<?php
/*
Plugin Name: Local by Flywheel Relative URL (for Live Links)
Plugin URI: http://getflywheel.com
Description: Makes WordPress URL functions relative to play nicely with Live Links.
Version: 1.0
Author: Flywheel
Author URI: http://getflywheel.com
License: GPLv2 or later
*/

if ( isset($_SERVER['HTTP_X_ORIGINAL_HOST']) && $_SERVER['HTTP_X_ORIGINAL_HOST'] ) {
  add_filter('template_include', 'make_links_ngrok', 0);

  remove_action('template_redirect', 'redirect_canonical');

  $filters = array(
      'wp_redirect',
      'bloginfo_url',
      'the_permalink',
      'wp_list_pages',
      'wp_list_categories',
      'the_content_more_link',
      'the_tags',
      'the_author_posts_link',
      'post_link',
      'post_type_link',
      'page_link',
      'attachment_link',
      'get_shortlink',
      'post_type_archive_link',
      'get_pagenum_link',
      'get_comments_pagenum_link',
      'term_link',
      'search_link',
      'day_link',
      'month_link',
      'year_link',
      'option_siteurl',
      'blog_option_siteurl',
      'option_home',
      'admin_url',
      'get_admin_url',
      'get_site_url',
      'network_admin_url',
      'home_url',
      'includes_url',
      'site_url',
      'site_option_siteurl',
      'network_home_url',
      'network_site_url',
      'get_the_author_url',
      'get_comment_link',
      'wp_get_attachment_image_src',
      'wp_get_attachment_thumb_url',
      'wp_get_attachment_url',
      'wp_login_url',
      'wp_logout_url',
      'wp_lostpassword_url',
      'get_stylesheet_uri',
      'get_locale_stylesheet_uri',
      'script_loader_src',
      'style_loader_src',
      'get_theme_root_uri',
      'plugins_url',
      'stylesheet_directory_uri',
      'template_directory_uri'
  );

  foreach ( $filters as $filter ) {
    add_filter($filter, 'make_link_ngrok');
  }
}

function make_links_ngrok($template) {
  if ( empty($_SERVER['HTTP_X_ORIGINAL_HOST']) ) {
    return $template;
  }

  ob_start('make_link_ngrok');
  return $template;
}

function make_link_ngrok($str) {
  $original_domain = str_replace('/^www./', '', $_SERVER['HTTP_X_FORWARDED_HOST']);
  $ngrok_domain = $_SERVER['HTTP_X_ORIGINAL_HOST'];

  $str = str_replace('www.' . $original_domain, $ngrok_domain, $str);
  $str = str_replace($original_domain, $ngrok_domain, $str);

  return $str;
}