<?php

/**
 * @file
 * The 'Event log' module remembers form submissions or other actions that were
 * performed on the website.
 *
 * @author Bas van Meurs
 * @copyright Cipix Internet
 */

/**
 * Implements hook_menu().
 */
function event_log_menu() {

  $items['admin/reports/events'] = array(
    'title' => 'Event log',
    'description' => 'Shows all logged events.',
    'page callback' => 'event_log_overview_page',
    'access arguments' => array('access event log'),
    'file' => 'event_log.admin.inc',
    'type' => MENU_NORMAL_ITEM,
  );

  $items['admin/reports/events/ajax-get-operations'] = array(
    'title' => 'AJAX callback for operations',
    'page callback' => 'event_log_overview_page_form_get_operations',
    'delivery callback' => 'ajax_deliver',
    'access arguments' => array('access event log'),
    'file' => 'event_log.admin.inc',
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Implements hook_permission().
 */
function event_log_permission() {
  return array(
    'access event log' => array(
      'title' => t('Access event log'),
      'description' => t('Allows a user to access the logged events.'),
    ),
  );
}

/**
 * Implements hook_cron().
 */
function event_log_cron() {
  // Cleanup the eventlog table.
  $row_limit = variable_get('eventlog_max_records', 0);

  // Get the oldest row lid that should not be deleted.
  if ($row_limit > 0) {
    $min_row = db_select('event_log', 'e')
      ->fields('e', array('lid'))
      ->orderBy('lid', 'DESC')
      ->range($row_limit-1, 1)
      ->execute()->fetchField();

    // Delete table entries older than the oldest row that should be preserved.
    // Delete a maximum of 50000 records.
    if ($min_row) {
      $ids = db_select('event_log', 'e')
        ->fields('e', array('lid'))
        ->condition('e.lid', $min_row, '<')
        ->orderBy('e.lid', 'ASC')
        ->range(0, 50000)
        ->execute()
        ->fetchCol();

      db_delete('event_log')
        ->condition('lid', $ids, 'IN')
        ->execute();
    }
  }
}

/**
 * Inserts the log record in the event log. Sets the lid.
 *
 * @param array $log
 *   The log record to be saved. This record contains the following fields:
 *   - {string} type
 *     The event type. This is usually the object type that is described by this
 *     event. Example: 'node' or 'user'. Required.
 *   - {string} operation
 *     The operation being performed. Example: 'insert'. Required.
 *   - {string} form_id
 *     The form_id of the submitted form. Optional.
 *   - {string} description
 *     A textual description of the event. Required.
 *   - {string} ref_numeric
 *     Reference to numeric id. Optional.
 *   - {string} ref_char
 *     Reference to alphabetical id. Optional.
 *   - {string} info
 *     Informative data, for example of the modified object. Optional.
 */
function event_log_insert(&$log) {
  if (php_sapi_name() == 'cli') {
    // Ignore CLI requests.
    return;
  }

  if (empty($log['created'])) {
    $log['created'] = REQUEST_TIME;
  }

  if (empty($log['uid'])) {
    global $user;
    $log['uid'] = $user->uid;
  }

  $ip = ip_address();
  if (empty($log['ip']) && !empty($ip)) {
    global $user;
    $log['ip'] = $ip;
  }

  if (!empty($log['info']) && !is_string($log['info'])) {
    $log['info'] = drupal_json_encode($log['info']);
  }

  if (!empty($log['info']) && (strlen($log['info']) > 20000)) {
    // Limit the amount of data to prevent the database from filling up too
    // quickly.
    $log['info'] = substr($log['info'], 0, 20000);
  }

  if (empty($log['path'])) {
    // If the menu is currently being rebuilt, menu_get_item will cause an
    // infinite loop. That's why we will check the cache directly.
    $router_items = &drupal_static('menu_get_item');
    if (!empty($router_items[$_GET['q']])) {
      $item = $router_items[$_GET['q']];
    }

    if (!empty($item)) {
      $log['path'] = $item['path'];
    }
  }


  drupal_write_record('event_log', $log);
}

/**
 * Returns all existing event handlers.
 * @return array
 *   An array with the event log handlers.
 */
function event_log_get_event_handlers() {
  $handlers = drupal_static(__FUNCTION__);
  if ($handlers === NULL) {
    $handlers = module_invoke_all('event_log_handlers');
    drupal_alter('event_log_handlers', $handlers);
  }
  return $handlers;
}

