URL if headers are sent. Returns false
 *                      if headers are not sent.
 */
function send_origin_headers() {
	$origin = get_http_origin();

	if ( is_allowed_http_origin( $origin ) ) {
		header( 'Access-Control-Allow-Origin: ' . $origin );
		header( 'Access-Control-Allow-Credentials: true' );
		if ( 'OPTIONS' === $_SERVER['REQUEST_METHOD'] ) {
			exit;
		}
		return $origin;
	}

	if ( 'OPTIONS' === $_SERVER['REQUEST_METHOD'] ) {
		status_header( 403 );
		exit;
	}

	return false;
}

/**
 * Validates a URL for safe use in the HTTP API.
 *
 * Examples of URLs that are considered unsafe:
 *
 * - ftp://example.com/caniload.php - Invalid protocol - only http and https are allowed.
 * - http:///example.com/caniload.php - Malformed URL.
 * - http://user:pass@example.com/caniload.php - Login information.
 * - http://exampleeeee.com/caniload.php - Invalid hostname, as the IP cannot be looked up in DNS.
 *
 * Examples of URLs that are considered unsafe by default:
 *
 * - http://192.168.0.1/caniload.php - IPs from LAN networks.
 *   This can be changed with the {@see 'http_request_host_is_external'} filter.
 * - http://198.143.164.252:81/caniload.php - By default, only 80, 443, and 8080 ports are allowed.
 *   This can be changed with the {@see 'http_allowed_safe_ports'} filter.
 *
 * @since 3.5.2
 *
 * @param string $url Request URL.
 * @return string|false URL or false on failure.
 */
function wp_http_validate_url( $url ) {
	if ( ! is_string( $url ) || '' === $url || is_numeric( $url ) ) {
		return false;
	}

	$original_url = $url;
	$url          = wp_kses_bad_protocol( $url, array( 'http', 'https' ) );
	if ( ! $url || strtolower( $url ) !== strtolower( $original_url ) ) {
		return false;
	}

	$parsed_url = parse_url( $url );
	if ( ! $parsed_url || empty( $parsed_url['host'] ) ) {
		return false;
	}

	if ( isset( $parsed_url['user'] ) || isset( $parsed_url['pass'] ) ) {
		return false;
	}

	if ( false !== strpbrk( $parsed_url['host'], ':#?[]' ) ) {
		return false;
	}

	$parsed_home = parse_url( get_option( 'home' ) );
	$same_host   = isset( $parsed_home['host'] ) && strtolower( $parsed_home['host'] ) === strtolower( $parsed_url['host'] );
	$host        = trim( $parsed_url['host'], '.' );

	if ( ! $same_host ) {
		if ( preg_match( '#^(([1-9]?\d|1\d\d|25[0-5]|2[0-4]\d)\.){3}([1-9]?\d|1\d\d|25[0-5]|2[0-4]\d)$#', $host ) ) {
			$ip = $host;
		} else {
			$ip = gethostbyname( $host );
			if ( $ip === $host ) { // Error condition for gethostbyname().
				return false;
			}
		}
		if ( $ip ) {
			$parts = array_map( 'intval', explode( '.', $ip ) );
			if ( 127 === $parts[0] || 10 === $parts[0] || 0 === $parts[0]
				|| ( 172 === $parts[0] && 16 <= $parts[1] && 31 >= $parts[1] )
				|| ( 192 === $parts[0] && 168 === $parts[1] )
			) {
				// If host appears local, reject unless specifically allowed.
				/**
				 * Checks if HTTP request is external or not.
				 *
				 * Allows to change and allow external requests for the HTTP request.
				 *
				 * @since 3.6.0
				 *
				 * @param bool   $external Whether HTTP request is external or not.
				 * @param string $host     Host name of the requested URL.
				 * @param string $url      Requested URL.
				 */
				if ( ! apply_filters( 'http_request_host_is_external', false, $host, $url ) ) {
					return false;
				}
			}
		}
	}

	if ( empty( $parsed_url['port'] ) ) {
		return $url;
	}

	$port = $parsed_url['port'];

