/*
* Automatically adding the product to the cart. Forrás: https://www.tychesoftwares.com/how-to-automatically-add-a-product-to-your-woocommerce-cart-in-3-different-scenarios/
*/

function aaptc_add_product_to_cart( $item_key, $product_id ) {

	$product_category_id 	= 123; // cricket bat category id

	$product_cats_ids 	= wc_get_product_term_ids( $product_id, 'product_cat' );

    if ( ! is_admin() && in_array( $product_category_id, $product_cats_ids ) ) {
        $free_product_id = 12989;  // Product Id of the free product which will get added to cart
        $found 		= false;

        //check if product already in cart
        if ( sizeof( WC()->cart->get_cart() ) > 0 ) {
            foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
                $_product = $values['data'];
                if ( $_product->get_id() == $free_product_id )
                    $found = true;
                
            }
            // if product not found, add it
            if ( ! $found )
                WC()->cart->add_to_cart( $free_product_id );
        } else {
            // if no products in cart, add it
            WC()->cart->add_to_cart( $free_product_id );
        }        
    }    
}

add_action( 'woocommerce_add_to_cart', 'aaptc_add_product_to_cart', 10, 2 );