d Product ID.
 * @param string $sep (default: ', ').
 * @param string $before (default: '').
 * @param string $after (default: '').
 * @return string
 */
function wc_get_product_category_list( $product_id, $sep = ', ', $before = '', $after = '' ) {
	return get_the_term_list( $product_id, 'product_cat', $before, $sep, $after );
}

/**
 * Returns the product tags in a list.
 *
 * @param int    $product_id Product ID.
 * @param string $sep (default: ', ').
 * @param string $before (default: '').
 * @param string $after (default: '').
 * @return string
 */
function wc_get_product_tag_list( $product_id, $sep = ', ', $before = '', $after = '' ) {
	return get_the_term_list( $product_id, 'product_tag', $before, $sep, $after );
}

/**
 * Callback for array filter to get visible only.
 *
 * @since  3.0.0
 * @param  WC_Product $product WC_Product object.
 * @return bool
 */
function wc_products_array_filter_visible( $product ) {
	return $product && is_a( $product, 'WC_Product' ) && $product->is_visible();
}

/**
 * Callback for array filter to get visible grouped products only.
 *
 * @since  3.1.0
 * @param  WC_Product $product WC_Product object.
 * @return bool
 */
function wc_products_array_filter_visible_grouped( $product ) {
	return $product && is_a( $product, 'WC_Product' ) && ( 'publish' === $product->get_status() || current_user_can( 'edit_product', $product->get_id() ) );
}

/**
 * Callback for array filter to get products the user can edit only.
 *
 * @since  3.0.0
 * @param  WC_Product $product WC_Product object.
 * @return bool
 */
function wc_products_array_filter_editable( $product ) {
	return $product && is_a( $product, 'WC_Product' ) && current_user_can( 'edit_product', $product->get_id() );
}

/**
 * Callback for array filter to get products the user can view only.
 *
 * @since  3.4.0
 * @param  WC_Product $product WC_Product object.
 * @return bool
 */
function wc_products_array_filter_readable( $product ) {
	return $product && is_a( $product, 'WC_Product' ) && current_user_can( 'read_product', $product->get_id() );
}

/**
 * Sort an array of products by a value.
 *
 * @since  3.0.0
 *
 * @param array  $products List of products to be ordered.
 * @param string $orderby Optional order criteria.
 * @param string $order Ascending or descending order.
 *
 * @return array
 */
function wc_products_array_orderby( $products, $orderby = 'date', $order = 'desc' ) {
	$orderby = strtolower( $orderby );
	$order   = strtolower( $order );
	switch ( $orderby ) {
		case 'title':
		case 'id':
		case 'date':
		case 'modified':
		case 'menu_order':
		case 'price':
			usort( $products, 'wc_products_array_orderby_' . $orderby );
			break;
		case 'none':
			break;
		default:
			shuffle( $products );
			break;
	}
	if ( 'desc' === $order ) {
		$products = array_reverse( $products );
	}
	return $products;
}

/**
 * Sort by title.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_title( $a, $b ) {
	return strcasecmp( $a->get_name(), $b->get_name() );
}

/**
 * Sort by id.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_id( $a, $b ) {
	if ( $a->get_id() === $b->get_id() ) {
		return 0;
	}
	return ( $a->get_id() < $b->get_id() ) ? -1 : 1;
}

/**
 * Sort by date.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_date( $a, $b ) {
	if ( $a->get_date_created() === $b->get_date_created() ) {
		return 0;
	}
	return ( $a->get_date_created() < $b->get_date_created() ) ? -1 : 1;
}

/**
 * Sort by modified.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_modified( $a, $b ) {
	if ( $a->get_date_modified() === $b->get_date_modified() ) {
		return 0;
	}
	return ( $a->get_date_modified() < $b->get_date_modified() ) ? -1 : 1;
}

