roblib_update_book_ocr/roblib_update_book_ocr.module

<?php

/**
 * @file
 * Module file for roblib_update_book_ocr.
 */

function roblib_update_book_ocr_islandora_paged_content_pages_management_tabs_alter(&$manage_tabs, $context) {
  $manage_tabs['manage_pages']['book_ocr'] = array(
   '#access' => islandora_object_access(ISLANDORA_ADD_DS, $context['object']),
    '#title' => t('Create or Update Book OCR'),
    '#type' => 'fieldset',
    'form' => drupal_get_form('roblib_update_book_ocr_manage_pages_ocr_form', $context['object']),
    '#collapsible' => TRUE,
    '#collapsed' => TRUE,
  );
}

/**
 * Derives the OCR datastreams in each child page.
 *
 * @param array $form
 *   The Drupal form.
 * @param array $form_state
 *   The Drupal form state.
 * @param AbstractObject $object
 *   The object to fetch the pages from.
 *
 * @return array
 *   The Drupal form.
 */
function roblib_update_book_ocr_manage_pages_ocr_form(array $form, array &$form_state, AbstractObject $object) {
  $form_state['object'] = $object;
  return array(
    'description' => array(
      '#type' => 'item',
      '#description' => t('Aggregates all the page level OCR into one OCR datastream at the book level.<br/>
        This will not generate OCR/HOCR at the page level.  The page level OCR must already exist.'),
    ),

    'submit' => array(
      '#disabled' => FALSE,
      '#type' => 'submit',
      '#value' => t('Create/Update Book OCR'),
    ),
  );
}

/**
 * Triggers a batch to derive the OCR datastreams in each page object.
 *
 * @param array $form
 *   The Drupal form.
 * @param array $form_state
 *   The Drupal form state.
 */
function roblib_update_book_ocr_manage_pages_ocr_form_submit(array $form, array &$form_state) {
  $object = $form_state['object'];
  $pages = array_keys(islandora_paged_content_get_pages($object));
  roblib_update_book_ocr_batch($pages, $object);
}


/**
 * Setup the batch.
 *
 * @param Array $pages
 *   A list of pages related to the book
 * @param string $pid
 *   The PID of the book.
 */
function roblib_update_book_ocr_batch($pages, $object) {
  $batch = [
    'title' => t('Updating/Creating Book OCR ...'),
    'operations' => [],
    'init_message' => t('starting'),
    'progress_message' => t('Processed @current out of @total.'),
    'error_message' => t('An error occurred during processing'),
    'finished' => 'roblib_update_book_ocr_batch_finished',
  ];
  $total = count($pages);
  foreach ($pages as $page) {
    $batch['operations'][] = [
      '_roblib_update_book_ocr_update_book',
      [$page, $total, $object->id],
    ];
  }
  batch_set($batch);
  batch_process('islandora/object/' . $object->id);
}

/**
 * Handles individual requests from the batch.
 *
 * @param array $page
 *   A page from a book.
 * @param array $context
 *   The batch context.
 */
function _roblib_update_book_ocr_update_book($page, $total, $parent_pid, &$context) {
  if (!isset($context['results']['pages_processed'])) {
    $context['results']['pages_processed'] = 1;
    $context['results']['ocr'] = '';
  }

  $context['results']['pages_processed']++;

  if (!isset($context['sandbox']['total'])) {
    $context['sandbox']['total'] = $total;
  }
  if (!isset($context['sandbox']['parent'])){
    $context['results']['parent'] = $parent_pid;
  }

  $context['message'] = t('Retrieving OCR for page !p %pid', [
    '!p' => $context['results']['pages_processed'],
    '%pid' => $page,
  ]);
  try {
    // keep as string for now, ocr should be in kilobytes.
    $context['results']['ocr'] .= roblib_update_book_ocr_get_ocr($page);
  } catch (Exception $e) {
    //TODO something
    $context['message'] = t('Error retrieving OCR for page !p %pid', [
      '!p' => $context['results']['pages_processed'],
      '%pid' => $page,
    ]);
    watchdog('roblib_update_book_ocr', $e->getMessage(), NULL, WATCHDOG_ERROR, NULL);
  }

  if ( $context['results']['pages_processed'] != $context['sandbox']['total']) {
    $context['finished'] =  $context['results']['pages_processed'] / $context['sandbox']['total'];
  }


}

function roblib_update_book_ocr($parent_id, $ocr) {
  $dsid = 'OCR';
  $parent_object = islandora_object_load($parent_id);
  if (!isset($parent_object[$dsid])) {
    $datastream = $parent_object->constructDatastream($dsid);
    $datastream->label = $dsid;
    $datastream->mimeType = 'text/plain';
    $datastream->content = $ocr;

  }
  else {
    $datastream = $parent_object[$dsid];
    $datastream->content = $ocr;
  }

  if (!isset($parent_object[$dsid])) {
    $parent_object->ingestDatastream($datastream);
  }
  unset($parent_object);
}

/**
 * Prepare a page object for update.
 *
 * @param array $page
 *   A page from a book.
 *
 *
 * @throws \Exception
 */
function roblib_update_book_ocr_get_ocr($page) {
  $dsid = 'OCR';
  $page_object = islandora_object_load($page);
  if (!isset($page_object[$dsid])) {
    $ocr = '';
    watchdog('roblib_update_book_ocr', t('Object %page did not contain an OCR datastream', array('%page' => $page)), NULL, WATCHDOG_INFO, NULL);
  }
  else {
    $ocr = $page_object[$dsid]->content;
  }

  unset($page_object);
  return $ocr;
}


/**
 * @param array $success
 * @param array $results
 * @param array $operations
 *
 * @return array|mixed|string|null
 */
function roblib_update_book_ocr_batch_finished($success, $results, $operations) {
  roblib_update_book_ocr($results['parent'], $results['ocr']);
  $message = t('Finished Processing OCR for the page objects, processed %total pages', array(
    '%total' => $results['pages_processed'] - 1,
   ));
  drupal_set_message($message, 'info');
  return t('Finished Processing Pages.');

}