comment.module

<?php

/**
 * @file
 * Enables users to comment on published content.
 *
 * When enabled, the Drupal comment module creates a discussion
 * board for each Drupal node. Users can post comments to discuss
 * a forum topic, weblog post, story, collaborative book page, etc.
 */

/**
 * Comment is awaiting approval.
 */
define('COMMENT_NOT_PUBLISHED', 0);

/**
 * Comment is published.
 */
define('COMMENT_PUBLISHED', 1);

/**
 * Comments are displayed in a flat list - expanded.
 */
define('COMMENT_MODE_FLAT', 0);

/**
 * Comments are displayed as a threaded list - expanded.
 */
define('COMMENT_MODE_THREADED', 1);

/**
 * Anonymous posters cannot enter their contact information.
 */
define('COMMENT_ANONYMOUS_MAYNOT_CONTACT', 0);

/**
 * Anonymous posters may leave their contact information.
 */
define('COMMENT_ANONYMOUS_MAY_CONTACT', 1);

/**
 * Anonymous posters are required to leave their contact information.
 */
define('COMMENT_ANONYMOUS_MUST_CONTACT', 2);

/**
 * Comment form should be displayed on a separate page.
 */
define('COMMENT_FORM_SEPARATE_PAGE', 0);

/**
 * Comment form should be shown below post or list of comments.
 */
define('COMMENT_FORM_BELOW', 1);

/**
 * Comments for this node are hidden.
 */
define('COMMENT_NODE_HIDDEN', 0);

/**
 * Comments for this node are closed.
 */
define('COMMENT_NODE_CLOSED', 1);

/**
 * Comments for this node are open.
 */
define('COMMENT_NODE_OPEN', 2);

/**
 * Implements hook_help().
 */
function comment_help($path, $arg) {
  switch ($path) {
    case 'admin/help#comment':
      $output = '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Comment module allows users to comment on site content, set commenting defaults and permissions, and moderate comments. For more information, see the online handbook entry for <a href="@comment">Comment module</a>.', array('@comment' => 'http://drupal.org/documentation/modules/comment/')) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Default and custom settings') . '</dt>';
      $output .= '<dd>' . t("Each <a href='@content-type'>content type</a> can have its own default comment settings configured as: <em>Open</em> to allow new comments, <em>Hidden</em> to hide existing comments and prevent new comments, or <em>Closed</em> to view existing comments, but prevent new comments. These defaults will apply to all new content created (changes to the settings on existing content must be done manually). Other comment settings can also be customized per content type, and can be overridden for any given item of content. When a comment has no replies, it remains editable by its author, as long as the author has a user account and is logged in.", array('@content-type' => url('admin/structure/types'))) . '</dd>';
      $output .= '<dt>' . t('Comment approval') . '</dt>';
      $output .= '<dd>' . t("Comments from users who have the <em>Skip comment approval</em> permission are published immediately. All other comments are placed in the <a href='@comment-approval'>Unapproved comments</a> queue, until a user who has permission to <em>Administer comments</em> publishes or deletes them. Published comments can be bulk managed on the <a href='@admin-comment'>Published comments</a> administration page.", array('@comment-approval' => url('admin/content/comment/approval'), '@admin-comment' => url('admin/content/comment'))) . '</dd>';
      $output .= '</dl>';
      return $output;
  }
}

/**
 * Implements hook_entity_info().
 */
function comment_entity_info() {
  $return = array(
    'comment' => array(
      'label' => t('Comment'),
      'base table' => 'comment',
      'uri callback' => 'comment_uri',
      'fieldable' => TRUE,
      'controller class' => 'CommentController',
      'entity keys' => array(
        'id' => 'cid',
        'bundle' => 'node_type',
        'label' => 'subject',
        'language' => 'language',
      ),
      'bundles' => array(),
      'view modes' => array(
        'full' => array(
          'label' => t('Full comment'),
          'custom settings' => FALSE,
        ),
      ),
      'static cache' => FALSE,
    ),
  );

