<?php
/**
 * Customize API: WP_Customize_Selective_Refresh class
 *
 * @package WordPress
 * @subpackage Customize
 * @since 4.5.0
 */

/**
 * Core Customizer class for implementing selective refresh.
 *
 * @since 4.5.0
 */
final class WP_Customize_Selective_Refresh {

	/**
	 * Query var used in requests to render partials.
	 *
	 * @since 4.5.0
	 */
	const RENDER_QUERY_VAR = 'wp_customize_render_partials';

	/**
	 * Customize manager.
	 *
	 * @since 4.5.0
	 * @access public
	 * @var WP_Customize_Manager
	 */
	public $manager;

	/**
	 * Registered instances of WP_Customize_Partial.
	 *
	 * @since 4.5.0
	 * @access protected
	 * @var WP_Customize_Partial[]
	 */
	protected $partials = array();

	/**
	 * Log of errors triggered when partials are rendered.
	 *
	 * @since 4.5.0
	 * @access private
	 * @var array
	 */
	protected $triggered_errors = array();

	/**
	 * Keep track of the current partial being rendered.
	 *
	 * @since 4.5.0
	 * @access private
	 * @var string
	 */
	protected $current_partial_id;

	/**
	 * Plugin bootstrap for Partial Refresh functionality.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @param WP_Customize_Manager $manager Manager instance.
	 */
	public function __construct( WP_Customize_Manager $manager ) {
		$this->manager = $manager;
		require_once( ABSPATH . WPINC . '/customize/class-wp-customize-partial.php' );

		add_action( 'customize_preview_init', array( $this, 'init_preview' ) );
	}

	/**
	 * Retrieves the registered partials.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @return array Partials.
	 */
	public function partials() {
		return $this->partials;
	}

	/**
	 * Adds a partial.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @param WP_Customize_Partial|string $id   Customize Partial object, or Panel ID.
	 * @param array                       $args Optional. Partial arguments. Default empty array.
	 * @return WP_Customize_Partial             The instance of the panel that was added.
	 */
	public function add_partial( $id, $args = array() ) {
		if ( $id instanceof WP_Customize_Partial ) {
			$partial = $id;
		} else {
			$class = 'WP_Customize_Partial';

			/** This filter (will be) documented in wp-includes/class-wp-customize-manager.php */
			$args = apply_filters( 'customize_dynamic_partial_args', $args, $id );

			/** This filter (will be) documented in wp-includes/class-wp-customize-manager.php */
			$class = apply_filters( 'customize_dynamic_partial_class', $class, $id, $args );

			$partial = new $class( $this, $id, $args );
		}

		$this->partials[ $partial->id ] = $partial;
		return $partial;
	}

	/**
	 * Retrieves a partial.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @param string $id Customize Partial ID.
	 * @return WP_Customize_Partial|null The partial, if set. Otherwise null.
	 */
	public function get_partial( $id ) {
		if ( isset( $this->partials[ $id ] ) ) {
			return $this->partials[ $id ];
		} else {
			return null;
		}
	}

	/**
	 * Removes a partial.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @param string $id Customize Partial ID.
	 */
	public function remove_partial( $id ) {
		unset( $this->partials[ $id ] );
	}

	/**
	 * Initializes the Customizer preview.
	 *
	 * @since 4.5.0
	 * @access public
	 */
	public function init_preview() {
		add_action( 'template_redirect', array( $this, 'handle_render_partials_request' ) );
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_preview_scripts' ) );
	}

	/**
	 * Enqueues preview scripts.
	 *
	 * @since 4.5.0
	 * @access public
	 */
	public function enqueue_preview_scripts() {
		wp_enqueue_script( 'customize-selective-refresh' );
		add_action( 'wp_footer', array( $this, 'export_preview_data' ), 1000 );
	}

	/**
	 * Exports data in preview after it has finished rendering so that partials can be added at runtime.
	 *
	 * @since 4.5.0
	 * @access public
	 */
	public function export_preview_data() {
		$partials = array();

		foreach ( $this->partials() as $partial ) {
			if ( $partial->check_capabilities() ) {
				$partials[ $partial->id ] = $partial->json();
			}
		}

