<?php

/**
 * @file
 * Provide synonyms feature for Drupal Taxonomy.
 */

/**
 * The default field name to be used as a source of synonyms for a term.
 */
define('SYNONYMS_DEFAULT_FIELD_NAME', 'synonyms_synonyms');

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

  $items['synonyms/autocomplete'] = array(
    'title' => 'Autocomplete Synonyms',
    'page callback' => 'synonyms_autocomplete',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Implements hook_synonyms_extractor_info().
 */
function synonyms_synonyms_extractor_info() {
  // Here we provide synonyms extractors that come along with Synonyms module.
  return array(
    'SynonymsSynonymsExtractor',
    'TaxonomySynonymsExtractor',
    'EntityReferenceSynonymsExtractor',
  );
}

/**
 * Public function.
 *
 * Provide info about what class reports ability to extract synonyms from
 * which field type. The output information of this function is collected via
 * hook_synonyms_extractor_info().
 *
 * @param string $field_type
 *   Optionally you may specify to get a class responsible for a specific field
 *   type only. If nothing is supplied, array of field_type => class_extractor
 *   relation is returned
 * @param bool $reset
 *   Whether collect all the info again from hooks, or cached info is fine
 *
 * @return array
 *   Key of this array denote the field type while value of the array denotes
 *   which class reports ability to extract synonyms from such field type.
 */
function synonyms_extractor_info($field_type = NULL, $reset = FALSE) {
  $cache = &drupal_static(__FUNCTION__);

  // Trying static cache.
  if (!is_array($cache) || $reset) {
    // Trying Drupal DB cache layer.
    $cid = 'synonyms_extractor_info';
    $cache = cache_get($cid);
    if (!isset($cache->data) || $reset) {
      // No cache has been found at all. So we call hooks and collect data.
      $info = array();

      $extractor_classes = module_invoke_all('synonyms_extractor_info');

      if (is_array($extractor_classes)) {
        foreach ($extractor_classes as $class) {
          if (class_exists($class) && is_subclass_of($class, 'AbstractSynonymsExtractor')) {
            foreach ($class::fieldTypesSupported() as $_field_type) {
              $info[$_field_type] = $class;
            }
          }
        }
      }

      // Letting whoever wants to implement any changes after preprocessing the
      // data.
      drupal_alter('synonyms_extractor_info', $info);

      // Validating that any changes made to $info do not break class hierarchy.
      foreach ($info as $k => $v) {
        if (!class_exists($v) || !is_subclass_of($v, 'AbstractSynonymsExtractor')) {
          unset($info[$k]);
        }
      }

      $cache = $info;
      cache_set($cid, $cache, 'cache', CACHE_TEMPORARY);
    }
    else {
      $cache = $cache->data;
    }
  }

  if (!is_null($field_type) && isset($cache[$field_type])) {
    return $cache[$field_type];
  }

  return $cache;
}

/**
 * Implements hook_node_update_index().
 */
function synonyms_node_update_index($node) {
  $output = '';
  foreach (field_info_instances('node', $node->type) as $instance) {
    // We go a field by field looking for taxonomy term reference and
    // if that vocabulary has enabled synonyms, we add term's synonyms
    // to the search index.
    $field_info = field_info_field($instance['field_name']);
    if ($field_info['type'] == 'taxonomy_term_reference') {
      // For each term referenced in this node we have to add synonyms.
      $_terms = field_get_items('node', $node, $instance['field_name']);
      if (is_array($_terms) && !empty($_terms)) {
        $terms = array();
        foreach ($_terms as $v) {
          $terms[] = $v['tid'];
        }
        $terms = taxonomy_term_load_multiple($terms);
        foreach ($terms as $term) {
          $synonyms = synonyms_get_term_synonyms($term);
          if (!empty($synonyms)) {
            $safe_synonyms = array();
            foreach ($synonyms as $synonym) {
              $safe_synonyms[] = $synonym['safe_value'];
            }
            $output .= '<strong>' . implode(', ', $safe_synonyms) . '</strong>';
          }
        }
      }
    }
  }
  return $output;
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function synonyms_form_taxonomy_form_vocabulary_alter(&$form, &$form_state) {
  if (isset($form_state['confirm_delete']) && $form_state['confirm_delete']) {
    return;
  }

  $form['synonyms'] = array(
    '#type' => 'fieldset',
    '#title' => t('Synonyms'),
    '#collapsible' => TRUE,
    '#tree' => TRUE,
  );

  $options = array(
    SYNONYMS_DEFAULT_FIELD_NAME => t('Default synonyms field'),
  );
  if (isset($form['#vocabulary']->vid)) {
    $instances = synonyms_instances_extract_applicapable($form['#vocabulary']);
    foreach ($instances as $instance) {
      // Here we prefer some informative text for the default synonyms field
      // rather its label.
      if ($instance['field_name'] != SYNONYMS_DEFAULT_FIELD_NAME) {
        $options[$instance['field_name']] = $instance['label'];
      }
    }
  }

