<?php
/**
 * WC_Product_Data_Store_CPT class file.
 *
 * @package WooCommerce\Classes
 */

use Automattic\Jetpack\Constants;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * WC Product Data Store: Stored in CPT.
 *
 * @version  3.0.0
 */
class WC_Product_Data_Store_CPT extends WC_Data_Store_WP implements WC_Object_Data_Store_Interface, WC_Product_Data_Store_Interface {

	/**
	 * Data stored in meta keys, but not considered "meta".
	 *
	 * @since 3.0.0
	 * @var array
	 */
	protected $internal_meta_keys = array(
		'_visibility',
		'_sku',
		'_price',
		'_regular_price',
		'_sale_price',
		'_sale_price_dates_from',
		'_sale_price_dates_to',
		'total_sales',
		'_tax_status',
		'_tax_class',
		'_manage_stock',
		'_stock',
		'_stock_status',
		'_backorders',
		'_low_stock_amount',
		'_sold_individually',
		'_weight',
		'_length',
		'_width',
		'_height',
		'_upsell_ids',
		'_crosssell_ids',
		'_purchase_note',
		'_default_attributes',
		'_product_attributes',
		'_virtual',
		'_downloadable',
		'_download_limit',
		'_download_expiry',
		'_featured',
		'_downloadable_files',
		'_wc_rating_count',
		'_wc_average_rating',
		'_wc_review_count',
		'_variation_description',
		'_thumbnail_id',
		'_file_paths',
		'_product_image_gallery',
		'_product_version',
		'_wp_old_slug',
		'_edit_last',
		'_edit_lock',
	);

	/**
	 * Meta data which should exist in the DB, even if empty.
	 *
	 * @since 3.6.0
	 *
	 * @var array
	 */
	protected $must_exist_meta_keys = array(
		'_tax_class',
	);

	/**
	 * If we have already saved our extra data, don't do automatic / default handling.
	 *
	 * @var bool
	 */
	protected $extra_data_saved = false;

	/**
	 * Stores updated props.
	 *
	 * @var array
	 */
	protected $updated_props = array();

	/*
	|--------------------------------------------------------------------------
	| CRUD Methods
	|--------------------------------------------------------------------------
	*/

	/**
	 * Method to create a new product in the database.
	 *
	 * @param WC_Product $product Product object.
	 */
	public function create( &$product ) {
		if ( ! $product->get_date_created( 'edit' ) ) {
			$product->set_date_created( time() );
		}

		$id = wp_insert_post(
			apply_filters(
				'woocommerce_new_product_data',
				array(
					'post_type'      => 'product',
					'post_status'    => $product->get_status() ? $product->get_status() : 'publish',
					'post_author'    => get_current_user_id(),
					'post_title'     => $product->get_name() ? $product->get_name() : __( 'Product', 'woocommerce' ),
					'post_content'   => $product->get_description(),
					'post_excerpt'   => $product->get_short_description(),
					'post_parent'    => $product->get_parent_id(),
					'comment_status' => $product->get_reviews_allowed() ? 'open' : 'closed',
					'ping_status'    => 'closed',
					'menu_order'     => $product->get_menu_order(),
					'post_password'  => $product->get_post_password( 'edit' ),
					'post_date'      => gmdate( 'Y-m-d H:i:s', $product->get_date_created( 'edit' )->getOffsetTimestamp() ),
					'post_date_gmt'  => gmdate( 'Y-m-d H:i:s', $product->get_date_created( 'edit' )->getTimestamp() ),
					'post_name'      => $product->get_slug( 'edit' ),
				)
			),
			true
		);

		if ( $id && ! is_wp_error( $id ) ) {
			$product->set_id( $id );

			$this->update_post_meta( $product, true );
			$this->update_terms( $product, true );
			$this->update_visibility( $product, true );
			$this->update_attributes( $product, true );
			$this->update_version_and_type( $product );
			$this->handle_updated_props( $product );
			$this->clear_caches( $product );

			$product->save_meta_data();
			$product->apply_changes();

			do_action( 'woocommerce_new_product', $id, $product );
		}
	}

	/**
	 * Method to read a product from the database.
	 *
	 * @param WC_Product $product Product object.
	 * @throws Exception If invalid product.
	 */
	public function read( &$product ) {
		$product->set_defaults();
		$post_object = get_post( $product->get_id() );

		if ( ! $product->get_id() || ! $post_object || 'product' !== $post_object->post_type ) {
			throw new Exception( __( 'Invalid product.', 'woocommerce' ) );
		}

		$product->set_props(
			array(
				'name'              => $post_object->post_title,
				'slug'              => $post_object->post_name,
				'date_created'      => 0 < $post_object->post_date_gmt ? wc_string_to_timestamp( $post_object->post_date_gmt ) : null,
				'date_modified'     => 0 < $post_object->post_modified_gmt ? wc_string_to_timestamp( $post_object->post_modified_gmt ) : null,
				'status'            => $post_object->post_status,
				'description'       => $post_object->post_content,
				'short_description' => $post_object->post_excerpt,
				'parent_id'         => $post_object->post_parent,
				'menu_order'        => $post_object->menu_order,
				'post_password'     => $post_object->post_password,
				'reviews_allowed'   => 'open' === $post_object->comment_status,
			)
		);

		$this->read_attributes( $product );
		$this->read_downloads( $product );
		$this->read_visibility( $product );
		$this->read_product_data( $product );
		$this->read_extra_data( $product );
		$product->set_object_read( true );

		do_action( 'woocommerce_product_read', $product->get_id() );
	}

	/**
	 * Method to update a product in the database.
	 *
	 * @param WC_Product $product Product object.
	 */
	public function update( &$product ) {
		$product->save_meta_data();
		$changes = $product->get_changes();

		// Only update the post when the post data changes.
		if ( array_intersect( array( 'description', 'short_description', 'name', 'parent_id', 'reviews_allowed', 'status', 'menu_order', 'date_created', 'date_modified', 'slug' ), array_keys( $changes ) ) ) {
			$post_data = array(
				'post_content'   => $product->get_description( 'edit' ),
				'post_excerpt'   => $product->get_short_description( 'edit' ),
				'post_title'     => $product->get_name( 'edit' ),
				'post_parent'    => $product->get_parent_id( 'edit' ),
				'comment_status' => $product->get_reviews_allowed( 'edit' ) ? 'open' : 'closed',
				'post_status'    => $product->get_status( 'edit' ) ? $product->get_status( 'edit' ) : 'publish',
				'menu_order'     => $product->get_menu_order( 'edit' ),
				'post_password'  => $product->get_post_password( 'edit' ),
				'post_name'      => $product->get_slug( 'edit' ),
				'post_type'      => 'product',
			);
			if ( $product->get_date_created( 'edit' ) ) {
				$post_data['post_date']     = gmdate( 'Y-m-d H:i:s', $product->get_date_created( 'edit' )->getOffsetTimestamp() );
				$post_data['post_date_gmt'] = gmdate( 'Y-m-d H:i:s', $product->get_date_created( 'edit' )->getTimestamp() );
			}
			if ( isset( $changes['date_modified'] ) && $product->get_date_modified( 'edit' ) ) {
				$post_data['post_modified']     = gmdate( 'Y-m-d H:i:s', $product->get_date_modified( 'edit' )->getOffsetTimestamp() );
				$post_data['post_modified_gmt'] = gmdate( 'Y-m-d H:i:s', $product->get_date_modified( 'edit' )->getTimestamp() );
			} else {
				$post_data['post_modified']     = current_time( 'mysql' );
				$post_data['post_modified_gmt'] = current_time( 'mysql', 1 );
			}

			/**
			 * When updating this object, to prevent infinite loops, use $wpdb
			 * to update data, since wp_update_post spawns more calls to the
			 * save_post action.
			 *
			 * This ensures hooks are fired by either WP itself (admin screen save),
			 * or an update purely from CRUD.
			 */
			if ( doing_action( 'save_post' ) ) {
				$GLOBALS['wpdb']->update( $GLOBALS['wpdb']->posts, $post_data, array( 'ID' => $product->get_id() ) );
				clean_post_cache( $product->get_id() );
			} else {
				wp_update_post( array_merge( array( 'ID' => $product->get_id() ), $post_data ) );
			}
			$product->read_meta_data( true ); // Refresh internal meta data, in case things were hooked into `save_post` or another WP hook.