  foreach (node_type_get_names() as $type => $name) {
    $return['comment']['bundles']['comment_node_' . $type] = array(
      'label' => t('@node_type comment', array('@node_type' => $name)),
      // Provide the node type/bundle name for other modules, so it does not
      // have to be extracted manually from the bundle name.
      'node bundle' => $type,
      'admin' => array(
        // Place the Field UI paths for comments one level below the
        // corresponding paths for nodes, so that they appear in the same set
        // of local tasks. Note that the paths use a different placeholder name
        // and thus a different menu loader callback, so that Field UI page
        // callbacks get a comment bundle name from the node type in the URL.
        // See comment_node_type_load() and comment_menu_alter().
        'path' => 'admin/structure/types/manage/%comment_node_type/comment',
        'bundle argument' => 4,
        'real path' => 'admin/structure/types/manage/' . str_replace('_', '-', $type) . '/comment',
        'access arguments' => array('administer content types'),
      ),
    );
  }

  return $return;
}

/**
 * Menu loader callback for Field UI paths.
 *
 * Return a comment bundle name from a node type in the URL.
 */
function comment_node_type_load($name) {
  if ($type = node_type_get_type(strtr($name, array('-' => '_')))) {
    return 'comment_node_' . $type->type;
  }
}

/**
 * Entity URI callback.
 */
function comment_uri($comment) {
  return array(
    'path' => 'comment/' . $comment->cid,
    'options' => array('fragment' => 'comment-' . $comment->cid),
  );
}

/**
 * Implements hook_field_extra_fields().
 */
function comment_field_extra_fields() {
  $return = array();

  foreach (node_type_get_types() as $type) {
    if (variable_get('comment_subject_field_' . $type->type, 1) == 1) {
      $return['comment']['comment_node_' . $type->type] = array(
        'form' => array(
          'author' => array(
            'label' => t('Author'),
            'description' => t('Author textfield'),
            'weight' => -2,
          ),
          'subject' => array(
            'label' => t('Subject'),
            'description' => t('Subject textfield'),
            'weight' => -1,
          ),
        ),
      );
    }
  }

  return $return;
}

/**
 * Implements hook_theme().
 */
function comment_theme() {
  return array(
    'comment_block' => array(
      'variables' => array(),
    ),
    'comment_preview' => array(
      'variables' => array('comment' => NULL),
    ),
    'comment' => array(
      'template' => 'comment',
      'render element' => 'elements',
    ),
    'comment_post_forbidden' => array(
      'variables' => array('node' => NULL),
    ),
    'comment_wrapper' => array(
      'template' => 'comment-wrapper',
      'render element' => 'content',
    ),
  );
}

/**
 * Implements hook_menu().
 */
function comment_menu() {
  $items['admin/content/comment'] = array(
    'title' => 'Comments',
    'description' => 'List and edit site comments and the comment approval queue.',
    'page callback' => 'comment_admin',
    'access arguments' => array('administer comments'),
    'type' => MENU_LOCAL_TASK | MENU_NORMAL_ITEM,
    'file' => 'comment.admin.inc',
  );
  // Tabs begin here.
  $items['admin/content/comment/new'] = array(
    'title' => 'Published comments',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  );
  $items['admin/content/comment/approval'] = array(
    'title' => 'Unapproved comments',
    'title callback' => 'comment_count_unpublished',
    'page arguments' => array('approval'),
    'access arguments' => array('administer comments'),
    'type' => MENU_LOCAL_TASK,
  );
  $items['comment/%'] = array(
    'title' => 'Comment permalink',
    'page callback' => 'comment_permalink',
    'page arguments' => array(1),
    'access arguments' => array('access comments'),
  );
  $items['comment/%/view'] = array(
    'title' => 'View comment',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  );
  // Every other comment path uses %, but this one loads the comment directly,
  // so we don't end up loading it twice (in the page and access callback).
  $items['comment/%comment/edit'] = array(
    'title' => 'Edit',
    'page callback' => 'comment_edit_page',
    'page arguments' => array(1),
    'access callback' => 'comment_access',
    'access arguments' => array('edit', 1),
    'type' => MENU_LOCAL_TASK,
    'weight' => 0,
  );
  $items['comment/%/approve'] = array(
    'title' => 'Approve',
    'page callback' => 'comment_approve',
    'page arguments' => array(1),
    'access arguments' => array('administer comments'),
    'file' => 'comment.pages.inc',
    'weight' => 1,
  );
  $items['comment/%/delete'] = array(
    'title' => 'Delete',
    'page callback' => 'comment_confirm_delete_page',
    'page arguments' => array(1),
    'access arguments' => array('administer comments'),
    'type' => MENU_LOCAL_TASK,
    'file' => 'comment.admin.inc',
    'weight' => 2,
  );
  $items['comment/reply/%node'] = array(
    'title' => 'Add new comment',
    'page callback' => 'comment_reply',
    'page arguments' => array(2),
    'access callback' => 'node_access',
    'access arguments' => array('view', 2),
    'file' => 'comment.pages.inc',
  );

