<?php

/**
 * @file
 * An abstracted facet API that can be used by various search backends.
 */

/**
 * Constant for the "AND" operator.
 */
define('FACETAPI_OPERATOR_AND', 'and');

/**
 * Constant for the "OR" operator.
 */
define('FACETAPI_OPERATOR_OR', 'or');

/**
 * String that represents a time gap of a year between two dates.
 */
define('FACETAPI_DATE_YEAR', 'YEAR');

/**
 * String that represents a time gap of a month between two dates.
 */
define('FACETAPI_DATE_MONTH', 'MONTH');

/**
 * String that represents a time gap of a day between two dates.
 */
define('FACETAPI_DATE_DAY', 'DAY');

/**
 * String that represents a time gap of an hour between two dates.
 */
define('FACETAPI_DATE_HOUR', 'HOUR');

/**
 * String that represents a time gap of a minute between two dates.
 */
define('FACETAPI_DATE_MINUTE', 'MINUTE');

/**
 * String that represents a time gap of a second between two dates.
 */
define('FACETAPI_DATE_SECOND', 'SECOND');

/**
 * Date string for ISO 8601 date formats.
 */
define('FACETAPI_DATE_ISO8601', 'Y-m-d\TH:i:s\Z');

/**
 * Regex pattern for range queries.
 */
define('FACETAPI_REGEX_RANGE', '/^[\[\{](\S+) TO (\S+)[\]\}]$/');

/**
 * Regex pattern for date queries.
 */
define('FACETAPI_REGEX_DATE', '/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/');

/**
 * Regex pattern for date ranges.
 */
define('FACETAPI_REGEX_DATE_RANGE', '/^\[(' . trim(FACETAPI_REGEX_DATE, '/^$') . ') TO (' . trim(FACETAPI_REGEX_DATE, '/^$') . ')\]$/');

// Calls block specific hooks and overrides.
require_once dirname(__FILE__) . '/facetapi.block.inc';

/**
 * Implements hook_facetapi_hook_info().
 */
function facetapi_hook_info() {
  return array(
    'facetapi_adapters' => array(
      'group' => 'facetapi',
    ),
    'facetapi_dependencies' => array(
      'group' => 'facetapi',
    ),
    'facetapi_empty_behaviors' => array(
      'group' => 'facetapi',
    ),
    'facetapi_facet_info' => array(
      'group' => 'facetapi',
    ),
    'facetapi_filters' => array(
      'group' => 'facetapi',
    ),
    'facetapi_query_types' => array(
      'group' => 'facetapi',
    ),
    'facetapi_realm_info' => array(
      'group' => 'facetapi',
    ),
    'facetapi_sort_info' => array(
      'group' => 'facetapi',
    ),
    'facetapi_url_processors' => array(
      'group' => 'facetapi',
    ),
    'facetapi_widgets' => array(
      'group' => 'facetapi',
    ),
    'current_search_items' => array(
      'group' => 'facetapi',
    ),
  );
}

/**
 * Implements hook_menu().
 */
function facetapi_menu() {
  $items = array();

  // Builds the realm settings forms for each searcher.
  foreach (facetapi_get_searcher_info() as $searcher => $searcher_info) {
    // Only build router items automatically if a path is provided.
    if (empty($searcher_info['path'])) {
      continue;
    }

    // Builds realm settings.
    $first = TRUE;
    foreach (facetapi_get_realm_info() as $realm_name => $realm) {
      if ($first) {
        $first = FALSE;

        // Add the first realm as a default local task.
        $items[$searcher_info['path'] . '/facets'] = array(
          'title' => 'Facets',
          'page callback' => 'drupal_get_form',
          'page arguments' => array('facetapi_realm_settings_form', $searcher, $realm_name),
          'access callback' => 'facetapi_access_callback',
          'type' => MENU_LOCAL_TASK,
          'file' => 'facetapi.admin.inc',
        );
        $items[$searcher_info['path'] . '/facets/' . $realm_name] = array(
          'title' => $realm['label'],
          'type' => MENU_DEFAULT_LOCAL_TASK,
          'weight' => $realm['weight'],
        );
      }
      else {
        // Add all additional realms as local tasks.
        $items[$searcher_info['path'] . '/facets/' . $realm_name] = array(
          'title' => $realm['label'],
          'page callback' => 'drupal_get_form',
          'page arguments' => array('facetapi_realm_settings_form', $searcher, $realm_name),
          'access callback' => 'facetapi_access_callback',
          'type' => MENU_LOCAL_TASK,
          'file' => 'facetapi.admin.inc',
        );
      }
    }
  }