		} else { // Only update post modified time to record this save event.
			$GLOBALS['wpdb']->update(
				$GLOBALS['wpdb']->posts,
				array(
					'post_modified'     => current_time( 'mysql' ),
					'post_modified_gmt' => current_time( 'mysql', 1 ),
				),
				array(
					'ID' => $product->get_id(),
				)
			);
			clean_post_cache( $product->get_id() );
		}

		$this->update_post_meta( $product );
		$this->update_terms( $product );
		$this->update_visibility( $product );
		$this->update_attributes( $product );
		$this->update_version_and_type( $product );
		$this->handle_updated_props( $product );
		$this->clear_caches( $product );

		$product->apply_changes();

		do_action( 'woocommerce_update_product', $product->get_id(), $product );
	}

	/**
	 * Method to delete a product from the database.
	 *
	 * @param WC_Product $product Product object.
	 * @param array      $args Array of args to pass to the delete method.
	 */
	public function delete( &$product, $args = array() ) {
		$id        = $product->get_id();
		$post_type = $product->is_type( 'variation' ) ? 'product_variation' : 'product';

		$args = wp_parse_args(
			$args,
			array(
				'force_delete' => false,
			)
		);

		if ( ! $id ) {
			return;
		}

		if ( $args['force_delete'] ) {
			do_action( 'woocommerce_before_delete_' . $post_type, $id );
			wp_delete_post( $id );
			$product->set_id( 0 );
			do_action( 'woocommerce_delete_' . $post_type, $id );
		} else {
			wp_trash_post( $id );
			$product->set_status( 'trash' );
			do_action( 'woocommerce_trash_' . $post_type, $id );
		}
	}

	/*
	|--------------------------------------------------------------------------
	| Additional Methods
	|--------------------------------------------------------------------------
	*/

	/**
	 * Read product data. Can be overridden by child classes to load other props.
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function read_product_data( &$product ) {
		$id                = $product->get_id();
		$post_meta_values  = get_post_meta( $id );
		$meta_key_to_props = array(
			'_sku'                   => 'sku',
			'_regular_price'         => 'regular_price',
			'_sale_price'            => 'sale_price',
			'_price'                 => 'price',
			'_sale_price_dates_from' => 'date_on_sale_from',
			'_sale_price_dates_to'   => 'date_on_sale_to',
			'total_sales'            => 'total_sales',
			'_tax_status'            => 'tax_status',
			'_tax_class'             => 'tax_class',
			'_manage_stock'          => 'manage_stock',
			'_backorders'            => 'backorders',
			'_low_stock_amount'      => 'low_stock_amount',
			'_sold_individually'     => 'sold_individually',
			'_weight'                => 'weight',
			'_length'                => 'length',
			'_width'                 => 'width',
			'_height'                => 'height',
			'_upsell_ids'            => 'upsell_ids',
			'_crosssell_ids'         => 'cross_sell_ids',
			'_purchase_note'         => 'purchase_note',
			'_default_attributes'    => 'default_attributes',
			'_virtual'               => 'virtual',
			'_downloadable'          => 'downloadable',
			'_download_limit'        => 'download_limit',
			'_download_expiry'       => 'download_expiry',
			'_thumbnail_id'          => 'image_id',
			'_stock'                 => 'stock_quantity',
			'_stock_status'          => 'stock_status',
			'_wc_average_rating'     => 'average_rating',
			'_wc_rating_count'       => 'rating_counts',
			'_wc_review_count'       => 'review_count',
			'_product_image_gallery' => 'gallery_image_ids',
		);

		$set_props = array();

		foreach ( $meta_key_to_props as $meta_key => $prop ) {
			$meta_value         = isset( $post_meta_values[ $meta_key ][0] ) ? $post_meta_values[ $meta_key ][0] : null;
			$set_props[ $prop ] = maybe_unserialize( $meta_value ); // get_post_meta only unserializes single values.
		}

		$set_props['category_ids']      = $this->get_term_ids( $product, 'product_cat' );
		$set_props['tag_ids']           = $this->get_term_ids( $product, 'product_tag' );
		$set_props['shipping_class_id'] = current( $this->get_term_ids( $product, 'product_shipping_class' ) );
		$set_props['gallery_image_ids'] = array_filter( explode( ',', $set_props['gallery_image_ids'] ) );

		$product->set_props( $set_props );
	}

	/**
	 * Re-reads stock from the DB ignoring changes.
	 *
	 * @param WC_Product $product Product object.
	 * @param int|float  $new_stock New stock level if already read.
	 */
	public function read_stock_quantity( &$product, $new_stock = null ) {
		$object_read = $product->get_object_read();
		$product->set_object_read( false ); // This makes update of qty go directly to data- instead of changes-array of the product object (which is needed as the data should hold status of the object as it was read from the db).
		$product->set_stock_quantity( is_null( $new_stock ) ? get_post_meta( $product->get_id(), '_stock', true ) : $new_stock );
		$product->set_object_read( $object_read );
	}

	/**
	 * Read extra data associated with the product, like button text or product URL for external products.
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function read_extra_data( &$product ) {
		foreach ( $product->get_extra_data_keys() as $key ) {
			$function = 'set_' . $key;
			if ( is_callable( array( $product, $function ) ) ) {
				$product->{$function}( get_post_meta( $product->get_id(), '_' . $key, true ) );
			}
		}
	}

	/**
	 * Convert visibility terms to props.
	 * Catalog visibility valid values are 'visible', 'catalog', 'search', and 'hidden'.
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function read_visibility( &$product ) {
		$terms           = get_the_terms( $product->get_id(), 'product_visibility' );
		$term_names      = is_array( $terms ) ? wp_list_pluck( $terms, 'name' ) : array();
		$featured        = in_array( 'featured', $term_names, true );
		$exclude_search  = in_array( 'exclude-from-search', $term_names, true );
		$exclude_catalog = in_array( 'exclude-from-catalog', $term_names, true );

		if ( $exclude_search && $exclude_catalog ) {
			$catalog_visibility = 'hidden';
		} elseif ( $exclude_search ) {
			$catalog_visibility = 'catalog';
		} elseif ( $exclude_catalog ) {
			$catalog_visibility = 'search';
		} else {
			$catalog_visibility = 'visible';
		}

		$product->set_props(
			array(
				'featured'           => $featured,
				'catalog_visibility' => $catalog_visibility,
			)
		);
	}

	/**
	 * Read attributes from post meta.
	 *
	 * @param WC_Product $product Product object.
	 */
	protected function read_attributes( &$product ) {
		$meta_attributes = get_post_meta( $product->get_id(), '_product_attributes', true );

		if ( ! empty( $meta_attributes ) && is_array( $meta_attributes ) ) {
			$attributes = array();
			foreach ( $meta_attributes as $meta_attribute_key => $meta_attribute_value ) {
				$meta_value = array_merge(
					array(
						'name'         => '',
						'value'        => '',
						'position'     => 0,
						'is_visible'   => 0,
						'is_variation' => 0,
						'is_taxonomy'  => 0,
					),
					(array) $meta_attribute_value
				);

				// Check if is a taxonomy attribute.
				if ( ! empty( $meta_value['is_taxonomy'] ) ) {
					if ( ! taxonomy_exists( $meta_value['name'] ) ) {
						continue;
					}
					$id      = wc_attribute_taxonomy_id_by_name( $meta_value['name'] );
					$options = wc_get_object_terms( $product->get_id(), $meta_value['name'], 'term_id' );
				} else {
					$id      = 0;
					$options = wc_get_text_attributes( $meta_value['value'] );
				}

				$attribute = new WC_Product_Attribute();
				$attribute->set_id( $id );
				$attribute->set_name( $meta_value['name'] );
				$attribute->set_options( $options );
				$attribute->set_position( $meta_value['position'] );
				$attribute->set_visible( $meta_value['is_visible'] );
				$attribute->set_variation( $meta_value['is_variation'] );
				$attributes[] = $attribute;
			}
			$product->set_attributes( $attributes );
		}
	}

	/**
	 * Read downloads from post meta.
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function read_downloads( &$product ) {
		$meta_values = array_filter( (array) get_post_meta( $product->get_id(), '_downloadable_files', true ) );

		if ( $meta_values ) {
			$downloads = array();
			foreach ( $meta_values as $key => $value ) {
				if ( ! isset( $value['name'], $value['file'] ) ) {
					continue;
				}
				$download = new WC_Product_Download();
				$download->set_id( $key );
				$download->set_name( $value['name'] ? $value['name'] : wc_get_filename_from_url( $value['file'] ) );
				$download->set_file( apply_filters( 'woocommerce_file_download_path', $value['file'], $product, $key ) );
				$downloads[] = $download;
			}
			$product->set_downloads( $downloads );
		}
	}

	/**
	 * Helper method that updates all the post meta for a product based on it's settings in the WC_Product class.
	 *
	 * @param WC_Product $product Product object.
	 * @param bool       $force Force update. Used during create.
	 * @since 3.0.0
	 */
	protected function update_post_meta( &$product, $force = false ) {
		$meta_key_to_props = array(
			'_sku'                   => 'sku',
			'_regular_price'         => 'regular_price',
			'_sale_price'            => 'sale_price',
			'_sale_price_dates_from' => 'date_on_sale_from',
			'_sale_price_dates_to'   => 'date_on_sale_to',
			'total_sales'            => 'total_sales',
			'_tax_status'            => 'tax_status',
			'_tax_class'             => 'tax_class',
			'_manage_stock'          => 'manage_stock',
			'_backorders'            => 'backorders',
			'_low_stock_amount'      => 'low_stock_amount',
			'_sold_individually'     => 'sold_individually',
			'_weight'                => 'weight',
			'_length'                => 'length',
			'_width'                 => 'width',
			'_height'                => 'height',
			'_upsell_ids'            => 'upsell_ids',
			'_crosssell_ids'         => 'cross_sell_ids',
			'_purchase_note'         => 'purchase_note',
			'_default_attributes'    => 'default_attributes',
			'_virtual'               => 'virtual',
			'_downloadable'          => 'downloadable',
			'_product_image_gallery' => 'gallery_image_ids',
			'_download_limit'        => 'download_limit',
			'_download_expiry'       => 'download_expiry',
			'_thumbnail_id'          => 'image_id',
			'_stock'                 => 'stock_quantity',
			'_stock_status'          => 'stock_status',
			'_wc_average_rating'     => 'average_rating',
			'_wc_rating_count'       => 'rating_counts',
			'_wc_review_count'       => 'review_count',
		);