  return $items;
}

/**
 * Implements hook_menu_alter().
 */
function comment_menu_alter(&$items) {
  // Add comments to the description for admin/content.
  $items['admin/content']['description'] = 'Administer content and comments.';

  // Adjust the Field UI tabs on admin/structure/types/manage/[node-type].
  // See comment_entity_info().
  $items['admin/structure/types/manage/%comment_node_type/comment/fields']['title'] = 'Comment fields';
  $items['admin/structure/types/manage/%comment_node_type/comment/fields']['weight'] = 3;
  $items['admin/structure/types/manage/%comment_node_type/comment/display']['title'] = 'Comment display';
  $items['admin/structure/types/manage/%comment_node_type/comment/display']['weight'] = 4;
}

/**
 * Returns a menu title which includes the number of unapproved comments.
 */
function comment_count_unpublished() {
  $count = db_query('SELECT COUNT(cid) FROM {comment} WHERE status = :status', array(
    ':status' => COMMENT_NOT_PUBLISHED,
  ))->fetchField();
  return t('Unapproved comments (@count)', array('@count' => $count));
}

/**
 * Implements hook_node_type_insert().
 *
 * Creates a comment body field for a node type created while the comment module
 * is enabled. For node types created before the comment module is enabled,
 * hook_modules_enabled() serves to create the body fields.
 *
 * @see comment_modules_enabled()
 */
function comment_node_type_insert($info) {
  _comment_body_field_create($info);
}

/**
 * Implements hook_node_type_update().
 */
function comment_node_type_update($info) {
  if (!empty($info->old_type) && $info->type != $info->old_type) {
    field_attach_rename_bundle('comment', 'comment_node_' . $info->old_type, 'comment_node_' . $info->type);
  }
}

/**
 * Implements hook_node_type_delete().
 */
function comment_node_type_delete($info) {
  field_attach_delete_bundle('comment', 'comment_node_' . $info->type);
  $settings = array(
    'comment',
    'comment_default_mode',
    'comment_default_per_page',
    'comment_anonymous',
    'comment_subject_field',
    'comment_preview',
    'comment_form_location',
  );
  foreach ($settings as $setting) {
    variable_del($setting . '_' . $info->type);
  }
}

 /**
 * Creates a comment_body field instance for a given node type.
 */
function _comment_body_field_create($info) {
  // Create the field if needed.
  if (!field_read_field('comment_body', array('include_inactive' => TRUE))) {
    $field = array(
      'field_name' => 'comment_body',
      'type' => 'text_long',
      'entity_types' => array('comment'),
    );
    field_create_field($field);
  }
  // Create the instance if needed.
  if (!field_read_instance('comment', 'comment_body', 'comment_node_' . $info->type, array('include_inactive' => TRUE))) {
    field_attach_create_bundle('comment', 'comment_node_' . $info->type);
    // Attaches the body field by default.
    $instance = array(
      'field_name' => 'comment_body',
      'label' => 'Comment',
      'entity_type' => 'comment',
      'bundle' => 'comment_node_' . $info->type,
      'settings' => array('text_processing' => 1),
      'required' => TRUE,
      'display' => array(
        'default' => array(
          'label' => 'hidden',
          'type' => 'text_default',
          'weight' => 0,
        ),
      ),
    );
    field_create_instance($instance);
  }
}

