<?php

/**
 * @file
 * Module for deleting all links in a menu.
 */

/**
 * Implements hook_menu().
 */
function menu_delete_all_links_menu() {
  $items = array();

  $items['admin/structure/menu/manage/%menu/delete_all'] = array(
    'title' => 'Delete all links from a menu',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('menu_delete_all_links_form', 4),
    'access arguments' => array('administer menu'),
  );

  return $items;
}

/**
 * Form builder function for confirmation of deletion.
 */
function menu_delete_all_links_form($form, &$form_state, $menu) {
  $form['#menu'] = $menu;
  $question = t('Are you sure you want to permanently delete all links from menu %menu?', array('%menu' => check_plain($menu['title'])));
  $path = 'admin/structure/menu/manage/' . $menu['menu_name'];
  $description = t('This will permanently delete all links in this menu.');
  $yes = t('Remove');
  return confirm_form($form, $question, $path, $description, $yes);
}

/**
 * Confirmation form submit handler.
 */
function menu_delete_all_links_form_submit($form, &$form_state) {
  $menu = $form['#menu'];

  // The order by clause selects child items first, trying to prevent cascading
  // deletes during the batch process.
  $query = "
    SELECT mlid
    FROM {menu_links}
    WHERE menu_name = :menu_name
    ORDER BY
      p9 DESC,
      p8 DESC,
      p7 DESC,
      p6 DESC,
      p5 DESC,
      p4 DESC,
      p3 DESC,
      p2 DESC,
      p1 DESC
  ";

  $result = db_query($query, array(':menu_name' => $menu['menu_name']));

  $mlids = array();
  foreach ($result as $record) {
    $mlids[] = $record->mlid;
  }

  if (!count($mlids)) {
    drupal_set_message(t('No links to delete in menu @menu.', array('@menu' => check_plain($menu['title']))));
    drupal_goto('admin/structure/menu/manage/' . $menu['menu_name']);
  }

  $chunks = array_chunk($mlids, 10);

  $operations = array();
  foreach ($chunks as $chunk) {
    $operations[] = array('menu_delete_all_links_processor', array($chunk));
  }

  $batch = array(
    'operations' => $operations,
    'finished' => 'menu_delete_all_links_finished',
    'title' => 'Deleting all menu links in chunks of 10',
  );

  batch_set($batch);

  $form_state['redirect'] = 'admin/structure/menu/manage/' . $menu['menu_name'];
}

/**
 * The batch processor function.
 */
function menu_delete_all_links_processor($chunk, &$context) {
  foreach ($chunk as $mlid) {
    menu_link_delete($mlid);
  }
}

/**
 * Batch 'finished' callback.
 */
function menu_delete_all_links_finished($success, $results, $operations) {
  if ($success) {
    drupal_set_message(t('Deleted all links in menu.'));
  }
  else {
    // An error occurred. $operations contains the operations that remained
    // unprocessed.
    $error_operation = reset($operations);
    drupal_set_message(t('An error occurred while processing @operation with arguments : @args', array(
      '@operation' => $error_operation[0],
      '@args' => print_r($error_operation[0], TRUE),
    )));
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function menu_delete_all_links_form_menu_edit_menu_alter(&$form, &$form_state, $form_id) {
  if (arg(3) != 'add') {
    $form['actions']['delete_all'] = array(
      '#type' => 'submit',
      '#value' => 'Delete all links',
      '#weight' => 10,
      '#submit' => array('menu_delete_all_links_menu_edit_menu_submit'),
    );
  }
}

/**
 * Custom submit handler for vocabulary edit form.
 */
function menu_delete_all_links_menu_edit_menu_submit($form, &$form_state) {
  $form_state['redirect'] = 'admin/structure/menu/manage/' . $form_state['values']['menu_name'] . '/delete_all';
}