<?php

/**
 * @file Batch processing API for processes to run in multiple HTTP requests.
 */

/**
 * State based dispatcher for batches.
 */
function _batch_page() {
  global $user;

  $batch =& batch_get();

  if (isset($_REQUEST['id']) && $data = db_result(db_query("SELECT batch FROM {batch} WHERE bid = %d AND sid = %d", $_REQUEST['id'], $user->sid))) {
    $batch = unserialize($data);
  }
  else {
    return FALSE;
  }

  // Register database update for end of processing.
  register_shutdown_function('_batch_shutdown');

  $op = isset($_REQUEST['op']) ? $_REQUEST['op'] : '';
  switch ($op) {
    case 'start':
      $output = _batch_start();
      break;

    case 'do':
      $output = _batch_do();
      break;

    case 'do_nojs':
      $output = _batch_progress_page_nojs();
      break;

    case 'finished':
      $output = _batch_finished();
      break;
  }

  return $output;
}

/**
 * Initiate the batch processing
 */
function _batch_start() {
  // Choose between the JS and non-JS version.
  // JS-enabled users are identified through the 'has_js' cookie set in drupal.js.
  // If the user did not visit any JS enabled page during his browser session,
  // he gets the non-JS version...
  if (isset($_COOKIE['has_js']) && $_COOKIE['has_js']) {
    return _batch_progress_page_js();
  }
  else {
    return _batch_progress_page_nojs();
  }
}

/**
 * Batch processing page with JavaScript support.
 */
function _batch_progress_page_js() {
  $batch = batch_get();
  $current_set = _batch_current_set();

  drupal_set_title($current_set['title']);
  drupal_add_js('misc/progress.js', 'core', 'header');

  $url = url($batch['url'], array('query' => array('id' => $batch['id'])));
  $js_setting = array(
    'batch' => array(
      'errorMessage' => $current_set['error_message'] .'<br/>'. $batch['error_message'],
      'initMessage' => $current_set['init_message'],
      'uri' => $url,
    ),
  );
  drupal_add_js($js_setting, 'setting');
  drupal_add_js('misc/batch.js', 'core', 'header', FALSE, TRUE);

  $output = '<div id="progress"></div>';
  return $output;
}

/**
 * Do one pass of execution and inform back the browser about progression.
 */
function _batch_do() {
  // HTTP POST required
  if ($_SERVER['REQUEST_METHOD'] != 'POST') {
    drupal_set_message(t('HTTP POST is required.'), 'error');
    drupal_set_title(t('Error'));
    return '';
  }

  list($percentage, $message) = _batch_process();

  drupal_set_header('Content-Type: text/plain; charset=utf-8');
  print drupal_to_js(array('status' => TRUE, 'percentage' => $percentage, 'message' => $message));
  exit();
}

/**
 * Batch processing page without JavaScript support.
 */
function _batch_progress_page_nojs() {
  $batch =& batch_get();
  $current_set = _batch_current_set();

  drupal_set_title($current_set['title']);

  $new_op = 'do_nojs';

  if (!isset($batch['running'])) {
    // This is the first page so return some output immediately.
    $percentage = 0;
    $message = $current_set['init_message'];
    $batch['running'] = TRUE;
  }
  else {
    // This is one of the later requests: do some processing first.

    // Error handling: if PHP dies due to a fatal error (e.g. non-existant
    // function), it will output whatever is in the output buffer,
    // followed by the error message.
    ob_start();
    $fallback = $current_set['error_message'] .'<br/>'. $batch['error_message'];
    $fallback = theme('maintenance_page', $fallback, FALSE);

    // We strip the end of the page using a marker in the template, so any
    // additional HTML output by PHP shows up inside the page rather than
    // below it. While this causes invalid HTML, the same would be true if
    // we didn't, as content is not allowed to appear after </html> anyway.
    list($fallback) = explode('<!--partial-->', $fallback);
    print $fallback;

    list($percentage, $message) = _batch_process($batch);
    if ($percentage == 100) {
      $new_op = 'finished';
    }

    // Processing successful; remove fallback.
    ob_end_clean();
  }

  $url = url($batch['url'], array('query' => array('id' => $batch['id'], 'op' => $new_op)));
  drupal_set_html_head('<meta http-equiv="Refresh" content="0; URL='. $url .'">');
  $output = theme('progress_bar', $percentage, $message);
  return $output;
}

