protected function _getDefaultEsiOptions($options) {
        $esiHelper = Mage::helper('turpentine/esi');
        $ttlParam = $esiHelper->getEsiTtlParam();
        $methodParam = $esiHelper->getEsiMethodParam();
        $cacheTypeParam = $esiHelper->getEsiCacheTypeParam();
        $defaults = array(
            $esiHelper->getEsiMethodParam()         => 'esi',
            $esiHelper->getEsiScopeParam()          => 'global',
            $esiHelper->getEsiCacheTypeParam()      => 'public',
            'dummy_blocks'      => array(),
            'registry_keys'     => array(),
        );
        $options = array_merge($defaults, $options);

        // set the default TTL
        if ( ! isset($options[$ttlParam])) {
            if ($options[$cacheTypeParam] == 'private' || $options[$cacheTypeParam] == 'customer_group') {
                switch ($options[$methodParam]) {
                    case 'ajax':
                        $options[$ttlParam] = '0';
                        break;

                    case 'esi':
                    default:
                        $options[$ttlParam] = $esiHelper->getDefaultEsiTtl();
                        break;
                }
            } else {
                $options[$ttlParam] = Mage::helper('turpentine/varnish')
                    ->getDefaultTtl();
            }
        }

        return $options;
    }