woocommerce-bulk-discount 2.4.5 performance improvements in gather_discount_coeffs

gather_discount_coeffs.php

<?php

/**
 * Performance improved gather_discount_coeffs function
 * code adapted from woocommerce-bulk-discount 2.4.5
 * by Nils Magnus Englund <nme@stepone.no>
 *  
 * NOTE: The code below is only compatible with WooCommerce 3.0 as-is.
 *       Should be easy enough to backport.
 *
 * Two modifications:
 *   - Cache result from quantity calculation for each product variation.
 *     This value will necessarily be the same for each variation.
 *   - Avoid nested unnecessary calls to get_product where just the ID will do.
 */

/**
 * Gather discount information to the array $this->discount_coeffs
 */
protected function gather_discount_coeffs() {
    global $woocommerce;
    $cart = $woocommerce->cart;
    $this->discount_coeffs = array();
    $cached_quantity_by_parent_id = array();
    if ( sizeof( $cart->cart_contents ) > 0 ) {
        foreach ( $cart->cart_contents as $cart_item_key => $values ) {
            $_product = $values['data'];
            $quantity = 0;
            if ( get_option( 'woocommerce_t4m_variations_separate', 'yes' ) == 'no' && $_product instanceof WC_Product_Variation && $this->get_parent($_product) ) {
                $_parent = $_product->get_parent_id();
                $_id = $_product->get_id();
                if (!isset($cached_quantity_by_parent_id[$_parent])) {
                    // Loop through all products in the cart again to group all products with the same parent ID as this one
                    $qt = 0;
                    foreach ($cart->cart_contents as $valuesInner) {
                        $p = $valuesInner['data'];
                        if ($p instanceof WC_Product_Variation && $p->get_parent_id() == $_parent) {
                            $qt += $valuesInner['quantity'];
                        }
                    }
                    $cached_quantity_by_parent_id[$_parent] = $qt;
                }
                $quantity = $cached_quantity_by_parent_id[$_parent];
            } else {
                $quantity = $values['quantity'];
            }
            $this->discount_coeffs[$this->get_actual_id( $_product )]['coeff'] = $this->get_discounted_coeff( $this->get_product_id($_product), $quantity );
            $this->discount_coeffs[$this->get_actual_id( $_product )]['orig_price'] = $_product->get_price();
            $this->discount_coeffs[$this->get_actual_id( $_product )]['quantity'] = $quantity;
        }
    }
}