/**
 * Implements hook_permission().
 */
function comment_permission() {
  return array(
    'administer comments' => array(
      'title' => t('Administer comments and comment settings'),
    ),
    'access comments' => array(
      'title' => t('View comments'),
    ),
    'post comments' => array(
      'title' => t('Post comments'),
    ),
    'skip comment approval' => array(
      'title' => t('Skip comment approval'),
    ),
    'edit own comments' => array(
      'title' => t('Edit own comments'),
    ),
  );
}

/**
 * Implements hook_block_info().
 */
function comment_block_info() {
  $blocks['recent']['info'] = t('Recent comments');
  $blocks['recent']['properties']['administrative'] = TRUE;

  return $blocks;
}

/**
 * Implements hook_block_configure().
 */
function comment_block_configure($delta = '') {
  $form['comment_block_count'] = array(
    '#type' => 'select',
    '#title' => t('Number of recent comments'),
    '#default_value' => variable_get('comment_block_count', 10),
    '#options' => drupal_map_assoc(array(2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30)),
  );

  return $form;
}

/**
 * Implements hook_block_save().
 */
function comment_block_save($delta = '', $edit = array()) {
  variable_set('comment_block_count', (int) $edit['comment_block_count']);
}

/**
 * Implements hook_block_view().
 *
 * Generates a block with the most recent comments.
 */
function comment_block_view($delta = '') {
  if (user_access('access comments')) {
    $block['subject'] = t('Recent comments');
    $block['content'] = theme('comment_block');

    return $block;
  }
}

/**
 * Redirects comment links to the correct page depending on comment settings.
 *
 * Since comments are paged there is no way to guarantee which page a comment
 * appears on. Comment paging and threading settings may be changed at any time.
 * With threaded comments, an individual comment may move between pages as
 * comments can be added either before or after it in the overall discussion.
 * Therefore we use a central routing function for comment links, which
 * calculates the page number based on current comment settings and returns
 * the full comment view with the pager set dynamically.
 *
 * @param $cid
 *   A comment identifier.
 * @return
 *   The comment listing set to the page on which the comment appears.
 */
function comment_permalink($cid) {
  if (($comment = comment_load($cid)) && ($node = node_load($comment->nid))) {

    // Find the current display page for this comment.
    $page = comment_get_display_page($comment->cid, $node->type);

    // Set $_GET['q'] and $_GET['page'] ourselves so that the node callback
    // behaves as it would when visiting the page directly.
    $_GET['q'] = 'node/' . $node->nid;
    $_GET['page'] = $page;

    // Return the node view, this will show the correct comment in context.
    return menu_execute_active_handler('node/' . $node->nid, FALSE);
  }
  drupal_not_found();
}

/**
 * Find the most recent comments that are available to the current user.
 *
 * @param integer $number
 *   (optional) The maximum number of comments to find. Defaults to 10.
 *
 * @return
 *   An array of comment objects or an empty array if there are no recent
 *   comments visible to the current user.
 */
function comment_get_recent($number = 10) {
  $query = db_select('comment', 'c');
  $query->innerJoin('node', 'n', 'n.nid = c.nid');
  $query->addTag('node_access');
  $comments = $query
    ->fields('c')
    ->condition('c.status', COMMENT_PUBLISHED)
    ->condition('n.status', NODE_PUBLISHED)
    ->orderBy('c.created', 'DESC')
    // Additionally order by cid to ensure that comments with the same timestamp
    // are returned in the exact order posted.
    ->orderBy('c.cid', 'DESC')
    ->range(0, $number)
    ->execute()
    ->fetchAll();

