $cache_expiration );
}
/**
* Retrieves the head element section.
*
* @since 5.9.0
*
* @param string $html The string of HTML to parse.
* @return string The `<head>..</head>` section on success. Given `$html` if not found.
*/
private function get_document_head( $html ) {
$head_html = $html;
// Find the opening `<head>` tag.
$head_start = strpos( $html, '<head' );
if ( false === $head_start ) {
// Didn't find it. Return the original HTML.
return $html;
}
// Find the closing `</head>` tag.
$head_end = strpos( $head_html, '</head>' );
if ( false === $head_end ) {
// Didn't find it. Find the opening `<body>` tag.
$head_end = strpos( $head_html, '<body' );
// Didn't find it. Return the original HTML.
if ( false === $head_end ) {
return $html;
}
}
// Extract the HTML from opening tag to the closing tag. Then add the closing tag.
$head_html = substr( $head_html, $head_start, $head_end );
$head_html .= '</head>';
return $head_html;
}
/**
* Gets all the meta tag elements that have a 'content' attribute.
*
* @since 5.9.0
*
* @param string $html The string of HTML to be parsed.
* @return array {
* A multidimensional indexed array on success, else empty array.
*
* @type string[] $0 Meta elements with a content attribute.
* @type string[] $1 Content attribute's opening quotation mark.
* @type string[] $2 Content attribute's value for each meta element.
* }
*/
private function get_meta_with_content_elements( $html ) {
/*
* Parse all meta elements with a content attribute.
*
* Why first search for the content attribute rather than directly searching for name=description element?
* tl;dr The content attribute's value will be truncated when it contains a > symbol.
*
* The content attribute's value (i.e. the description to get) can have HTML in it and be well-formed as
* it's a string to the browser. Imagine what happens when attempting to match for the name=description
* first. Hmm, if a > or /> symbol is in the content attribute's value, then it terminates the match
* as the element's closing symbol. But wait, it's in the content attribute and is not the end of the
* element. This is a limitation of using regex. It can't determine "wait a minute this is inside of quotation".
* If this happens, what gets matched is not the entire element or all of the content.
*
* Why not search for the name=description and then content="(.*)"?
* The attribute order could be opposite. Plus, additional attributes may exist including being between
* the name and content attributes.
*
* Why not lookahead?
* Lookahead is not constrained to stay within the element. The first <meta it finds may not include
* the name or content, but rather could be from a different element downstream.
*/
$pattern = '#<meta\s' .
/*
* Allows for additional attributes before the content attribute.
* Searches for anything other than > symbol.
*/
'[^>]*' .
/*
* Find the content attribute. When found, capture its value (.*).
*
* Allows for (a) single or double quotes and (b) whitespace in the value.
*
* Why capture the opening quotation mark, i.e. (["\']), and then backreference,
* i.e \1, for the closing quotation mark?
* To ensure the closing quotation mark matches the opening one. Why? Attribute values
* can contain quotation marks, such as an apostrophe in the content.
*/
'content=(["\']??)(.*)\1' .
/*
* Allows for additional attributes after the content attribute.
* Searches for anything other than > symbol.
*/
'[^>]*' .
/*
* \/?> searches for the closing > symbol, which can be in either /> or > format.
* # ends the pattern.
*/
'\/?>#' .
/*
* These are the options:
* - i : case-insensitive
* - s : allows newline characters for the . match (needed for multiline elements)
* - U means non-greedy matching
*/
'isU';
preg_match_all( $pattern, $html, $elements );
return $elements;
}
/**
* Gets the metadata from a target meta element.
*
* @since 5.9.0
*
* @param array $meta_elements {
* A multi-dimensional indexed array on success, else empty array.
*
* @type string[] $0 Meta elements with a content attribute.
* @type string[] $1 Content attribute's opening quotation mark.
* @type string[] $2 Content attribute's value for each meta element.
* }
* @param string $attr Attribute that identifies the element with the target metadata.
* @param string $attr_value The attribute's value that identifies the element with the target metadata.
* @return string The metadata on success. Empty string if not found.
*/
private function get_metadata_from_meta_element( $meta_elements, $attr, $attr_value ) {
// Bail out if there are no meta elements.
if ( empty( $meta_elements[0] ) ) {
return '';
}
$metadata = '';
$pattern = '#' .
/*
* Target this attribute and value to find the metadata element.
*
* Allows for (a) no, single, double quotes and (b) whitespace in the value.
*
* Why capture the opening quotation mark, i.e. (["\']), and then backreference,
* i.e \1, for the closing quotation mark?
* To ensure the closing quotation mark matches the opening one. Why? Attribute values
* can contain quotation marks, such as an apostrophe in the content.
*/
$attr . '=([\"\']??)\s*' . $attr_value . '\s*\1' .
/*
* These are the options:
* - i : case-insensitive
* - s : allows newline characters for the . match (needed for multiline elements)
* - U means non-greedy matching
*/
'#isU';
// Find the metadata element.
foreach ( $meta_elements[0] as $index => $element ) {
preg_match( $pattern, $element, $match );
// This is not the metadata element. Skip it.
if ( empty( $match ) ) {
continue;
}
/*
* Found the metadata element.
* Get the metadata from its matching content array.
*/
if ( isset( $meta_elements[2][ $index ] ) && is_string( $meta_elements[2][ $index ] ) ) {
$metadata = trim( $meta_elements[2][ $index ] );
}
break;
}
return $metadata;
}
}