/**
 * Form submission callback.
 */
function event_log_form_submit(&$form, &$form_state) {
  if (!empty($form_state['__event_log_logged'])) {
    // Some forms are submitted twice, for instance the node_form.
    // We will only call the submit callback once.
    return;
  }

  $form_state['__event_log_logged'] = TRUE;

  // Get form id.
  $form_id = $form['#form_id'];

  // Dispatch the submission to the correct event handler.
  $handlers = event_log_get_event_handlers();
  foreach ($handlers as $type => $handler) {
    $dispatch = FALSE;
    if (!empty($handler['form_ids']) && in_array($form_id, $handler['form_ids'])) {
      $dispatch = TRUE;
    }
    elseif (!empty($handler['form_ids_regexp'])) {
      foreach ($handler['form_ids_regexp'] as $regexp) {
        if (preg_match($regexp, $form_id)) {
          $dispatch = TRUE;
          break;
        }
      }
    }

    if ($dispatch) {
      // Dispatch!
      $function = $handler['form_submit_callback'];
      if (function_exists($function)) {
        $log = $function($form, $form_state, $form_id);
        if (!empty($log)) {
          // Log the event.
          $log['type'] = $type;
          $log['form_id'] = $form_id;
          event_log_insert($log);
        }
      }
    }
  }
}

/**
 * Implements hook_form_alter().
 */
function event_log_form_alter(&$form, &$form_state, $form_id) {
  // Add submit callback to ANY form action.
  event_log_add_submit_handler($form, 'event_log_form_submit');

  if ($form_id == 'system_logging_settings') {
    $form['eventlog'] = array(
      '#type' => 'fieldset',
      '#title' => t('Eventlog'),
      '#description' => t('Settings for the eventlog messages table.'),
      '#collapsible' => TRUE,
      '#collapsed' => FALSE,
    );

    $form['eventlog']['eventlog_max_records'] = array(
      '#type' => 'select',
      '#title' => t('Eventlog messages to keep'),
      '#description' => t('The maximum number of messages to keep in the database event log. Requires a cron maintenance task.'),
      '#options' => array(
        0 => t('All'),
        1000 => '1000',
        2500 => '2500',
        5000 => '5000',
        10000 => '10000',
        25000 => '25000',
        50000 => '50000',
        100000 => '100000',
        250000 => '250000',
        500000 => '500000',
        1000000 => '1000000',
      ),
      '#default_value' => variable_get('eventlog_max_records', 'all'),
      '#required' => FALSE,
    );
  }
}

/**
 * Adds a submit handler to all submit hooks in the form tree.
 * @param array &$element
 *   A form element or the form itself.
 * @param string $callback
 *   The callback to be added.
 */
function event_log_add_submit_handler(&$element, $callback) {
  if (array_key_exists("#submit", $element)) {
    $element["#submit"][] = $callback;
  }
  $keys = element_children($element);
  foreach ($keys as $key) {
    if (is_array($element[$key])) {
      event_log_add_submit_handler($element[$key], $callback);
    }
  }
}

/**
 * Implements hook_views_api().
 */
function event_log_views_api() {
  return array(
    'api' => 3,
  );
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function event_log_form_event_log_overview_page_form_alter(&$form, &$form_state) {
  // No token checking and/or caching.
  unset($form['#token']);
  $form_state['no_cache'] = TRUE;
}