		$exports = array(
			'partials'       => $partials,
			'renderQueryVar' => self::RENDER_QUERY_VAR,
			'l10n'           => array(
				'shiftClickToEdit' => __( 'Shift-click to edit this element.' ),
				/* translators: %s: document.write() */
				'badDocumentWrite' => sprintf( __( '%s is forbidden' ), 'document.write()' ),
			),
		);

		// Export data to JS.
		echo sprintf( '<script>var _customizePartialRefreshExports = %s;</script>', wp_json_encode( $exports ) );
	}

	/**
	 * Registers dynamically-created partials.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @see WP_Customize_Manager::add_dynamic_settings()
	 *
	 * @param array $partial_ids The partial ID to add.
	 * @return array Added WP_Customize_Partial instances.
	 */
	public function add_dynamic_partials( $partial_ids ) {
		$new_partials = array();

		foreach ( $partial_ids as $partial_id ) {

			// Skip partials already created.
			$partial = $this->get_partial( $partial_id );
			if ( $partial ) {
				continue;
			}

			$partial_args = false;
			$partial_class = 'WP_Customize_Partial';

			/**
			 * Filters a dynamic partial's constructor arguments.
			 *
			 * For a dynamic partial to be registered, this filter must be employed
			 * to override the default false value with an array of args to pass to
			 * the WP_Customize_Partial constructor.
			 *
			 * @since 4.5.0
			 *
			 * @param false|array $partial_args The arguments to the WP_Customize_Partial constructor.
			 * @param string      $partial_id   ID for dynamic partial.
			 */
			$partial_args = apply_filters( 'customize_dynamic_partial_args', $partial_args, $partial_id );
			if ( false === $partial_args ) {
				continue;
			}

			/**
			 * Filters the class used to construct partials.
			 *
			 * Allow non-statically created partials to be constructed with custom WP_Customize_Partial subclass.
			 *
			 * @since 4.5.0
			 *
			 * @param string $partial_class WP_Customize_Partial or a subclass.
			 * @param string $partial_id    ID for dynamic partial.
			 * @param array  $partial_args  The arguments to the WP_Customize_Partial constructor.
			 */
			$partial_class = apply_filters( 'customize_dynamic_partial_class', $partial_class, $partial_id, $partial_args );

			$partial = new $partial_class( $this, $partial_id, $partial_args );

			$this->add_partial( $partial );
			$new_partials[] = $partial;
		}
		return $new_partials;
	}

	/**
	 * Checks whether the request is for rendering partials.
	 *
	 * Note that this will not consider whether the request is authorized or valid,
	 * just that essentially the route is a match.
	 *
	 * @since 4.5.0
	 * @access public
	 *
	 * @return bool Whether the request is for rendering partials.
	 */
	public function is_render_partials_request() {
		return ! empty( $_POST[ self::RENDER_QUERY_VAR ] );
	}

	/**
	 * Handles PHP errors triggered during rendering the partials.
	 *
	 * These errors will be relayed back to the client in the Ajax response.
	 *
	 * @since 4.5.0
	 * @access private
	 *
	 * @param int    $errno   Error number.
	 * @param string $errstr  Error string.
	 * @param string $errfile Error file.
	 * @param string $errline Error line.
	 * @return true Always true.
	 */
	public function handle_error( $errno, $errstr, $errfile = null, $errline = null ) {
		$this->triggered_errors[] = array(
			'partial'      => $this->current_partial_id,
			'error_number' => $errno,
			'error_string' => $errstr,
			'error_file'   => $errfile,
			'error_line'   => $errline,
		);
		return true;
	}

	/**
	 * Handles the Ajax request to return the rendered partials for the requested placements.
	 *
	 * @since 4.5.0
	 * @access public
	 */
	public function handle_render_partials_request() {
		if ( ! $this->is_render_partials_request() ) {
			return;
		}

		$this->manager->remove_preview_signature();