  $items['admin/config/search/facetapi/%facetapi_adapter/%facetapi_realm/%facetapi_facet/edit'] = array(
    'title' => 'Configure facet display',
    'load arguments' => array(4),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('facetapi_facet_display_form', 4, 5, 6),
    'access callback' => 'facetapi_access_callback',
    'type' => MENU_LOCAL_ACTION,
    'context' => MENU_CONTEXT_INLINE,
    'weight' => -15,
    'file' => 'facetapi.admin.inc',
  );

  $items['admin/config/search/facetapi/%facetapi_adapter/%facetapi_realm/%facetapi_dependencies/dependencies'] = array(
    'title' => 'Configure facet dependencies',
    'load arguments' => array(4),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('facetapi_facet_dependencies_form', 4, 5, 6),
    'access callback' => 'facetapi_access_callback',
    'type' => MENU_LOCAL_ACTION,
    'context' => MENU_CONTEXT_INLINE,
    'weight' => -10,
    'file' => 'facetapi.admin.inc',
  );

  $items['admin/config/search/facetapi/%facetapi_adapter/%facetapi_realm/%facetapi_filters/filters'] = array(
    'title' => 'Configure facet filters',
    'load arguments' => array(4),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('facetapi_facet_filters_form', 4, 5, 6),
    'access callback' => 'facetapi_access_callback',
    'type' => MENU_LOCAL_ACTION,
    'context' => MENU_CONTEXT_INLINE,
    'weight' => -5,
    'file' => 'facetapi.admin.inc',
  );

  $items['admin/config/search/facetapi/%facetapi_adapter/%facetapi_realm/%facetapi_facet/export'] = array(
    'title' => 'Export facet configuration',
    'load arguments' => array(4),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('facetapi_export_form', 4, 5, 6),
    'access callback' => 'facetapi_access_callback',
    'type' => MENU_NORMAL_ITEM,
    'file' => 'facetapi.admin.inc',
  );

  $items['admin/config/search/facetapi/%facetapi_adapter/%facetapi_realm/%facetapi_facet/revert'] = array(
    'title' => 'Revert facet configuration',
    'load arguments' => array(4),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('facetapi_revert_form', 4, 5, 6),
    'access callback' => 'facetapi_access_callback',
    'type' => MENU_NORMAL_ITEM,
    'file' => 'facetapi.admin.inc',
  );

  return $items;
}

/**
 * Implements hook_ctools_plugin_type().
 */
function facetapi_ctools_plugin_type() {
  return array(
    'adapters' => array(
      'use hooks' => TRUE,
    ),
    'dependencies' => array(
      'use hooks' => TRUE,
    ),
    'empty_behaviors' => array(
      'use hooks' => TRUE,
    ),
    'filters' => array(
      'use hooks' => TRUE,
    ),
    'query_types' => array(
      'use hooks' => TRUE,
    ),
    'url_processors' => array(
      'use hooks' => TRUE,
    ),
    'widgets' => array(
      'use hooks' => TRUE,
    ),
  );
}

/**
 * Implements hook_theme().
 */
function facetapi_theme() {
  return array(
    'facetapi_title' => array(
      'arguments' => array('title' => NULL, 'facet' => array()),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_facet_missing' => array(
      'arguments' => array('field_name' => NULL),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_count' => array(
      'arguments' => array('count' => NULL),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_link_inactive' => array(
      'arguments' => array('text' => NULL, 'path' => NULL, 'options' => array(), 'count' => 0),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_link_active' => array(
      'arguments' => array('text' => NULL, 'path' => NULL, 'options' => array()),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_deactivate_widget' => array(
      'arguments' => array('text' => NULL),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_accessible_markup' => array(
      'arguments' => array('text' => NULL, 'active' => NULL),
      'file' => 'facetapi.theme.inc',
    ),
    'facetapi_realm_settings_table' => array(
      'render element' => 'element',
      'file' => 'facetapi.admin.inc',
    ),
    'facetapi_sort_settings_table' => array(
      'render element' => 'element',
      'file' => 'facetapi.admin.inc',
    ),
    'facetapi_filter_settings_table' => array(
      'render element' => 'element',
      'file' => 'facetapi.admin.inc',
    ),
  );
}

/**
 * Custom access callback. Checks if the user has either the "administer search"
 * OR "administer facets" permissions.
 *
 * @param stdClass|NULL $account
 *   (optional) The account to check, if not given use currently logged in user.
 *
 * @return boolean
 *   TRUE if the user has access to the resource, FALSE otherwise.
 */
function facetapi_access_callback($account = NULL) {
  global $user;
  if (!isset($account)) {
    $account = $user;
  }
  return user_access('administer search', $account) || user_access('administer facets', $account);
}

/**
 * Implements hook_permission().
 */
function facetapi_permission() {
  return array(
    'administer facets' => array(
      'title' => t('Administer Facets'),
    ),
  );
}