  return $comments ? $comments : array();
}

/**
 * Calculate page number for first new comment.
 *
 * @param $num_comments
 *   Number of comments.
 * @param $new_replies
 *   Number of new replies.
 * @param $node
 *   The first new comment node.
 * @return
 *   "page=X" if the page number is greater than zero; empty string otherwise.
 */
function comment_new_page_count($num_comments, $new_replies, $node) {
  $mode = variable_get('comment_default_mode_' . $node->type, COMMENT_MODE_THREADED);
  $comments_per_page = variable_get('comment_default_per_page_' . $node->type, 50);
  $pagenum = NULL;
  $flat = $mode == COMMENT_MODE_FLAT ? TRUE : FALSE;
  if ($num_comments <= $comments_per_page) {
    // Only one page of comments.
    $pageno = 0;
  }
  elseif ($flat) {
    // Flat comments.
    $count = $num_comments - $new_replies;
    $pageno = $count / $comments_per_page;
  }
  else {
    // Threaded comments: we build a query with a subquery to find the first
    // thread with a new comment.

    // 1. Find all the threads with a new comment.
    $unread_threads_query = db_select('comment')
      ->fields('comment', array('thread'))
      ->condition('nid', $node->nid)
      ->condition('status', COMMENT_PUBLISHED)
      ->orderBy('created', 'DESC')
      ->orderBy('cid', 'DESC')
      ->range(0, $new_replies);

    // 2. Find the first thread.
    $first_thread = db_select($unread_threads_query, 'thread')
      ->fields('thread', array('thread'))
      ->orderBy('SUBSTRING(thread, 1, (LENGTH(thread) - 1))')
      ->range(0, 1)
      ->execute()
      ->fetchField();

    // Remove the final '/'.
    $first_thread = substr($first_thread, 0, -1);

    // Find the number of the first comment of the first unread thread.
    $count = db_query('SELECT COUNT(*) FROM {comment} WHERE nid = :nid AND status = :status AND SUBSTRING(thread, 1, (LENGTH(thread) - 1)) < :thread', array(
      ':status' => COMMENT_PUBLISHED,
      ':nid' => $node->nid,
      ':thread' => $first_thread,
    ))->fetchField();

    $pageno = $count / $comments_per_page;
  }

  if ($pageno >= 1) {
    $pagenum = array('page' => intval($pageno));
  }

  return $pagenum;
}

/**
 * Returns HTML for a list of recent comments to be displayed in the comment block.
 *
 * @ingroup themeable
 */
function theme_comment_block() {
  $items = array();
  $number = variable_get('comment_block_count', 10);
  foreach (comment_get_recent($number) as $comment) {
    $items[] = l($comment->subject, 'comment/' . $comment->cid, array('fragment' => 'comment-' . $comment->cid)) . '&nbsp;<span>' . t('@time ago', array('@time' => format_interval(REQUEST_TIME - $comment->changed))) . '</span>';
  }

  if ($items) {
    return theme('item_list', array('items' => $items));
  }
  else {
    return t('No comments available.');
  }
}

/**
 * Implements hook_node_view().
 */
function comment_node_view($node, $view_mode) {
  $links = array();

