Limit maximum number of points discount

functions.php

<?php

/**
 * Limit TOTAL discount (coupons + points) to a maximum percentage
 * 
 * This ensures customers can't stack coupon codes with points
 * to get more than a specified total discount.
 */
add_filter('wpgens_loyalty_calculate_points_discount', function($discount_amount, $points, $conversion_rate) {
    if (!function_exists('WC') || !WC()->cart) {
        return $discount_amount;
    }

    $cart = WC()->cart;
    
    // Maximum total discount allowed (points + coupons) as percentage
    $max_total_discount_percent = 25;
    
    // Get cart subtotal (before discounts)
    $cart_subtotal = $cart->get_subtotal() + $cart->get_subtotal_tax();
    
    if ($cart_subtotal <= 0) {
        return $discount_amount;
    }
    
    // Calculate maximum total discount allowed
    $max_total_discount = ($cart_subtotal * $max_total_discount_percent) / 100;
    
    // Get current coupon discounts (excludes points coupon)
    $coupon_discount = 0;
    foreach ($cart->get_applied_coupons() as $coupon_code) {
        // Skip loyalty points coupons
        if (strpos($coupon_code, 'loyalty_points_') === 0) {
            continue;
        }
        $coupon_discount += $cart->get_coupon_discount_amount($coupon_code, $cart->display_cart_ex_tax);
    }
    
    // Calculate remaining discount allowance for points
    $remaining_allowance = $max_total_discount - $coupon_discount;
    
    // If coupons already exceed the limit, no points discount allowed
    if ($remaining_allowance <= 0) {
        return 0;
    }
    
    // Cap points discount to remaining allowance
    return min($discount_amount, $remaining_allowance);
}, 20, 3);