WooCommerce - Automatically add product to cart on visit

functions.php

<?php // Do not include this if already open!

/**
 * Code goes in theme functions.php.
 */
if ( class_exists( 'WooCommerce' ) ) {
	add_action( 'template_redirect', 'wc_auto_add_product_to_cart' );
}

/**
 * Add product item to cart on site visit.
 */
function wc_auto_add_product_to_cart() {
	$product = get_page_by_title( 'Sunglasses', OBJECT, 'product' );

	if ( is_object( $product ) && $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->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 );
		}
	}
}