WOO add coupon via url

function woocommerce_detect_coupon_code() {
	// Check if custom URI with coupon URL is requested
	if(!empty($_GET['code'])) {

		// Check if cart/shop page is set & redirect to it
		// $shop_page_id = wc_get_page_id('shop');
		// $cart_page_id = wc_get_page_id('cart');

    if(!empty($cart_page_id) && WC()->cart->get_cart_contents_count() > 0) {
		// 	$redirect_page = $cart_page_id;
		// } 
	    // else if(!empty($shop_page_id)) {
		// 	$redirect_page = $shop_page_id;
		// } 	

		$coupon_code = sanitize_text_field($_GET['code']);

		// Set-up session
		if(!WC()->session->has_session()) {
			WC()->session->set_customer_session_cookie(true);
		}

		// Add the discount code
		if(!WC()->cart->has_discount($coupon_code)) {
			WC()->cart->add_discount($coupon_code);
		}

		// Do redirect
		if(!empty($redirect_page)) {
			wp_safe_redirect( wc_get_page_permalink( 'shop' ));
			exit();
		}

	}
}
add_action('template_redirect', 'woocommerce_detect_coupon_code', 0);