/**
 * Sort by menu order.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_menu_order( $a, $b ) {
	if ( $a->get_menu_order() === $b->get_menu_order() ) {
		return 0;
	}
	return ( $a->get_menu_order() < $b->get_menu_order() ) ? -1 : 1;
}

/**
 * Sort by price low to high.
 *
 * @since  3.0.0
 * @param  WC_Product $a First WC_Product object.
 * @param  WC_Product $b Second WC_Product object.
 * @return int
 */
function wc_products_array_orderby_price( $a, $b ) {
	if ( $a->get_price() === $b->get_price() ) {
		return 0;
	}
	return ( $a->get_price() < $b->get_price() ) ? -1 : 1;
}

/**
 * Queue a product for syncing at the end of the request.
 *
 * @param int $product_id Product ID.
 */
function wc_deferred_product_sync( $product_id ) {
	global $wc_deferred_product_sync;

	if ( empty( $wc_deferred_product_sync ) ) {
		$wc_deferred_product_sync = array();
	}

	$wc_deferred_product_sync[] = $product_id;
}

/**
 * See if the lookup table is being generated already.
 *
 * @since 3.6.0
 * @return bool
 */
function wc_update_product_lookup_tables_is_running() {
	$table_updates_pending = WC()->queue()->search(
		array(
			'status'   => 'pending',
			'group'    => 'wc_update_product_lookup_tables',
			'per_page' => 1,
		)
	);

	return (bool) count( $table_updates_pending );
}

/**
 * Populate lookup table data for products.
 *
 * @since 3.6.0
 */
function wc_update_product_lookup_tables() {
	global $wpdb;

	$is_cli = Constants::is_true( 'WP_CLI' );

	if ( ! $is_cli ) {
		WC_Admin_Notices::add_notice( 'regenerating_lookup_table' );
	}

	// Note that the table is not yet generated.
	update_option( 'woocommerce_product_lookup_table_is_generating', true );

	// Make a row per product in lookup table.
	$wpdb->query(
		"
		INSERT IGNORE INTO {$wpdb->wc_product_meta_lookup} (`product_id`)
		SELECT
			posts.ID
		FROM {$wpdb->posts} posts
		WHERE
			posts.post_type IN ('product', 'product_variation')
		"
	);

	// List of column names in the lookup table we need to populate.
	$columns = array(
		'min_max_price',
		'stock_quantity',
		'sku',
		'stock_status',
		'average_rating',
		'total_sales',
		'downloadable',
		'virtual',
		'onsale',
		'tax_class',
		'tax_status', // When last column is updated, woocommerce_product_lookup_table_is_generating is updated.
	);

	foreach ( $columns as $index => $column ) {
		if ( $is_cli ) {
			wc_update_product_lookup_tables_column( $column );
		} else {
			WC()->queue()->schedule_single(
				time() + $index,
				'wc_update_product_lookup_tables_column',
				array(
					'column' => $column,
				),
				'wc_update_product_lookup_tables'
			);
		}
	}

	// Rating counts are serialised so they have to be unserialised before populating the lookup table.
	if ( $is_cli ) {
		$rating_count_rows = $wpdb->get_results(
			"
			SELECT post_id, meta_value FROM {$wpdb->postmeta}
			WHERE meta_key = '_wc_rating_count'
			AND meta_value != ''
			AND meta_value != 'a:0:{}'
			",
			ARRAY_A
		);
		wc_update_product_lookup_tables_rating_count( $rating_count_rows );
	} else {
		WC()->queue()->schedule_single(
			time() + 10,
			'wc_update_product_lookup_tables_rating_count_batch',
			array(
				'offset' => 0,
				'limit'  => 50,
			),
			'wc_update_product_lookup_tables'
		);
	}
}