////
////
//// facetapi_*_load() functions
////
////

/**
 * Instantiates the adapter plugin associated with the searcher.
 *
 * @param $searcher
 *   The machine readable name of searcher.
 *
 * @return FacetapiAdapter
 *   The adapter object, FALSE if the object can't be loaded.
 */
function facetapi_adapter_load($searcher) {
  $adapters = &drupal_static(__FUNCTION__, array());
  if (!isset($adapters[$searcher])) {
    $searcher_info = facetapi_get_searcher_info();
    if (isset($searcher_info[$searcher]['adapter'])) {
      ctools_include('plugins');
      $id = $searcher_info[$searcher]['adapter'];
      $class = ctools_plugin_load_class('facetapi', 'adapters', $id, 'handler');
      $adapters[$searcher] = ($class) ? new $class($searcher_info[$searcher]) : FALSE;
    }
    else {
      $adapters[$searcher] = FALSE;
    }
  }
  return $adapters[$searcher];
}

/**
 * Loads the dependency plugins associated with the facet.
 *
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $searcher
 *   The machine readable name of the searcher module.
 *
 * @return array
 *   An array of FacetapiDependency objects, FALSE if no plugins.
 */
function facetapi_dependencies_load($facet_name, $searcher) {
  $dependencies = array();
  $facet = facetapi_facet_load($facet_name, $searcher);
  if ($facet && ($adapter = facetapi_adapter_load($searcher))) {
    foreach ($facet['dependency plugins'] as $id) {
      // NOTE: CTools plugin component is loaded by facetapi_adapter_load().
      $class = ctools_plugin_load_class('facetapi', 'dependencies', $id, 'handler');
      $settings = $adapter->getFacet($facet)->getSettings();
      $dependencies[] = new $class($id, $adapter, $facet, $settings);
    }
  }
  return ($dependencies) ? $dependencies : FALSE;
}

/**
 * Returns array of filter options available to the facet.
 *
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $searcher
 *   The machine readable name of the searcher.
 *
 * @return array
 *   An array of FacetapiFilter objects, FALSE if no plugins.
 */
function facetapi_filters_load($facet_name, $searcher) {
  $filters = array('plugins' => array());
  if ($filters['facet'] = facetapi_facet_load($facet_name, $searcher)) {
    $filters['plugins'] = facetapi_get_filters($filters['facet']);
  }
  return ($filters['plugins']) ? $filters : FALSE;
}

/**
 * Returns a realm definition.
 *
 * @param $realm_name
 *   The machine readable name of the realm.
 *
 * @return array
 *   An array containing the realm definition, FALSE if the realm is invalid.
 *   - name: The machine name of the realm.
 *   - label: The human readable name of the realm displayed in the admin UI.
 *   - description: The description of the realm displayed in the admin UI.
 *   - element type: The type of element facets are rendered as, such as 'links'
 *     or 'form elements'.
 *   - default widget: The default widget plugin id for facets in the realm.
 *   - settings callback: A callback that alters the realm settings form.
 *   - sortable: Whether the facets can be sorted via the admin UI.
 *   - weight: The weight of the realm's menu item in comparison to the others.
 */
function facetapi_realm_load($realm_name) {
  $realm_info = facetapi_get_realm_info();
  return (isset($realm_info[$realm_name])) ? $realm_info[$realm_name] : FALSE;
}

/**
 * Returns a facet definition.
 *
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $searcher
 *   The machine readable name of the searcher.
 *
 * @return
 *   An array containing the facet definition, FALSE if the facet is invalid.
 *   - name: Machine readable name of the facet.
 *   - label: Human readable name of the facet displayed in settings forms.
 *   - description: Description of the facet displayed in settings forms.
 *   - field: The field name used by the backend to store and retrieve data from
 *     the search index it is associated with.
 *   - field alias: The query string variable inside of the filter key used to
 *     pass the filter information through the query string.
 *   - field api name: The machine readable name of the Field API field data the
 *     facet is associated with, FALSE if it is not associated with a field.
 *   - field api bundles: An array of entity names that this field contains
 *     bundle information for.
 *   - query types: The query type plugins that that this facet supports. For
 *     example, numeric fields support "term" and "range_filter" queries.
 *   - alter callbacks: Callbacks that alter the initialized render array
 *     returned by the query type plugin. Defaults to an empty array.
 *   - dependency plugins: An array of dependency plugin IDs that are supported
 *     by this facet.
 *   - default widget: The widget plugin ID used if no plugin has been selected
 *     or the one selected is not valid.
 *   - allowed operators: An array keyed by operator constant to boolean values
 *     specifying whether the operator is supported.
 *   - facet missing allowed: Whether or not missing facets are allowed.
 *   - facet mincount allowed: Whether or not the facet supports the "minimum
 *     facet count" setting.
 *   - weight: The weight of the facet
 *   - map callback: The callback used to map the raw values returned by the
 *     index to something human readable.
 *   - map options: An array of options passed to the map callback.
 *   - hierarchy callback: A callback that maps the parent / child relationships
 *     of the facet data, defaults to FALSE meaning the list is flat.
 *   - values callback: In instances where facet data is not returned by the
 *     backend, provide a list of values that can be used.
 *   - min callback: For facets containing ranges, a callback returning the
 *     minimum value in the index.
 *   - max callback: For facets containing ranges, a callback returning the
 *     maximum value in the index.
 *   - default sorts: An array of available sorts. Each item is an array
 *     containing two values, the first being the item being filtered on, the
 *     second being the SORT_* constant.
 */
function facetapi_facet_load($facet_name, $searcher) {
  $facet_info = facetapi_get_facet_info($searcher);
  return (isset($facet_info[$facet_name])) ? $facet_info[$facet_name] : FALSE;
}

