Direct checkout in WooCommerce for non-WPLMS theme.

functions.php

add_action( 'template_redirect', 'vibe_product_woocommerce_direct_checkout');
	function vibe_product_woocommerce_direct_checkout(){

	  	if(in_array('woocommerce/woocommerce.php', apply_filters('active_plugins', get_option('active_plugins'))) || (function_exists('vibe_check_plugin_installed') && vibe_check_plugin_installed( 'woocommerce/woocommerce.php')) || function_exists('WC')){
	        
      		if( is_single() && get_post_type() == 'product' && isset($_GET['redirect'])){ 
          		global $woocommerce; 
          		$found = false;
          		$product_id = get_the_ID();
          		$courses = vibe_sanitize(get_post_meta(get_the_ID(),'vibe_courses',false));
          
          		if(isset($courses) && is_array($courses) && count($courses)){
            		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 );
                		$cart_url = esc_url( wc_get_cart_url() ); 
                		wp_redirect( $cart_url); 
            		}else{
		              	WC()->cart->add_to_cart( $product_id );
		              	$cart_url = esc_url( wc_get_cart_url() ); 
		              	wp_redirect( $cart_url);
            		}
            		exit();
          		}
      		}
	  	} // End if WooCommerce Installed
	}