		// Make sure to take extra data (like product url or text for external products) into account.
		$extra_data_keys = $product->get_extra_data_keys();

		foreach ( $extra_data_keys as $key ) {
			$meta_key_to_props[ '_' . $key ] = $key;
		}

		$props_to_update = $force ? $meta_key_to_props : $this->get_props_to_update( $product, $meta_key_to_props );

		foreach ( $props_to_update as $meta_key => $prop ) {
			$value = $product->{"get_$prop"}( 'edit' );
			$value = is_string( $value ) ? wp_slash( $value ) : $value;
			switch ( $prop ) {
				case 'virtual':
				case 'downloadable':
				case 'manage_stock':
				case 'sold_individually':
					$value = wc_bool_to_string( $value );
					break;
				case 'gallery_image_ids':
					$value = implode( ',', $value );
					break;
				case 'date_on_sale_from':
				case 'date_on_sale_to':
					$value = $value ? $value->getTimestamp() : '';
					break;
			}

			$updated = $this->update_or_delete_post_meta( $product, $meta_key, $value );

			if ( $updated ) {
				$this->updated_props[] = $prop;
			}
		}

		// Update extra data associated with the product like button text or product URL for external products.
		if ( ! $this->extra_data_saved ) {
			foreach ( $extra_data_keys as $key ) {
				$meta_key = '_' . $key;
				$function = 'get_' . $key;
				if ( ! array_key_exists( $meta_key, $props_to_update ) ) {
					continue;
				}
				if ( is_callable( array( $product, $function ) ) ) {
					$value   = $product->{$function}( 'edit' );
					$value   = is_string( $value ) ? wp_slash( $value ) : $value;
					$updated = $this->update_or_delete_post_meta( $product, $meta_key, $value );

					if ( $updated ) {
						$this->updated_props[] = $key;
					}
				}
			}
		}

		if ( $this->update_downloads( $product, $force ) ) {
			$this->updated_props[] = 'downloads';
		}
	}

	/**
	 * Handle updated meta props after updating meta data.
	 *
	 * @since 3.0.0
	 * @param WC_Product $product Product Object.
	 */
	protected function handle_updated_props( &$product ) {
		$price_is_synced = $product->is_type( array( 'variable', 'grouped' ) );

		if ( ! $price_is_synced ) {
			if ( in_array( 'regular_price', $this->updated_props, true ) || in_array( 'sale_price', $this->updated_props, true ) ) {
				if ( $product->get_sale_price( 'edit' ) >= $product->get_regular_price( 'edit' ) ) {
					update_post_meta( $product->get_id(), '_sale_price', '' );
					$product->set_sale_price( '' );
				}
			}

			if ( in_array( 'date_on_sale_from', $this->updated_props, true ) || in_array( 'date_on_sale_to', $this->updated_props, true ) || in_array( 'regular_price', $this->updated_props, true ) || in_array( 'sale_price', $this->updated_props, true ) || in_array( 'product_type', $this->updated_props, true ) ) {
				if ( $product->is_on_sale( 'edit' ) ) {
					update_post_meta( $product->get_id(), '_price', $product->get_sale_price( 'edit' ) );
					$product->set_price( $product->get_sale_price( 'edit' ) );
				} else {
					update_post_meta( $product->get_id(), '_price', $product->get_regular_price( 'edit' ) );
					$product->set_price( $product->get_regular_price( 'edit' ) );
				}
			}
		}

		if ( in_array( 'stock_quantity', $this->updated_props, true ) ) {
			if ( $product->is_type( 'variation' ) ) {
				do_action( 'woocommerce_variation_set_stock', $product );
			} else {
				do_action( 'woocommerce_product_set_stock', $product );
			}
		}

		if ( in_array( 'stock_status', $this->updated_props, true ) ) {
			if ( $product->is_type( 'variation' ) ) {
				do_action( 'woocommerce_variation_set_stock_status', $product->get_id(), $product->get_stock_status(), $product );
			} else {
				do_action( 'woocommerce_product_set_stock_status', $product->get_id(), $product->get_stock_status(), $product );
			}
		}

		if ( array_intersect( $this->updated_props, array( 'sku', 'regular_price', 'sale_price', 'date_on_sale_from', 'date_on_sale_to', 'total_sales', 'average_rating', 'stock_quantity', 'stock_status', 'manage_stock', 'downloadable', 'virtual', 'tax_status', 'tax_class' ) ) ) {
			$this->update_lookup_table( $product->get_id(), 'wc_product_meta_lookup' );
		}

		// Trigger action so 3rd parties can deal with updated props.
		do_action( 'woocommerce_product_object_updated_props', $product, $this->updated_props );

		// After handling, we can reset the props array.
		$this->updated_props = array();
	}

	/**
	 * For all stored terms in all taxonomies, save them to the DB.
	 *
	 * @param WC_Product $product Product object.
	 * @param bool       $force Force update. Used during create.
	 * @since 3.0.0
	 */
	protected function update_terms( &$product, $force = false ) {
		$changes = $product->get_changes();

		if ( $force || array_key_exists( 'category_ids', $changes ) ) {
			$categories = $product->get_category_ids( 'edit' );

			if ( empty( $categories ) && get_option( 'default_product_cat', 0 ) ) {
				$categories = array( get_option( 'default_product_cat', 0 ) );
			}

			wp_set_post_terms( $product->get_id(), $categories, 'product_cat', false );
		}
		if ( $force || array_key_exists( 'tag_ids', $changes ) ) {
			wp_set_post_terms( $product->get_id(), $product->get_tag_ids( 'edit' ), 'product_tag', false );
		}
		if ( $force || array_key_exists( 'shipping_class_id', $changes ) ) {
			wp_set_post_terms( $product->get_id(), array( $product->get_shipping_class_id( 'edit' ) ), 'product_shipping_class', false );
		}
	}

	/**
	 * Update visibility terms based on props.
	 *
	 * @since 3.0.0
	 *
	 * @param WC_Product $product Product object.
	 * @param bool       $force Force update. Used during create.
	 */
	protected function update_visibility( &$product, $force = false ) {
		$changes = $product->get_changes();

		if ( $force || array_intersect( array( 'featured', 'stock_status', 'average_rating', 'catalog_visibility' ), array_keys( $changes ) ) ) {
			$terms = array();

			if ( $product->get_featured() ) {
				$terms[] = 'featured';
			}

			if ( 'outofstock' === $product->get_stock_status() ) {
				$terms[] = 'outofstock';
			}

			$rating = min( 5, round( $product->get_average_rating(), 0 ) );

			if ( $rating > 0 ) {
				$terms[] = 'rated-' . $rating;
			}

			switch ( $product->get_catalog_visibility() ) {
				case 'hidden':
					$terms[] = 'exclude-from-search';
					$terms[] = 'exclude-from-catalog';
					break;
				case 'catalog':
					$terms[] = 'exclude-from-search';
					break;
				case 'search':
					$terms[] = 'exclude-from-catalog';
					break;
			}

			if ( ! is_wp_error( wp_set_post_terms( $product->get_id(), $terms, 'product_visibility', false ) ) ) {
				do_action( 'woocommerce_product_set_visibility', $product->get_id(), $product->get_catalog_visibility() );
			}
		}
	}

	/**
	 * Update attributes which are a mix of terms and meta data.
	 *
	 * @param WC_Product $product Product object.
	 * @param bool       $force Force update. Used during create.
	 * @since 3.0.0
	 */
	protected function update_attributes( &$product, $force = false ) {
		$changes = $product->get_changes();

		if ( $force || array_key_exists( 'attributes', $changes ) ) {
			$attributes  = $product->get_attributes();
			$meta_values = array();

			if ( $attributes ) {
				foreach ( $attributes as $attribute_key => $attribute ) {
					$value = '';

					if ( is_null( $attribute ) ) {
						if ( taxonomy_exists( $attribute_key ) ) {
							// Handle attributes that have been unset.
							wp_set_object_terms( $product->get_id(), array(), $attribute_key );
						} elseif ( taxonomy_exists( urldecode( $attribute_key ) ) ) {
							// Handle attributes that have been unset.
							wp_set_object_terms( $product->get_id(), array(), urldecode( $attribute_key ) );
						}
						continue;

					} elseif ( $attribute->is_taxonomy() ) {
						wp_set_object_terms( $product->get_id(), wp_list_pluck( (array) $attribute->get_terms(), 'term_id' ), $attribute->get_name() );
					} else {
						$value = wc_implode_text_attributes( $attribute->get_options() );
					}

					// Store in format WC uses in meta.
					$meta_values[ $attribute_key ] = array(
						'name'         => $attribute->get_name(),
						'value'        => $value,
						'position'     => $attribute->get_position(),
						'is_visible'   => $attribute->get_visible() ? 1 : 0,
						'is_variation' => $attribute->get_variation() ? 1 : 0,
						'is_taxonomy'  => $attribute->is_taxonomy() ? 1 : 0,
					);
				}
			}
			// Note, we use wp_slash to add extra level of escaping. See https://codex.wordpress.org/Function_Reference/update_post_meta#Workaround.
			$this->update_or_delete_post_meta( $product, '_product_attributes', wp_slash( $meta_values ) );
		}
	}

