'The handler for the route is invalid' ), array( 'status' => 500 ) );
				}

				if ( ! is_wp_error( $response ) ) {
					// Remove the redundant preg_match argument.
					unset( $args[0] );

					$request->set_url_params( $args );
					$request->set_attributes( $handler );

					$defaults = array();

					foreach ( $handler['args'] as $arg => $options ) {
						if ( isset( $options['default'] ) ) {
							$defaults[ $arg ] = $options['default'];
						}
					}

					$request->set_default_params( $defaults );

					$check_required = $request->has_valid_params();
					if ( is_wp_error( $check_required ) ) {
						$response = $check_required;
					} else {
						$check_sanitized = $request->sanitize_params();
						if ( is_wp_error( $check_sanitized ) ) {
							$response = $check_sanitized;
						}
					}
				}

				/**
				 * Filters the response before executing any REST API callbacks.
				 *
				 * Allows plugins to perform additional validation after a
				 * request is initialized and matched to a registered route,
				 * but before it is executed.
				 *
				 * Note that this filter will not be called for requests that
				 * fail to authenticate or match to a registered route.
				 *
				 * @since 4.7.0
				 *
				 * @param WP_HTTP_Response $response Result to send to the client. Usually a WP_REST_Response.
				 * @param WP_REST_Server   $handler  ResponseHandler instance (usually WP_REST_Server).
				 * @param WP_REST_Request  $request  Request used to generate the response.
				 */
				$response = apply_filters( 'rest_request_before_callbacks', $response, $handler, $request );

				if ( ! is_wp_error( $response ) ) {
					// Check permission specified on the route.
					if ( ! empty( $handler['permission_callback'] ) ) {
						$permission = call_user_func( $handler['permission_callback'], $request );

						if ( is_wp_error( $permission ) ) {
							$response = $permission;
						} elseif ( false === $permission || null === $permission ) {
							$response = new WP_Error( 'rest_forbidden', __( 'Sorry, you are not allowed to do that.' ), array( 'status' => rest_authorization_required_code() ) );
						}
					}
				}

				if ( ! is_wp_error( $response ) ) {
					/**
					 * Filters the REST dispatch request result.
					 *
					 * Allow plugins to override dispatching the request.
					 *
					 * @since 4.4.0
					 * @since 4.5.0 Added `$route` and `$handler` parameters.
					 *
					 * @param bool            $dispatch_result Dispatch result, will be used if not empty.
					 * @param WP_REST_Request $request         Request used to generate the response.
					 * @param string          $route           Route matched for the request.
					 * @param array           $handler         Route handler used for the request.
					 */
					$dispatch_result = apply_filters( 'rest_dispatch_request', null, $request, $route, $handler );

					// Allow plugins to halt the request via this filter.
					if ( null !== $dispatch_result ) {
						$response = $dispatch_result;
					} else {
						$response = call_user_func( $callback, $request );
					}
				}

				/**
				 * Filters the response immediately after executing any REST API
				 * callbacks.
				 *
				 * Allows plugins to perform any needed cleanup, for example,
				 * to undo changes made during the {@see 'rest_request_before_callbacks'}
				 * filter.
				 *
				 * Note that this filter will not be called for requests that
				 * fail to authenticate or match to a registered route.
				 *
				 * Note that an endpoint's `permission_callback` can still be
				 * called after this filter - see `rest_send_allow_header()`.
				 *
				 * @since 4.7.0
				 *
				 * @param WP_HTTP_Response $response Result to send to the client. Usually a WP_REST_Response.
				 * @param WP_REST_Server   $handler  ResponseHandler instance (usually WP_REST_Server).
				 * @param WP_REST_Request  $request  Request used to generate the response.
				 */
				$response = apply_filters( 'rest_request_after_callbacks', $response, $handler, $request );

				if ( is_wp_error( $response ) ) {
					$response = $this->error_to_response( $response );
				} else {
					$response = rest_ensure_response( $response );
				}

				$response->set_matched_route( $route );
				$response->set_matched_handler( $handler );

				return $response;
			}
		}

		return $this->error_to_response( new WP_Error( 'rest_no_route', __( 'No route was found matching the URL and request method' ), array( 'status' => 404 ) ) );
	}

	/**
	 * Returns if an error occurred during most recent JSON encode/decode.
	 *
	 * Strings to be translated will be in format like
	 * "Encoding error: Maximum stack depth exceeded".
	 *
	 * @since 4.4.0
	 *
	 * @return bool|string Boolean false or string error message.
	 */
	protected function get_json_last_error() {
		// See https://core.trac.wordpress.org/ticket/27799.
		if ( ! function_exists( 'json_last_error' ) ) {
			return false;
		}

