Cart bulk quantity discount for specific product tag IDs in WooCommerce

I want to create a function to create conditional bulk dynamic pricing for WooCommerce, different unit prices based on the quantity added to cart.

I have two product tags ids (326, 327) and there is a bunch of product in each tag. I want to give a different discount for both tags and for the same quantity.

Tag ID 326
15% discount above 10 units
20% discount above 25 units

Tag ID 327
20% discount above 10 units
35% discount above 25 units.

This is the code I am working with:

add_action( 'woocommerce_before_calculate_totals', 'woocommerce_quantity_based_pricing', 9999 );
function woocommerce_quantity_based_pricing( $cart ) {
 
    if ( is_admin() && ! defined( 'DOING_AJAX' ) ) return;
 
    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 ) return;
     
    
    if( has_term( 326, 'product_tag' ) ) {
        $threshold1 = 10; 
        $discount1 = 0.15;
        $threshold2 = 25; 
        $discount2 = 0.3;
} elseif( has_term( 327, 'product_tag' ) ) {
        $threshold1 = 10; 
        $discount1 = 0.2; 
        $threshold2 = 25; 
        $discount2 = 0.35; 
}
    
    foreach ( $cart->get_cart() as $cart_item_key => $cart_item ) {
      if ( $cart_item['quantity'] >= $threshold1 && $cart_item['quantity'] < $threshold2 ) {
         $price = round( $cart_item['data']->get_price() * ( 1 - $discount1 ), 2 );
         $cart_item['data']->set_price( $price );
      } elseif ( $cart_item['quantity'] >= $threshold2 ) {
         $price = round( $cart_item['data']->get_price() * ( 1 - $discount2 ), 2 );
         $cart_item['data']->set_price( $price );
      }    
    }
    
 }

Unfortunately without the desired result. Any advice?

Solution

To apply a discount based on product tag IDs, you can use WC_Product::get_tag_ids(), and then compare it.

I have provided an extra piece of code via the woocommerce_cart_item_price hook, which will allow you to strikethrough the original price and show the new price next to it

So you get:

// Used to calculate totals
function action_woocommerce_before_calculate_totals( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;
    
    // Set Tag IDs
    $tag_id_1 = 326;
    $tag_id_2 = 327;
    
    // Tag ID 1
    // 15% discount above 10 units 
    $tag_id_1_threshold_1 = 10;
    $tag_id_1_discount_1  = 0.15;
    // 20% discount above 25 units
    $tag_id_1_threshold_2 = 25;
    $tag_id_1_discount_2 = 0.20;
    
    // Tag ID 2
    // 20% discount above 10 units 
    $tag_id_2_threshold_1 = 10;
    $tag_id_2_discount_1  = 0.20;
    // 35% discount above 25 units
    $tag_id_2_threshold_2 = 25;
    $tag_id_2_discount_2 = 0.35;

    // Loop through cart items
    foreach ( $cart->get_cart() as $cart_item_key => $cart_item ) {
        // Get price
        $price = $cart_item['data']->get_price();
        
        // Get quantity
        $quantity = $cart_item['quantity'];
        
        // Get product tag ID's
        $tag_ids = $cart_item['data']->get_tag_ids();
        
        // Check for tag ID
        if ( in_array ( $tag_id_1, $tag_ids ) ) {
            // Compare
            if ( $quantity >= $tag_id_1_threshold_1 && $quantity < $tag_id_1_threshold_2 ) {
                $discount = $tag_id_1_discount_1;
            } elseif ( $quantity >= $tag_id_1_threshold_2 ) {
                $discount = $tag_id_1_discount_2;
            }
        } elseif ( in_array ( $tag_id_2, $tag_ids ) ) {
            // Compare
            if ( $quantity >= $tag_id_2_threshold_1 && $quantity < $tag_id_2_threshold_2 ) {
                $discount = $tag_id_2_discount_1;
            } elseif ( $quantity >= $tag_id_2_threshold_2 ) {
                $discount = $tag_id_2_discount_2;
            }               
        }
        
        // Isset & NOT empty
        if ( isset( $discount ) && ! empty( $discount ) ) {         
            // Set new price
            $cart_item['data']->set_price( $price * ( 1 - $discount ) );
            
            // Reset
            $discount = '';
        }
    }
}
add_action( 'woocommerce_before_calculate_totals', 'action_woocommerce_before_calculate_totals', 10, 1 );  

// Strikethrough the original price
function filter_woocommerce_cart_item_price( $price_html, $cart_item, $cart_item_key ) {
    // Get the product object
    $product = $cart_item['data'];
    
    // Is a WC product
    if ( is_a( $product, 'WC_Product' ) ) {
        // Get reqular price
        $regular_price = $product->get_regular_price();
        
        // New price
        $new_price = $cart_item['data']->get_price();
        
        // NOT empty and NOT equal
        if ( ! empty ( $regular_price ) && $regular_price != $new_price ) {
            // Output
            $price_html = '<del>' . wc_price( $regular_price ) . '</del> <ins>' . wc_price( $new_price ) . '</ins>';        
        }
    }

    return $price_html;
}
add_filter( 'woocommerce_cart_item_price', 'filter_woocommerce_cart_item_price', 10, 3 );