	/**
	 * Controls the list of ports considered safe in HTTP API.
	 *
	 * Allows to change and allow external requests for the HTTP request.
	 *
	 * @since 5.9.0
	 *
	 * @param int[]  $allowed_ports Array of integers for valid ports.
	 * @param string $host          Host name of the requested URL.
	 * @param string $url           Requested URL.
	 */
	$allowed_ports = apply_filters( 'http_allowed_safe_ports', array( 80, 443, 8080 ), $host, $url );
	if ( is_array( $allowed_ports ) && in_array( $port, $allowed_ports, true ) ) {
		return $url;
	}

	if ( $parsed_home && $same_host && isset( $parsed_home['port'] ) && $parsed_home['port'] === $port ) {
		return $url;
	}

	return false;
}

/**
 * Marks allowed redirect hosts safe for HTTP requests as well.
 *
 * Attached to the {@see 'http_request_host_is_external'} filter.
 *
 * @since 3.6.0
 *
 * @param bool   $is_external
 * @param string $host
 * @return bool
 */
function allowed_http_request_hosts( $is_external, $host ) {
	if ( ! $is_external && wp_validate_redirect( 'http://' . $host ) ) {
		$is_external = true;
	}
	return $is_external;
}

/**
 * Adds any domain in a multisite installation for safe HTTP requests to the
 * allowed list.
 *
 * Attached to the {@see 'http_request_host_is_external'} filter.
 *
 * @since 3.6.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param bool   $is_external
 * @param string $host
 * @return bool
 */
function ms_allowed_http_request_hosts( $is_external, $host ) {
	global $wpdb;
	static $queried = array();
	if ( $is_external ) {
		return $is_external;
	}
	if ( get_network()->domain === $host ) {
		return true;
	}
	if ( isset( $queried[ $host ] ) ) {
		return $queried[ $host ];
	}
	$queried[ $host ] = (bool) $wpdb->get_var( $wpdb->prepare( "SELECT domain FROM $wpdb->blogs WHERE domain = %s LIMIT 1", $host ) );
	return $queried[ $host ];
}

/**
 * A wrapper for PHP's parse_url() function that handles consistency in the return values
 * across PHP versions.
 *
 * PHP 5.4.7 expanded parse_url()'s ability to handle non-absolute URLs, including
 * schemeless and relative URLs with "://" in the path. This function works around
 * those limitations providing a standard output on PHP 5.2~5.4+.
 *
 * Secondly, across various PHP versions, schemeless URLs containing a ":" in the query
 * are being handled inconsistently. This function works around those differences as well.
 *
 * @since 4.4.0
 * @since 4.7.0 The `$component` parameter was added for parity with PHP's `parse_url()`.
 *
 * @link https://www.php.net/manual/en/function.parse-url.php
 *
 * @param string $url       The URL to parse.
 * @param int    $component The specific component to retrieve. Use one of the PHP
 *                          predefined constants to specify which one.
 *                          Defaults to -1 (= return all parts as an array).
 * @return mixed False on parse failure; Array of URL components on success;
 *               When a specific component has been requested: null if the component
 *               doesn't exist in the given URL; a string or - in the case of
 *               PHP_URL_PORT - integer when it does. See parse_url()'s return values.
 */
function wp_parse_url( $url, $component = -1 ) {
	$to_unset = array();
	$url      = (string) $url;

	if ( str_starts_with( $url, '//' ) ) {
		$to_unset[] = 'scheme';
		$url        = 'placeholder:' . $url;
	} elseif ( str_starts_with( $url, '/' ) ) {
		$to_unset[] = 'scheme';
		$to_unset[] = 'host';
		$url        = 'placeholder://placeholder' . $url;
	}

	$parts = parse_url( $url );

	if ( false === $parts ) {
		// Parsing failure.
		return $parts;
	}

	// Remove the placeholder values.
	foreach ( $to_unset as $key ) {
		unset( $parts[ $key ] );
	}

	return _get_component_from_parsed_url_array( $parts, $component );
}

/**
 * Retrieves a specific component from a parsed URL array.
 *
 * @internal
 *
 * @since 4.7.0
 * @access private
 *
 * @link https://www.php.net/manual/en/function.parse-url.php
 *
 * @param array|false $url_parts The parsed URL. Can be false if the URL failed to parse.
 * @param int         $component The specific component to retrieve. Use one of the PHP
 *                               predefined constants to specify which one.
 *                               Defaults to -1 (= return all parts as an array).
 * @return mixed False on parse failure; Array of URL components on success;
 *               When a specific component has been requested: null if the component
 *               doesn't exist in the given URL; a string or - in the case of
 *               PHP_URL_PORT - integer when it does. See parse_url()'s return values.
 */
function _get_component_from_parsed_url_array( $url_parts, $component = -1 ) {
	if ( -1 === $component ) {
		return $url_parts;
	}

	$key = _wp_translate_php_url_constant_to_key( $component );
	if ( false !== $key && is_array( $url_parts ) && isset( $url_parts[ $key ] ) ) {
		return $url_parts[ $key ];
	} else {
		return null;
	}
}

