custom_i18n_redirect.module

<?php

/**
 * @file
 * Internationalization (i18n) module.
 *
 * Redirect to language path when we have a translation for the current language.
 */

/**
 * Implements hook_help().
 */
function custom_i18n_redirect_help($path, $arg) {
  switch ($path) {
    case 'admin/config/regional/i18n':
      if (!module_exists('i18n_node')) {
        $output = '<p>' . t('To have <em>Translation redirect</em> working with your content you should <a href="@admin_modules">enable the <em>Multilingual content</em> module</a>.', array('@admin_modules' => url('admin/modules'))) . '</p>';
        return $output;
      }
  }
}

/**
 * Implements hook_init()
 */
function custom_i18n_redirect_init() {
  $path = $_GET['q'];
  $language = i18n_language_interface();

  // Not for logged in users nor for home page
  if (!$path || drupal_is_front_page() || !empty($GLOBALS['user']->uid)) {
    return;
  }

  $translations = i18n_get_path_translations($path);
  if (isset($translations[$language->language]) && $translations[$language->language]['href'] != $path) {
    drupal_goto($translations[$language->language]['href'], array('language' => $language), 301);
  }
  else {
    // Here we working with node, since question about node redirections
    $node = menu_get_object();
    if ($node && $node->language && ($node->language != $language->language)) {
      $languages = language_list();
      if (isset($languages[$node->language])) {
        $language = $languages[$node->language];
        drupal_goto('node/' . $node->nid, array('language' => $language), 301);
      }
    }
  }

}