  if ($node->comment != COMMENT_NODE_HIDDEN) {
    if ($view_mode == 'rss') {
      // Add a comments RSS element which is a URL to the comments of this node.
      $node->rss_elements[] = array(
        'key' => 'comments',
        'value' => url('node/' . $node->nid, array('fragment' => 'comments', 'absolute' => TRUE))
      );
    }
    elseif ($view_mode == 'teaser') {
      // Teaser view: display the number of comments that have been posted,
      // or a link to add new comments if the user has permission, the node
      // is open to new comments, and there currently are none.
      if (user_access('access comments')) {
        if (!empty($node->comment_count)) {
          $links['comment-comments'] = array(
            'title' => format_plural($node->comment_count, '1 comment', '@count comments'),
            'href' => "node/$node->nid",
            'attributes' => array('title' => t('Jump to the first comment of this posting.')),
            'fragment' => 'comments',
            'html' => TRUE,
          );
          // Show a link to the first new comment.
          if ($new = comment_num_new($node->nid)) {
            $links['comment-new-comments'] = array(
              'title' => format_plural($new, '1 new comment', '@count new comments'),
              'href' => "node/$node->nid",
              'query' => comment_new_page_count($node->comment_count, $new, $node),
              'attributes' => array('title' => t('Jump to the first new comment of this posting.')),
              'fragment' => 'new',
              'html' => TRUE,
            );
          }
        }
      }
      if ($node->comment == COMMENT_NODE_OPEN) {
        if (user_access('post comments')) {
          $links['comment-add'] = array(
            'title' => t('Add new comment'),
            'href' => "comment/reply/$node->nid",
            'attributes' => array('title' => t('Add a new comment to this page.')),
            'fragment' => 'comment-form',
          );
        }
        else {
          $links['comment_forbidden'] = array(
            'title' => theme('comment_post_forbidden', array('node' => $node)),
            'html' => TRUE,
          );
        }
      }
    }
    elseif ($view_mode != 'search_index' && $view_mode != 'search_result') {
      // Node in other view modes: add a "post comment" link if the user is
      // allowed to post comments and if this node is allowing new comments.
      // But we don't want this link if we're building the node for search
      // indexing or constructing a search result excerpt.
      if ($node->comment == COMMENT_NODE_OPEN) {
        $comment_form_location = variable_get('comment_form_location_' . $node->type, COMMENT_FORM_BELOW);
        if (user_access('post comments')) {
          // Show the "post comment" link if the form is on another page, or
          // if there are existing comments that the link will skip past.
          if ($comment_form_location == COMMENT_FORM_SEPARATE_PAGE || (!empty($node->comment_count) && user_access('access comments'))) {
            $links['comment-add'] = array(
              'title' => t('Add new comment'),
              'attributes' => array('title' => t('Share your thoughts and opinions related to this posting.')),
              'href' => "node/$node->nid",
              'fragment' => 'comment-form',
            );
            if ($comment_form_location == COMMENT_FORM_SEPARATE_PAGE) {
              $links['comment-add']['href'] = "comment/reply/$node->nid";
            }
          }
        }
        else {
          $links['comment_forbidden'] = array(
            'title' => theme('comment_post_forbidden', array('node' => $node)),
            'html' => TRUE,
          );
        }
      }
    }

    $node->content['links']['comment'] = array(
      '#theme' => 'links__node__comment',
      '#links' => $links,
      '#attributes' => array('class' => array('links', 'inline')),
    );

    // Only append comments when we are building a node on its own node detail
    // page. We compare $node and $page_node to ensure that comments are not
    // appended to other nodes shown on the page, for example a node_reference
    // displayed in 'full' view mode within another node.
    if ($node->comment && $view_mode == 'full' && node_is_page($node) && empty($node->in_preview)) {
      $node->content['comments'] = comment_node_page_additions($node);
    }
  }
}

/**
 * Build the comment-related elements for node detail pages.
 *
 * @param $node
 *  A node object.
 */
function comment_node_page_additions($node) {
  $additions = array();

  // Only attempt to render comments if the node has visible comments.
  // Unpublished comments are not included in $node->comment_count, so show
  // comments unconditionally if the user is an administrator.
  if (($node->comment_count && user_access('access comments')) || user_access('administer comments')) {
    $mode = variable_get('comment_default_mode_' . $node->type, COMMENT_MODE_THREADED);
    $comments_per_page = variable_get('comment_default_per_page_' . $node->type, 50);
    if ($cids = comment_get_thread($node, $mode, $comments_per_page)) {
      $comments = comment_load_multiple($cids);
      comment_prepare_thread($comments);
      $build = comment_view_multiple($comments, $node);
      $build['pager']['#theme'] = 'pager';
      $additions['comments'] = $build;
    }
  }