/**
 * Translates a PHP_URL_* constant to the named array keys PHP uses.
 *
 * @internal
 *
 * @since 4.7.0
 * @access private
 *
 * @link https://www.php.net/manual/en/url.constants.php
 *
 * @param int $constant PHP_URL_* constant.
 * @return string|false The named key or false.
 */
function _wp_translate_php_url_constant_to_key( $constant ) {
	$translation = array(
		PHP_URL_SCHEME   => 'scheme',
		PHP_URL_HOST     => 'host',
		PHP_URL_PORT     => 'port',
		PHP_URL_USER     => 'user',
		PHP_URL_PASS     => 'pass',
		PHP_URL_PATH     => 'path',
		PHP_URL_QUERY    => 'query',
		PHP_URL_FRAGMENT => 'fragment',
	);

	if ( isset( $translation[ $constant ] ) ) {
		return $translation[ $constant ];
	} else {
		return false;
	}
}
			'id'     => array(
						'description' => __( 'The ID for the autosave.' ),
						'type'        => 'integer',
					),
				),
				array(
					'methods'             => WP_REST_Server::READABLE,
					'callback'            => array( $this, 'get_item' ),
					'permission_callback' => array( $this->revisions_controller, 'get_item_permissions_check' ),
					'args'                => array(
						'context' => $this->get_context_param( array( 'default' => 'view' ) ),
					),
				),
				'schema' => array( $this, 'get_public_item_schema' ),
			)
		);
	}

	/**
	 * Prepares the item for the REST response.
	 *
	 * @since 6.4.0
	 *
	 * @param WP_Post         $item    Post revision object.
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response Response object.
	 */
	public function prepare_item_for_response( $item, $request ) {
		$template = _build_block_template_result_from_post( $item );
		$response = $this->parent_controller->prepare_item_for_response( $template, $request );

		$fields = $this->get_fields_for_response( $request );
		$data   = $response->get_data();

		if ( in_array( 'parent', $fields, true ) ) {
			$data['parent'] = (int) $item->post_parent;
		}

		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
		$data    = $this->filter_response_by_context( $data, $context );

		// Wrap the data in a response object.
		$response = new WP_REST_Response( $data );

		if ( rest_is_field_included( '_links', $fields ) || rest_is_field_included( '_embedded', $fields ) ) {
			$links = $this->prepare_links( $template );
			$response->add_links( $links );
		}

		return $response;
	}

	/**
	 * Gets the autosave, if the ID is valid.
	 *
	 * @since 6.4.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_Post|WP_Error Autosave post object if ID is valid, WP_Error otherwise.
	 */
	public function get_item( $request ) {
		$parent = $this->get_parent( $request['parent'] );
		if ( is_wp_error( $parent ) ) {
			return $parent;
		}

		$autosave = wp_get_post_autosave( $parent->ID );

		if ( ! $autosave ) {
			return new WP_Error(
				'rest_post_no_autosave',
				__( 'There is no autosave revision for this template.' ),
				array( 'status' => 404 )
			);
		}

		$response = $this->prepare_item_for_response( $autosave, $request );
		return $response;
	}

	/**
	 * Get the parent post.
	 *
	 * @since 6.4.0
	 *
	 * @param int $parent_id Supplied ID.
	 * @return WP_Post|WP_Error Post object if ID is valid, WP_Error otherwise.
	 */
	protected function get_parent( $parent_id ) {
		return $this->revisions_controller->get_parent( $parent_id );
	}

	/**
	 * Prepares links for the request.
	 *
	 * @since 6.4.0
	 *
	 * @param WP_Block_Template $template Template.
	 * @return array Links for the given post.
	 */
	protected function prepare_links( $template ) {
		$links = array(
			'self'   => array(
				'href' => rest_url( sprintf( '/%s/%s/%s/%s/%d', $this->namespace, $this->parent_base, $template->id, $this->rest_base, $template->wp_id ) ),
			),
			'parent' => array(
				'href' => rest_url( sprintf( '/%s/%s/%s', $this->namespace, $this->parent_base, $template->id ) ),
			),
		);

		return $links;
	}

	/**
	 * Retrieves the autosave's schema, conforming to JSON Schema.
	 *
	 * @since 6.4.0
	 *
	 * @return array Item schema data.
	 */
	public function get_item_schema() {
		if ( $this->schema ) {
			return $this->add_additional_fields_schema( $this->schema );
		}

		$this->schema = $this->revisions_controller->get_item_schema();

		return $this->add_additional_fields_schema( $this->schema );
	}
}