drupal/modules/book.module

<?php
// $Id$

/**
 * @file
 * Allows users to collaboratively author a book.
 */

/**
 * Implementation of hook_node_name().
 */
function book_node_name($node) {
  return t('book page');
}

/**
 * Implementation of hook_perm().
 */
function book_perm() {
  return array('create book pages', 'maintain books', 'edit own book pages');
}

/**
 * Implementation of hook_access().
 */
function book_access($op, $node) {
  global $user;

  if ($op == 'create') {
    // Only registered users can create book pages.  Given the nature
    // of the book module this is considered to be a good/safe idea.
    return user_access('create book pages');
  }

  if ($op == 'update') {
    // Only registered users can update book pages.  Given the nature
    // of the book module this is considered to be a good/safe idea.
    // One can only update a book page if there are no suggested updates
    // of that page waiting for approval.  That is, only updates that
    // don't overwrite the current or pending information are allowed.

    if ((user_access('maintain books') && !$node->moderate) || ($node->uid == $user->uid && user_access('edit own book pages'))) {
      return TRUE;
    }
    else {
       // do nothing. node-access() will determine further access
    }
  }
}

/**
 * Implementation of hook_link().
 */
function book_link($type, $node = 0, $main = 0) {

  $links = array();

  if ($type == 'node' && isset($node->parent)) {
    if (!$main) {
      if (book_access('create', $node)) {
        $links[] = l(t('add child page'), "node/add/book/parent/$node->nid");
      }
      $links[] = l(t('printer-friendly version'), 'book/print/'. $node->nid, array('title' => t('Show a printer-friendly version of this book page and its sub-pages.')));
    }
  }

  return $links;
}

/**
 * Implementation of hook_menu().
 */
function book_menu($may_cache) {
  $items = array();

  if ($may_cache) {
    $items[] = array('path' => 'book', 'title' => t('books'),
      'access' => user_access('access content'), 'type' => MENU_NORMAL_ITEM, 'weight' => 5);
    $items[] = array('path' => 'node/add/book', 'title' => t('book page'),
      'access' => user_access('create book pages'));
    $items[] = array('path' => 'admin/node/book', 'title' => t('books'),
      'callback' => 'book_admin',
      'access' => user_access('administer nodes'),
      'weight' => 4);
    $items[] = array('path' => 'admin/node/book/orphan', 'title' => t('orphan pages'),
      'callback' => 'book_admin_orphan',
      'access' => user_access('administer nodes'),
      'weight' => 8);
    $items[] = array('path' => 'book', 'title' => t('books'),
      'callback' => 'book_render',
      'access' => user_access('access content'),
      'type' => MENU_SUGGESTED_ITEM);
    $items[] = array('path' => 'book/print', 'title' => t('printer-friendly version'),
      'callback' => 'book_print',
      'access' => user_access('access content'),
      'type' => MENU_CALLBACK);
  }
  else {
    // To avoid SQL overhead, check whether we are on a node page and whether the
    // user is allowed to maintain books.
    if (arg(0) == 'node' && is_numeric(arg(1)) && user_access('maintain books')) {
      // Only add the outline-tab for non-book pages:
      $result = db_query(db_rewrite_sql("SELECT n.nid FROM {node} n WHERE n.nid = %d AND n.type != 'book'"), arg(1));
      if (db_num_rows($result) > 0) {
        $items[] = array('path' => 'node/'. arg(1) .'/outline', 'title' => t('outline'),
          'callback' => 'book_outline', 'access' => user_access('maintain books'),
          'type' => MENU_LOCAL_TASK, 'weight' => 2);
      }
    }
  }

  return $items;
}

/**
 * Implementation of hook_block().
 *
 * Displays the book table of contents in a block when the current page is a
 * single-node view of a book node.
 */
function book_block($op = 'list', $delta = 0) {
  $block = array();
  if ($op == 'list') {
    $block[0]['info'] = t('Book navigation');
    return $block;
  }
  else if ($op == 'view') {
    // Only display this block when the user is browsing a book:
    if (arg(0) == 'node' && is_numeric(arg(1))) {
      $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, b.parent FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.nid = %d'), arg(1));
      if (db_num_rows($result) > 0) {
        $node = db_fetch_object($result);

        $path = book_location($node);
        $path[] = $node;

        $expand = array();
        foreach ($path as $key => $node) {
          $expand[] = $node->nid;
        }

