Widget & Sidebar Endpoints for the WordPress REST API v2

sidebar.php

<?php

use WP_REST_Server;
use WP_REST_Request;
use WP_REST_Response;
use WP_Error;

class Sidebar extends \WP_REST_Controller {

	/**
	 * Register the routes for the objects of the controller.
	 */
	public function register_routes() {
		$version   = '2';
		$namespace = 'wp/v' . $version;
		$base      = '/sidebar';

		register_rest_route(
			$namespace,
			$base,
			array(
				'methods'             => WP_REST_Server::READABLE,
				'callback'            => array( $this, 'get_items' ),
				'permission_callback' => array( $this, 'permissions_check' )
			)
		);

		register_rest_route(
			$namespace,
			$base . '/(?P<sidebar_id>[^/]+)',
			array(
				'methods'              => WP_REST_Server::READABLE,
				'callback'             => array( $this, 'get_item' ),
				'permissions_callback' => array( $this, 'permissions_check' )
			)
		);
	}

	/**
	 * Get a collection of items.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function get_items( $request ) {
		global $wp_registered_sidebars, $sidebars_widgets;

		$data = [ ];
		foreach ( $wp_registered_sidebars as $item ) {
			$itemdata = new WP_REST_Response( $item );

			$itemdata->add_link(
				'self',
				rest_url( 'wp/v2/sidebar/' . $item['id'] )
			);

			foreach ( $sidebars_widgets[ $item['id'] ] as $widget ) {
				preg_match( '/^(.+)-(\d+)$/', $widget, $matches );
				$itemdata->add_link(
					'widgets',
					rest_url( 'wp/v2/widget/' . $matches[1] . '/' . $matches[2] ),
					array( 'embeddable' => true )
				);
			}

			$data[] = $this->prepare_response_for_collection( $itemdata );
		}

		return rest_ensure_response( $data );
	}

	/**
	 * Get one item from the collection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function get_item( $request ) {
		global $wp_registered_sidebars, $sidebars_widgets;

		$sidebar_id = $request->get_param( 'sidebar_id' );

		if ( ! isset( $wp_registered_sidebars[ $sidebar_id ] ) ) {
			return new WP_Error( 404 );
		}

		$itemdata = new WP_REST_Response( $wp_registered_sidebars[ $sidebar_id ] );

		$itemdata->add_link(
			'self',
			rest_url( 'wp/v2/sidebar/' . $sidebar_id )
		);

		foreach ( $sidebars_widgets[ $sidebar_id ] as $widget ) {
			preg_match( '/^(.+)-(\d+)$/', $widget, $matches );
			$itemdata->add_link(
				'widgets',
				rest_url( 'wp/v2/widget/' . $matches[1] . '/' . $matches[2] ),
				array( 'embeddable' => true )
			);
		}

		return $itemdata;
	}

	/**
	 * Check if a given request has access.
	 *
	 * @return WP_Error|bool
	 */
	public function permissions_check() {
		return current_user_can( 'edit_theme_options' );
	}

}

widget.php

<?php

use WP_REST_Server;
use WP_REST_Request;
use WP_REST_Response;
use WP_Error;

class Widget extends \WP_REST_Controller {

	/**
	 * Register the routes for the objects of the controller.
	 */
	public function register_routes() {
		$version   = '2';
		$namespace = 'wp/v' . $version;
		$base      = '/widget';

		register_rest_route(
			$namespace,
			$base,
			array(
				'methods'              => WP_REST_Server::READABLE,
				'callback'             => array( $this, 'get_registered_items' ),
				'permission_callback'  => array( $this, 'permissions_check' )
			)
		);