////
////
//// facetapi_get_*() functions
////
////

/**
 * Returns all defined searcher definitions.
 *
 * @return array
 *   An array of searcher information. Each array is keyed by the machine
 *   readable searcher name and contains the following items:
 *   - name: The machine readable name of the searcher.
 *   - label: The human readable name of the searcher displayed in the admin UI.
 *   - adapter: The adapter plugin ID associated with the searcher.
 *   - url processor: The URL processor plugin ID associated with the searcher.
 *   - types: An array containing the types of content indexed by the searcher.
 *     A type is usually an entity such as 'node', but it can be a non-entity
 *     value as well.
 *   - path: The MENU_DEFAULT_LOCAL_TASK item which the admin UI page is added
 *     to as a MENU_LOCAL_TASK. An empty string if the backend manages the admin
 *     UI menu items internally.
 *   - supports facet missing: TRUE if the searcher supports "missing" facets.
 *   - supports facet mincount: TRUE if the searcher supports the minimum facet
 *     count setting.
 *   - include default facets: TRUE if the searcher should include the facets
 *     defined in facetapi_facetapi_facet_info() when indexing node content,
 *     FALSE if they should be skipped.
 */
function facetapi_get_searcher_info() {
  $searcher_info = array();
  foreach (module_implements('facetapi_searcher_info') as $module) {
    // Iterates over the module's searcher definition.
    foreach ((array) module_invoke($module, 'facetapi_searcher_info') as $searcher => $info) {
      // @see http://drupal.org/node/1167974
      // Converts "type" to an array and stores in "types".
      // @todo Remove in later versions.
      if (isset($info['type']) && !isset($info['types'])) {
        $info['types'] = array($info['type']);
      }

      // @see http://drupal.org/node/1304010
      // Converts "url_processor" to "url processor" for consistency.
      // @todo Remove in later versions.
      if (isset($info['url_processor']) && !isset($info['url processor'])) {
        $info['url processor'] = $info['url_processor'];
      }

      $info += array(
        'module' => $module,
        'name' => $searcher,
        'path' => '',
        'types' => array('node'),
        'url processor' => 'standard',
        'supports facet missing' => FALSE,
        'supports facet mincount' => FALSE,
        'include default facets' => TRUE,
      );

      // @see http://drupal.org/node/1167974
      // Makes sure old style "type" is present.
      if (!isset($info['type'])) {
        $info['type'] = $info['types'][key($info['types'])];
      }

      // Maps "types" so we can do faster lookups via isset().
      $info['types'] = drupal_map_assoc($info['types']);
      $searcher_info[$searcher] = $info;
    }
  }

  drupal_alter('facetapi_searcher_info', $searcher_info);
  array_walk($searcher_info, 'facetapi_map_assoc', 'types');
  return $searcher_info;
}

/**
 * Returns a list of active searchers.
 *
 * An active searcher means that facet data is parsed and processed by the
 * backend. Any searcher's adapter who's FacetapiAdapter::addActiveFilters() was
 * called is automatically added to this list.
 *
 * @return array
 *   An associative array of active adapters
 */
function facetapi_get_active_searchers() {
  $searchers = &drupal_static('facetapi_active_searchers', array());
  return $searchers;
}

/**
 * Returns all defined realm definitions.
 *
 * @return array
 *   An array of realm definitions. Each definition is an array keyed by the
 *   machine readable name of the realm. See the return value of the
 *   facetapi_realm_load() function for the structure of the definitions.
 */
function facetapi_get_realm_info() {
  $realm_info = &drupal_static(__FUNCTION__);
  if (NULL === $realm_info) {
    $realm_info = module_invoke_all('facetapi_realm_info');
    foreach ($realm_info as $realm_name => $realm) {
      $realm_info[$realm_name] += array(
        'name' => $realm_name,
        'label' => $realm_name,
        'description' => '',
        'default widget' => '',
        'settings callback' => FALSE,
        'element type' => 'links',
        'sortable' => TRUE,
        'weight' => 0,
      );
    }
    drupal_alter('facetapi_realm_info', $realm_info);
    uasort($realm_info, 'drupal_sort_weight');
  }
  return $realm_info;
}