        $block['subject'] = check_plain($path[0]->title);
        $block['content'] = book_tree($expand[0], 5, $expand);
      }
    }

    return $block;
  }
}

/**
 * Implementation of hook_load().
 */
function book_load($node) {
  global $user;

  $book = db_fetch_object(db_query('SELECT parent, weight, log FROM {book} WHERE nid = %d', $node->nid));

  if (arg(2) == 'edit' && !user_access('administer nodes')) {
    // If a user is about to update a book page, we overload some
    // fields to reflect the changes.
    if ($user->uid) {
      $book->uid = $user->uid;
      $book->name = $user->name;
    }
    else {
      $book->uid = 0;
      $book->name = '';
    }
  }

  return $book;
}

/**
 * Implementation of hook_insert().
 */
function book_insert($node) {
  db_query("INSERT INTO {book} (nid, parent, weight, log) VALUES (%d, %d, %d, '%s')", $node->nid, $node->parent, $node->weight, $node->log);
}

/**
 * Implementation of hook_update().
 */
function book_update($node) {
  db_query("UPDATE {book} SET parent = %d, weight = %d, log = '%s' WHERE nid = %d", $node->parent, $node->weight, $node->log, $node->nid);
}

/**
 * Implementation of hook_delete().
 */
function book_delete(&$node) {
  db_query('DELETE FROM {book} WHERE nid = %d', $node->nid);
}

/**
 * Implementation of hook_validate().
 */
function book_validate(&$node) {
  // Set default values for non-administrators.
  if (!user_access('administer nodes')) {
    $node->weight = 0;
    $node->revision = 1;
  }
}

/**
 * Implementation of hook_form().
 */
function book_form(&$node) {
  global $user;

  $op = $_POST['op'];

  $output = form_select(t('Parent'), 'parent', ($node->parent ? $node->parent : arg(4)), book_toc($node->nid), t('The parent that this page belongs in. Note that pages whose parent is &lt;top-level&gt; are regarded as independent, top-level books.'));

  if (function_exists('taxonomy_node_form')) {
    $output .= implode('', taxonomy_node_form('book', $node));
  }

  $output .= form_textarea(t('Body'), 'body', $node->body, 60, 20, '', NULL, TRUE);
  $output .= filter_form('format', $node->format);
  $output .= form_textarea(t('Log message'), 'log', $node->log, 60, 5, t('An explanation of the additions or updates being made to help other authors understand your motivations.'));

  if (user_access('administer nodes')) {
    $output .= form_weight(t('Weight'), 'weight', $node->weight, 15, t('Pages at a given level are ordered first by weight and then by title.'));
  }
  else {
    // If a regular user updates a book page, we create a new revision
    // authored by that user:
    $output .= form_hidden('revision', 1);
  }

  return $output;
}

/**
 * Implementation of function book_outline()
 * Handles all book outline operations.
 */
function book_outline() {

  $op = $_POST['op'];
  $edit = $_POST['edit'];
  $node = node_load(array('nid' => arg(1)));

  if ($node->nid) {
    switch ($op) {
      case t('Add to book outline'):
        db_query('INSERT INTO {book} (nid, parent, weight) VALUES (%d, %d, %d)', $node->nid, $edit['parent'], $edit['weight']);
        drupal_set_message(t('The post has been added to the book.'));
        drupal_goto("node/$node->nid");
        break;

      case t('Update book outline'):
        db_query('UPDATE {book} SET parent = %d, weight = %d WHERE nid = %d', $edit['parent'], $edit['weight'], $node->nid);
        drupal_set_message(t('The book outline has been updated.'));
        drupal_goto("node/$node->nid");
        break;

      case t('Remove from book outline'):
        db_query('DELETE FROM {book} WHERE nid = %d', $node->nid);
        drupal_set_message(t('The post has been removed from the book.'));
        drupal_goto("node/$node->nid");
        break;

      default:
        $page = db_fetch_object(db_query('SELECT * FROM {book} WHERE nid = %d', $node->nid));

        $output  = form_select(t('Parent'), 'parent', $page->parent, book_toc($node->nid), t('The parent page in the book.'));
        $output .= form_weight(t('Weight'), 'weight', $node->weight, 15, t('Pages at a given level are ordered first by weight and then by title.'));

        if ($page->nid) {
          $output .= form_submit(t('Update book outline'));
          $output .= form_submit(t('Remove from book outline'));
        }
        else {
          $output .= form_submit(t('Add to book outline'));
        }

        drupal_set_title(check_plain($node->title));
        return form($output);
    }
  }
}


