namespaces.module

<?php
// $Id$ 

/**
 * @file Module that handles adding extra namespaces to a Drupal environment.
 * 
 * Each module that provides a custom namespace should implement 
 * hook_namespaces(). This hook returns an associative array containing
 * a namespace as key and a unique identifier as value.
 */

/**
 * Implementation of hook_hook_info()
 */
function namespaces_hook_info() {
  return array(
    'namespaces' => array(
      'namespaces' => array(
        'namespaces' => array(
          'runs when' => t('The final page is being build, to establish extra namespaces that need adding')
        )
      )
    )
  );
}

/**
 * Implementation of hook_preprocess_page().
 * 
 * Adds an extra variable to each page, containing the namespace definitions.
 */
function namespaces_preprocess_page(&$variables) {
  $namespaces = namespaces_list_available();
  $nss = array();
  foreach ($namespaces as $ns => $id) {
    $nss[] = sprintf('xml:%s="%s"', $ns, $id);
  }
  if (!empty($ns)) {
    $variables['namespaces'] = implode(' ', $nss);
  }
  else {
    $variables['namespaces'] = '';
  }
}

/**
 * Return the list of namespaces that have been defined by modules.
 * 
 * @return A list of available namespaces that have been defined previously.
 */
function namespaces_list_available() {
  $namespaces = cache_get('available_namespaces');
  if (!is_array($namespaces)) {
    $namespaces = module_invoke_all('namespaces');
    foreach ($namespaces as $ns => $id) {
      if ((strlen($ns) < 1) || (strlen($id) < 1)) {
        // Remove empty entries
        unset ($namespaces[$ns]);
      }
    }
    cache_set('available_namespaces', $namespaces, 'cache', CACHE_TEMPORARY);
  }

  return $namespaces;
}

/**
 * Check whether a namespace has been defined.
 * 
 * @param $namespace The namespace to check.
 * @return TRUE if a namespace exists, FALSE if otherwise.
 */
function namespaces_is_available($namespace) {
  $namespaces = namespaces_list_available();

  return isset($namespaces[$namespace]);
}