		register_rest_route(
			$namespace,
			$base . '/(?P<id_base>[^/]+)',
			array(
				array(
					'methods'              => WP_REST_Server::READABLE,
					'callback'             => array( $this, 'get_items' ),
					'permissions_callback' => array( $this, 'permissions_check' ),
				),
				array(
					'methods'              => WP_REST_Server::CREATABLE,
					'callback'             => array( $this, 'create_item' ),
					'permissions_callback' => array( $this, 'permissions_check' ),
					'args'                 => array(
						'sidebar_id' => array(
							'required' => true
						)
					)
				)
			)
		);

		register_rest_route(
			$namespace,
			$base . '/(?P<id_base>[^/]+)/(?P<widget_number>[\d]+)',
			array(
				array(
					'methods'              => WP_REST_Server::READABLE,
					'callback'             => array( $this, 'get_item' ),
					'permissions_callback' => array( $this, 'permissions_check' ),
				),
				array(
					'methods'              => WP_REST_Server::EDITABLE,
					'callback'             => array( $this, 'update_item' ),
					'permissions_callback' => array( $this, 'permissions_check' )
				),
				array(
					'methods'              => WP_REST_Server::DELETABLE,
					'callback'             => array( $this, 'delete_item' ),
					'permissions_callback' => array( $this, 'permissions_check' )
				)
			)
		);
	}

	/**
	 * Get a collection of items.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function get_registered_items( $request ) {
		global $wp_widget_factory;

		$data = array();
		foreach ( $wp_widget_factory->widgets as $key => $item ) {
			$item->class = $key;
			$itemdata    = new WP_REST_Response( $item );
			$itemdata->add_link(
				'registered-widgets',
				rest_url( 'wp/v2/widget/' . $item->id_base ),
				array( 'embeddable' => true )
			);
			$data[] = $this->prepare_response_for_collection( $itemdata );
		}

		return rest_ensure_response( $data );
	}

	/**
	 * Get subcollection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function get_items( $request ) {
		$id_base = $request->get_param( 'id_base' );

		$widget_options = get_option( 'widget_' . $id_base );
		unset( $widget_options['_multiwidget'] );

		$data = [ ];
		foreach ( $widget_options as $number => $item ) {
			if ( $number == 1 ) {
				continue;
			}

			$item = $this->get_widget_item( $id_base, $number );
			if ( ! $item ) {
				return new WP_Error( 404 );
			}

			$itemdata = new WP_REST_Response( $item );
			$itemdata->add_link(
				'self',
				rest_url( 'wp/v2/widget/' . $id_base . '/' . $number )
			);
			$data[] = $this->prepare_response_for_collection( $itemdata );
		}

		return rest_ensure_response( $data );
	}

	/**
	 * Get one item from the collection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function get_item( $request ) {
		$id_base = $request->get_param( 'id_base' );
		$number  = absint( $request->get_param( 'widget_number' ) );

		$item = $this->get_widget_item( $id_base, $number );
		if ( ! $item ) {
			return new WP_Error( 404 );
		}

		$itemdata = new WP_REST_Response( $item );
		$itemdata->add_link(
			'self',
			rest_url( 'wp/v2/widget/' . $id_base . '/' . $number )
		);

		return $itemdata;
	}

	/**
	 * Create one item from the collection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function create_item( $request ) {
		global $wp_widget_factory, $wp_registered_widgets;

		$sidebar_id = $request->get_param( 'sidebar_id' );
		$id_base    = $request->get_param( 'id_base' );

		$widget_options = $option_keys = get_option( 'widget_' . $id_base );
		unset( $option_keys['_multiwidget'] );
		$option_keys = array_keys( $option_keys );
		$last_key    = array_pop( $option_keys );
		$number      = $last_key + 1;

		$widget = wp_filter_object_list( $wp_widget_factory->widgets, array( 'id_base' => $id_base ) );
		$widget = array_pop( $widget );

		$widget_options[ $number ] = @$widget->update( array(), array() );
		update_option( 'widget_' . $id_base, $widget_options );