/**
 * Return the the most recent revision that matches the specified conditions.
 */
function book_revision_load($page, $conditions = array()) {

  $revisions = array_reverse(node_revision_list($page));

  foreach ($revisions as $revision) {

    // Extract the specified revision:
    $node = node_revision_load($page, $revision);

    // Check to see if the conditions are met:
    $status = TRUE;

    foreach ($conditions as $key => $value) {
      if ($node->$key != $value) {
        $status = FALSE;
      }
    }

    if ($status) {
      return $node;
    }
  }
}

/**
 * Return the path (call stack) to a certain book page.
 */
function book_location($node, $nodes = array()) {
  $parent = db_fetch_object(db_query(db_rewrite_sql('SELECT n.nid, n.title, b.parent, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.nid = %d'), $node->parent));
  if ($parent->title) {
    $nodes = book_location($parent, $nodes);
    array_push($nodes, $parent);
  }
  return $nodes;
}

function book_location_down($node, $nodes = array()) {
  $last_direct_child = db_fetch_object(db_query(db_rewrite_sql('SELECT n.nid, n.title, b.parent, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = %d ORDER BY b.weight DESC, n.title DESC'), $node->nid));
  if ($last_direct_child) {
    array_push($nodes, $last_direct_child);
    $nodes = book_location_down($last_direct_child, $nodes);
  }
  return $nodes;
}

/**
 * Fetch the node object of the previous page of the book.
 */
function book_prev($node) {
  // If the parent is zero, we are at the start of a book so there is no previous.
  if ($node->parent == 0) {
    return NULL;
  }

  // Previous on the same level:
  $direct_above = db_fetch_object(db_query(db_rewrite_sql("SELECT n.nid, n.title FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = %d AND n.status = 1 AND n.moderate = 0 AND (b.weight < %d OR (b.weight = %d AND n.title < '%s')) ORDER BY b.weight DESC, n.title DESC"), $node->parent, $node->weight, $node->weight, $node->title));
  if ($direct_above) {
    // Get last leaf of $above.
    $path = book_location_down($direct_above);

    return $path ? (count($path) > 0 ? array_pop($path) : NULL) : $direct_above;
  }
  else {
    // Direct parent:
    $prev = db_fetch_object(db_query(db_rewrite_sql('SELECT n.nid, n.title FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.nid = %d AND n.status = 1 AND n.moderate = 0'), $node->parent));
    return $prev;
  }
}

/**
 * Fetch the node object of the next page of the book.
 */
function book_next($node) {
  // get first direct child
  $child = db_fetch_object(db_query(db_rewrite_sql('SELECT n.nid, n.title, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = %d AND n.status = 1 AND n.moderate = 0 ORDER BY b.weight ASC, n.title ASC'), $node->nid));
  if ($child) {
    return $child;
  }

  // No direct child: get next for this level or any parent in this book.
  array_push($path = book_location($node), $node); // Path to top-level node including this one.

  while (($leaf = array_pop($path)) && count($path)) {
    $next = db_fetch_object(db_query(db_rewrite_sql("SELECT n.nid, n.title, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = %d AND n.status = 1 AND n.moderate = 0 AND (b.weight > %d OR (b.weight = %d AND n.title > '%s')) ORDER BY b.weight ASC, n.title ASC"), $leaf->parent, $leaf->weight, $leaf->weight, $leaf->title));
    if ($next) {
      return $next;
    }
  }
}

function book_content($node, $teaser = FALSE) {
  $op = $_POST['op'];

  // Always display the most recently approved revision of a node
  // (if any) unless we have to display this page in the context of
  // the moderation queue.
  if ($op != t('Preview') && $node->moderate && arg(0) != 'queue') {
    $revision = book_revision_load($node, array('moderate' => 0, 'status' => 1));

    if ($revision) {
      $node = $revision;
    }
  }

  // Extract the page body.
  $node = node_prepare($node, $teaser);

  return $node;
}

/**
 * Implementation of hook_view().
 *
 * If not displayed on the main page, we render the node as a page in the
 * book with extra links to the previous and next pages.
 */
function book_view(&$node, $teaser = FALSE, $page = FALSE) {
  $node = book_content($node, $teaser);

  if (!$teaser && $node->moderate) {
    $node->body .= '<div class="log"><div class="title">'. t('Log') .':</div>'. $node->log .'</div>';
  }
}

