Untitled

/**
 * For vendor coupons, validate minimum spend against only that vendor's
 * products in the cart, not the full cart subtotal.
 */
add_filter( 'woocommerce_coupon_validate_minimum_amount', function( $is_below_minimum, $coupon, $subtotal ) {

    // Get the vendor who owns this coupon via post_author.
    $coupon_vendor_id = (int) get_post_field( 'post_author', $coupon->get_id() );

    // If there's no vendor ID (e.g. admin coupon), leave default WC behaviour.
    if ( ! $coupon_vendor_id ) {
        return $is_below_minimum;
    }

    $minimum = (float) $coupon->get_minimum_amount();

    // No minimum set — nothing to validate.
    if ( $minimum <= 0 ) {
        return false;
    }

    // Sum only the cart items that belong to this vendor.
    $vendor_subtotal = 0.0;

    if ( WC()->cart && ! WC()->cart->is_empty() ) {
        foreach ( WC()->cart->get_cart() as $cart_item ) {
            $product_id        = $cart_item['product_id'];
            $product_vendor_id = (int) marketking()->get_product_vendor( $product_id );

            if ( $product_vendor_id === $coupon_vendor_id ) {
                $vendor_subtotal += (float) $cart_item['line_subtotal'];
            }
        }
    }

    // Return true  → minimum not met → WC throws the error.
    // Return false → minimum met     → validation passes.
    return $minimum > $vendor_subtotal;

}, 10, 3 );