/**
 * Populate lookup table column data.
 *
 * @since 3.6.0
 * @param string $column Column name to set.
 */
function wc_update_product_lookup_tables_column( $column ) {
	if ( empty( $column ) ) {
		return;
	}
	global $wpdb;
	switch ( $column ) {
		case 'min_max_price':
			$wpdb->query(
				"
				UPDATE
					{$wpdb->wc_product_meta_lookup} lookup_table
					INNER JOIN (
						SELECT lookup_table.product_id, MIN( meta_value+0 ) as min_price, MAX( meta_value+0 ) as max_price
						FROM {$wpdb->wc_product_meta_lookup} lookup_table
						LEFT JOIN {$wpdb->postmeta} meta1 ON lookup_table.product_id = meta1.post_id AND meta1.meta_key = '_price'
						WHERE
							meta1.meta_value <> ''
						GROUP BY lookup_table.product_id
					) as source on source.product_id = lookup_table.product_id
				SET
					lookup_table.min_price = source.min_price,
					lookup_table.max_price = source.max_price
				"
			);
			break;
		case 'stock_quantity':
			$wpdb->query(
				"
				UPDATE
					{$wpdb->wc_product_meta_lookup} lookup_table
					LEFT JOIN {$wpdb->postmeta} meta1 ON lookup_table.product_id = meta1.post_id AND meta1.meta_key = '_manage_stock'
					LEFT JOIN {$wpdb->postmeta} meta2 ON lookup_table.product_id = meta2.post_id AND meta2.meta_key = '_stock'
				SET
					lookup_table.stock_quantity = meta2.meta_value
				WHERE
					meta1.meta_value = 'yes'
				"
			);
			break;
		case 'sku':
		case 'stock_status':
		case 'average_rating':
		case 'total_sales':
		case 'tax_class':
		case 'tax_status':
			if ( 'total_sales' === $column ) {
				$meta_key = 'total_sales';
			} elseif ( 'average_rating' === $column ) {
				$meta_key = '_wc_average_rating';
			} else {
				$meta_key = '_' . $column;
			}
			$column = esc_sql( $column );
			// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$wpdb->query(
				$wpdb->prepare(
					"
					UPDATE
						{$wpdb->wc_product_meta_lookup} lookup_table
						LEFT JOIN {$wpdb->postmeta} meta ON lookup_table.product_id = meta.post_id AND meta.meta_key = %s
					SET
						lookup_table.`{$column}` = meta.meta_value
					",
					$meta_key
				)
			);
			// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			break;
		case 'downloadable':
		case 'virtual':
			$column   = esc_sql( $column );
			$meta_key = '_' . $column;
			// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$wpdb->query(
				$wpdb->prepare(
					"
					UPDATE
						{$wpdb->wc_product_meta_lookup} lookup_table
						LEFT JOIN {$wpdb->postmeta} meta1 ON lookup_table.product_id = meta1.post_id AND meta1.meta_key = %s
					SET
						lookup_table.`{$column}` = IF ( meta1.meta_value = 'yes', 1, 0 )
					",
					$meta_key
				)
			);
			// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			break;
		case 'onsale':
			$column   = esc_sql( $column );
			$decimals = absint( wc_get_price_decimals() );

			// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$wpdb->query(
				$wpdb->prepare(
					"
					UPDATE
						{$wpdb->wc_product_meta_lookup} lookup_table
						LEFT JOIN {$wpdb->postmeta} meta1 ON lookup_table.product_id = meta1.post_id AND meta1.meta_key = '_price'
						LEFT JOIN {$wpdb->postmeta} meta2 ON lookup_table.product_id = meta2.post_id AND meta2.meta_key = '_sale_price'
	  					LEFT JOIN {$wpdb->postmeta} meta3 ON lookup_table.product_id = meta3.post_id AND meta3.meta_key = '_regular_price'
					SET
						lookup_table.`{$column}` = IF (
							CAST( meta1.meta_value AS DECIMAL ) >= 0
							AND CAST( meta2.meta_value AS CHAR ) != ''
							AND CAST( meta1.meta_value AS DECIMAL( 10, %d ) ) = CAST( meta2.meta_value AS DECIMAL( 10, %d ) )
							AND CAST( meta3.meta_value AS DECIMAL( 10, %d ) ) > CAST( meta2.meta_value AS DECIMAL( 10, %d ) )
						, 1, 0 )
					",
					$decimals,
					$decimals,
					$decimals,
					$decimals
				)
			);
			// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			break;
	}