/**
 * Implementation of hook_nodeapi().
 *
 * Appends book navigation to all nodes in the book.
 */
function book_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {
    case 'view':
      if (!$teaser) {
        $book = db_fetch_array(db_query('SELECT * FROM {book} WHERE nid = %d', $node->nid));
        if ($book) {
          if ($node->moderate && user_access('administer nodes')) {
            drupal_set_message(t("The post has been submitted for moderation and won't be accessible until it has been approved."));
          }

          foreach ($book as $key => $value) {
            $node->$key = $value;
          }
          $node = theme('book_navigation', $node);
          if ($page) {
            menu_set_location($node->breadcrumb);
          }
        }
      }
      break;
  }
}

/**
 * Prepares both the custom breadcrumb trail and the forward/backward
 * navigation for a node presented as a book page.
 *
 * @ingroup themeable
 */
function theme_book_navigation($node) {
  $path = book_location($node);

  // Construct the breadcrumb:

  $node->breadcrumb = array(); // Overwrite the trail with a book trail.
  foreach ($path as $level) {
    $node->breadcrumb[] = array('path' => 'node/'. $level->nid, 'title' =>  $level->title);
  }
  $node->breadcrumb[] = array('path' => 'node/'. $node->nid);

  if ($node->nid) {
    $output .= '<div class="book">';

    if ($tree = book_tree($node->nid)) {
      $output .= '<div class="tree">'. $tree .'</div>';
    }

    if ($prev = book_prev($node)) {
      $links .= '<div class="prev">';
      $links .= l(t('previous'), 'node/'. $prev->nid, array('title' => t('View the previous page.')));
      $links .= '</div>';
      $titles .= '<div class="prev">'. check_plain($prev->title) .'</div>';
    }
    else {
      $links .= '<div class="prev">&nbsp;</div>'; // Make an empty div to fill the space.
    }
    if ($next = book_next($node)) {
      $links .= '<div class="next">';
      $links .= l(t('next'), 'node/'. $next->nid, array('title' => t('View the next page.')));
      $links .= '</div>';
      $titles .= '<div class="next">'. check_plain($next->title) .'</div>';
    }
    else {
      $links .= '<div class="next">&nbsp;</div>'; // Make an empty div to fill the space.
    }
    if ($node->parent) {
      $links .= '<div class="up">';
      $links .= l(t('up'), 'node/'. $node->parent, array('title' => t('View this page\'s parent section.')));
      $links .= '</div>';
    }

    $output .= '<div class="nav">';
    $output .= ' <div class="links">'. $links .'</div>';
    $output .= ' <div class="titles">'. $titles .'</div>';
    $output .= '</div>';
    $output .= '</div>';
  }

  $node->body = $node->body.$output;

  return $node;
}

function book_toc_recurse($nid, $indent, $toc, $children, $exclude) {
  if ($children[$nid]) {
    foreach ($children[$nid] as $foo => $node) {
      if (!$exclude || $exclude != $node->nid) {
        $toc[$node->nid] = $indent .' '. $node->title;
        $toc = book_toc_recurse($node->nid, $indent .'--', $toc, $children, $exclude);
      }
    }
  }

  return $toc;
}

function book_toc($exclude = 0) {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, b.parent, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.status = 1 ORDER BY b.weight, n.title'));

  while ($node = db_fetch_object($result)) {
    if (!$children[$node->parent]) {
      $children[$node->parent] = array();
    }
    array_push($children[$node->parent], $node);
  }

  $toc = array();

  // If the user is an administrator, add the top-level book page;
  // only administrators can start new books.
  if (user_access('administer nodes')) {
    $toc[0] = '<'. t('top-level') .'>';
  }

