Delay Intercom execution in WordPress

delay_intercom_wordpress.php

// Intercom plugin adds Intercom script to critical render path, sets it to be not defered
// And adds the script in WordPress in a way it doesn't leave much options to alter it in order to delay Intercom execution and prevent it to be render blocking
// Altering buffer in WP generally in not a great idea, but since we have no choice, let's make sure we are altering it in a way it doesn't break things
// If you use WP Rocket -- use 'rocket_buffer' filter instead

add_action( 'init', 'sz_buffer_process_post' ); //we use 'init' action to use ob_start()
function sz_buffer_process_post() {
    ob_start();
}

add_action('shutdown', function() {
    $final = '';
    $levels = ob_get_level();
    for ($i = 0; $i < $levels; $i++) {
        $final .= ob_get_contents();
        ob_clean();
    }
    $final_output = apply_filters( 'sz_filter_final_html', $final);
    echo $final_output;
}, 0);

// Delay Intercom by varying HTML output via buffer
add_filter( 'sz_filter_final_html', 'sz_filter_html_intercom', 10, 1);
function sz_filter_html_intercom( $html ) {
    $current_url = home_url($_SERVER['REQUEST_URI']);
    if (!is_admin() && !is_user_logged_in() && (strpos($current_url, 'xmlrpc.php') === false)){
        //these checks needed if you are not using WP Rocket buffer

        //Main thing is here:
        preg_match_all( '/<script.*w\.Intercom=i.*<\/script>/U', $html, $found_scripts ); //in case it is more than one occurences
        foreach ( $found_scripts[0] as $found_script ) {
            $replace_script = str_replace( 'data-cfasync="false"', 'defer', $found_script ); // defer loading
            $replace_script = str_replace( "function l(){", "function l(){ setTimeout(function () {", $replace_script ); //and delay execution
            $replace_script = str_replace( 'x.parentNode.insertBefore(s,x);', 'x.parentNode.insertBefore(s,x);}, 3000);', $replace_script );
            $html           = str_replace( $found_script, $replace_script, $html );
           
           //Many thanks to @wppunk for helping out with this part
           
        }
    }
    return $html;
}


/**
* There is an alternative to regex -- using DOMDocument -- but mind, the output might be broken if there are errors in $html input

        $dom = new DOMDocument;
        $dom->loadHTML($html);
        foreach ($dom->getElementsByTagName('script') as $tag) {
            if (strpos($tag->nodeValue, "var ic=w.Intercom") !== false) {
                $tag->setAttribute('defer', '');
                $tag->removeAttribute('data-cfasync');
                $tag->nodeValue = str_replace("function l(){", "function l(){ setTimeout(function () {", $tag->nodeValue);
                $tag->nodeValue = str_replace('x.parentNode.insertBefore(s,x);', 'x.parentNode.insertBefore(s,x);}, 3000);', $tag->nodeValue);
            }
        }
        $html = $dom->saveHtml();
**/