  $form['synonyms']['synonyms'] = array(
    '#type' => 'checkboxes',
    '#title' => t('Synonyms Fields'),
    '#options' => $options,
    '#description' => t('<p>This option allows you to assign synonym fields for each term of the vocabulary, allowing to reduce the amount of duplicates.</p><p><b>Important note:</b> unticking %default_field on a production website will result in loss of your synonyms.</p>', array('%default_field' => $options[SYNONYMS_DEFAULT_FIELD_NAME])),
    '#default_value' => synonyms_synonyms_fields($form['#vocabulary']),
  );

  // Adding out own submit handler.
  $form['#submit'][] = 'synonyms_taxonomy_form_vocabulary_submit';
}

/**
 * Implements hook_field_widget_info().
 */
function synonyms_field_widget_info() {
  return array(
    'synonyms_autocomplete' => array(
      'label' => t('Synonyms friendly autocomplete term widget'),
      'field types' => array('taxonomy_term_reference'),
      'settings' => array(
        'size' => 60,
        'autocomplete_path' => 'synonyms/autocomplete',
      ),
      'behaviors' => array(
        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
      ),
    ),
  );
}

/**
 * Implements hook_field_widget_settings_form().
 */
function synonyms_field_widget_settings_form($field, $instance) {
  $widget = $instance['widget'];
  $settings = $widget['settings'];

  $form = array();

  $form['auto_creation'] = array(
    '#type' => 'checkbox',
    '#title' => t('Allow auto-creation?'),
    '#description' => t('Whether users may create a new term by typing in a non-existing name into this field.'),
    '#default_value' => isset($settings['auto_creation']) ? $settings['auto_creation'] : 0,
  );

  return $form;
}

/**
 * Implements hook_field_widget_form().
 */
function synonyms_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
  $tags = array();
  foreach ($items as $item) {
    $tags[$item['tid']] = isset($item['taxonomy_term']) ? $item['taxonomy_term'] : taxonomy_term_load($item['tid']);
  }

  $element += array(
    '#type' => 'textfield',
    '#default_value' => taxonomy_implode_tags($tags),
    '#autocomplete_path' => $instance['widget']['settings']['autocomplete_path'] . '/' . $field['field_name'],
    '#size' => $instance['widget']['settings']['size'],
    '#maxlength' => 1024,
    '#element_validate' => array('taxonomy_autocomplete_validate', 'synonyms_autocomplete_validate'),
    '#auto_creation' => isset($instance['widget']['settings']['auto_creation']) ? $instance['widget']['settings']['auto_creation'] : 0,
  );

  return $element;
}

/**
 * Implements hook_field_widget_error().
 */
function synonyms_field_widget_error($element, $error, $form, &$form_state) {
  form_error($element, $error['message']);
}

/**
 * Form element validate handler.
 *
 * Handle validation for taxonomy term synonym-friendly autocomplete element.
 */
function synonyms_autocomplete_validate($element, &$form_state) {
  // After taxonomy_autocomplete_validate() has finished its job
  // it might left terms in the format for autocreation. Since our field
  // supports auto creation as a configurable option, we have to make sure
  // auto creation terms are allowed.
  $value = drupal_array_get_nested_value($form_state['values'], $element['#parents']);
  if (!$element['#auto_creation']) {
    // Deleting all the terms meant to be auto-created.
    foreach ($value as $delta => $term) {
      if ($term['tid'] == 'autocreate') {
        unset($value[$delta]);
      }
    }
    $value = array_values($value);
  }

  form_set_value($element, $value, $form_state);
}

/**
 * Submit hanlder for Taxonomy vocabulary edit form.
 *
 * Store extra values attached to form in this module.
 */
function synonyms_taxonomy_form_vocabulary_submit($form, &$form_state) {
  $values = $form_state['values'];

  if ($values['op'] == $form['actions']['submit']['#value']) {
    if (isset($form['#vocabulary']->vid)) {
      $vocabulary = taxonomy_vocabulary_load($form['#vocabulary']->vid);
    }
    else {
      // As a fallback, if this is a just created vocabulary, we try to pull it
      // up by the just submitted machine name.
      $vocabulary = taxonomy_vocabulary_machine_name_load($values['machine_name']);
    }

    // Preprocessing values keeping only field names of the checked fields.
    foreach ($values['synonyms']['synonyms'] as $k => $v) {
      if (!$v) {
        unset($values['synonyms']['synonyms'][$k]);
      }
    }
    $values['synonyms']['synonyms'] = array_values($values['synonyms']['synonyms']);
    $settings = synonyms_vocabulary_settings($vocabulary);
    $settings = $values['synonyms'] + $settings;
    synonyms_vocabulary_settings_save($vocabulary, $settings);
  }
}