  $toc = book_toc_recurse(0, '', $toc, $children, $exclude);

  return $toc;
}

function book_tree_recurse($nid, $depth, $children, $unfold = array()) {
  if ($depth > 0) {
    if ($children[$nid]) {
      foreach ($children[$nid] as $foo => $node) {
        if (in_array($node->nid, $unfold)) {
          if ($tree = book_tree_recurse($node->nid, $depth - 1, $children, $unfold)) {
            $output .= '<li class="expanded">';
            $output .= l($node->title, 'node/'. $node->nid);
            $output .= '<ul>'. $tree .'</ul>';
            $output .= '</li>';
          }
          else {
            $output .= '<li class="leaf">'. l($node->title, 'node/'. $node->nid) .'</li>';
          }
        }
        else {
          if ($tree = book_tree_recurse($node->nid, 1, $children)) {
            $output .= '<li class="collapsed">'. l($node->title, 'node/'. $node->nid) .'</li>';
          }
          else {
            $output .= '<li class="leaf">'. l($node->title, 'node/'. $node->nid) .'</li>';
          }
        }
      }
    }
  }

  return $output;
}

function book_tree($parent = 0, $depth = 3, $unfold = array()) {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, b.parent, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.status = 1 AND n.moderate = 0 ORDER BY b.weight, n.title'));

  while ($node = db_fetch_object($result)) {
    $list = $children[$node->parent] ? $children[$node->parent] : array();
    array_push($list, $node);
    $children[$node->parent] = $list;
  }

  if ($tree = book_tree_recurse($parent, $depth, $children, $unfold)) {
    return '<div class="menu"><ul>'. $tree .'</ul></div>';
  }
}

/**
 * Menu callback; prints a listing of all books.
 */
function book_render() {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = 0 AND n.status = 1 AND n.moderate = 0 ORDER BY b.weight, n.title'));

  return $output;
}

/**
 * Menu callback; generates printer-friendly book page with all descendants.
 */
function book_print($nid = 0, $depth = 1) {
  global $base_url;
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.status = 1 AND n.nid = %d AND n.moderate = 0 ORDER BY b.weight, n.title'), $nid);

  while ($page = db_fetch_object($result)) {
    // load the node:
    $node = node_load(array('nid' => $page->nid));

    if ($node) {
      // output the content:
      if (node_hook($node, 'content')) {
        $node = node_invoke($node, 'content');
      }
      // Allow modules to change $node->body before viewing.
      node_invoke_nodeapi($node, 'view', $node->body, false);

      $output .= '<h1 id="'. $node->nid .'" name="'. $node->nid .'" class="book-h'. $depth .'">'. check_plain($node->title) .'</h1>';

      if ($node->body) {
        $output .= $node->body;
      }
    }
  }

  $output .= book_print_recurse($nid, $depth);

  $html = '<html><head><title>'. check_plain($node->title) .'</title>';
  $html .= '<base href="'. $base_url .'/" />';
  $html .= "<style type=\"text/css\">\n@import url(misc/print.css);\n</style>";
  $html .= '</head><body>'. $output .'</body></html>';

  print $html;
}

function book_print_recurse($parent = '', $depth = 1) {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, b.weight FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE n.status = 1 AND b.parent = %d AND n.moderate = 0 ORDER BY b.weight, n.title'), $parent);

  while ($page = db_fetch_object($result)) {
    // Load the node:
    $node = node_load(array('nid' => $page->nid));

    // Take the most recent approved revision:
    if ($node->moderate) {
      $node = book_revision_load($node, array('moderate' => 0, 'status' => 1));
    }

    if ($node) {
      // Output the content:
      if (node_hook($node, 'content')) {
        $node = node_invoke($node, 'content');
      }
      // Allow modules to change $node->body before viewing.
      node_invoke_nodeapi($node, 'view', $node->body, false);

      $output .= '<h1 id="'. $node->nid .'" name="'. $node->nid .'" class="book-h'. $depth .'">'. check_plain($node->title) .'</h1>';

      if ($node->body) {
        $output .= '<ul>'. $node->body .'</ul>';
      }

      $output .= book_print_recurse($node->nid, $depth + 1);
    }
  }

  return $output;
}

function book_admin_edit_line($node, $depth = 0) {
  return array('<div style="padding-left: '. (25 * $depth) .'px;">'. form_textfield(NULL, $node->nid .'][title', $node->title, 64, 255) .'</div>', form_weight(NULL, $node->nid .'][weight', $node->weight, 15), l(t('view'), 'node/'. $node->nid), l(t('edit'), 'node/'. $node->nid .'/edit'), l(t('delete'), 'node/'.$node->nid.'/delete'));
}

function book_admin_edit_book($nid, $depth = 1) {
  $result = db_query(db_rewrite_sql('SELECT n.nid FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = %d ORDER BY b.weight, n.title'), $nid);

  while ($node = db_fetch_object($result)) {
    $node = node_load(array('nid' => $node->nid));
    $rows[] = book_admin_edit_line($node, $depth);
    $rows = array_merge($rows, book_admin_edit_book($node->nid, $depth + 1));
  }

  return $rows;
}

/**
 * Display an administrative view of the hierarchy of a book.
 */
function book_admin_edit($nid, $depth = 0) {
  $node = node_load(array('nid' => $nid));
  if ($node->nid) {
    $header = array(t('Title'), t('Weight'), array('data' => t('Operations'), 'colspan' => '3'));
    $rows[] = book_admin_edit_line($node);
    $rows = array_merge($rows, book_admin_edit_book($nid));