	/**
	 * Update downloads.
	 *
	 * @since 3.0.0
	 * @param WC_Product $product Product object.
	 * @param bool       $force Force update. Used during create.
	 * @return bool If updated or not.
	 */
	protected function update_downloads( &$product, $force = false ) {
		$changes = $product->get_changes();

		if ( $force || array_key_exists( 'downloads', $changes ) ) {
			$downloads   = $product->get_downloads();
			$meta_values = array();

			if ( $downloads ) {
				foreach ( $downloads as $key => $download ) {
					// Store in format WC uses in meta.
					$meta_values[ $key ] = $download->get_data();
				}
			}

			if ( $product->is_type( 'variation' ) ) {
				do_action( 'woocommerce_process_product_file_download_paths', $product->get_parent_id(), $product->get_id(), $downloads );
			} else {
				do_action( 'woocommerce_process_product_file_download_paths', $product->get_id(), 0, $downloads );
			}

			return $this->update_or_delete_post_meta( $product, '_downloadable_files', wp_slash( $meta_values ) );
		}
		return false;
	}

	/**
	 * Make sure we store the product type and version (to track data changes).
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function update_version_and_type( &$product ) {
		$old_type = WC_Product_Factory::get_product_type( $product->get_id() );
		$new_type = $product->get_type();

		wp_set_object_terms( $product->get_id(), $new_type, 'product_type' );
		update_post_meta( $product->get_id(), '_product_version', Constants::get_constant( 'WC_VERSION' ) );

		// Action for the transition.
		if ( $old_type !== $new_type ) {
			$this->updated_props[] = 'product_type';
			do_action( 'woocommerce_product_type_changed', $product, $old_type, $new_type );
		}
	}

	/**
	 * Clear any caches.
	 *
	 * @param WC_Product $product Product object.
	 * @since 3.0.0
	 */
	protected function clear_caches( &$product ) {
		wc_delete_product_transients( $product->get_id() );
		if ( $product->get_parent_id( 'edit' ) ) {
			wc_delete_product_transients( $product->get_parent_id( 'edit' ) );
			WC_Cache_Helper::invalidate_cache_group( 'product_' . $product->get_parent_id( 'edit' ) );
		}
		WC_Cache_Helper::invalidate_attribute_count( array_keys( $product->get_attributes() ) );
		WC_Cache_Helper::invalidate_cache_group( 'product_' . $product->get_id() );
	}

	/*
	|--------------------------------------------------------------------------
	| wc-product-functions.php methods
	|--------------------------------------------------------------------------
	*/

	/**
	 * Returns an array of on sale products, as an array of objects with an
	 * ID and parent_id present. Example: $return[0]->id, $return[0]->parent_id.
	 *
	 * @return array
	 * @since 3.0.0
	 */
	public function get_on_sale_products() {
		global $wpdb;

		$exclude_term_ids            = array();
		$outofstock_join             = '';
		$outofstock_where            = '';
		$non_published_where         = '';
		$product_visibility_term_ids = wc_get_product_visibility_term_ids();

		if ( 'yes' === get_option( 'woocommerce_hide_out_of_stock_items' ) && $product_visibility_term_ids['outofstock'] ) {
			$exclude_term_ids[] = $product_visibility_term_ids['outofstock'];
		}

		if ( count( $exclude_term_ids ) ) {
			$outofstock_join  = " LEFT JOIN ( SELECT object_id FROM {$wpdb->term_relationships} WHERE term_taxonomy_id IN ( " . implode( ',', array_map( 'absint', $exclude_term_ids ) ) . ' ) ) AS exclude_join ON exclude_join.object_id = id';
			$outofstock_where = ' AND exclude_join.object_id IS NULL';
		}

		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
		return $wpdb->get_results(
			"
			SELECT posts.ID as id, posts.post_parent as parent_id
			FROM {$wpdb->posts} AS posts
			INNER JOIN {$wpdb->wc_product_meta_lookup} AS lookup ON posts.ID = lookup.product_id
			$outofstock_join
			WHERE posts.post_type IN ( 'product', 'product_variation' )
			AND posts.post_status = 'publish'
			AND lookup.onsale = 1
			$outofstock_where
			AND posts.post_parent NOT IN (
				SELECT ID FROM `$wpdb->posts` as posts
				WHERE posts.post_type = 'product'
				AND posts.post_parent = 0
				AND posts.post_status != 'publish'
			)
			GROUP BY posts.ID
			"
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
	}

	/**
	 * Returns a list of product IDs ( id as key => parent as value) that are
	 * featured. Uses get_posts instead of wc_get_products since we want
	 * some extra meta queries and ALL products (posts_per_page = -1).
	 *
	 * @return array
	 * @since 3.0.0
	 */
	public function get_featured_product_ids() {
		$product_visibility_term_ids = wc_get_product_visibility_term_ids();

		return get_posts(
			array(
				'post_type'      => array( 'product', 'product_variation' ),
				'posts_per_page' => -1,
				'post_status'    => 'publish',
				'tax_query'      => array( // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_tax_query
					'relation' => 'AND',
					array(
						'taxonomy' => 'product_visibility',
						'field'    => 'term_taxonomy_id',
						'terms'    => array( $product_visibility_term_ids['featured'] ),
					),
					array(
						'taxonomy' => 'product_visibility',
						'field'    => 'term_taxonomy_id',
						'terms'    => array( $product_visibility_term_ids['exclude-from-catalog'] ),
						'operator' => 'NOT IN',
					),
				),
				'fields'         => 'id=>parent',
			)
		);
	}

	/**
	 * Check if product sku is found for any other product IDs.
	 *
	 * @since 3.0.0
	 * @param int    $product_id Product ID.
	 * @param string $sku Will be slashed to work around https://core.trac.wordpress.org/ticket/27421.
	 * @return bool
	 */
	public function is_existing_sku( $product_id, $sku ) {
		global $wpdb;

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		return (bool) $wpdb->get_var(
			$wpdb->prepare(
				"
				SELECT posts.ID
				FROM {$wpdb->posts} as posts
				INNER JOIN {$wpdb->wc_product_meta_lookup} AS lookup ON posts.ID = lookup.product_id
				WHERE
				posts.post_type IN ( 'product', 'product_variation' )
				AND posts.post_status != 'trash'
				AND lookup.sku = %s
				AND lookup.product_id <> %d
				LIMIT 1
				",
				wp_slash( $sku ),
				$product_id
			)
		);
	}

	/**
	 * Return product ID based on SKU.
	 *
	 * @since 3.0.0
	 * @param string $sku Product SKU.
	 * @return int
	 */
	public function get_product_id_by_sku( $sku ) {
		global $wpdb;

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		$id = $wpdb->get_var(
			$wpdb->prepare(
				"
				SELECT posts.ID
				FROM {$wpdb->posts} as posts
				INNER JOIN {$wpdb->wc_product_meta_lookup} AS lookup ON posts.ID = lookup.product_id
				WHERE
				posts.post_type IN ( 'product', 'product_variation' )
				AND posts.post_status != 'trash'
				AND lookup.sku = %s
				LIMIT 1
				",
				$sku
			)
		);

		return (int) apply_filters( 'woocommerce_get_product_id_by_sku', $id, $sku );
	}

	/**
	 * Returns an array of IDs of products that have sales starting soon.
	 *
	 * @since 3.0.0
	 * @return array
	 */
	public function get_starting_sales() {
		global $wpdb;

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		return $wpdb->get_col(
			$wpdb->prepare(
				"SELECT postmeta.post_id FROM {$wpdb->postmeta} as postmeta
				LEFT JOIN {$wpdb->postmeta} as postmeta_2 ON postmeta.post_id = postmeta_2.post_id
				LEFT JOIN {$wpdb->postmeta} as postmeta_3 ON postmeta.post_id = postmeta_3.post_id
				WHERE postmeta.meta_key = '_sale_price_dates_from'
					AND postmeta_2.meta_key = '_price'
					AND postmeta_3.meta_key = '_sale_price'
					AND postmeta.meta_value > 0
					AND postmeta.meta_value < %s
					AND postmeta_2.meta_value != postmeta_3.meta_value",
				time()
			)
		);
	}

	/**
	 * Returns an array of IDs of products that have sales which are due to end.
	 *
	 * @since 3.0.0
	 * @return array
	 */
	public function get_ending_sales() {
		global $wpdb;

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		return $wpdb->get_col(
			$wpdb->prepare(
				"SELECT postmeta.post_id FROM {$wpdb->postmeta} as postmeta
				LEFT JOIN {$wpdb->postmeta} as postmeta_2 ON postmeta.post_id = postmeta_2.post_id
				LEFT JOIN {$wpdb->postmeta} as postmeta_3 ON postmeta.post_id = postmeta_3.post_id
				WHERE postmeta.meta_key = '_sale_price_dates_to'
					AND postmeta_2.meta_key = '_price'
					AND postmeta_3.meta_key = '_regular_price'
					AND postmeta.meta_value > 0
					AND postmeta.meta_value < %s
					AND postmeta_2.meta_value != postmeta_3.meta_value",
				time()
			)
		);
	}

