prevent coupons when points applied.

functions.php

<?php

// Add this to your main plugin file or in a hooks class
add_filter('woocommerce_coupon_is_valid', 'prevent_coupons_when_points_applied', 10, 3);

function prevent_coupons_when_points_applied($is_valid, $coupon, $discount_object) {
    // Skip validation for loyalty points coupons themselves
    if (strpos($coupon->get_code(), 'loyalty_points_') === 0) {
        return $is_valid;
    }
    
    // Check if any points coupon is currently applied
    if (function_exists('WC') && WC()->cart) {
        $applied_coupons = WC()->cart->get_applied_coupons();
        
        foreach ($applied_coupons as $applied_coupon_code) {
            if (strpos($applied_coupon_code, 'loyalty_points_') === 0) {
                // Verify the points coupon is still valid via transient
                $coupon_data = get_transient('loyalty_coupon_' . $applied_coupon_code);
                if ($coupon_data && $coupon_data['user_id'] === get_current_user_id()) {
                    throw new Exception(__('Coupons cannot be used when loyalty points are applied. Please remove points discount first.', 'wpgens-points-and-rewards-program'));
                }
            }
        }
    }
    
    return $is_valid;
}