/**
 * Implementation of hook_requirements().
 */
function hs_views_taxonomy_requirements($phase) {
  $requirements = array();

  if ($phase == 'runtime') {
    $pattern = <<<EOT
function _views_build_filters_form(\$view) {
  // When the form is retrieved through an AJAX callback, the cache hasn't
  // been loaded yet. The cache is necesssary for _views_get_filters().
  views_load_cache();
EOT;
    $views_with_patch_257004 = preg_match('#'. preg_quote($pattern) .'#m', file_get_contents(drupal_get_path('module', 'views') .'/views.module'));

    if ($views_with_patch_257004) {
      $value = t('The Views module is new enough.');
      $description = '';
      $severity = REQUIREMENT_OK;
    }
    else {
      $value = t('The Views module is outdated.');
      $description = t("The version of Views that you have installed is either
        older than May 11, 2008, or doesn't have the obligatory patch applied.
        Please apply the <a href=\"!patch_url\">patch</a> or update to a newer
        version of the Views module!"
      );
      $severity = REQUIREMENT_ERROR;      
    }

    $requirements['hs_views_taxonomy'] = array(
      'title' => t('Hierarchical Select Views Taxonomy'),
      'value' => $value,
      'description' => $description,
      'severity' => $severity,
    );
  }

  return $requirements;
}