	/**
	 * Find a matching (enabled) variation within a variable product.
	 *
	 * @since  3.0.0
	 * @param  WC_Product $product Variable product.
	 * @param  array      $match_attributes Array of attributes we want to try to match.
	 * @return int Matching variation ID or 0.
	 */
	public function find_matching_product_variation( $product, $match_attributes = array() ) {
		global $wpdb;

		$meta_attribute_names = array();

		// Get attributes to match in meta.
		foreach ( $product->get_attributes() as $attribute ) {
			if ( ! $attribute->get_variation() ) {
				continue;
			}
			$meta_attribute_names[] = 'attribute_' . sanitize_title( $attribute->get_name() );
		}

		// Get the attributes of the variations.
		$query = $wpdb->prepare(
			"
			SELECT postmeta.post_id, postmeta.meta_key, postmeta.meta_value, posts.menu_order FROM {$wpdb->postmeta} as postmeta
			LEFT JOIN {$wpdb->posts} as posts ON postmeta.post_id=posts.ID
			WHERE postmeta.post_id IN (
				SELECT ID FROM {$wpdb->posts}
				WHERE {$wpdb->posts}.post_parent = %d
				AND {$wpdb->posts}.post_status = 'publish'
				AND {$wpdb->posts}.post_type = 'product_variation'
			)
			",
			$product->get_id()
		);

		$query .= ' AND postmeta.meta_key IN ( "' . implode( '","', array_map( 'esc_sql', $meta_attribute_names ) ) . '" )';

		$query .= ' ORDER BY posts.menu_order ASC, postmeta.post_id ASC;';

		$attributes = $wpdb->get_results( $query ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared

		if ( ! $attributes ) {
			return 0;
		}

		$sorted_meta = array();

		foreach ( $attributes as $m ) {
			$sorted_meta[ $m->post_id ][ $m->meta_key ] = $m->meta_value; // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_key
		}

		/**
		 * Check each variation to find the one that matches the $match_attributes.
		 *
		 * Note: Not all meta fields will be set which is why we check existance.
		 */
		foreach ( $sorted_meta as $variation_id => $variation ) {
			$match = true;

			// Loop over the variation meta keys and values i.e. what is saved to the products. Note: $attribute_value is empty when 'any' is in use.
			foreach ( $variation as $attribute_key => $attribute_value ) {
				$match_any_value = '' === $attribute_value;

				if ( ! $match_any_value && ! array_key_exists( $attribute_key, $match_attributes ) ) {
					$match = false; // Requires a selection but no value was provide.
				}

				if ( array_key_exists( $attribute_key, $match_attributes ) ) { // Value to match was provided.
					if ( ! $match_any_value && $match_attributes[ $attribute_key ] !== $attribute_value ) {
						$match = false; // Provided value does not match variation.
					}
				}
			}

			if ( true === $match ) {
				return $variation_id;
			}
		}

		if ( version_compare( get_post_meta( $product->get_id(), '_product_version', true ), '2.4.0', '<' ) ) {
			/**
			 * Pre 2.4 handling where 'slugs' were saved instead of the full text attribute.
			 * Fallback is here because there are cases where data will be 'synced' but the product version will remain the same.
			 */
			return ( array_map( 'sanitize_title', $match_attributes ) === $match_attributes ) ? 0 : $this->find_matching_product_variation( $product, array_map( 'sanitize_title', $match_attributes ) );
		}

		return 0;
	}

	/**
	 * Creates all possible combinations of variations from the attributes, without creating duplicates.
	 *
	 * @since  3.6.0
	 * @todo   Add to interface in 4.0.
	 * @param  WC_Product $product Variable product.
	 * @param  int        $limit Limit the number of created variations.
	 * @return int        Number of created variations.
	 */
	public function create_all_product_variations( $product, $limit = -1 ) {
		$count = 0;

		if ( ! $product ) {
			return $count;
		}

		$attributes = wc_list_pluck( array_filter( $product->get_attributes(), 'wc_attributes_array_filter_variation' ), 'get_slugs' );

		if ( empty( $attributes ) ) {
			return $count;
		}

		// Get existing variations so we don't create duplicates.
		$existing_variations = array_map( 'wc_get_product', $product->get_children() );
		$existing_attributes = array();

		foreach ( $existing_variations as $existing_variation ) {
			$existing_attributes[] = $existing_variation->get_attributes();
		}

		$possible_attributes = array_reverse( wc_array_cartesian( $attributes ) );

		foreach ( $possible_attributes as $possible_attribute ) {
			// Allow any order if key/values -- do not use strict mode.
			if ( in_array( $possible_attribute, $existing_attributes ) ) { // phpcs:ignore WordPress.PHP.StrictInArray.MissingTrueStrict
				continue;
			}
			$variation = wc_get_product_object( 'variation' );
			$variation->set_parent_id( $product->get_id() );
			$variation->set_attributes( $possible_attribute );
			$variation_id = $variation->save();

			do_action( 'product_variation_linked', $variation_id );

			$count ++;

			if ( $limit > 0 && $count >= $limit ) {
				break;
			}
		}

		return $count;
	}

	/**
	 * Make sure all variations have a sort order set so they can be reordered correctly.
	 *
	 * @param int $parent_id Product ID.
	 */
	public function sort_all_product_variations( $parent_id ) {
		global $wpdb;

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		$ids   = $wpdb->get_col(
			$wpdb->prepare(
				"SELECT ID FROM {$wpdb->posts} WHERE post_type = 'product_variation' AND post_parent = %d AND post_status = 'publish' ORDER BY menu_order ASC, ID ASC",
				$parent_id
			)
		);
		$index = 1;

		foreach ( $ids as $id ) {
			// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
			$wpdb->update( $wpdb->posts, array( 'menu_order' => ( $index++ ) ), array( 'ID' => absint( $id ) ) );
		}
	}

	/**
	 * Return a list of related products (using data like categories and IDs).
	 *
	 * @since 3.0.0
	 * @param array $cats_array  List of categories IDs.
	 * @param array $tags_array  List of tags IDs.
	 * @param array $exclude_ids Excluded IDs.
	 * @param int   $limit       Limit of results.
	 * @param int   $product_id  Product ID.
	 * @return array
	 */
	public function get_related_products( $cats_array, $tags_array, $exclude_ids, $limit, $product_id ) {
		global $wpdb;

		$args = array(
			'categories'  => $cats_array,
			'tags'        => $tags_array,
			'exclude_ids' => $exclude_ids,
			'limit'       => $limit + 10,
		);

		$related_product_query = (array) apply_filters( 'woocommerce_product_related_posts_query', $this->get_related_products_query( $cats_array, $tags_array, $exclude_ids, $limit + 10 ), $product_id, $args );

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery, WordPress.DB.PreparedSQL.NotPrepared
		return $wpdb->get_col( implode( ' ', $related_product_query ) );
	}

	/**
	 * Builds the related posts query.
	 *
	 * @since 3.0.0
	 *
	 * @param array $cats_array  List of categories IDs.
	 * @param array $tags_array  List of tags IDs.
	 * @param array $exclude_ids Excluded IDs.
	 * @param int   $limit       Limit of results.
	 *
	 * @return array
	 */
	public function get_related_products_query( $cats_array, $tags_array, $exclude_ids, $limit ) {
		global $wpdb;

		$include_term_ids            = array_merge( $cats_array, $tags_array );
		$exclude_term_ids            = array();
		$product_visibility_term_ids = wc_get_product_visibility_term_ids();

		if ( $product_visibility_term_ids['exclude-from-catalog'] ) {
			$exclude_term_ids[] = $product_visibility_term_ids['exclude-from-catalog'];
		}

		if ( 'yes' === get_option( 'woocommerce_hide_out_of_stock_items' ) && $product_visibility_term_ids['outofstock'] ) {
			$exclude_term_ids[] = $product_visibility_term_ids['outofstock'];
		}

		$query = array(
			'fields' => "
				SELECT DISTINCT ID FROM {$wpdb->posts} p
			",
			'join'   => '',
			'where'  => "
				WHERE 1=1
				AND p.post_status = 'publish'
				AND p.post_type = 'product'

			",
			'limits' => '
				LIMIT ' . absint( $limit ) . '
			',
		);

		if ( count( $exclude_term_ids ) ) {
			$query['join']  .= " LEFT JOIN ( SELECT object_id FROM {$wpdb->term_relationships} WHERE term_taxonomy_id IN ( " . implode( ',', array_map( 'absint', $exclude_term_ids ) ) . ' ) ) AS exclude_join ON exclude_join.object_id = p.ID';
			$query['where'] .= ' AND exclude_join.object_id IS NULL';
		}

		if ( count( $include_term_ids ) ) {
			$query['join'] .= " INNER JOIN ( SELECT object_id FROM {$wpdb->term_relationships} INNER JOIN {$wpdb->term_taxonomy} using( term_taxonomy_id ) WHERE term_id IN ( " . implode( ',', array_map( 'absint', $include_term_ids ) ) . ' ) ) AS include_join ON include_join.object_id = p.ID';
		}

		if ( count( $exclude_ids ) ) {
			$query['where'] .= ' AND p.ID NOT IN ( ' . implode( ',', array_map( 'absint', $exclude_ids ) ) . ' )';
		}

		return $query;
	}

	/**
	 * Update a product's stock amount directly in the database.
	 *
	 * Updates both post meta and lookup tables. Ignores manage stock setting on the product.
	 *
	 * @param int            $product_id_with_stock Product ID.
	 * @param int|float|null $stock_quantity        Stock quantity.
	 */
	protected function set_product_stock( $product_id_with_stock, $stock_quantity ) {
		global $wpdb;