/**
 * Returns all defined facet definitions available to the searcher.
 *
 * @param $searcher
 *   A string containing the machine readable name of the searcher.
 *
 * @return array
 *   An array of facet definitions. Each definition is an array keyed by the
 *   machine readable name of the facet. See the return value of the
 *   facetapi_facet_load() function for the structure of the definitions.
 */
function facetapi_get_facet_info($searcher) {
  $facet_info = &drupal_static(__FUNCTION__, array());

  // Gets facet info if we haven't gotten it already.
  if (!isset($facet_info[$searcher])) {

    // Builds cache ID.
    global $language;
    $cid = 'facetapi:facet_info:' . $searcher . ':' . $language->language;

    // Checks if our results are cached.
    $cache = cache_get($cid);
    if (!empty($cache->data)) {
      $facet_info[$searcher] = $cache->data;
    }
    else {
      $searcher_info = facetapi_get_searcher_info();
      $facet_info[$searcher] = array();

      // Invokes hook_facetapi_facet_info(), normalizes facets.
      foreach (module_implements('facetapi_facet_info') as $module) {
        $facets = call_user_func($module . '_facetapi_facet_info', $searcher_info[$searcher]);
        if (!$facets || !is_array($facets)) {
          $facets = array();
        }

        // Iterates over facet definitions, merges defaults.
        foreach ($facets as $facet_name => $info) {

          // @see http://drupal.org/node/1161434
          // Converts "query type" to an array and stores in "query types".
          // @todo Remove in later versions.
          if (isset($info['query type']) && !isset($info['query types'])) {
            $info['query types'] = array($info['query type']);
          }

          $facet_info[$searcher][$facet_name] = $info;
          $facet_info[$searcher][$facet_name] += array(
            'name' => $facet_name,
            'label' => $facet_name,
            'description' => '',
            'field' => $facet_name,
            'field alias' => isset($info['field']) ? $info['field'] : $facet_name,
            'field api name' => FALSE,
            'field api bundles' => array(),
            'query types' => array('term'),
            'alter callbacks' => array(),
            'dependency plugins' => array(),
            'default widget' => FALSE,
            'allowed operators' => array(FACETAPI_OPERATOR_AND => TRUE, FACETAPI_OPERATOR_OR => TRUE),
            'facet missing allowed' => FALSE,
            'facet mincount allowed' => FALSE,
            'weight' => 0,
            'map callback' => FALSE,
            'map options' => array(),
            'hierarchy callback' => FALSE,
            'values callback' => FALSE,
            'min callback' => FALSE,
            'max callback' => FALSE,
            'default sorts' => array(
              array('active', SORT_DESC),
              array('count', SORT_DESC),
              array('display', SORT_ASC),
            ),
          );

          // @see http://drupal.org/node/1161434
          // Makes sure old style "query type" is present.
          // @todo Remove in later versions.
          if (!isset($facet_info[$searcher][$facet_name]['query type'])) {
            $type = key($facet_info[$searcher][$facet_name]['query types']);
            $facet_info[$searcher][$facet_name]['type'] = $type;
          }
        }
      }

      // Invokes alter hook, sorts and returns.
      drupal_alter('facetapi_facet_info', $facet_info[$searcher], $searcher_info[$searcher]);
      array_walk($facet_info[$searcher], 'facetapi_map_assoc', 'field api bundles');
      uasort($facet_info[$searcher], 'drupal_sort_weight');

      // Caches the result.
      cache_set($cid, $facet_info[$searcher], 'cache', CACHE_TEMPORARY);
    }
  }
  return $facet_info[$searcher];
}

/**
 * Implements hook_field_create_instance().
 */
function facetapi_field_create_instance($instance) {
  cache_clear_all('facetapi:facet_info:', 'cache', TRUE);
}

/**
 * Implements hook_field_delete_instance().
 */
function facetapi_field_delete_instance($instance) {
  cache_clear_all('facetapi:facet_info:', 'cache', TRUE);
}

/**
 * Wrapper around drupal_map_assoc() for a key in all items of an array.
 *
 * Useful as an array_walk() callback.
 *
 * @param array &$array
 *   The array being modified.
 * @param $name
 *   The key of the array being modified, usually the name of a definition.
 * @param $key
 *   The key in the array being passed to drupal_map_assoc().
 */
function facetapi_map_assoc(&$array, $name, $key) {
  $array[$key] = drupal_map_assoc($array[$key]);
}

