Renders a notice and prevents checkout if the cart contains products in certain combination of categories | woocommerce

woo-prevent-checkout-conditional

/**
 * LG :: Renders a notice and prevents checkout if the cart contains products in catering AND non-catering
 */
function lg_wc_prevent_checkout_for_category() {

	//	If the cart is empty, then we bail out of this function
	if (WC()->cart->is_empty()) {
		return;
	}
	
	// set the slug of the category for which we disallow checkout
	$category = 'catering';
	
	// get the product category
	$product_cat = get_term_by( 'slug', $category, 'product_cat' );
	
	// sanity check to prevent fatals if the term doesn't exist
	if ( is_wp_error( $product_cat ) ) {
		return;
	}
	
	$category_name = '<a href="' . get_term_link( $category, 'product_cat' ) . '">' . $product_cat->name . '</a>';
	
	// check if this category is the only thing in the cart
	if ( lg_woo_is_category_all_or_nothing( $category ) ) {

		// if true then escape this because it's all good
		return;
	}
	else {
		// otherwise post a notice to explain why checkout is blocked
		wc_add_notice( sprintf( 'hi there! looks like your cart contains products from the %1$s and pickup categories &ndash; catering items must be ordered separately from pickup items to check out.', $category_name ), 'error' );
	}
}
add_action( 'woocommerce_check_cart_items', 'lg_wc_prevent_checkout_for_category' );

/**
 * Checks if a cart contains exclusively products in a given category
 * 
 * @param string $category the slug of the product category
 * @return bool - true if the cart only contains the given category
 */
function lg_woo_is_category_all_or_nothing( $category ) {
    // start with a count of zero 
    $cat_count = 0;
        
	// loop through cart to count items that have our category
	foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
		
		if ( has_term( $category, 'product_cat', $cart_item['data']->get_id() ) ) {
			$cat_count = $cat_count+1;
		}
	}
        
	// return true if count of category = nothing or all of the items 
	return $cat_count === 0 || $cat_count === WC()->cart->get_cart_contents_count();

}