/**
 * Advance batch processing for 1 second (or process the whole batch if it
 * was not set for progressive execution).
 */
function _batch_process() {
  $batch =& batch_get();
  $current_set =& _batch_current_set();

  while (!$current_set['success']) {
    $task_message = NULL;
    $finished = 1;
    if ((list($function, $args) = reset($current_set['operations'])) && function_exists($function)) {
      // Build the 'batch context' array, execute the function call, and retrieve the user message.
      $batch_context = array('sandbox' => &$current_set['sandbox'], 'results' => &$current_set['results'], 'finished' => &$finished, 'message' => '');
      call_user_func_array($function, array_merge($args, array(&$batch_context)));
      $task_message = $batch_context['message'];
    }
    if ($finished == 1) {
      // Make sure this step isn't counted double.
      $finished = 0;
      // Remove the operation, and clear the sandbox to reduce the stored data.
      array_shift($current_set['operations']);
      $current_set['sandbox'] = array();

      // If the batch set is completed, browse through the remaining sets
      // until we find one that acually has operations.
      while (empty($current_set['operations']) && ($current_set['success'] = TRUE) && _batch_next_set()) {
        $current_set =& _batch_current_set();
      }
    }
    // Progressive mode : stop after 1 second
    if ($batch['progressive'] && timer_read('page') > 1000) {
      break;
    }
  }

  if ($batch['progressive']) {
    $remaining  = count($current_set['operations']);
    $total      = $current_set['total'];
    $current    = $total - $remaining + $finished;
    $percentage = $total ? floor($current / $total * 100) : 100;
    $values = array(
      '@remaining'  => $remaining,
      '@total'      => $total,
      '@current'    => floor($current),
      '@percentage' => $percentage,
      );
    $progress_message = strtr($current_set['progress_message'], $values);

    $message = $progress_message .'<br/>';
    $message.= $task_message ? $task_message : '&nbsp';

    return array($percentage, $message);
  }
  else {
    return _batch_finished();
  }

}

/**
 * Retrieve the batch set being currently processed.
 */
function &_batch_current_set() {
  $batch =& batch_get();
  return $batch['sets'][$batch['current_set']];
}

/**
 * Move execution to the next batch set if any, executing the stored
 * form _submit callbacks along the way (possibly inserting additional batch sets)
 */
function _batch_next_set() {
  $batch =& batch_get();
  if (isset($batch['sets'][$batch['current_set']+1])) {
    $batch['current_set']++;
    $current_set =& _batch_current_set();
    if (isset($current_set['form submit']) && (list($function, $args) = $current_set['form submit']) && function_exists($function)) {
      // We have to keep our own copy of $form_values, to account
      // for possible alteration by the submit callback.
      if (isset($batch['form_values'])) {
        $args[1] = $batch['form_values'];
      }
      $redirect = call_user_func_array($function, $args);
      // Store the form_values only if needed, to limit the
      // amount of data we store in the batch.
      if (isset($batch['sets'][$batch['current_set']+1])) {
        $batch['form_values'] = $args[1];
      }
      if (isset($redirect)) {
        $batch['redirect'] = $redirect;
      }
    }
    return TRUE;
  }
}

/**
 * End the batch :
 * Call the 'finished' callbacks to allow custom handling of results,
 * and resolve page redirection.
 */
function _batch_finished() {
  $batch =& batch_get();

  // Execute the 'finished' callbacks.
  foreach($batch['sets'] as $key => $batch_set) {
    if (isset($batch_set['finished']) && function_exists($batch_set['finished'])) {
      $batch_set['finished']($batch_set['success'], $batch_set['results'], $batch_set['operations']);
    }
  }

  // Cleanup the batch table and unset the global $batch variable.
  db_query("DELETE FROM {batch} WHERE bid = %d", $batch['id']);
  $_batch = $batch;
  $batch = NULL;

  // Redirect if needed.
  if ($_batch['progressive']) {
    if (isset($_batch['destination'])) {
      $_REQUEST['destination'] = $_batch['destination'];
    }
    $redirect = isset($_batch['redirect']) ? $_batch['redirect'] : $_batch['source_page'];
    $form_redirect = isset($_batch['form_redirect']) ? $_batch['form_redirect'] : NULL;
    // Let drupal_redirect_form handle redirection logic, using a bare pseudo form
    // to limit the amount of data we store in the batch.
    drupal_redirect_form(array('#redirect' => $form_redirect), $redirect);

    // If we get here, $form['redirect']['#redirect'] was FALSE, and we are most
    // probably dealing with a multistep form - not supported at the moment.
    // Redirect to the originating page - first step of the form.
    drupal_goto($_batch['source_page']);
  }
}

/**
 * Store tha batch data for next request, or clear the table if the batch is finished.
 */
function _batch_shutdown() {
  if ($batch = batch_get()) {
    db_query("UPDATE {batch} SET batch = '%s' WHERE bid = %d", serialize($batch), $batch['id']);
  }
}