		// Generate SQL.
		$sql = $wpdb->prepare(
			"UPDATE {$wpdb->postmeta} SET meta_value = %f WHERE post_id = %d AND meta_key='_stock'",
			$stock_quantity,
			$product_id_with_stock
		);

		$sql = apply_filters( 'woocommerce_update_product_stock_query', $sql, $product_id_with_stock, $stock_quantity, 'set' );

		$wpdb->query( $sql ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.PreparedSQL.NotPrepared

		// Cache delete is required (not only) to set correct data for lookup table (which reads from cache).
		// Sometimes I wonder if it shouldn't be part of update_lookup_table.
		wp_cache_delete( $product_id_with_stock, 'post_meta' );

		$this->update_lookup_table( $product_id_with_stock, 'wc_product_meta_lookup' );
	}

	/**
	 * Update a product's stock amount directly.
	 *
	 * Uses queries rather than update_post_meta so we can do this in one query (to avoid stock issues).
	 * Ignores manage stock setting on the product and sets quantities directly in the db: post meta and lookup tables.
	 * Uses locking to update the quantity. If the lock is not acquired, change is lost.
	 *
	 * @since  3.0.0 this supports set, increase and decrease.
	 * @param  int            $product_id_with_stock Product ID.
	 * @param  int|float|null $stock_quantity Stock quantity.
	 * @param  string         $operation Set, increase and decrease.
	 * @return int|float New stock level.
	 */
	public function update_product_stock( $product_id_with_stock, $stock_quantity = null, $operation = 'set' ) {
		global $wpdb;

		// Ensures a row exists to update.
		add_post_meta( $product_id_with_stock, '_stock', 0, true );

		if ( 'set' === $operation ) {
			$new_stock = wc_stock_amount( $stock_quantity );

			// Generate SQL.
			$sql = $wpdb->prepare(
				"UPDATE {$wpdb->postmeta} SET meta_value = %f WHERE post_id = %d AND meta_key='_stock'",
				$new_stock,
				$product_id_with_stock
			);
		} else {
			$current_stock = wc_stock_amount(
				$wpdb->get_var(
					$wpdb->prepare(
						"SELECT meta_value FROM {$wpdb->postmeta} WHERE post_id = %d AND meta_key='_stock';",
						$product_id_with_stock
					)
				)
			);

			// Calculate new value for filter below. Set multiplier to subtract or add the meta_value.
			switch ( $operation ) {
				case 'increase':
					$new_stock = $current_stock + wc_stock_amount( $stock_quantity );
					$multiplier = 1;
					break;
				default:
					$new_stock = $current_stock - wc_stock_amount( $stock_quantity );
					$multiplier = -1;
					break;
			}

			// Generate SQL.
			$sql = $wpdb->prepare(
				"UPDATE {$wpdb->postmeta} SET meta_value = meta_value %+f WHERE post_id = %d AND meta_key='_stock'",
				wc_stock_amount( $stock_quantity ) * $multiplier, // This will either subtract or add depending on operation.
				$product_id_with_stock
			);
		}

		$sql = apply_filters( 'woocommerce_update_product_stock_query', $sql, $product_id_with_stock, $new_stock, $operation );

		$wpdb->query( $sql ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.PreparedSQL.NotPrepared

		// Cache delete is required (not only) to set correct data for lookup table (which reads from cache).
		// Sometimes I wonder if it shouldn't be part of update_lookup_table.
		wp_cache_delete( $product_id_with_stock, 'post_meta' );

		$this->update_lookup_table( $product_id_with_stock, 'wc_product_meta_lookup' );

		/**
		 * Fire an action for this direct update so it can be detected by other code.
		 *
		 * @since 3.6
		 * @param int $product_id_with_stock Product ID that was updated directly.
		 */
		do_action( 'woocommerce_updated_product_stock', $product_id_with_stock );

		return $new_stock;
	}

	/**
	 * Update a product's sale count directly.
	 *
	 * Uses queries rather than update_post_meta so we can do this in one query for performance.
	 *
	 * @since  3.0.0 this supports set, increase and decrease.
	 * @param  int      $product_id Product ID.
	 * @param  int|null $quantity Quantity.
	 * @param  string   $operation set, increase and decrease.
	 */
	public function update_product_sales( $product_id, $quantity = null, $operation = 'set' ) {
		global $wpdb;
		add_post_meta( $product_id, 'total_sales', 0, true );

		// Update stock in DB directly.
		switch ( $operation ) {
			case 'increase':
				// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
				$wpdb->query(
					$wpdb->prepare(
						"UPDATE {$wpdb->postmeta} SET meta_value = meta_value + %f WHERE post_id = %d AND meta_key='total_sales'",
						$quantity,
						$product_id
					)
				);
				break;
			case 'decrease':
				// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
				$wpdb->query(
					$wpdb->prepare(
						"UPDATE {$wpdb->postmeta} SET meta_value = meta_value - %f WHERE post_id = %d AND meta_key='total_sales'",
						$quantity,
						$product_id
					)
				);
				break;
			default:
				// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
				$wpdb->query(
					$wpdb->prepare(
						"UPDATE {$wpdb->postmeta} SET meta_value = %f WHERE post_id = %d AND meta_key='total_sales'",
						$quantity,
						$product_id
					)
				);
				break;
		}

		wp_cache_delete( $product_id, 'post_meta' );

		$this->update_lookup_table( $product_id, 'wc_product_meta_lookup' );

		/**
		 * Fire an action for this direct update so it can be detected by other code.
		 *
		 * @since 3.6
		 * @param int $product_id Product ID that was updated directly.
		 */
		do_action( 'woocommerce_updated_product_sales', $product_id );
	}

	/**
	 * Update a products average rating meta.
	 *
	 * @since 3.0.0
	 * @todo Deprecate unused function?
	 * @param WC_Product $product Product object.
	 */
	public function update_average_rating( $product ) {
		update_post_meta( $product->get_id(), '_wc_average_rating', $product->get_average_rating( 'edit' ) );
		self::update_visibility( $product, true );
	}

	/**
	 * Update a products review count meta.
	 *
	 * @since 3.0.0
	 * @todo Deprecate unused function?
	 * @param WC_Product $product Product object.
	 */
	public function update_review_count( $product ) {
		update_post_meta( $product->get_id(), '_wc_review_count', $product->get_review_count( 'edit' ) );
	}

	/**
	 * Update a products rating counts.
	 *
	 * @since 3.0.0
	 * @todo Deprecate unused function?
	 * @param WC_Product $product Product object.
	 */
	public function update_rating_counts( $product ) {
		update_post_meta( $product->get_id(), '_wc_rating_count', $product->get_rating_counts( 'edit' ) );
	}

	/**
	 * Get shipping class ID by slug.
	 *
	 * @since 3.0.0
	 * @param string $slug Product shipping class slug.
	 * @return int|false
	 */
	public function get_shipping_class_id_by_slug( $slug ) {
		$shipping_class_term = get_term_by( 'slug', $slug, 'product_shipping_class' );
		if ( $shipping_class_term ) {
			return $shipping_class_term->term_id;
		} else {
			return false;
		}
	}

	/**
	 * Returns an array of products.
	 *
	 * @param  array $args Args to pass to WC_Product_Query().
	 * @return array|object
	 * @see wc_get_products
	 */
	public function get_products( $args = array() ) {
		$query = new WC_Product_Query( $args );
		return $query->get_products();
	}

	/**
	 * Search product data for a term and return ids.
	 *
	 * @param  string     $term Search term.
	 * @param  string     $type Type of product.
	 * @param  bool       $include_variations Include variations in search or not.
	 * @param  bool       $all_statuses Should we search all statuses or limit to published.
	 * @param  null|int   $limit Limit returned results. @since 3.5.0.
	 * @param  null|array $include Keep specific results. @since 3.6.0.
	 * @param  null|array $exclude Discard specific results. @since 3.6.0.
	 * @return array of ids
	 */
	public function search_products( $term, $type = '', $include_variations = false, $all_statuses = false, $limit = null, $include = null, $exclude = null ) {
		global $wpdb;

		$custom_results = apply_filters( 'woocommerce_product_pre_search_products', false, $term, $type, $include_variations, $all_statuses, $limit );

		if ( is_array( $custom_results ) ) {
			return $custom_results;
		}

		$post_types   = $include_variations ? array( 'product', 'product_variation' ) : array( 'product' );
		$join_query   = '';
		$type_where   = '';
		$status_where = '';
		$limit_query  = '';

		// When searching variations we should include the parent's meta table for use in searches.
		if ( $include_variations ) {
			$join_query = " LEFT JOIN {$wpdb->wc_product_meta_lookup} parent_wc_product_meta_lookup
			 ON posts.post_type = 'product_variation' AND parent_wc_product_meta_lookup.product_id = posts.post_parent ";
		}

		/**
		 * Hook woocommerce_search_products_post_statuses.
		 *
		 * @since 3.7.0
		 * @param array $post_statuses List of post statuses.
		 */
		$post_statuses = apply_filters(
			'woocommerce_search_products_post_statuses',
			current_user_can( 'edit_private_products' ) ? array( 'private', 'publish' ) : array( 'publish' )
		);

