WWPP – Exclude products from Cart Subtotal Price Discounts if they have an individual price or belong to a specific category

  /**

   * Recalculate the cart subtotal discount to exclude products that:

   * - belong to a specific product category e.g., 'music' , OR

   * - have an individual wholesale price set for the customer's role.

   */

  add_filter( 'wwpp_cart_subtotal_based_discount', 'wwpp_recalculate_discount_for_eligible_items' );

  function wwpp_recalculate_discount_for_eligible_items( $discount ) {

      global $wc_wholesale_prices;

      $cart = WC()->cart;

      if ( ! $cart ) {

          return $discount;

      }

      $wholesale_role = $wc_wholesale_prices->wwp_wholesale_roles->getUserWholesaleRole();

      if ( empty( $wholesale_role ) ) {

          return $discount;

      }

      // Build eligible subtotal, skipping excluded products.

      $eligible_subtotal = 0.0;

      foreach ( $cart->get_cart() as $cart_item ) {

          $product_id   = $cart_item['product_id'];

          $variation_id = $cart_item['variation_id'] ?? 0;

          $id_to_check  = $variation_id > 0 ? $variation_id : $product_id;

          // Exclude: a specific category e.g., 'music'.

          if ( has_term( 'music', 'product_cat', $product_id ) ) {

              continue;

          }

          // Exclude: product has an individual wholesale price for this role.

          $individual_price = get_post_meta( $id_to_check, $wholesale_role[0] . '_wholesale_price', true );

          if ( ! empty( $individual_price ) ) {

              continue;

          }

          $eligible_subtotal += (float) $cart_item['line_total'];

      }

      // Recalculate discount against the eligible subtotal only.

      $discount_mapping = get_option( 'wwpp_option_wholesale_role_cart_subtotal_price_based_discount_mapping', array() );

      // Sort descending by threshold so the highest qualifying rule matches first.

      usort( $discount_mapping, fn( $a, $b ) => $b['subtotal_price'] <=> $a['subtotal_price'] );

      $new_amount = 0.0;

      foreach ( $discount_mapping as $mapping ) {

          if ( $mapping['wholesale_role'] !== $wholesale_role[0] ) {

              continue;

          }

          if ( $eligible_subtotal >= (float) $mapping['subtotal_price'] ) {

              $new_amount = 'percent-discount' === $mapping['discount_type']

                  ? $eligible_subtotal * ( (float) $mapping['discount_amount'] / 100 )

                  : (float) $mapping['discount_amount'];

              break;

          }

      }

      $discount['discount_amount'] = $new_amount;

      return $discount;

  }