  // Append comment form if needed.
  if (user_access('post comments') && $node->comment == COMMENT_NODE_OPEN && (variable_get('comment_form_location_' . $node->type, COMMENT_FORM_BELOW) == COMMENT_FORM_BELOW)) {
    $build = drupal_get_form("comment_node_{$node->type}_form", (object) array('nid' => $node->nid));
    $additions['comment_form'] = $build;
  }

  if ($additions) {
    $additions += array(
      '#theme' => 'comment_wrapper__node_' . $node->type,
      '#node' => $node,
      'comments' => array(),
      'comment_form' => array(),
    );
  }

  return $additions;
}

/**
 * Retrieve comments for a thread.
 *
 * @param $node
 *   The node whose comment(s) needs rendering.
 * @param $mode
 *   The comment display mode; COMMENT_MODE_FLAT or COMMENT_MODE_THREADED.
 * @param $comments_per_page
 *   The amount of comments to display per page.
 *
 * To display threaded comments in the correct order we keep a 'thread' field
 * and order by that value. This field keeps this data in
 * a way which is easy to update and convenient to use.
 *
 * A "thread" value starts at "1". If we add a child (A) to this comment,
 * we assign it a "thread" = "1.1". A child of (A) will have "1.1.1". Next
 * brother of (A) will get "1.2". Next brother of the parent of (A) will get
 * "2" and so on.
 *
 * First of all note that the thread field stores the depth of the comment:
 * depth 0 will be "X", depth 1 "X.X", depth 2 "X.X.X", etc.
 *
 * Now to get the ordering right, consider this example:
 *
 * 1
 * 1.1
 * 1.1.1
 * 1.2
 * 2
 *
 * If we "ORDER BY thread ASC" we get the above result, and this is the
 * natural order sorted by time. However, if we "ORDER BY thread DESC"
 * we get:
 *
 * 2
 * 1.2
 * 1.1.1
 * 1.1
 * 1
 *
 * Clearly, this is not a natural way to see a thread, and users will get
 * confused. The natural order to show a thread by time desc would be:
 *
 * 2
 * 1
 * 1.2
 * 1.1
 * 1.1.1
 *
 * which is what we already did before the standard pager patch. To achieve
 * this we simply add a "/" at the end of each "thread" value. This way, the
 * thread fields will look like this:
 *
 * 1/
 * 1.1/
 * 1.1.1/
 * 1.2/
 * 2/
 *
 * we add "/" since this char is, in ASCII, higher than every number, so if
 * now we "ORDER BY thread DESC" we get the correct order. However this would
 * spoil the reverse ordering, "ORDER BY thread ASC" -- here, we do not need
 * to consider the trailing "/" so we use a substring only.
 */
function comment_get_thread($node, $mode, $comments_per_page) {
  $query = db_select('comment', 'c')->extend('PagerDefault');
  $query->addField('c', 'cid');
  $query
    ->condition('c.nid', $node->nid)
    ->addTag('node_access')
    ->addTag('comment_filter')
    ->addMetaData('node', $node)
    ->limit($comments_per_page);

  $count_query = db_select('comment', 'c');
  $count_query->addExpression('COUNT(*)');
  $count_query
    ->condition('c.nid', $node->nid)
    ->addTag('node_access')
    ->addTag('comment_filter')
    ->addMetaData('node', $node);

  if (!user_access('administer comments')) {
    $query->condition('c.status', COMMENT_PUBLISHED);
    $count_query->condition('c.status', COMMENT_PUBLISHED);
  }
  if ($mode === COMMENT_MODE_FLAT) {
    $query->orderBy('c.cid', 'ASC');
  }
  else {
    // See comment above. Analysis reveals that this doesn't cost too
    // much. It scales much much better than having the whole comment
    // structure.
    $query->addExpression('SUBSTRING(c.thread, 1, (LENGTH(c.thread) - 1))', 'torder');
    $query->orderBy('torder', 'ASC');
  }

  $query->setCountQuery($count_query);
  $cids = $query->execute()->fetchCol();

  return $cids;
}

/**
 * Loop over comment thread, noting indentation level.
 *
 * @param array $comments
 *   An array of comment objects, keyed by cid.
 * @return
 *   The $comments argument is altered by reference with indentation information.
 */
function comment_prepare_thread(&$comments) {
  // A flag stating if we are still searching for first new comment on the thread.
  $first_new = TRUE;