		$sidebars_widgets = get_option( 'sidebars_widgets', array() );
		if ( is_array( $sidebars_widgets ) && isset( $sidebars_widgets['array_version'] ) ) {
			unset( $sidebars_widgets['array_version'] );
		}
		$sidebars_widgets[ $sidebar_id ][] = $id_base . '-' . $number;
		update_option( 'sidebars_widgets', $sidebars_widgets );

		$wp_registered_widgets[ $id_base . '-' . $number ] = array(
			'name'        => $widget->name,
			'id'          => $id_base . '-' . $number,
			'params'      => array(
				array(
					'number' => $number
				)
			),
			'classname'   => $widget->widget_options['classname'],
			'description' => $widget->widget_options['description'] ?? '',
		);

		$itemdata = new WP_REST_Response( $this->get_widget_item( $id_base, $number ), 201, array(
			'Location' => rest_url( 'wp/v2/widget/' . $id_base . '/' . $number )
		) );
		$itemdata->add_link(
			'self',
			rest_url( 'wp/v2/widget/' . $id_base . '/' . $number )
		);

		return $itemdata;
	}

	/**
	 * Update one item from the collection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function update_item( $request ) {
		global $wp_registered_widgets;

		$id_base = $request->get_param( 'id_base' );
		$number  = absint( $request->get_param( 'widget_number' ) );

		$item = $this->get_widget_item( $id_base, $number );
		if ( ! $item ) {
			return new WP_Error( 404 );
		}

		/** @var \WP_Widget $widget */
		$widget = $wp_registered_widgets[ $id_base . '-' . $number ]['callback'][0];

		$widget_options            = get_option( 'widget_' . $id_base );
		$widget_options[ $number ] = $widget->update( $request->get_json_params(), $item['options'] );
		@update_option( 'widget_' . $id_base, $widget_options );

		return $this->get_widget_item( $id_base, $number );
	}

	/**
	 * Delete one item from the collection.
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 *
	 * @return WP_Error|WP_REST_Response
	 */
	public function delete_item( $request ) {
		$id_base   = $request->get_param( 'id_base' );
		$number    =  absint( $request->get_param( 'widget_number' ) );
		$widget_id = $id_base . '-' . $number;

		$widget_options = get_option( 'widget_' . $id_base );
		unset( $widget_options[ $number ] );
		update_option( 'widget_' . $id_base, $widget_options );

		$sidebars_widgets = get_option( 'sidebars_widgets', array() );
		if ( is_array( $sidebars_widgets ) && isset( $sidebars_widgets['array_version'] ) ) {
			unset( $sidebars_widgets['array_version'] );
		}
		foreach ( $sidebars_widgets as $sidebar_id => $widgets ) {
			$deleted = false;
			foreach ( $widgets as $key => $id ) {
				if ( $id == $widget_id ) {
					$deleted = true;
					unset( $sidebars_widgets[ $sidebar_id ][ $key ] );
					break;
				}
			}
			if ( $deleted ) {
				break;
			}
		}
		update_option( 'sidebars_widgets', $sidebars_widgets );

		return rest_ensure_response( true );
	}

	protected function get_widget_item( $id_base, $number ) {
		global $wp_registered_widgets;

		if ( ! isset( $wp_registered_widgets[ $id_base . '-' . $number ] ) ) {
			return false;
		}

		$widget_options = get_option( 'widget_' . $id_base );

		$widget            = $wp_registered_widgets[ $id_base . '-' . $number ];
		$widget['id_base'] = $id_base;
		$widget['options'] = $widget_options[ $number ];
		unset( $widget['callback'] );

		return $widget;
	}

	/**
	 * Check if a given request has access.
	 *
	 * @return WP_Error|bool
	 */
	public function permissions_check() {
		return current_user_can( 'edit_theme_options' );
	}


}

This is nice for widget and sidebar management but what about getting the output of a sidebar and its widgets? I'm talking about the dynamic_sidebar('foobar-sidebar') output for a specific page?