<?php

/**
 * Implements hook_views_api().
 */
function draggableviews_book_views_api() {
  return array(
    'api' => 3,
    'path' => drupal_get_path('module', 'draggableviews_book'),
  );
}

/**
 * Implements hook_ctools_plugin_directory().
 */
function draggableviews_book_ctools_plugin_directory($module, $plugin) {
  if (($module == 'draggableviews') && ($plugin == 'handler' || $plugin == 'hierarchy_handler')) {
    return 'handlers';
  }
}

/**
 * Implements hook_menu_alter().
 *
 * Set custom access callback to "Order Outline" view.
 */
function draggableviews_book_menu_alter(&$items) {
  $items['node/%/book']['access callback'] = '_draggableviews_book_access';
  $items['node/%/book']['access arguments'] = array(1);
}

/**
 * Check whether item has children.
 */
function _draggableviews_book_access($nid) {
  return db_query('SELECT has_children FROM {menu_links} WHERE module = :module AND link_path = :link_path', array(':module' => 'book', ':link_path' => 'node/' . $nid))->fetchField();
}

/**
 * Implements hook_views_post_execute().
 *
 * We manually sort results array according to the weights of depth levels.
 */
function draggableviews_book_views_post_execute($view) {
  if (!isset($view->result[0]->draggableviews_book_mlid)) {
    return;
  }

  // First prepare array of mlid keyed items.
  $keyed_result = array();
  foreach ($view->result as $result_item) {
    $result_item->weight = array();
    $keyed_result[$result_item->draggableviews_book_mlid] = $result_item;
  }

  // Set the weights arrays for every item. This collects weights of all parents
  // plus its own weight. Weights are saved according to depth levels.
  foreach ($keyed_result as &$item) {
    _draggableviews_book_result_set_weight($item, $keyed_result);
  }

  // Sort items with custom sort callback.
  usort($keyed_result, '_draggableviews_book_uasort');

  $view->result = $keyed_result;
}

/**
 * Set the weight array of item.
 */
function _draggableviews_book_result_set_weight(&$item, $result) {
  // If weight is already calculated we simply return it.
  if (!empty($item->weight)) {
    return $item->weight;
  }

  // Load weights array of parent (if parent item is available).
  $parent_weight = array();
  if (isset($result[$item->draggableviews_book_plid])) {
    $parent_weight = _draggableviews_book_result_set_weight($result[$item->draggableviews_book_plid], $result);
  }

  // Set the weight as sum of parents weights and
  // its own weight according to depth.
  $item->weight = $parent_weight + array($item->draggableviews_book_depth => $item->draggableviews_book_weight);

  return $item->weight;
}

/**
 * Custom sort callback based on weights arrays.
 */
function _draggableviews_book_uasort($item1, $item2) {
  for ($i = 0; $i < 10; $i++) {
    // Item 1 is less than item 2.
    if (isset($item1->weight[$i]) && !isset($item2->weight[$i])) {
      return 1;
    }

    // Item 2 is less than item 1.
    if (!isset($item1->weight[$i]) && isset($item2->weight[$i])) {
      return -1;
    }

    if (isset($item1->weight[$i]) && isset($item2->weight[$i])) {
      if ($item1->weight[$i] != $item2->weight[$i]) {
        return ($item1->weight[$i] < $item2->weight[$i]) ? -1 : 1;
      }
      elseif (isset($item1->weight[$i+1]) || isset($item2->weight[$i+1])) {
        // Loop again as there are more weights at a greater depth to compare.
        continue;
      }
      else {
        // By elimination, we know the weight and depth are the same.  Sort by title.
        return strcmp($item1->node_title, $item2->node_title);

      }
    }
  }
}