est object.
	 * @return array
	 */
	public function query_args( $args, $request ) {
		$args['post_status']     = array_keys( wc_get_order_statuses() );
		$args['post_parent__in'] = array( absint( $request['order_id'] ) );

		return $args;
	}

	/**
	 * Create a single item.
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_Error|WP_REST_Response
	 */
	public function create_item( $request ) {
		if ( ! empty( $request['id'] ) ) {
			/* translators: %s: post type */
			return new WP_Error( "woocommerce_rest_{$this->post_type}_exists", sprintf( __( 'Cannot create existing %s.', 'woocommerce' ), $this->post_type ), array( 'status' => 400 ) );
		}

		$order_data = get_post( (int) $request['order_id'] );

		if ( empty( $order_data ) ) {
			return new WP_Error( 'woocommerce_rest_invalid_order', __( 'Order is invalid', 'woocommerce' ), 400 );
		}

		if ( 0 > $request['amount'] ) {
			return new WP_Error( 'woocommerce_rest_invalid_order_refund', __( 'Refund amount must be greater than zero.', 'woocommerce' ), 400 );
		}

		// Create the refund.
		$refund = wc_create_refund( array(
			'order_id'       => $order_data->ID,
			'amount'         => $request['amount'],
			'reason'         => empty( $request['reason'] ) ? null : $request['reason'],
			'refund_payment' => is_bool( $request['api_refund'] ) ? $request['api_refund'] : true,
			'restock_items'  => true,
		) );

		if ( is_wp_error( $refund ) ) {
			return new WP_Error( 'woocommerce_rest_cannot_create_order_refund', $refund->get_error_message(), 500 );
		}

		if ( ! $refund ) {
			return new WP_Error( 'woocommerce_rest_cannot_create_order_refund', __( 'Cannot create order refund, please try again.', 'woocommerce' ), 500 );
		}

		$post = get_post( $refund->get_id() );
		$this->update_additional_fields_for_object( $post, $request );

		/**
		 * Fires after a single item is created or updated via the REST API.
		 *
		 * @param WP_Post         $post      Post object.
		 * @param WP_REST_Request $request   Request object.
		 * @param boolean         $creating  True when creating item, false when updating.
		 */
		do_action( "woocommerce_rest_insert_{$this->post_type}", $post, $request, true );

		$request->set_param( 'context', 'edit' );
		$response = $this->prepare_item_for_response( $post, $request );
		$response = rest_ensure_response( $response );
		$response->set_status( 201 );
		$response->header( 'Location', rest_url( sprintf( '/%s/%s/%d', $this->namespace, $this->rest_base, $post->ID ) ) );

		return $response;
	}

	/**
	 * Get the Order's schema, conforming to JSON Schema.
	 *
	 * @return array
	 */
	public function get_item_schema() {
		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => $this->post_type,
			'type'       => 'object',
			'properties' => array(
				'id' => array(
					'description' => __( 'Unique identifier for the resource.', 'woocommerce' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit' ),
					'readonly'    => true,
				),
				'date_created' => array(
					'description' => __( "The date the order refund was created, in the site's timezone.", 'woocommerce' ),
					'type'        => 'date-time',
					'context'     => array( 'view', 'edit' ),
					'readonly'    => true,
				),
				'amount' => array(
					'description' => __( 'Refund amount.', 'woocommerce' ),
					'type'        => 'string',
					'context'     => array( 'view', 'edit' ),
				),
				'reason' => array(
					'description' => __( 'Reason for refund.', 'woocommerce' ),
					'type'        => 'string',
					'context'     => array( 'view', 'edit' ),
				),
				'line_items' => array(
					'description' => __( 'Line items data.', 'woocommerce' ),
					'type'        => 'array',
					'context'     => array( 'view', 'edit' ),
					'readonly'    => true,
					'items'       => array(
						'type'       => 'object',
						'properties' => array(
							'id' => array(
								'description' => __( 'Item ID.', 'woocommerce' ),
								'type'        => 'integer',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'name' => array(
								'description' => __( 'Product name.', 'woocommerce' ),
								'type'        => 'mixed',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'sku' => array(
								'description' => __( 'Product SKU.', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'product_id' => array(
								'description' => __( 'Product ID.', 'woocommerce' ),
								'type'        => 'mixed',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'variation_id' => array(
								'description' => __( 'Variation ID, if applicable.', 'woocommerce' ),
								'type'        => 'integer',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'quantity' => array(
								'description' => __( 'Quantity ordered.', 'woocommerce' ),
								'type'        => 'integer',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'tax_class' => array(
								'description' => __( 'Tax class of product.', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'price' => array(
								'description' => __( 'Product price.', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'subtotal' => array(
								'description' => __( 'Line subtotal (before discounts).', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'subtotal_tax' => array(
								'description' => __( 'Line subtotal tax (before discounts).', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'total' => array(
								'description' => __( 'Line total (after discounts).', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'total_tax' => array(
								'description' => __( 'Line total tax (after discounts).', 'woocommerce' ),
								'type'        => 'string',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
							),
							'taxes' => array(
								'description' => __( 'Line taxes.', 'woocommerce' ),
								'type'        => 'array',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
								'items'       => array(
									'type'       => 'object',
									'properties' => array(
										'id' => array(
											'description' => __( 'Tax rate ID.', 'woocommerce' ),
											'type'        => 'integer',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
										'total' => array(
											'description' => __( 'Tax total.', 'woocommerce' ),
											'type'        => 'string',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
										'subtotal' => array(
											'description' => __( 'Tax subtotal.', 'woocommerce' ),
											'type'        => 'string',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
									),
								),
							),
							'meta' => array(
								'description' => __( 'Line item meta data.', 'woocommerce' ),
								'type'        => 'array',
								'context'     => array( 'view', 'edit' ),
								'readonly'    => true,
								'items'       => array(
									'type'       => 'object',
									'properties' => array(
										'key' => array(
											'description' => __( 'Meta key.', 'woocommerce' ),
											'type'        => 'string',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
										'label' => array(
											'description' => __( 'Meta label.', 'woocommerce' ),
											'type'        => 'string',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
										'value' => array(
											'description' => __( 'Meta value.', 'woocommerce' ),
											'type'        => 'mixed',
											'context'     => array( 'view', 'edit' ),
											'readonly'    => true,
										),
									),
								),
							),
						),
					),
				),
			),
		);

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

	/**
	 * Get the query params for collections.
	 *
	 * @return array
	 */
	public function get_collection_params() {
		$params = parent::get_collection_params();

		$params['dp'] = array(
			'default'           => wc_get_price_decimals(),
			'description'       => __( 'Number of decimal points to use in each resource.', 'woocommerce' ),
			'type'              => 'integer',
			'sanitize_callback' => 'absint',
			'validate_callback' => 'rest_validate_request_arg',
		);

		return $params;
	}
}