WooCommerce Progressive discount based on cart subtotal if there are no discounted items

I am using the following code that applies progressive discounts based on order amount.

add_action('woocommerce_cart_calculate_fees', 'woo_discount_total');
function woo_discount_total(WC_Cart $cart) {

    if( is_admin() && !defined('DOING_AJAX') ) {
        return;
    }
    $woo_current_price = $cart->subtotal;

    if($woo_current_price >= 3000 && $woo_current_price <= 9990) {
        $discount = $cart->subtotal * 0.02; // 0.02 = 2%
        $cart->add_fee('Sale 2% ', -$discount);
    }
    elseif($woo_current_price >= 10000) {
        $discount = $cart->subtotal * 0.05; // 0.05 = 5%
        $cart->add_fee('Sale 5% ', -$discount);
    }
}

But there is a problem. If there is a product on sale with a 15% discount in the cart, then all discounts are summed.

As far as I understand, I need to spell out the conditions?

What I would like is:

• If there are discounted items in the cart, my discounts are ignored.
• If there are no discounted items in the cart, my discounts continue to work.

How can this be implemented?

A discounted item could be:

• an "on sale" item (a product which price is on sale),
• an item discounted by a coupon applied to cart.

In the code below I have implemented both, so if a coupon is applied or if there is an "on sale" item, Your custom progressive discount based on cart subtotal will not be applied.

Try:

// Conditional function that check if there are cart items "on sale"
function has_items_on_sale( $cart ) {
    // Loop through cart items
    foreach ( $cart->get_cart() as $item ) {
        if ( $item['data']->is_on_sale() ) {
            return true;
        }
    }
    return false;
}

// Progressive discount based on cart subtotal
add_action( 'woocommerce_cart_calculate_fees', 'subtotal_based_progressive_discount' );
function subtotal_based_progressive_discount( $cart ) {
    if( is_admin() && !defined('DOING_AJAX') ) {
        return;
    }
    // Exit if a cart item is on sale
    if( has_items_on_sale( $cart ) ) {
        return;
    }
    // Exit if a coupon has been applied to cart
    if( $cart->get_applied_coupons() ) {
        return;
    }

    $subtotal = $cart->subtotal;
    $percent  = 0;

    if( $subtotal >= 3000 && $subtotal < 10000 ) {
        $percent = 2; // 2 %
    } elseif( $subtotal >= 10000 ) {
        $percent = 5; // 5 %
    }

    if( $percent > 0 ) {
        $cart->add_fee( __('Sale') . " {$percent}%", -($subtotal * $percent / 100) );
    }
}

It should work.

Addition:

Progressive discount based on cart item subtotal excluding "on sale" items.

Alternatively, you can use the following to apply a progressive discount on the subtotal excluding "on sale" items (if there is no applied coupons):

// Utility function: Get cart subtotal excluding on sale items
function get_subtotal_excluding_on_sale_items( $cart, $subtotal = 0 ) {
    // Loop through cart items
    foreach ( $cart->get_cart() as $item ) {
        if ( ! $item['data']->is_on_sale() ) {
            $subtotal = $item['line_subtotal'] + $item['line_subtotal_tax'];
        }
    }
    return $subtotal;
}

// Progressive discount based on cart subtotal
add_action( 'woocommerce_cart_calculate_fees', 'subtotal_based_progressive_discount' );
function subtotal_based_progressive_discount( $cart ) {
    if( is_admin() && !defined('DOING_AJAX') ) {
        return;
    }
    
    // Exit if a coupon has been applied to cart (optional)
    if( $cart->get_applied_coupons() ) {
        return;
    }

    $subtotal = get_subtotal_excluding_on_sale_items( $cart );
    $percent  = 0;

    if( $subtotal >= 3000 && $subtotal < 10000 ) {
        $percent = 2; // 2 %
    } elseif( $subtotal >= 10000 ) {
        $percent = 5; // 5 %
    }

    if( $percent > 0 ) {
        $cart->add_fee( __('Sale') . " {$percent}%", -($subtotal * $percent / 100) );
    }
}

It should work.