		$last_error_code = json_last_error();

		if ( ( defined( 'JSON_ERROR_NONE' ) && JSON_ERROR_NONE === $last_error_code ) || empty( $last_error_code ) ) {
			return false;
		}

		return json_last_error_msg();
	}

	/**
	 * Retrieves the site index.
	 *
	 * This endpoint describes the capabilities of the site.
	 *
	 * @since 4.4.0
	 *
	 * @param array $request {
	 *     Request.
	 *
	 *     @type string $context Context.
	 * }
	 * @return array Index entity
	 */
	public function get_index( $request ) {
		// General site data.
		$available = array(
			'name'            => get_option( 'blogname' ),
			'description'     => get_option( 'blogdescription' ),
			'url'             => get_option( 'siteurl' ),
			'home'            => home_url(),
			'gmt_offset'      => get_option( 'gmt_offset' ),
			'timezone_string' => get_option( 'timezone_string' ),
			'namespaces'      => array_keys( $this->namespaces ),
			'authentication'  => array(),
			'routes'          => $this->get_data_for_routes( $this->get_routes(), $request['context'] ),
		);

		$response = new WP_REST_Response( $available );

		$response->add_link( 'help', 'http://v2.wp-api.org/' );

		/**
		 * Filters the API root index data.
		 *
		 * This contains the data describing the API. This includes information
		 * about supported authentication schemes, supported namespaces, routes
		 * available on the API, and a small amount of data about the site.
		 *
		 * @since 4.4.0
		 *
		 * @param WP_REST_Response $response Response data.
		 */
		return apply_filters( 'rest_index', $response );
	}

	/**
	 * Retrieves the index for a namespace.
	 *
	 * @since 4.4.0
	 *
	 * @param WP_REST_Request $request REST request instance.
	 * @return WP_REST_Response|WP_Error WP_REST_Response instance if the index was found,
	 *                                   WP_Error if the namespace isn't set.
	 */
	public function get_namespace_index( $request ) {
		$namespace = $request['namespace'];

		if ( ! isset( $this->namespaces[ $namespace ] ) ) {
			return new WP_Error( 'rest_invalid_namespace', __( 'The specified namespace could not be found.' ), array( 'status' => 404 ) );
		}

		$routes = $this->namespaces[ $namespace ];
		$endpoints = array_intersect_key( $this->get_routes(), $routes );

		$data = array(
			'namespace' => $namespace,
			'routes' => $this->get_data_for_routes( $endpoints, $request['context'] ),
		);
		$response = rest_ensure_response( $data );

		// Link to the root index.
		$response->add_link( 'up', rest_url( '/' ) );

		/**
		 * Filters the namespace index data.
		 *
		 * This typically is just the route data for the namespace, but you can
		 * add any data you'd like here.
		 *
		 * @since 4.4.0
		 *
		 * @param WP_REST_Response $response Response data.
		 * @param WP_REST_Request  $request  Request data. The namespace is passed as the 'namespace' parameter.
		 */
		return apply_filters( 'rest_namespace_index', $response, $request );
	}

	/**
	 * Retrieves the publicly-visible data for routes.
	 *
	 * @since 4.4.0
	 *
	 * @param array  $routes  Routes to get data for.
	 * @param string $context Optional. Context for data. Accepts 'view' or 'help'. Default 'view'.
	 * @return array Route data to expose in indexes.
	 */
	public function get_data_for_routes( $routes, $context = 'view' ) {
		$available = array();

		// Find the available routes.
		foreach ( $routes as $route => $callbacks ) {
			$data = $this->get_data_for_route( $route, $callbacks, $context );
			if ( empty( $data ) ) {
				continue;
			}

			/**
			 * Filters the REST endpoint data.
			 *
			 * @since 4.4.0
			 *
			 * @param WP_REST_Request $request Request data. The namespace is passed as the 'namespace' parameter.
			 */
			$available[ $route ] = apply_filters( 'rest_endpoints_description', $data );
		}

		/**
		 * Filters the publicly-visible data for routes.
		 *
		 * This data is exposed on indexes and can be used by clients or
		 * developers to investigate the site and find out how to use it. It
		 * acts as a form of self-documentation.
		 *
		 * @since 4.4.0
		 *
		 * @param array $available Map of route to route data.
		 * @param array $routes    Internal route data as an associative array.
		 */
		return apply_filters( 'rest_route_data', $available, $routes );
	}

	/**
	 * Retrieves publicly-visible data for the route.
	 *
	 * @since 4.4.0
	 *
	 * @param string $route     Route to get data for.
	 * @param array  $callbacks Callbacks to convert to data.
	 * @param string $context   Optional. Context for the data. Accepts 'view' or 'help'. Default 'view'.
	 * @return array|null Data for the route, or null if no publicly-visible data.
	 */
	public function get_data_for_route( $route, $callbacks, $context = 'view' ) {
		$data = array(
			'namespace' => '',
			'methods' => array(),
			'endpoints' => array(),
		);

		if ( isset( $this->route_options[ $route ] ) ) {
			$options = $this->route_options[ $route ];

			if ( isset( $options['namespace'] ) ) {
				$data['namespace'] = $options['namespace'];
			}

			if ( isset( $options['schema'] ) && 'help' === $context ) {
				$data['schema'] = call_user_func( $options['schema'] );
			}
		}