	// Final column - mark complete.
	if ( 'tax_status' === $column ) {
		delete_option( 'woocommerce_product_lookup_table_is_generating' );
	}
}
add_action( 'wc_update_product_lookup_tables_column', 'wc_update_product_lookup_tables_column' );

/**
 * Populate rating count lookup table data for products.
 *
 * @since 3.6.0
 * @param array $rows Rows of rating counts to update in lookup table.
 */
function wc_update_product_lookup_tables_rating_count( $rows ) {
	if ( ! $rows || ! is_array( $rows ) ) {
		return;
	}
	global $wpdb;

	foreach ( $rows as $row ) {
		$count = array_sum( (array) maybe_unserialize( $row['meta_value'] ) );
		$wpdb->update(
			$wpdb->wc_product_meta_lookup,
			array(
				'rating_count' => absint( $count ),
			),
			array(
				'product_id' => absint( $row['post_id'] ),
			)
		);
	}
}

/**
 * Populate a batch of rating count lookup table data for products.
 *
 * @since 3.6.2
 * @param array $offset Offset to query.
 * @param array $limit  Limit to query.
 */
function wc_update_product_lookup_tables_rating_count_batch( $offset = 0, $limit = 0 ) {
	global $wpdb;

	if ( ! $limit ) {
		return;
	}

	$rating_count_rows = $wpdb->get_results(
		$wpdb->prepare(
			"
			SELECT post_id, meta_value FROM {$wpdb->postmeta}
			WHERE meta_key = '_wc_rating_count'
			AND meta_value != ''
			AND meta_value != 'a:0:{}'
			ORDER BY post_id ASC
			LIMIT %d, %d
			",
			$offset,
			$limit
		),
		ARRAY_A
	);

	if ( $rating_count_rows ) {
		wc_update_product_lookup_tables_rating_count( $rating_count_rows );
		WC()->queue()->schedule_single(
			time() + 1,
			'wc_update_product_lookup_tables_rating_count_batch',
			array(
				'offset' => $offset + $limit,
				'limit'  => $limit,
			),
			'wc_update_product_lookup_tables'
		);
	}
}
add_action( 'wc_update_product_lookup_tables_rating_count_batch', 'wc_update_product_lookup_tables_rating_count_batch', 10, 2 );

/**
 * Attach product featured image. Use image filename to match a product sku when product is not provided.
 *
 * @since 8.5.0
 * @param int        $attachment_id Media attachment ID.
 * @param WC_Product $product Optional product object.
 * @return void
 */
function wc_product_attach_featured_image( $attachment_id, $product = null ) {
	$attachment_post = get_post( $attachment_id );
	if ( ! $attachment_post ) {
		return;
	}

	if ( null === $product && wc_get_container()->get( MatchImageBySKU::class )->is_enabled() ) {
		// On upload the attachment post title is the uploaded file's filename.
		$file_name = pathinfo( $attachment_post->post_title, PATHINFO_FILENAME );
		if ( ! $file_name ) {
			return;
		}

		$product_id = wc_get_product_id_by_sku( $file_name );
		$product    = wc_get_product( $product_id );
	}

	if ( ! $product ) {
		return;
	}

	$product->set_image_id( $attachment_id );
	$product->save();
	if ( 0 === $attachment_post->post_parent ) {
		wp_update_post(
			array(
				'ID'          => $attachment_id,
				'post_parent' => $product->get_id(),
			)
		);
	}
}
add_action( 'add_attachment', 'wc_product_attach_featured_image' );