history.module

<?php

/**
 * @file
 * Records which users have read which content.
 *
 * @todo
 * - Generic helper for _forum_user_last_visit() + history_read().
 * - Generic helper for node_mark().
 */
use Drupal\node\Plugin\Core\Entity\Node;

/**
 * Entities changed before this time are always shown as read.
 *
 * Entities changed within this time may be marked as new, updated, or read,
 * depending on their state for the current user. Defaults to 30 days ago.
 */
define('HISTORY_READ_LIMIT', REQUEST_TIME - 30 * 24 * 60 * 60);

/**
 * Retrieves the timestamp for the current user's last view of a specified node.
 *
 * @param int $nid
 *   A node ID.
 *
 * @return int
 *   If a node has been previously viewed by the user, the timestamp in seconds
 *   of when the last view occurred; otherwise, zero.
 */
function history_read($nid) {
  global $user;
  $history =& drupal_static(__FUNCTION__, array());
  if (!isset($history[$nid])) {
    $history[$nid] = db_query("SELECT timestamp FROM {history} WHERE uid = :uid AND nid = :nid", array(
      ':uid' => $user->uid,
      ':nid' => $nid,
    ))
      ->fetchObject();
  }
  return isset($history[$nid]->timestamp) ? $history[$nid]->timestamp : 0;
}

/**
 * Updates 'last viewed' timestamp of the specified entity for the current user.
 *
 * @param $nid
 *   The node ID that has been read.
 * @param $account
 *   (optional) The user account to update the history for. Defaults to the
 *   current user.
 */
function history_write($nid, $account = NULL) {
  global $user;
  if (!isset($account)) {
    $account = $user;
  }
  if ($account->uid) {
    db_merge('history')
      ->key(array(
      'uid' => $account->uid,
      'nid' => $nid,
    ))
      ->fields(array(
      'timestamp' => REQUEST_TIME,
    ))
      ->execute();
  }
}

/**
 * Implements hook_cron().
 */
function history_cron() {
  db_delete('history')
    ->condition('timestamp', HISTORY_READ_LIMIT, '<')
    ->execute();
}

/**
 * Implements hook_node_delete().
 */
function history_node_delete(Node $node) {
  db_delete('history')
    ->condition('nid', $node->nid)
    ->execute();
}

/**
 * Implements hook_user_cancel().
 */
function history_user_cancel($edit, $account, $method) {
  switch ($method) {
    case 'user_cancel_reassign':
      db_delete('history')
        ->condition('uid', $account->uid)
        ->execute();
      break;
  }
}

/**
 * Implements hook_user_delete().
 */
function history_user_delete($account) {
  db_delete('history')
    ->condition('uid', $account->uid)
    ->execute();
}