/**
 * Returns all sort definitions.
 *
 * @return array
 *   An associative array of sort definitions keyed by sort name. Each sort
 *   definition contains:
 *   - name: The machine readable name of the sort.
 *   - title: The human readable name of the sort displayed in the admin UI.
 *   - callback: The uasort() callback the render array is passed to.
 *   - description: The description of the sort displayed in the admin UI.
 *   - weight: The default weight of the sort specifying its processing order.
 */
function facetapi_get_sort_info() {
  $sort_info = &drupal_static(__FUNCTION__);
  if (NULL === $sort_info) {
    $sort_info = module_invoke_all('facetapi_sort_info');
    foreach ($sort_info as $sort_name => $info) {
      $sort_info[$sort_name] += array(
        'name' => $sort_name,
        'label' => $sort_name,
        'callback' => '',
        'requirements' => array(),
        'description' => '',
        'weight' => 0,
      );
    }
    drupal_alter('facetapi_sort_info', $sort_info);
  }
  return $sort_info;
}

/**
 * Returns all filter definitions available to the facet.
 *
 * Each filter plugin must pass all the requirements checks specified in its
 * definition. Only plugins that pass all requirements are returned.
 *
 * @param array $facet
 *   The facet definition as returned by facetapi_facet_load().
 *
 * @return array
 *   An associative array of filter plugin definitions keyed by the plugin ID.
 *   Each filter plugin definition contains:
 *   - handler: An associative array containing:
 *     - label: The human readable name of the plugin displayed in the admin UI.
 *     - description: The description of the plugin displayed in the admin UI.
 *     - class: The class containing the plugin.
 */
function facetapi_get_filters(array $facet) {
  $plugins = array();

  // Iterates over all defined plugins.
  foreach (ctools_get_plugins('facetapi', 'filters') as $id => $plugin) {
    $plugin['handler'] += array(
      'label' => $id,
      'description' => '',
      'requirements' => array(),
    );

    // Checks requirements.
    if (facetapi_check_requirements($plugin['handler']['requirements'], array(), $facet)) {
      $plugins[$id] = $plugin;
    }
  }

  return $plugins;
}

/**
 * Gets raw settings from the datbase, caches as a satic variable.
 *
 * Avoid using this function directly as it will not load default settings. Use
 * the FacetapiAdapter::getFacetSettings*() method instead.
 *
 * @param $searcher
 *   A string containing the searcher.
 *
 * @return array
 *   An array of settings keyed by name.
 *
 * @see FacetapiAdapter::getFacetSettings()
 * @see FacetapiAdapter::getFacetSettingsGlobal()
 */
function facetapi_get_searcher_settings($searcher) {
  $settings = &drupal_static(__FUNCTION__, array());
  if (!isset($settings[$searcher])) {
    ctools_include('export');
    $args = array('searcher' => $searcher);
    $settings[$searcher] = ctools_export_load_object('facetapi', 'conditions', $args);
  }
  return $settings[$searcher];
}

/**
 * Returns all enabled facet definitions available to the searcher.
 *
 * If a realm is passed, this function returns all facets enabled in the realm.
 * If no realm is passed, this function returns all facets that are enabled in
 * at least one realm.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm, pass NULL to return all facets that
 *   are enabled in at least one realm.
 *
 * @return array
 *   An array of facet definitions. Each definition is an array keyed by the
 *   machine readable name of the facet. See the return value of the
 *   facetapi_facet_load() function for the structure of the definitions.
 */
function facetapi_get_enabled_facets($searcher, $realm_name = NULL) {
  $enabled_facets = &drupal_static(__FUNCTION__, array());
  $cid = $searcher . ':' . (string) $realm_name;
  if (!isset($enabled_facets[$cid])) {
    $facets = array();

    // Gets cached settings, finds enabled facets.
    $cached = facetapi_get_searcher_settings($searcher);
    foreach ($cached as $name => $settings) {
      $test_enabled = (NULL === $realm_name || $realm_name == $settings->realm);
      if ($test_enabled && $settings->enabled) {
        $facets[$settings->facet] = $settings->facet;
      }
    }

    // Gets facet definitions for all enabled facets.
    $facet_info = facetapi_get_facet_info($searcher);
    $enabled_facets[$cid] = array_intersect_key($facet_info, $facets);
  }
  return $enabled_facets[$cid];
}

////
////
//// Utility functions
////
////

/**
 * Translates a string via the translator module.
 *
 * @param $name
 *   The name of the string in "textgroup:object_type:object_key:property_name"
 *   format.
 * @param $string
 *   The string being translated.
 * @param $langcode
 *   The language code to translate to a language other than what is used to
 *   display the page. Defaults to NULL, which uses the current language.
 *
 * @return
 *   The translated string.
 */
function facetapi_translate_string($name, $string, $langcode = NULL) {
  if ($module = variable_get('facetapi:translator_module', NULL)) {
    $function = $module . '_facetapi_translate_string';
    if (function_exists($function)) {
      $string = $function($name, $string, $langcode);
    }
  }
  return $string;
}

