abstract class LLMS_REST_Controller_Stubs extends WP_REST_Controller {

	/**
	 * Base Resource
	 *
	 * For example: "courses" or "students".
	 *
	 * @var string
	 */
	protected $rest_base;

	/**
	 * Get object.
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param int $id Object ID.
	 * @return object|WP_Error
	 */
	abstract protected function get_object( $id );

	/**
	 * Determine if the current user can view the requested item.
	 *
	 * @since 1.0.0-beta.1
	 * @since 1.0.0-beta.10 Add text domain to i18n functions.
	 *
	 * @param int $item_id WP_User id.
	 * @return bool
	 */
	protected function check_read_item_permissions( $item_id ) {

		// Translators: %s = method name.
		return llms_rest_server_error( sprintf( __( "Method '%s' not implemented. Must be overridden in subclass.", 'lifterlms' ), __METHOD__ ) );

	}

	/**
	 * Determine if the current user can view the object.
	 *
	 * @since 1.0.0-beta.7
	 * @since 1.0.0-beta.10 Add text domain to i18n functions.
	 *
	 * @param object $object Object.
	 * @return bool
	 */
	protected function check_read_object_permissions( $object ) {

		// Translators: %s = method name.
		return llms_rest_server_error( sprintf( __( "Method '%s' not implemented. Must be overridden in subclass.", 'lifterlms' ), __METHOD__ ) );

	}

	/**
	 * Insert the prepared data into the database.
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param array           $prepared Prepared item data.
	 * @param WP_REST_Request $request  Request object.
	 * @return obj Object Instance of object from $this->get_object().
	 */
	protected function create_object( $prepared, $request ) {

		// @todo: add version to message.

		// Translators: %s = method name.
		_doing_it_wrong( 'LLMS_REST_Controller::create_object', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );

		// For example.
		return $this->get_object( $this->get_object_id( $prepared ) );

	}

	/**
	 * Retrieve an ID from the object
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param obj $object Item object.
	 * @return int
	 */
	protected function get_object_id( $object ) {
		if ( is_object( $object ) && ! empty( $object->id ) ) {
			return $object->id;
		} elseif ( is_array( $object ) && ! empty( $object['id'] ) ) {
			return $object['id'];
		} elseif ( method_exists( $object, 'get_id' ) ) {
			return $object->get_id();
		} elseif ( method_exists( $object, 'get' ) ) {
			return $object->get( 'id' );
		}

		// @todo: add version to message.

		// Translators: %s = method name.
		_doing_it_wrong( 'LLMS_REST_Controller::get_object_id', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );

		// For example.
		return 0;

	}

	/**
	 * Retrieve a query object based on arguments from a `get_items()` (collection) request.
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param array           $prepared Array of collection arguments.
	 * @param WP_REST_Request $request  Request object.
	 * @return object
	 */
	protected function get_objects_query( $prepared, $request ) {

		// Translators: %s = method name.
		_doing_it_wrong( 'LLMS_REST_Controller::get_objects_query', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );

		// For example.
		return new WP_Query( $prepared );

	}

	/**
	 * Retrieve an array of objects from the result of $this->get_objects_query().
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param obj $query Objects query result.
	 * @return obj[]
	 */
	protected function get_objects_from_query( $query ) {

		// Translators: %s = method name.
		_doing_it_wrong( 'LLMS_REST_Controller::get_objects_from_query', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );

		// For example.
		return array();

	}

	/**
	 * Retrieve pagination information from an objects query.
	 *
	 * @since 1.0.0-beta.1
	 *
	 * @param obj             $query    Objects query result.
	 * @param array           $prepared Array of collection arguments.
	 * @param WP_REST_Request $request  Request object.
	 * @return array {
	 *     Array of pagination information.
	 *
	 *     @type int $current_page Current page number.
	 *     @type int $total_results Total number of results.
	 *     @type int $total_pages Total number of results pages.
	 * }
	 */
	protected function get_pagination_data_from_query( $query, $prepared, $request ) {

		// Translators: %s = method name.
		_doing_it_wrong( 'LLMS_REST_Controller::get_pagination_data_from_query', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );

		// For example.
		return array(
			'current_page'  => 1,
			'total_results' => 1,
			'total_pages'   => 1,
		);

	}

	/**
	 * Prepares data of a single object for response.
	 *
	 * @since 1.0.0-beta.27
	 *
	 * @param obj             $object  Raw object from database.
	 * @param WP_REST_Request $request Request object.
	 * @return array
	 */
	protected function prepare_object_data_for_response( $object, $request ) {

		$data            = $this->prepare_object_for_response( $object, $request );
		$response_fields = $this->get_fields_for_response( $request );
		// Include meta data registered via `register_meta()`.
		if ( rest_is_field_included( 'meta', $response_fields ) ) {
			$data['meta'] = $this->meta->get_value( $this->get_object_id( $object ), $request );
			// Exclude disallowed meta.
			$data['meta'] = $this->exclude_disallowed_meta_fields( $data['meta'] );
		}

		// Include custom REST fields registered via `register_rest_field()`.
		$data = $this->add_additional_fields_to_object( $data, $request );

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

		return $data;

	}

	/**
	 * Prepare an object for response.
	 *
	 * @since 1.0.0-beta.1
	 * @since 1.0.0-beta.3 Conditionally throw `_doing_it_wrong()`.
	 * @since 1.0.0-beta.27 Exclude additional fields added via `register_rest_field`.
	 *
	 * @param object          $object  Raw object from database.
	 * @param WP_REST_Request $request Request object.
	 * @return array
	 */
	protected function prepare_object_for_response( $object, $request ) {

		if ( ! method_exists( $object, 'get' ) ) {
			// Translators: %s = method name.
			_doing_it_wrong( 'LLMS_REST_Controller::prepare_object_for_response', sprintf( __( "Method '%s' must be overridden.", 'lifterlms' ), __METHOD__ ), '1.0.0-beta.1' );
		}

		$prepared          = array();
		$map               = array_flip( $this->map_schema_to_database() );
		$fields            = $this->get_fields_for_response( $request );
		$additional_fields = array_keys( $this->get_additional_fields() );