  // A counter that helps track how indented we are.
  $divs = 0;

  foreach ($comments as $key => $comment) {
    if ($first_new && $comment->new != MARK_READ) {
      // Assign the anchor only for the first new comment. This avoids duplicate
      // id attributes on a page.
      $first_new = FALSE;
      $comment->first_new = TRUE;
    }

    // The $divs element instructs #prefix whether to add an indent div or
    // close existing divs (a negative value).
    $comment->depth = count(explode('.', $comment->thread)) - 1;
    if ($comment->depth > $divs) {
      $comment->divs = 1;
      $divs++;
    }
    else {
      $comment->divs = $comment->depth - $divs;
      while ($comment->depth < $divs) {
        $divs--;
      }
    }
    $comments[$key] = $comment;
  }

  // The final comment must close up some hanging divs
  $comments[$key]->divs_final = $divs;
}

/**
 * Generate an array for rendering the given comment.
 *
 * @param $comment
 *   A comment object.
 * @param $node
 *   The node the comment is attached to.
 * @param $view_mode
 *   View mode, e.g. 'full', 'teaser'...
 * @param $langcode
 *   (optional) A language code to use for rendering. Defaults to the global
 *   content language of the current request.
 *
 * @return
 *   An array as expected by drupal_render().
 */
function comment_view($comment, $node, $view_mode = 'full', $langcode = NULL) {
  if (!isset($langcode)) {
    $langcode = $GLOBALS['language_content']->language;
  }

  // Populate $comment->content with a render() array.
  comment_build_content($comment, $node, $view_mode, $langcode);

  $build = $comment->content;
  // We don't need duplicate rendering info in comment->content.
  unset($comment->content);

  $build += array(
    '#theme' => 'comment__node_' . $node->type,
    '#comment' => $comment,
    '#node' => $node,
    '#view_mode' => $view_mode,
    '#language' => $langcode,
  );

  if (empty($comment->in_preview)) {
    $prefix = '';
    $is_threaded = isset($comment->divs) && variable_get('comment_default_mode_' . $node->type, COMMENT_MODE_THREADED) == COMMENT_MODE_THREADED;

    // Add 'new' anchor if needed.
    if (!empty($comment->first_new)) {
      $prefix .= "<a id=\"new\"></a>\n";
    }

    // Add indentation div or close open divs as needed.
    if ($is_threaded) {
      $prefix .= $comment->divs <= 0 ? str_repeat('</div>', abs($comment->divs)) : "\n" . '<div class="indented">';
    }

    // Add anchor for each comment.
    $prefix .= "<a id=\"comment-$comment->cid\"></a>\n";
    $build['#prefix'] = $prefix;

    // Close all open divs.
    if ($is_threaded && !empty($comment->divs_final)) {
      $build['#suffix'] = str_repeat('</div>', $comment->divs_final);
    }
  }

  // Allow modules to modify the structured comment.
  $type = 'comment';
  drupal_alter(array('comment_view', 'entity_view'), $build, $type);

  return $build;
}

/**
 * Builds a structured array representing the comment's content.
 *
 * The content built for the comment (field values, comments, file attachments or
 * other comment components) will vary depending on the $view_mode parameter.
 *
 * @param $comment
 *   A comment object.
 * @param $node
 *   The node the comment is attached to.
 * @param $view_mode
 *   View mode, e.g. 'full', 'teaser'...
 * @param $langcode
 *   (optional) A language code to use for rendering. Defaults to the global
 *   content language of the current request.
 */
function comment_build_content($comment, $node, $view_mode = 'full', $langcode = NULL) {
  if (!isset($langcode)) {
    $langcode = $GLOBALS['language_content']->language;
  }

  // Remove previously built content, if exists.
  $comment->content = array();

  // Allow modules to change the view mode.
  $context = array(
    'entity_type' => 'comment',
    'entity' => $comment,
    'langcode' => $langcode,
  );