/**
 * Tests whether a searcher is active or not.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 *
 * @return FacetapiAdapter
 *   The adapter object, FALSE if the object can't be loaded.
 */
function facetapi_is_active_searcher($searcher) {
  $searchers = facetapi_get_active_searchers();
  return (isset($searchers[$searcher]));
}

/**
 * Adds an active searcher to the list.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 *
 * @see facetapi_get_active_searchers();
 */
function facetapi_add_active_searcher($searcher) {
  $searchers = &drupal_static('facetapi_active_searchers', array());
  $searchers[$searcher] = $searcher;
}

/**
 * Tests whether a single facet is enabled in a given realm.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm, pass NULL to test if the facet is
 *   enabled in at least one realm.
 * @param $facet_name
 *   The machine readable name of the facet.
 *
 * @return
 *   A boolean flagging whether the facet is enabled in the passed realm.
 */
function facetapi_facet_enabled($searcher, $realm_name, $facet_name) {
  $enabled_facets = facetapi_get_enabled_facets($searcher, $realm_name, $facet_name);
  return isset($enabled_facets[$facet_name]);
}

/**
 * Builds a facet realm.
 *
 * Converts the facet data into a render array suitable for passing to the
 * drupal_render() function.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm.
 *
 * @return array
 *   The realm's render array.
 */
function facetapi_build_realm($searcher, $realm_name) {
  $adapter = facetapi_adapter_load($searcher);
  return ($adapter) ? $adapter->buildRealm($realm_name) : array();
}

/**
 * Checks requirements.
 *
 * Requirements fail if at least one requirements callback returns FALSE. Note
 * that if no requirement callbacks are passed, this function will return TRUE.
 *
 * @param array $requirements
 *   The requirements keyed by callback to options.
 * @param array $realm
 *   The realm definition.
 * @param array $facet
 *   The facet definition.
 *
 * @return
 *   A boolean flagging whether all requirements were passed.
 */
function facetapi_check_requirements(array $requirements, array $realm, array $facet) {
  $return = TRUE;
  module_load_include('inc', 'facetapi', 'facetapi.requirements');
  foreach ($requirements as $callback => $options) {
    if (!call_user_func($callback, $realm, $facet, $options)) {
      $return = FALSE;
      break;
    }
  }
  return $return;
}

/**
 * Enables or disables a facet for this page load only.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm, pass NULL for all realms.
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $status
 *   A boolean flagging whether the facet is enabled or disabled.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.  If set to
 *   TRUE, the list of enabled facets won't be rebuild and the active items
 *   won't be re-processed.  Note that these tasks will have to be performed
 *   manually in order for the status to be properly set.
 */
function facetapi_set_facet_status($searcher, $realm_name, $facet_name, $status, $batch_process) {
  // Rebuild static if not batch processing.
  if (!$batch_process) {
    drupal_static('facetapi_get_enabled_facets', array(), TRUE);
  }

  // Pulls the list of enabled facets so we can modify it here.
  facetapi_get_enabled_facets($searcher, $realm_name);
  $enabled_facets = &drupal_static('facetapi_get_enabled_facets', array());

  // Performs the operation by setting or unsetting the facet.
  $cid = $searcher . ':' . (string) $realm_name;
  if ($status && !isset($enabled_facets[$cid][$facet_name])) {
    if ($facet = facetapi_facet_load($facet_name, $searcher)) {
      // Add facet to static, which enables it.
      $enabled_facets[$cid][$facet_name] = $facet;
      // If facet isn't already globally enabled, enable it.
      if (!isset($enabled_facets[$searcher . ':'][$facet_name])) {
        // Ensure sure static is set before modifying it.
        facetapi_get_enabled_facets($searcher, NULL);
        $enabled_facets[$searcher . ':'][$facet_name] = $facet;
      }
    }
  }
  elseif (!$status && isset($enabled_facets[$cid][$facet_name])) {
    // Removes facet to static, which disables it.
    unset($enabled_facets[$cid][$facet_name]);
    // If acting globally, disable facet in all realms.
    if (!$realm_name) {
      foreach (facetapi_get_realm_info() as $realm) {
        // Ensure sure static is set before unsetting the facet.
        facetapi_get_enabled_facets($searcher, $realm['name']);
        unset($enabled_facets[$searcher . ':' . $realm['name']][$facet_name]);
      }
    }
  }
  else {
    return;
  }

  // Re-process the active items since the list of active facets has changed.
  if (!$batch_process && ($adapter = facetapi_adapter_load($searcher))) {
    $adapter->processActiveItems();
  }
}