		// See if search term contains OR keywords.
		if ( stristr( $term, ' or ' ) ) {
			$term_groups = preg_split( '/\s+or\s+/i', $term );
		} else {
			$term_groups = array( $term );
		}

		$search_where   = '';
		$search_queries = array();

		foreach ( $term_groups as $term_group ) {
			// Parse search terms.
			if ( preg_match_all( '/".*?("|$)|((?<=[\t ",+])|^)[^\t ",+]+/', $term_group, $matches ) ) {
				$search_terms = $this->get_valid_search_terms( $matches[0] );
				$count        = count( $search_terms );

				// if the search string has only short terms or stopwords, or is 10+ terms long, match it as sentence.
				if ( 9 < $count || 0 === $count ) {
					$search_terms = array( $term_group );
				}
			} else {
				$search_terms = array( $term_group );
			}

			$term_group_query = '';
			$searchand        = '';

			foreach ( $search_terms as $search_term ) {
				$like = '%' . $wpdb->esc_like( $search_term ) . '%';

				// Variations should also search the parent's meta table for fallback fields.
				if ( $include_variations ) {
					$variation_query = $wpdb->prepare( ' OR ( wc_product_meta_lookup.sku = "" AND parent_wc_product_meta_lookup.sku LIKE %s ) ', $like );
				} else {
					$variation_query = '';
				}

				$term_group_query .= $wpdb->prepare( " {$searchand} ( ( posts.post_title LIKE %s) OR ( posts.post_excerpt LIKE %s) OR ( posts.post_content LIKE %s ) OR ( wc_product_meta_lookup.sku LIKE %s ) $variation_query)", $like, $like, $like, $like ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
				$searchand         = ' AND ';
			}

			if ( $term_group_query ) {
				$search_queries[] = $term_group_query;
			}
		}

		if ( ! empty( $search_queries ) ) {
			$search_where = ' AND (' . implode( ') OR (', $search_queries ) . ') ';
		}

		if ( ! empty( $include ) && is_array( $include ) ) {
			$search_where .= ' AND posts.ID IN(' . implode( ',', array_map( 'absint', $include ) ) . ') ';
		}

		if ( ! empty( $exclude ) && is_array( $exclude ) ) {
			$search_where .= ' AND posts.ID NOT IN(' . implode( ',', array_map( 'absint', $exclude ) ) . ') ';
		}

		if ( 'virtual' === $type ) {
			$type_where = ' AND ( wc_product_meta_lookup.virtual = 1 ) ';
		} elseif ( 'downloadable' === $type ) {
			$type_where = ' AND ( wc_product_meta_lookup.downloadable = 1 ) ';
		}

		if ( ! $all_statuses ) {
			$status_where = " AND posts.post_status IN ('" . implode( "','", $post_statuses ) . "') ";
		}

		if ( $limit ) {
			$limit_query = $wpdb->prepare( ' LIMIT %d ', $limit );
		}

		// phpcs:ignore WordPress.VIP.DirectDatabaseQuery.DirectQuery
		$search_results = $wpdb->get_results(
			// phpcs:disable
			"SELECT DISTINCT posts.ID as product_id, posts.post_parent as parent_id FROM {$wpdb->posts} posts
			 LEFT JOIN {$wpdb->wc_product_meta_lookup} wc_product_meta_lookup ON posts.ID = wc_product_meta_lookup.product_id
			 $join_query
			WHERE posts.post_type IN ('" . implode( "','", $post_types ) . "')
			$search_where
			$status_where
			$type_where
			ORDER BY posts.post_parent ASC, posts.post_title ASC
			$limit_query
			"
			// phpcs:enable
		);

		$product_ids = wp_parse_id_list( array_merge( wp_list_pluck( $search_results, 'product_id' ), wp_list_pluck( $search_results, 'parent_id' ) ) );

		if ( is_numeric( $term ) ) {
			$post_id   = absint( $term );
			$post_type = get_post_type( $post_id );

			if ( 'product_variation' === $post_type && $include_variations ) {
				$product_ids[] = $post_id;
			} elseif ( 'product' === $post_type ) {
				$product_ids[] = $post_id;
			}

			$product_ids[] = wp_get_post_parent_id( $post_id );
		}

		return wp_parse_id_list( $product_ids );
	}

	/**
	 * Get the product type based on product ID.
	 *
	 * @since 3.0.0
	 * @param int $product_id Product ID.
	 * @return bool|string
	 */
	public function get_product_type( $product_id ) {
		$cache_key    = WC_Cache_Helper::get_cache_prefix( 'product_' . $product_id ) . '_type_' . $product_id;
		$product_type = wp_cache_get( $cache_key, 'products' );

		if ( $product_type ) {
			return $product_type;
		}

		$post_type = get_post_type( $product_id );

		if ( 'product_variation' === $post_type ) {
			$product_type = 'variation';
		} elseif ( 'product' === $post_type ) {
			$terms        = get_the_terms( $product_id, 'product_type' );
			$product_type = ! empty( $terms ) ? sanitize_title( current( $terms )->name ) : 'simple';
		} else {
			$product_type = false;
		}

		wp_cache_set( $cache_key, $product_type, 'products' );

		return $product_type;
	}

	/**
	 * Add ability to get products by 'reviews_allowed' in WC_Product_Query.
	 *
	 * @since 3.2.0
	 * @param string   $where Where clause.
	 * @param WP_Query $wp_query WP_Query instance.
	 * @return string
	 */
	public function reviews_allowed_query_where( $where, $wp_query ) {
		global $wpdb;

		if ( isset( $wp_query->query_vars['reviews_allowed'] ) && is_bool( $wp_query->query_vars['reviews_allowed'] ) ) {
			if ( $wp_query->query_vars['reviews_allowed'] ) {
				$where .= " AND $wpdb->posts.comment_status = 'open'";
			} else {
				$where .= " AND $wpdb->posts.comment_status = 'closed'";
			}
		}

		return $where;
	}

	/**
	 * Get valid WP_Query args from a WC_Product_Query's query variables.
	 *
	 * @since 3.2.0
	 * @param array $query_vars Query vars from a WC_Product_Query.
	 * @return array
	 */
	protected function get_wp_query_args( $query_vars ) {

		// Map query vars to ones that get_wp_query_args or WP_Query recognize.
		$key_mapping = array(
			'status'         => 'post_status',
			'page'           => 'paged',
			'include'        => 'post__in',
			'stock_quantity' => 'stock',
			'average_rating' => 'wc_average_rating',
			'review_count'   => 'wc_review_count',
		);
		foreach ( $key_mapping as $query_key => $db_key ) {
			if ( isset( $query_vars[ $query_key ] ) ) {
				$query_vars[ $db_key ] = $query_vars[ $query_key ];
				unset( $query_vars[ $query_key ] );
			}
		}

		// Map boolean queries that are stored as 'yes'/'no' in the DB to 'yes' or 'no'.
		$boolean_queries = array(
			'virtual',
			'downloadable',
			'sold_individually',
			'manage_stock',
		);
		foreach ( $boolean_queries as $boolean_query ) {
			if ( isset( $query_vars[ $boolean_query ] ) && '' !== $query_vars[ $boolean_query ] ) {
				$query_vars[ $boolean_query ] = $query_vars[ $boolean_query ] ? 'yes' : 'no';
			}
		}

		// These queries cannot be auto-generated so we have to remove them and build them manually.
		$manual_queries = array(
			'sku'        => '',
			'featured'   => '',
			'visibility' => '',
		);
		foreach ( $manual_queries as $key => $manual_query ) {
			if ( isset( $query_vars[ $key ] ) ) {
				$manual_queries[ $key ] = $query_vars[ $key ];
				unset( $query_vars[ $key ] );
			}
		}

		$wp_query_args = parent::get_wp_query_args( $query_vars );

		if ( ! isset( $wp_query_args['date_query'] ) ) {
			$wp_query_args['date_query'] = array();
		}
		if ( ! isset( $wp_query_args['meta_query'] ) ) {
			$wp_query_args['meta_query'] = array(); // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_query
		}

		// Handle product types.
		if ( 'variation' === $query_vars['type'] ) {
			$wp_query_args['post_type'] = 'product_variation';
		} elseif ( is_array( $query_vars['type'] ) && in_array( 'variation', $query_vars['type'], true ) ) {
			$wp_query_args['post_type']   = array( 'product_variation', 'product' );
			$wp_query_args['tax_query'][] = array( // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_tax_query
				'relation' => 'OR',
				array(
					'taxonomy' => 'product_type',
					'field'    => 'slug',
					'terms'    => $query_vars['type'],
				),
				array(
					'taxonomy' => 'product_type',
					'field'    => 'id',
					'operator' => 'NOT EXISTS',
				),
			);
		} else {
			$wp_query_args['post_type']   = 'product';
			$wp_query_args['tax_query'][] = array(
				'taxonomy' => 'product_type',
				'field'    => 'slug',
				'terms'    => $query_vars['type'],
			);
		}

		// Handle product categories.
		if ( ! empty( $query_vars['category'] ) ) {
			$wp_query_args['tax_query'][] = array(
				'taxonomy' => 'product_cat',
				'field'    => 'slug',
				'terms'    => $query_vars['category'],
			);
		}

