Automatically add product to cart on visit

wc-auto-add-product-to-cart.php

/**
 * Automatically add product to cart on visit
 */
add_action( 'template_redirect', 'add_product_to_cart' );
function add_product_to_cart() {
	if ( ! is_admin() ) {
		$product_id = 64; //replace with your own product id
		$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() == $product_id )
					$found = true;
			}
			// if product not found, add it
			if ( ! $found )
				WC()->cart->add_to_cart( $product_id );
		} else {
			// if no products in cart, add it
			WC()->cart->add_to_cart( $product_id );
		}
	}
}

I want to offer option to remove the product from cart, if the customer doesn't want it. How can I do that?

try this because it only adds the product if the cart is empty:
/**

• Automatically add product to cart on visit
  */
  add_action( 'template_redirect', 'add_product_to_cart' );
  function add_product_to_cart()
  {
  // check if cart contents are empty
  if ( WC()->cart->get_cart_contents_count() == 0 )
  {
  // this code only runs the first time the hook is fired
  if ( ! is_admin() )
  {
  $product_id = 2765; //replace with your own product id
  WC()->cart->add_to_cart( $product_id );
  }
  }
  }