/**
 * Enables a facet for this page load only.
 *
 * If you are enabling facets in the block realm, you will have to force the
 * delta mapping so that the block can be configured even if it is disabled via
 * the Facet API interface. Otherwise you will not be able to assign the block
 * to a region because it won't be available in admin/structure/block.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm, pass NULL for all realms.
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.
 *
 * @see facetapi_set_facet_status()
 * @see hook_facetapi_force_delta_mapping().
 */
function facetapi_set_facet_enabled($searcher, $realm_name, $facet_name, $batch_process = FALSE) {
  return facetapi_set_facet_status($searcher, $realm_name, $facet_name, TRUE, $batch_process);
}

/**
 * Disables a facet for this page load only.
 *
 * @param $searcher
 *   The machine readable name of the searcher.
 * @param $realm_name
 *   The machine readable name of the realm, pass NULL for all realms.
 * @param $facet_name
 *   The machine readable name of the facet.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.
 *
 * @see facetapi_set_facet_status()
 */
function facetapi_set_facet_disabled($searcher, $realm_name, $facet_name, $batch_process = FALSE) {
  return facetapi_set_facet_status($searcher, $realm_name, $facet_name, FALSE, $batch_process);
}

/**
 * Sets the facet status in a given realm, stores settings in the database.
 *
 * @param FacetapiAdapter $adapter
 *   The adapter object of the searcher the settings are being modified for.
 * @param array $realm
 *   The realm definition as returned by facetapi_realm_load().
 * @param array $facet
 *   The facet definition as returned by facetapi_facet_load().
 * @param $status
 *   Flags whether or not the facet is being enabled or disabled.
 * @param $weight
 *   If the realm is sortable, allows the assigning of a weight. Pass FALSE to
 *   maintain the previously stored value.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.  If set to
 *   TRUE, the caches and statics won't be reset.
 *
 * @reutrn
 *   TRUE if the operation succeeded, FALSE otherwise.
 */
function facetapi_save_facet_status(FacetapiAdapter $adapter, array $realm, array $facet, $status, $weight, $batch_process) {
  // Loads the realm settings, sets enabled flag and weight.
  $settings = $adapter->getFacet($facet)->getSettings($realm);
  $settings->enabled = ($status) ? 1 : 0;
  if (FALSE !== $weight) {
    $settings->settings['weight'] = $realm['sortable'] ? $weight : 0;
  }

  // Saves the settings in the database, stores the result.
  // NOTE: CTools export componenet loaded in the getSettings() method.
  $success = (FALSE !== ctools_export_crud_save('facetapi', $settings));

  // Clears caches and statics if we are not batch processing.
  if ($success && !$batch_process) {
    drupal_static('facetapi_get_searcher_settings', array(), TRUE);
    drupal_static('facetapi_get_enabled_facets', array(), TRUE);
    if ('block' == $realm['name']) {
      cache_clear_all(NULL, 'cache_block');
      cache_clear_all('facetapi:delta_map', 'cache');
    }
  }

  return $success;
}

/**
 * Enables a facet in a given realm, stores settings in the database.
 *
 * @param FacetapiAdapter $adapter
 *   The adapter object of the searcher the settings are being modified for.
 * @param array $realm
 *   The realm definition as returned by facetapi_realm_load().
 * @param array $facet
 *   The facet definition as returned by facetapi_facet_load().
 * @param $weight
 *   If the realm is sortable, allows the assigning of a weight. Pass FALSE to
 *   maintain the previously stored value.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.
 *
 * @reutrn
 *   TRUE if the operation succeeded, FALSE otherwise.
 */
function facetapi_save_facet_enabled(FacetapiAdapter $adapter, array $realm, array $facet, $weight = FALSE, $batch_process = FALSE) {
  return facetapi_save_facet_status($adapter, $realm, $facet, TRUE, $weight, $batch_process);
}

/**
 * Disables a facet in a given realm, stores settings in the database.
 *
 * @param FacetapiAdapter $adapter
 *   The adapter object of the searcher the settings are being modified for.
 * @param array $realm
 *   The realm definition as returned by facetapi_realm_load().
 * @param array $facet
 *   The facet definition as returned by facetapi_facet_load().
 * @param $weight
 *   If the realm is sortable, allows the assigning of a weight. Pass FALSE to
 *   maintain the previously stored value.
 * @param $batch_process
 *   A boolean flagging whether batch processing is being performed.
 *
 * @reutrn
 *   TRUE if the operation succeeded, FALSE otherwise.
 */
function facetapi_save_facet_disabled(FacetapiAdapter $adapter, array $realm, array $facet, $weight = FALSE, $batch_process = FALSE) {
  return facetapi_save_facet_status($adapter, $realm, $facet, FALSE, $weight, $batch_process);
}
