<?php

/**
 * @file
 * Drupal hook implementations for the Better Statistics module.
 */

/**
 * Current and minimum Statistics API version. For internal use only!
 */
define('BETTER_STATISTICS_API_VERSION', 1.0);
define('BETTER_STATISTICS_API_MIN_VERSION', 1.0);

/**
 * Implements hook_menu_alter().
 *
 * Redirects core's link to access log details page.
 */
function better_statistics_menu_alter(&$items) {
  $items['admin/reports/access/%']['page callback'] = 'better_statistics_access_log';
  $items['admin/reports/access/%']['module'] = 'better_statistics';
  $items['admin/reports/access/%']['file'] = 'better_statistics.admin.inc';
}

/**
 * Implements hook_schema_alter().
 *
 * Reflects the customizations chosen by the user in the schema.
 */
function better_statistics_schema_alter(&$schema) {
  // Fetch the fields defined by this module.
  $fields = variable_get('better_statistics_fields', better_statistics_get_default_fields());

  // For each field defined, add it to the schema.
  foreach ($fields as $field => $data) {
    $schema['accesslog']['fields'][$field] = $data['schema'];
  }
}


/**
 * Implements hook_module_implements_alter().
 *
 * Ensures this module fires before Statistics' exit hook so that we don't
 * double up on data. Note we're not removing Statistics' hook entirely because
 * Statistics also handles node count data.
 */
function better_statistics_module_implements_alter(&$implementations, $hook) {
  if ($hook == 'exit') {
    // Ensure our hook fires before statistics.
    $implementations['better_statistics'] = -1;
  }
}


/**
 * Implements hook_ctools_plugin_api_hook_name().
 *
 * Report to CTools that we use hook_statistics_api instead of
 * hook_ctools_plugin_api().
 */
function better_statistics_ctools_plugin_api_hook_name() {
  return 'statistics_api';
}


/**
 * Implements hook_exit().
 *
 * Gathers additional data and inserts our data into accesslog.
 */
function better_statistics_exit() {
  // If statistics access log is set to run, run our code.
  if (variable_get('statistics_enable_access_log', 0)) {

    // Force a recheck on cache status, just in case this function was called
    // before the X-Drupal-Cache header was set.
    $cache_status = better_statistics_served_from_cache(TRUE);

    // @see statistics_exit()
    drupal_bootstrap(DRUPAL_BOOTSTRAP_SESSION);
    include_once DRUPAL_ROOT . '/includes/unicode.inc';

    // Load all relevant module.statistics.inc files for hook invocations.
    better_statistics_load_active_incs();

    // Allow all modules to react before logging begins.
    module_invoke_all('better_statistics_prelog');

    // Log the request if the request is loggable.
    if (better_statistics_request_is_loggable()) {
      // Get all declared fields and their computed values.
      $fields = better_statistics_get_fields_data();

      // Allow modules to log statistics data.
      module_invoke_all('better_statistics_log', $fields);
    }
  }

  // Keep statistics from writing additional data to the accesslog.
  global $conf;
  $conf['statistics_enable_access_log'] = FALSE;
}


/**
 * Implements hook_views_api().
 */
function better_statistics_views_api() {
  return array(
    'api' => 3,
    'path' => drupal_get_path('module', 'better_statistics') . '/views',
  );
}


/**
 * Implements hook_flush_caches().
 *
 * When all caches are flushed, detect any updates we need to make on active
 * fields. This is implemented not to declare a cache table for flushing, but to
 * react when all caches are flushed.
 */
function better_statistics_flush_caches() {
  module_load_include('inc', 'better_statistics', 'better_statistics.admin');
  _better_statistics_update_fields();

  return array();
}


/**
 * Implements hook_form_FORM_ID_alter().
 *
 * @see _better_statistics_form_statistics_settings_form_alter()
 */
function better_statistics_form_statistics_settings_form_alter(&$form, &$form_state, $form_id) {
  module_load_include('inc', 'better_statistics', 'better_statistics.admin');
  _better_statistics_form_statistics_settings_form_alter($form, $form_state, $form_id);
}


/**
 * Implements hook_form_FORM_ID_alter().
 *
 * @see _better_statistics_form_system_performance_settings_form_alter()
 */
function better_statistics_form_system_performance_settings_alter(&$form, &$form_state, $form_id) {
  module_load_include('inc', 'better_statistics', 'better_statistics.admin');
  _better_statistics_form_system_performance_settings_alter($form, $form_state, $form_id);
}


