<?php
// $Id: poormanscron.module,v 1.18.2.2.2.4 2010-05-08 23:03:43 davereid Exp $

/**
 * @file
 * A module which runs Drupal cron jobs without the cron application.
 */

/**
 * Implements hook_menu().
 */
function poormanscron_menu($may_cache) {
  if ($may_cache) {
    $items[] = array(
      'path' => 'poormanscron/run-cron-check',
      'title' => t('Run Poormanscron'),
      'callback' => 'poormanscron_run_cron_check',
      'access' => poormanscron_run_cron_check_access(),
      'type' => MENU_CALLBACK,
    );
  }
  else {
    if (poormanscron_run_cron_check_access()) {
      drupal_add_js(drupal_get_path('module', 'poormanscron') . '/poormanscron.js');
      $settings = array(
        'basePath' => url('poormanscron'),
        'runNext' => variable_get('cron_last', 0) + variable_get('cron_safe_threshold', 10800),
      );
      drupal_add_js(array('cron' => $settings), 'setting');
    }
  }
  return $items;
}

/**
 * Implements hook_robotstxt().
 */
function poormanscron_robotstxt() {
  return array(
    'Disallow: /poormanscron/',
    'Disallow: /?q=poormanscron/',
  );
}

/**
 * Checks if the feature to automatically run cron is enabled.
 *
 * Also used as a menu access callback for this feature.
 *
 * @return
 *   TRUE if cron threshold is enabled, FALSE otherwise.
 *
 * @see poormanscron_run_cron_check()
 */
function poormanscron_run_cron_check_access() {
  return variable_get('cron_safe_threshold', 10800) > 0;
}

/**
 * Menu callback; executes cron via an image callback.
 *
 * This callback runs cron in a separate HTTP request to prevent "mysterious"
 * slow-downs of regular HTTP requests. It is invoked via an AJAX request
 * (if the client's browser supports JavaScript).
 *
 * @see poormanscron_run_cron_check_access()
 */
function poormanscron_run_cron_check() {
  $time = time();
  $cron_run = FALSE;
  $cron_threshold = variable_get('cron_safe_threshold', 10800);

  // Cron threshold semaphore is used to avoid errors every time the image
  // callback is displayed when a previous cron is still running.
  $threshold_semaphore = variable_get('cron_threshold_semaphore', FALSE);
  if ($threshold_semaphore) {
    if ($time - $threshold_semaphore > 3600) {
      // Either cron has been running for more than an hour or the semaphore
      // was not reset due to a database error.
      watchdog('cron', t('Cron has been running for more than an hour and is most likely stuck.'), WATCHDOG_ERROR);

      // Release the cron threshold semaphore.
      variable_del('cron_threshold_semaphore');
    }
  }
  else {
    // Run cron automatically if it has never run or threshold was crossed.
    $cron_last = variable_get('cron_last', 0);
    if ($time - $cron_last > $cron_threshold) {
      // Force the current user to anonymous to ensure consistent permissions
      // on cron runs.
      session_save_session(FALSE);
      $original_user = $GLOBALS['user'];
      $GLOBALS['user'] = drupal_anonymous_user();

      // Lock cron threshold semaphore.
      variable_set('cron_threshold_semaphore', $time);

      // Run cron!
      $cron_run = drupal_cron_run();

      // Release the cron threshold semaphore.
      variable_del('cron_threshold_semaphore');

      // Restore the user.
      $GLOBALS['user'] = $original_user;
      session_save_session(TRUE);

      if ($cron_run) {
        // Truncate the page cache so that cached pages get a new timestamp for
        // the next cron run.
        cache_clear_all('*', 'cache_page', TRUE);
      }
    }
  }

  $cron_last = variable_get('cron_last', 0);
  drupal_set_header('Expires: ' . gmdate('D, d M Y H:i:s O', $cron_last + $cron_threshold));

  // @todo Should we allow this to be cached?
  exit;
}

/**
 * Implements hook_form_alter().
 */
function poormanscron_form_alter($form_id, &$form) {
  if ($form_id == 'system_site_information_settings') {
    $form['cron_safe_threshold'] = array(
      '#type' => 'select',
      '#title' => t('Automatically run cron'),
      '#default_value' => variable_get('cron_safe_threshold', 10800),
      '#options' => array(0 => t('Never')) + drupal_map_assoc(array(3600, 10800, 21600, 43200, 86400, 604800), 'format_interval'),
      '#description' => t('When enabled, the site will check whether cron has been run in the configured interval and automatically run it upon the next page request. For more information visit the <a href="@status-report-url">status report page</a>.', array('@status-report-url' => url('admin/reports/status'))),
    );
    $form['buttons'] += array('#weight' => 100);
    $form['#submit'] = array_merge(array('poormanscron_site_information_settings_submit' => array()), $form['#submit']);
  }
}

/**
 * Form submit callback; clears the page cache if cron settings were changed.
 */
function poormanscron_site_information_settings_submit($form_id, $form_values) {
  if (variable_get('cron_safe_threshold', 10800) != $form_values['cron_safe_threshold']) {
    cache_clear_all('*', 'cache_page', TRUE);
  }
}