		// Handle product tags.
		if ( ! empty( $query_vars['tag'] ) ) {
			unset( $wp_query_args['tag'] );
			$wp_query_args['tax_query'][] = array(
				'taxonomy' => 'product_tag',
				'field'    => 'slug',
				'terms'    => $query_vars['tag'],
			);
		}

		// Handle shipping classes.
		if ( ! empty( $query_vars['shipping_class'] ) ) {
			$wp_query_args['tax_query'][] = array(
				'taxonomy' => 'product_shipping_class',
				'field'    => 'slug',
				'terms'    => $query_vars['shipping_class'],
			);
		}

		// Handle total_sales.
		// This query doesn't get auto-generated since the meta key doesn't have the underscore prefix.
		if ( isset( $query_vars['total_sales'] ) && '' !== $query_vars['total_sales'] ) {
			$wp_query_args['meta_query'][] = array(
				'key'     => 'total_sales',
				'value'   => absint( $query_vars['total_sales'] ),
				'compare' => '=',
			);
		}

		// Handle SKU.
		if ( $manual_queries['sku'] ) {
			// Check for existing values if wildcard is used.
			if ( '*' === $manual_queries['sku'] ) {
				$wp_query_args['meta_query'][] = array(
					array(
						'key'     => '_sku',
						'compare' => 'EXISTS',
					),
					array(
						'key'     => '_sku',
						'value'   => '',
						'compare' => '!=',
					),
				);
			} else {
				$wp_query_args['meta_query'][] = array(
					'key'     => '_sku',
					'value'   => $manual_queries['sku'],
					'compare' => 'LIKE',
				);
			}
		}

		// Handle featured.
		if ( '' !== $manual_queries['featured'] ) {
			$product_visibility_term_ids = wc_get_product_visibility_term_ids();
			if ( $manual_queries['featured'] ) {
				$wp_query_args['tax_query'][] = array(
					'taxonomy' => 'product_visibility',
					'field'    => 'term_taxonomy_id',
					'terms'    => array( $product_visibility_term_ids['featured'] ),
				);
				$wp_query_args['tax_query'][] = array(
					'taxonomy' => 'product_visibility',
					'field'    => 'term_taxonomy_id',
					'terms'    => array( $product_visibility_term_ids['exclude-from-catalog'] ),
					'operator' => 'NOT IN',
				);
			} else {
				$wp_query_args['tax_query'][] = array(
					'taxonomy' => 'product_visibility',
					'field'    => 'term_taxonomy_id',
					'terms'    => array( $product_visibility_term_ids['featured'] ),
					'operator' => 'NOT IN',
				);
			}
		}

		// Handle visibility.
		if ( $manual_queries['visibility'] ) {
			switch ( $manual_queries['visibility'] ) {
				case 'search':
					$wp_query_args['tax_query'][] = array(
						'taxonomy' => 'product_visibility',
						'field'    => 'slug',
						'terms'    => array( 'exclude-from-search' ),
						'operator' => 'NOT IN',
					);
					break;
				case 'catalog':
					$wp_query_args['tax_query'][] = array(
						'taxonomy' => 'product_visibility',
						'field'    => 'slug',
						'terms'    => array( 'exclude-from-catalog' ),
						'operator' => 'NOT IN',
					);
					break;
				case 'visible':
					$wp_query_args['tax_query'][] = array(
						'taxonomy' => 'product_visibility',
						'field'    => 'slug',
						'terms'    => array( 'exclude-from-catalog', 'exclude-from-search' ),
						'operator' => 'NOT IN',
					);
					break;
				case 'hidden':
					$wp_query_args['tax_query'][] = array(
						'taxonomy' => 'product_visibility',
						'field'    => 'slug',
						'terms'    => array( 'exclude-from-catalog', 'exclude-from-search' ),
						'operator' => 'AND',
					);
					break;
			}
		}

		// Handle date queries.
		$date_queries = array(
			'date_created'      => 'post_date',
			'date_modified'     => 'post_modified',
			'date_on_sale_from' => '_sale_price_dates_from',
			'date_on_sale_to'   => '_sale_price_dates_to',
		);
		foreach ( $date_queries as $query_var_key => $db_key ) {
			if ( isset( $query_vars[ $query_var_key ] ) && '' !== $query_vars[ $query_var_key ] ) {

				// Remove any existing meta queries for the same keys to prevent conflicts.
				$existing_queries = wp_list_pluck( $wp_query_args['meta_query'], 'key', true );
				foreach ( $existing_queries as $query_index => $query_contents ) {
					unset( $wp_query_args['meta_query'][ $query_index ] );
				}

				$wp_query_args = $this->parse_date_for_wp_query( $query_vars[ $query_var_key ], $db_key, $wp_query_args );
			}
		}

		// Handle paginate.
		if ( ! isset( $query_vars['paginate'] ) || ! $query_vars['paginate'] ) {
			$wp_query_args['no_found_rows'] = true;
		}

		// Handle reviews_allowed.
		if ( isset( $query_vars['reviews_allowed'] ) && is_bool( $query_vars['reviews_allowed'] ) ) {
			add_filter( 'posts_where', array( $this, 'reviews_allowed_query_where' ), 10, 2 );
		}

		// Handle orderby.
		if ( isset( $query_vars['orderby'] ) && 'include' === $query_vars['orderby'] ) {
			$wp_query_args['orderby'] = 'post__in';
		}

		return apply_filters( 'woocommerce_product_data_store_cpt_get_products_query', $wp_query_args, $query_vars, $this );
	}

	/**
	 * Query for Products matching specific criteria.
	 *
	 * @since 3.2.0
	 *
	 * @param array $query_vars Query vars from a WC_Product_Query.
	 *
	 * @return array|object
	 */
	public function query( $query_vars ) {
		$args = $this->get_wp_query_args( $query_vars );

		if ( ! empty( $args['errors'] ) ) {
			$query = (object) array(
				'posts'         => array(),
				'found_posts'   => 0,
				'max_num_pages' => 0,
			);
		} else {
			$query = new WP_Query( $args );
		}

		if ( isset( $query_vars['return'] ) && 'objects' === $query_vars['return'] && ! empty( $query->posts ) ) {
			// Prime caches before grabbing objects.
			update_post_caches( $query->posts, array( 'product', 'product_variation' ) );
		}

		$products = ( isset( $query_vars['return'] ) && 'ids' === $query_vars['return'] ) ? $query->posts : array_filter( array_map( 'wc_get_product', $query->posts ) );

		if ( isset( $query_vars['paginate'] ) && $query_vars['paginate'] ) {
			return (object) array(
				'products'      => $products,
				'total'         => $query->found_posts,
				'max_num_pages' => $query->max_num_pages,
			);
		}

		return $products;
	}

	/**
	 * Get data to save to a lookup table.
	 *
	 * @since 3.6.0
	 * @param int    $id ID of object to update.
	 * @param string $table Lookup table name.
	 * @return array
	 */
	protected function get_data_for_lookup_table( $id, $table ) {
		if ( 'wc_product_meta_lookup' === $table ) {
			$price_meta   = (array) get_post_meta( $id, '_price', false );
			$manage_stock = get_post_meta( $id, '_manage_stock', true );
			$stock        = 'yes' === $manage_stock ? wc_stock_amount( get_post_meta( $id, '_stock', true ) ) : null;
			$price        = wc_format_decimal( get_post_meta( $id, '_price', true ) );
			$sale_price   = wc_format_decimal( get_post_meta( $id, '_sale_price', true ) );
			return array(
				'product_id'     => absint( $id ),
				'sku'            => get_post_meta( $id, '_sku', true ),
				'virtual'        => 'yes' === get_post_meta( $id, '_virtual', true ) ? 1 : 0,
				'downloadable'   => 'yes' === get_post_meta( $id, '_downloadable', true ) ? 1 : 0,
				'min_price'      => reset( $price_meta ),
				'max_price'      => end( $price_meta ),
				'onsale'         => $sale_price && $price === $sale_price ? 1 : 0,
				'stock_quantity' => $stock,
				'stock_status'   => get_post_meta( $id, '_stock_status', true ),
				'rating_count'   => array_sum( (array) get_post_meta( $id, '_wc_rating_count', true ) ),
				'average_rating' => get_post_meta( $id, '_wc_average_rating', true ),
				'total_sales'    => get_post_meta( $id, 'total_sales', true ),
				'tax_status'     => get_post_meta( $id, '_tax_status', true ),
				'tax_class'      => get_post_meta( $id, '_tax_class', true ),
			);
		}
		return array();
	}

	/**
	 * Get primary key name for lookup table.
	 *
	 * @since 3.6.0
	 * @param string $table Lookup table name.
	 * @return string
	 */
	protected function get_primary_key_for_lookup_table( $table ) {
		if ( 'wc_product_meta_lookup' === $table ) {
			return 'product_id';
		}
		return '';
	}

	/**
	 * Returns query statement for getting current `_stock` of a product.
	 *
	 * @internal MAX function below is used to make sure result is a scalar.
	 * @param int $product_id Product ID.
	 * @return string|void Query statement.
	 */
	public function get_query_for_stock( $product_id ) {
		global $wpdb;
		return $wpdb->prepare(
			"
			SELECT COALESCE ( MAX( meta_value ), 0 ) FROM $wpdb->postmeta as meta_table
			WHERE meta_table.meta_key = '_stock'
			AND meta_table.post_id = %d
			",
			$product_id
		);
	}
}