/**
 * Submit handler for the Better Statistics configuration form.
 *
 * @see _better_statistics_settings_form_submit()
 */
function better_statistics_settings_form_submit($form, &$form_state) {
  module_load_include('inc', 'better_statistics', 'better_statistics.admin');
  _better_statistics_settings_form_submit($form, $form_state);
}


/**
 * Implements hook_statistics_api().
 */
function better_statistics_statistics_api() {
  return array(
    // In your module, do not use this constant!
    'api' => BETTER_STATISTICS_API_VERSION,
    'path' => drupal_get_path('module', 'better_statistics'),
  );
}


/**
 * Returns default fields in the exact same form expected of fields exposed via
 * hook_better_statistics_fields().
 */
function better_statistics_get_default_fields() {
  static $default_fields;

  if (!isset($default_fields)) {
    // In some contexts, drupal_get_schema_unproccessed may be unavailable, so
    // here, we get the accesslog schema the same way it does.
    require_once DRUPAL_ROOT . '/modules/statistics/statistics.install';
    $schema = module_invoke('statistics', 'schema');

    // Expose Drupal Core's accesslog fields to our own API.
    $accesslog = $schema['accesslog'];
    foreach ($accesslog['fields'] as $field => $schema) {
      $default_fields[$field] = array(
        'schema' => $schema,
        'views_field' => FALSE,
        'callback' => 'better_statistics_get_field_value',
      );
    }
  }

  return $default_fields;
}


/**
 * Returns data for all valid, declared fields in preparation for DB insertion.
 */
function better_statistics_get_fields_data() {
  $fields = variable_get('better_statistics_fields', better_statistics_get_default_fields());
  $field_data = array();

  // Loop through all custom fields.
  foreach ($fields as $field => $data) {
    // Only insert data into this field if there's a callback to get data.
    if (is_callable($data['callback'])) {
      $field_data[$field] = $data['callback']($field);
    }
  }

  return $field_data;
}


/**
 * Loads module.statistics.inc files for all active fields.
 */
function better_statistics_load_active_incs() {
  // Prevent this function from loading it multiple times.
  static $loaded;

  if (empty($loaded)) {
    $loaded = TRUE;

    // Include this module's API file because of how core fields are implemented.
    require_once(dirname(__FILE__) . '/better_statistics.statistics.inc');

    // Loop through each file stored in the active incs list and include it.
    // These are stored in a variable rather than being assembled dynamically
    // due to the nature of cached pages and their bootstrap status.
    $incs = variable_get('better_statistics_active_incs', array());
    foreach ($incs as $file) {
      // If there's an inc file and it hasn't been loaded yet, load it.
      if (file_exists($file)) {
        require_once($file);
      }
    }
  }
}


/**
 * Determines the loggability of the current request.
 *
 * @return
 *   TRUE if the current page can be logged, FALSE otherwise.
 */
function better_statistics_request_is_loggable($allow_logging = NULL) {
  $allow_logging_static = &drupal_static(__FUNCTION__, TRUE);

  if (isset($allow_logging)) {
    $allow_logging_static = $allow_logging;
  }

  return $allow_logging_static;
}

/**
 * Determines whether or not the current request is being served from cache.
 *
 * Note that you may need to use === to determine the cache status of the page,
 * because some requests will return NULL, which evaluates to FALSE.
 *
 * @param boolean $recheck
 *   (optional) If set to TRUE, cache status will be manually re-checked.
 *
 * @return
 *   A boolean TRUE if the page is being served from cache, FALSE if the page is
 *   cacheable, but not served from cache. NULL is returned in the case when the
 *   page was never cacheable to begin with.
 */
function better_statistics_served_from_cache($recheck = FALSE) {
  static $cached;

  if (!isset($cached) || $recheck) {
    $headers = headers_list();
    $hit = array_search('X-Drupal-Cache: HIT', $headers);
    $miss = array_search('X-Drupal-Cache: MISS', $headers);

    // If neither a hit nor miss header are present, the page wasn't cacheable
    // to begin with. Return NULL.
    if ($hit !== FALSE) {
      $cached = TRUE;
    }
    elseif ($miss !== FALSE) {
      $cached = FALSE;
    }
    else {
      $cached = NULL;
    }
  }

  return $cached;
}