		$route = preg_replace( '#\(\?P<(\w+?)>.*?\)#', '{$1}', $route );

		foreach ( $callbacks as $callback ) {
			// Skip to the next route if any callback is hidden.
			if ( empty( $callback['show_in_index'] ) ) {
				continue;
			}

			$data['methods'] = array_merge( $data['methods'], array_keys( $callback['methods'] ) );
			$endpoint_data = array(
				'methods' => array_keys( $callback['methods'] ),
			);

			if ( isset( $callback['args'] ) ) {
				$endpoint_data['args'] = array();
				foreach ( $callback['args'] as $key => $opts ) {
					$arg_data = array(
						'required' => ! empty( $opts['required'] ),
					);
					if ( isset( $opts['default'] ) ) {
						$arg_data['default'] = $opts['default'];
					}
					if ( isset( $opts['enum'] ) ) {
						$arg_data['enum'] = $opts['enum'];
					}
					if ( isset( $opts['description'] ) ) {
						$arg_data['description'] = $opts['description'];
					}
					if ( isset( $opts['type'] ) ) {
						$arg_data['type'] = $opts['type'];
					}
					if ( isset( $opts['items'] ) ) {
						$arg_data['items'] = $opts['items'];
					}
					$endpoint_data['args'][ $key ] = $arg_data;
				}
			}

			$data['endpoints'][] = $endpoint_data;

			// For non-variable routes, generate links.
			if ( strpos( $route, '{' ) === false ) {
				$data['_links'] = array(
					'self' => rest_url( $route ),
				);
			}
		}

		if ( empty( $data['methods'] ) ) {
			// No methods supported, hide the route.
			return null;
		}

		return $data;
	}

	/**
	 * Sends an HTTP status code.
	 *
	 * @since 4.4.0
	 *
	 * @param int $code HTTP status.
	 */
	protected function set_status( $code ) {
		status_header( $code );
	}

	/**
	 * Sends an HTTP header.
	 *
	 * @since 4.4.0
	 *
	 * @param string $key Header key.
	 * @param string $value Header value.
	 */
	public function send_header( $key, $value ) {
		/*
		 * Sanitize as per RFC2616 (Section 4.2):
		 *
		 * Any LWS that occurs between field-content MAY be replaced with a
		 * single SP before interpreting the field value or forwarding the
		 * message downstream.
		 */
		$value = preg_replace( '/\s+/', ' ', $value );
		header( sprintf( '%s: %s', $key, $value ) );
	}

	/**
	 * Sends multiple HTTP headers.
	 *
	 * @since 4.4.0
	 *
	 * @param array $headers Map of header name to header value.
	 */
	public function send_headers( $headers ) {
		foreach ( $headers as $key => $value ) {
			$this->send_header( $key, $value );
		}
	}

	/**
	 * Removes an HTTP header from the current response.
	 *
	 * @since 4.8.0
	 *
	 * @param string $key Header key.
	 */
	public function remove_header( $key ) {
		if ( function_exists( 'header_remove' ) ) {
			// In PHP 5.3+ there is a way to remove an already set header.
			header_remove( $key );
		} else {
			// In PHP 5.2, send an empty header, but only as a last resort to
			// override a header already sent.
			foreach ( headers_list() as $header ) {
				if ( 0 === stripos( $header, "$key:" ) ) {
					$this->send_header( $key, '' );
					break;
				}
			}
		}
	}

	/**
	 * Retrieves the raw request entity (body).
	 *
	 * @since 4.4.0
	 *
	 * @global string $HTTP_RAW_POST_DATA Raw post data.
	 *
	 * @return string Raw request data.
	 */
	public static function get_raw_data() {
		global $HTTP_RAW_POST_DATA;

		/*
		 * A bug in PHP < 5.2.2 makes $HTTP_RAW_POST_DATA not set by default,
		 * but we can do it ourself.
		 */
		if ( ! isset( $HTTP_RAW_POST_DATA ) ) {
			$HTTP_RAW_POST_DATA = file_get_contents( 'php://input' );
		}

		return $HTTP_RAW_POST_DATA;
	}

	/**
	 * Extracts headers from a PHP-style $_SERVER array.
	 *
	 * @since 4.4.0
	 *
	 * @param array $server Associative array similar to `$_SERVER`.
	 * @return array Headers extracted from the input.
	 */
	public function get_headers( $server ) {
		$headers = array();

		// CONTENT_* headers are not prefixed with HTTP_.
		$additional = array( 'CONTENT_LENGTH' => true, 'CONTENT_MD5' => true, 'CONTENT_TYPE' => true );

		foreach ( $server as $key => $value ) {
			if ( strpos( $key, 'HTTP_' ) === 0 ) {
				$headers[ substr( $key, 5 ) ] = $value;
			} elseif ( isset( $additional[ $key ] ) ) {
				$headers[ $key ] = $value;
			}
		}

		return $headers;
	}
}