affiliatewp-woocommerce-product-cat-fix.php

add_filter( 'rewrite_rules_array', function( $rules ) {

	if ( ! function_exists( 'WC' ) || ! function_exists( 'affiliate_wp' ) ) {
		return $rules;
	}

	if ( true === version_compare( WC()->version, '3.0.0', '>=' ) ) {
		$permalinks = wc_get_permalink_structure();
	} else {
		$permalinks = get_option( 'woocommerce_permalinks' );
	}

	$category_base = empty( $permalinks['category_base'] ) ? _x( 'product-category', 'slug', 'woocommerce' ) : $permalinks['category_base'];
	$ref           = affiliate_wp()->tracking->get_referral_var();

	$category_rules = array(
		$category_base . '/(.+?)/' . $ref . '(/(.*))?/?$' => 'index.php?product_cat=$matches[1]&' . $ref . '=$matches[3]'
	);

	$rules = array_merge( $category_rules, $rules );

	return $rules;

}, 11 );