    $output .= theme('table', $header, $rows);
    $output .= form_submit(t('Save book pages'));

    drupal_set_title(check_plain($node->title));
    return form($output);
  }
  else {
    drupal_not_found();
  }
}

function book_admin_save($nid, $edit = array()) {
  if ($nid) {
    $book = node_load(array('nid' => $nid));

    foreach ($edit as $nid => $value) {
      // Check to see whether the title needs updating:
      $title = db_result(db_query('SELECT title FROM {node} WHERE nid = %d', $nid));
      if ($title != $value['title']) {
        db_query("UPDATE {node} SET title = '%s' WHERE nid = %d", $value['title'], $nid);
      }

      // Check to see whether the weight needs updating:
      $weight = db_result(db_query('SELECT weight FROM {book} WHERE nid = %d', $nid));
      if ($weight != $value['weight']) {
        db_query('UPDATE {book} SET weight = %d WHERE nid = %d', $value['weight'], $nid);
      }
    }

    $message = t('The book %title has been updated.', array('%title' => theme('placeholder', $book->title)));
    watchdog('content', $message);

    return $message;
  }
}

/**
 * Menu callback; displays a listing of all orphaned book pages.
 */
function book_admin_orphan() {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title, n.status, b.parent FROM {node} n INNER JOIN {book} b ON n.nid = b.nid'));

  while ($page = db_fetch_object($result)) {
    $pages[$page->nid] = $page;
  }

  if ($pages) {
    $output .= '<h3>'. t('Orphan pages') .'</h3>';
    $header = array(t('Title'), t('Weight'), array('data' => t('Operations'), 'colspan' => '3'));
    foreach ($pages as $nid => $node) {
      if ($node->parent && empty($pages[$node->parent])) {
        $rows[] = book_admin_edit_line($node, $depth);
        $rows = array_merge($rows, book_admin_edit_book($node->nid, $depth + 1));
      }
    }
    $output .= theme('table', $header, $rows);
  }

  return $output;
}

/**
 * Menu callback; displays the book administration page.
 */
function book_admin($nid = 0) {
  $op = $_POST['op'];
  $edit = $_POST['edit'];

  if ($op == t('Save book pages')) {
    drupal_set_message(book_admin_save($nid, $edit));
  }

  if ($nid) {
    return book_admin_edit($nid);
  }
  else {
    return book_admin_overview();
  }
}

function book_admin_overview() {
  $result = db_query(db_rewrite_sql('SELECT n.nid, n.title FROM {node} n INNER JOIN {book} b ON n.nid = b.nid WHERE b.parent = 0 ORDER BY b.weight, n.title'));
  while ($book = db_fetch_object($result)) {
    $rows[] = array(l($book->title, "node/$book->nid"), l(t('outline'), "admin/node/book/$book->nid"));
  }
  $headers = array(t('Book'), t('Operations'));