		/*
		 * Note that is_customize_preview() returning true will entail that the
		 * user passed the 'customize' capability check and the nonce check, since
		 * WP_Customize_Manager::setup_theme() is where the previewing flag is set.
		 */
		if ( ! is_customize_preview() ) {
			status_header( 403 );
			wp_send_json_error( 'expected_customize_preview' );
		} else if ( ! isset( $_POST['partials'] ) ) {
			status_header( 400 );
			wp_send_json_error( 'missing_partials' );
		}

		$partials = json_decode( wp_unslash( $_POST['partials'] ), true );

		if ( ! is_array( $partials ) ) {
			wp_send_json_error( 'malformed_partials' );
		}

		$this->add_dynamic_partials( array_keys( $partials ) );

		/**
		 * Fires immediately before partials are rendered.
		 *
		 * Plugins may do things like call wp_enqueue_scripts() and gather a list of the scripts
		 * and styles which may get enqueued in the response.
		 *
		 * @since 4.5.0
		 *
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		do_action( 'customize_render_partials_before', $this, $partials );

		set_error_handler( array( $this, 'handle_error' ), error_reporting() );

		$contents = array();

		foreach ( $partials as $partial_id => $container_contexts ) {
			$this->current_partial_id = $partial_id;

			if ( ! is_array( $container_contexts ) ) {
				wp_send_json_error( 'malformed_container_contexts' );
			}

			$partial = $this->get_partial( $partial_id );

			if ( ! $partial || ! $partial->check_capabilities() ) {
				$contents[ $partial_id ] = null;
				continue;
			}

			$contents[ $partial_id ] = array();

			// @todo The array should include not only the contents, but also whether the container is included?
			if ( empty( $container_contexts ) ) {
				// Since there are no container contexts, render just once.
				$contents[ $partial_id ][] = $partial->render( null );
			} else {
				foreach ( $container_contexts as $container_context ) {
					$contents[ $partial_id ][] = $partial->render( $container_context );
				}
			}
		}
		$this->current_partial_id = null;

		restore_error_handler();

		/**
		 * Fires immediately after partials are rendered.
		 *
		 * Plugins may do things like call wp_footer() to scrape scripts output and return them
		 * via the {@see 'customize_render_partials_response'} filter.
		 *
		 * @since 4.5.0
		 *
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		do_action( 'customize_render_partials_after', $this, $partials );

		$response = array(
			'contents' => $contents,
		);

		if ( defined( 'WP_DEBUG_DISPLAY' ) && WP_DEBUG_DISPLAY ) {
			$response['errors'] = $this->triggered_errors;
		}

		/**
		 * Filters the response from rendering the partials.
		 *
		 * Plugins may use this filter to inject `$scripts` and `$styles`, which are dependencies
		 * for the partials being rendered. The response data will be available to the client via
		 * the `render-partials-response` JS event, so the client can then inject the scripts and
		 * styles into the DOM if they have not already been enqueued there.
		 *
		 * If plugins do this, they'll need to take care for any scripts that do `document.write()`
		 * and make sure that these are not injected, or else to override the function to no-op,
		 * or else the page will be destroyed.
		 *
		 * Plugins should be aware that `$scripts` and `$styles` may eventually be included by
		 * default in the response.
		 *
		 * @since 4.5.0
		 *
		 * @param array $response {
		 *     Response.
		 *
		 *     @type array $contents Associative array mapping a partial ID its corresponding array of contents
		 *                           for the containers requested.
		 *     @type array $errors   List of errors triggered during rendering of partials, if `WP_DEBUG_DISPLAY`
		 *                           is enabled.
		 * }
		 * @param WP_Customize_Selective_Refresh $this     Selective refresh component.
		 * @param array                          $partials Placements' context data for the partials rendered in the request.
		 *                                                 The array is keyed by partial ID, with each item being an array of
		 *                                                 the placements' context data.
		 */
		$response = apply_filters( 'customize_render_partials_response', $response, $this, $partials );

		wp_send_json_success( $response );
	}
}