drupal/core/modules/statistics/statistics.module

<?php

/**
 * @file
 * Logs and displays content statistics for a site.
 */

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Url;
use Drupal\node\NodeInterface;

/**
 * Implements hook_help().
 */
function statistics_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.statistics':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Statistics module shows you how often content is viewed. This is useful in determining which pages of your site are most popular. For more information, see the <a href=":statistics_do">online documentation for the Statistics module</a>.', [':statistics_do' => 'https://www.drupal.org/documentation/modules/statistics/']) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Displaying popular content') . '</dt>';
      $output .= '<dd>' . t('The module includes a <em>Popular content</em> block that displays the most viewed pages today and for all time, and the last content viewed. To use the block, enable <em>Count content views</em> on the <a href=":statistics-settings">Statistics page</a>, and then you can enable and configure the block on the <a href=":blocks">Block layout page</a>.', [':statistics-settings' => Url::fromRoute('statistics.settings')->toString(), ':blocks' => (\Drupal::moduleHandler()->moduleExists('block')) ? Url::fromRoute('block.admin_display')->toString() : '#']) . '</dd>';
      $output .= '<dt>' . t('Page view counter') . '</dt>';
      $output .= '<dd>' . t('The Statistics module includes a counter for each page that increases whenever the page is viewed. To use the counter, enable <em>Count content views</em> on the <a href=":statistics-settings">Statistics page</a>, and set the necessary <a href=":permissions">permissions</a> (<em>View content hits</em>) so that the counter is visible to the users.', [':statistics-settings' => Url::fromRoute('statistics.settings')->toString(), ':permissions' => Url::fromRoute('user.admin_permissions', [], ['fragment' => 'module-statistics'])->toString()]) . '</dd>';
      $output .= '</dl>';
      return $output;

    case 'statistics.settings':
      return '<p>' . t('Settings for the statistical information that Drupal will keep about the site.') . '</p>';
  }
}

/**
 * Implements hook_ENTITY_TYPE_view() for node entities.
 */
function statistics_node_view(array &$build, EntityInterface $node, EntityViewDisplayInterface $display, $view_mode) {
  if (!$node->isNew() && $view_mode == 'full' && node_is_page($node) && empty($node->in_preview)) {
    $build['#attached']['library'][] = 'statistics/drupal.statistics';
    $settings = ['data' => ['nid' => $node->id()], 'url' => \Drupal::request()->getBasePath() . '/' . drupal_get_path('module', 'statistics') . '/statistics.php'];
    $build['#attached']['drupalSettings']['statistics'] = $settings;
  }
}

/**
 * Implements hook_node_links_alter().
 */
function statistics_node_links_alter(array &$links, NodeInterface $entity, array &$context) {
  if ($context['view_mode'] != 'rss') {
    $links['#cache']['contexts'][] = 'user.permissions';
    if (\Drupal::currentUser()->hasPermission('view post access counter')) {
      $statistics = \Drupal::service('statistics.storage.node')->fetchView($entity->id());
      if ($statistics) {
        $statistics_links['statistics_counter']['title'] = \Drupal::translation()->formatPlural($statistics->getTotalCount(), '1 view', '@count views');
        $links['statistics'] = [
          '#theme' => 'links__node__statistics',
          '#links' => $statistics_links,
          '#attributes' => ['class' => ['links', 'inline']],
        ];
      }
      $links['#cache']['max-age'] = \Drupal::config('statistics.settings')->get('display_max_age');
    }
  }
}

/**
 * Implements hook_cron().
 */
function statistics_cron() {
  $storage = \Drupal::service('statistics.storage.node');
  $storage->resetDayCount();
  $max_total_count = $storage->maxTotalCount();
  \Drupal::state()->set('statistics.node_counter_scale', 1.0 / max(1.0, $max_total_count));
}

/**
 * Implements hook_ENTITY_TYPE_predelete() for node entities.
 */
function statistics_node_predelete(EntityInterface $node) {
  // Clean up statistics table when node is deleted.
  $id = $node->id();
  return \Drupal::service('statistics.storage.node')->deleteViews($id);
}

/**
 * Implements hook_ranking().
 */
function statistics_ranking() {
  if (\Drupal::config('statistics.settings')->get('count_content_views')) {
    return [
      'views' => [
        'title' => t('Number of views'),
        'join' => [
          'type' => 'LEFT',
          'table' => 'node_counter',
          'alias' => 'node_counter',
          'on' => 'node_counter.nid = i.sid',
        ],
        // Inverse law that maps the highest view count on the site to 1 and 0
        // to 0. Note that the ROUND here is necessary for PostgreSQL and SQLite
        // in order to ensure that the :statistics_scale argument is treated as
        // a numeric type, because the PostgreSQL PDO driver sometimes puts
        // values in as strings instead of numbers in complex expressions like
        // this.
        'score' => '2.0 - 2.0 / (1.0 + node_counter.totalcount * (ROUND(:statistics_scale, 4)))',
        'arguments' => [':statistics_scale' => \Drupal::state()->get('statistics.node_counter_scale', 0)],
      ],
    ];
  }
}

/**
 * Implements hook_preprocess_HOOK() for block templates.
 */
function statistics_preprocess_block(&$variables) {
  if ($variables['configuration']['provider'] == 'statistics') {
    $variables['attributes']['role'] = 'navigation';
  }
}

/**
 * Implements hook_block_alter().
 *
 * Removes the "popular" block from display if the module is not configured
 * to count content views.
 */
function statistics_block_alter(&$definitions) {
  $statistics_count_content_views = \Drupal::config('statistics.settings')->get('count_content_views');
  if (empty($statistics_count_content_views)) {
    unset($definitions['statistics_popular_block']);
  }
}