  return theme('table', $headers, $rows);
}

/**
 * Implementation of hook_help().
 */
function book_help($section) {
  switch ($section) {
    case 'admin/help#book':
      return t("
      <p>The book organises content into a nested hierarchical structure. It is particularly good for manuals, Frequently Asked Questions (FAQs) and the like, allowing you to have chapters, sections, etc.</p>
      <p>A book is simply a collection of nodes that have been linked together. These nodes are usually of type <em>book page</em>, but you can insert nodes of any type into a book outline. Every node in the book has a <em>parent</em> node which  \"contains\" it. This is how book.module establishes its hierarchy. At any given level in the hierarchy, a book can contain many nodes. All these sibling nodes are sorted according to the <em>weight</em> that you give them.</p>
      <p>Book pages contain a <em>log message</em> field which helps your users understand the motivation behind an edit of a book page. Each edited version of a book page is stored as a new revision of a node. This capability makes it easy to revert to an old version of a page, should that be desirable.</p>
      <p>Like other node types, book submissions and edits may be subject to moderation, depending on your configuration.  Similarly, books use <a href=\"%permissions\">permissions</a> to determine who may read and write to them. Only administrators are allowed to create new books, which are really just nodes whose parent is <em>&lt;top-level&gt;</em>.  To include an existing node in your book, click on the \"outline\"-tab on the node's page.  This enables you to place the node wherever you'd like within the book hierarchy. To add a new node into your book, use the <a href=\"%create\">create content &raquo; book page</a> link.</p>
      <p>Administrators may review the hierarchy of their books by clicking on the <a href=\"%collaborative-book\">collaborative book</a> link in the administration pages. There, nodes may be edited, reorganized, removed from book, and deleted. This behavior may change in the future. When a parent node is deleted, it may leave behind child nodes.  These nodes are now <em>orphans</em>. Administrators should periodically <a href=\"%orphans-book\">review their books for orphans</a> and reaffiliate those pages as desired. Finally, administrators may also <a href=\"%export-book\">export their books</a> to a single, flat HTML page which is suitable for printing.</p>
      <h3>Maintaining a FAQ using a collaborative book</h3>
      <p>Collaborative books let you easily set up a Frequently Asked Questions (FAQ) section on your web site. The main benefit is that you don't have to write all the questions/answers by yourself - let the community do it for you!</p>
      <p>In order to set up the FAQ, you have to create a new book which will hold all your content. To do so, click on the <a href=\"%create\">create content &raquo; book page</a> link. Give it a thoughtful title, and body. A title like \"Estonia Travel - FAQ\" is nice. You may always edit these fields later. You will probably want to designate <em>&lt;top-level&gt;</em> as the parent of this page. Leave the <em>log message</em> and <em>type</em> fields blank for now. After you have submitted this book page, you are ready to begin filling up your book with questions that are frequently asked.</p>
      <p>Whenever you come across a post which you want to include in your FAQ, click on the <em>administer</em> link. Then click on the <em>edit book outline</em> button at the bottom of the page. Then place the relevant post wherever is most appropriate in your book by selecting a <em>parent</em>. Books are quite flexible. They can have sections like <em>Flying to Estonia</em>, <em>Eating in Estonia</em> and so on. As you get more experienced with the book module, you can reorganize posts in your book so that it stays organized.</p>
      <p>Notes:</p><ul><li>Any comments attached to those relevant posts which you designate as book pages will also be transported into your book. This is a great feature, since much wisdom is shared via comments. Remember that all future comments and edits will automatically be reflected in your book.</li><li>You may wish to edit the title of posts when adding them to your FAQ. This is done on the same page as the <em>Edit book outline</em> button. Clear titles improve navigability enormously.</li><li>Book pages may come from any content type (blog, story, page, etc.). If you are creating a post solely for inclusion in your book, then use the <a href=\"%create\">create content &raquo; book page</a> link.</li><li>If you don't see the <em>administer</em> link, then you probably have insufficient <a href=\"%permissions\">permissions</a>.</li></ul>", array('%permissions' => url('admin/access/permissions'), "%create" => url('node/add/book'), '%collaborative-book' => url('admin/node/book'), '%orphans-book' => url('admin/node/book/orphan'), '%export-book' => url('book/print')));
    case 'admin/modules#description':
      return t('Allows users to collaboratively author a book.');
    case 'admin/node/book':
      return t('<p>The book module offers a mean to organize content, authored by many users, in an online manual, outline or FAQ.</p>');
    case 'admin/node/book/orphan':
      return t('<p>Pages in a book are like a tree. As pages are edited, reorganized and removed, child pages might be left with no link to the rest of the book.  Such pages are referred to as "orphan pages".  On this page, administrators can review their books for orphans and reattach those pages as desired.</p>');
    case 'node/add#book':
      return t("A book is a collaborative writing effort: users can collaborate writing the pages of the book, positioning the pages in the right order, and reviewing or modifying pages previously written.  So when you have some information to share or when you read a page of the book and you didn't like it, or if you think a certain page could have been written better, you can do something about it.");
  }

  if (arg(0) == 'node' && is_numeric(arg(1)) && arg(2) == 'outline') {
    return t('The outline feature allows you to include posts in the <a href="%book">book hierarchy</a>.', array('%book' => url('book')));
  }
}

?>