/**
 * @snippet       Add tax for dealers shipping to California
 * @author        André Le Comte
 */ 
function add_CA_cart_tax() {
global $woocommerce;
$taxable_states = array('CA');
$taxable_roles = array('customer');
$user_data = get_userdata( get_current_user_id() );
$user_roles = $user_data->roles;
if( in_array('customer', $user_roles) && in_array( WC()->customer->shipping_state, $taxable_states) ) {
 $surcharge = 0.083 * WC()->cart->subtotal; // 8.3% tax based on shipping location
 $woocommerce->cart->add_fee( __('California tax', 'woocommerce'), $surcharge );
}
}
 
add_action( 'woocommerce_cart_calculate_fees', 'add_CA_cart_tax' );

/**
 * @snippet   Add field to checkout with conditional fee
 * @author    André Le Comte
 **/
add_action( 'woocommerce_after_order_notes', 'custom_checkout_field' );
 
function custom_checkout_field( $checkout ) {
 
 //Check if user is a dealer
 $user_is_dealer = is_user_a_dealer( 117 );
 
 //User is dealer so show additional fields
 if ( $user_is_dealer === true ) {
 echo '<div id="my_custom_checkout_field"><h3>' . __( 'Ship to store' ) . '</h3><p style="margin: 0 0 8px;">Ship to store</p>';
 
 woocommerce_form_field( 'ship_to_store_checkbox', array(
 'type'  => 'checkbox',
 'class' => array( 'ship-to-store-checkbox form-row-wide' ),
 'label' => __( 'Yes' ),
 ), $checkout->get_value( 'ship_to_store_checkbox' ) );
 
 echo '</div>';
 }
 
}
 
/**
 * @snippet Check if user is logged in as a dealer
 * @author André Le Comte
 */
function is_user_a_dealer( $product_id ) {
 //Check to see if user has product in cart
 global $woocommerce;
 
 //flag no book in cart
 $book_in_cart = false;
 
 foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values ) {
 $_product = $values['data'];
 
 if ( $_product->id === $product_id ) {
 //book is in cart!
 $book_in_cart = true;
 
 }
 }
 
 return $book_in_cart;
 
}