/**
 * Page callback: Outputs JSON for taxonomy autocomplete suggestions.
 *
 * This callback outputs term name suggestions in response to Ajax requests
 * made by the synonyms autocomplete widget for taxonomy term reference
 * fields. The output is a JSON object of plain-text term suggestions,
 * keyed by the user-entered value with the completed term name appended.
 * Term names containing commas are wrapped in quotes. The search is made
 * with consideration of synonyms.
 *
 * @param string $field_name
 *   The name of the term reference field.
 * @param string $tags_typed
 *   (optional) A comma-separated list of term names entered in the
 *   autocomplete form element. Only the last term is used for autocompletion.
 *   Defaults to '' (an empty string).
 */
function synonyms_autocomplete($field_name, $tags_typed = '') {
  // How many suggestions maximum we are able to output.
  $max_suggestions = 10;

  // If the request has a '/' in the search text, then the menu system will have
  // split it into multiple arguments, recover the intended $tags_typed.
  $args = func_get_args();
  // Shift off the $field_name argument.
  array_shift($args);
  $tags_typed = implode('/', $args);

  // Make sure the field exists and is a taxonomy field.
  if (!($field = field_info_field($field_name)) || $field['type'] != 'taxonomy_term_reference') {
    // Error string. The JavaScript handler will realize this is not JSON and
    // will display it as debugging information.
    print t('Taxonomy field @field_name not found.', array('@field_name' => $field_name));
    exit;
  }

  // The user enters a comma-separated list of tags. We only autocomplete the
  // last tag.
  $tags_typed = drupal_explode_tags($tags_typed);
  $tag_last = drupal_strtolower(array_pop($tags_typed));

  $term_matches = array();
  if ($tag_last != '') {
    // Part of the criteria for the query come from the field's own settings.
    $vocabularies = array();
    $tmp = taxonomy_vocabulary_get_names();
    foreach ($field['settings']['allowed_values'] as $tree) {
      $vocabularies[$tmp[$tree['vocabulary']]->vid] = $tree['vocabulary'];
    }
    $vocabularies = taxonomy_vocabulary_load_multiple(array_keys($vocabularies));

    // Firstly getting a list of tids that match by $term->name.
    $query = db_select('taxonomy_term_data', 't');
    $query->addTag('translatable');
    $query->addTag('term_access');

    // Do not select already entered terms.
    if (!empty($tags_typed)) {
      $query->condition('t.name', $tags_typed, 'NOT IN');
    }
    // Select rows that match by term name.
    $tags_return = $query
      ->fields('t', array('tid', 'name'))
      ->condition('t.vid', array_keys($vocabularies))
      ->condition('t.name', '%' . db_like($tag_last) . '%', 'LIKE')
      ->range(0, $max_suggestions)
      ->execute()
      ->fetchAllKeyed();

    // Converting results into another format.
    foreach ($tags_return as $tid => $name) {
      $tags_return[$tid] = array('name' => $name);
    }

    $synonym_tids = array();
    // Now we go vocabulary by vocabulary looking through synonym fields.
    foreach ($vocabularies as $vocabulary) {
      // Now we go a synonym field by synonym field gathering suggestions.
      // Since officially EntityFieldQuery doesn't support OR conditions
      // we are enforced to go a field by field querying multiple times the DB.
      $bundle = field_extract_bundle('taxonomy_term', $vocabulary);
      foreach (synonyms_synonyms_fields($vocabulary) as $field) {
        $field = field_info_field($field);
        $instance = field_info_instance('taxonomy_term', $field['field_name'], $bundle);
        if (count($tags_return) + count($synonym_tids) > $max_suggestions) {
          // We have collected enough suggestions and the ongoing queries
          // will be just a waste of time.
          break;
        }
        $query = new EntityFieldQuery();
        $query->entityCondition('entity_type', 'taxonomy_term')
            ->entityCondition('bundle', $vocabulary->machine_name);

        // We let the class that defines this field type as a source of synonyms
        // filter our and provide its suggestions based on this field.
        $class = synonyms_extractor_info($field['type']);
        $class::processEntityFieldQuery($tag_last, $query, $field, $instance);

        if (!empty($tags_typed)) {
          $query->propertyCondition('name', $tags_typed, 'NOT IN');
        }
        if (!empty($tags_return)) {
          // We don't want to search among the terms already found by term name.
          $query->entityCondition('entity_id', array_keys($tags_return), 'NOT IN');
        }
        if (!empty($synonym_tids)) {
          // Nor we want to search among the terms already mached by previous
          // synonym fields.
          $query->entityCondition('entity_id', $synonym_tids, 'NOT IN');
        }
        $tmp = $query->execute();
        if (!empty($tmp)) {
          // Merging the results.
          $tmp = array_keys($tmp['taxonomy_term']);
          $synonym_tids = array_merge($synonym_tids, $tmp);
        }
      }
    }
    if (!empty($synonym_tids)) {
      $synonym_tids = array_slice($synonym_tids, 0, $max_suggestions - count($tags_return));
      foreach (taxonomy_term_load_multiple($synonym_tids) as $synonym_term) {
        $tags_return[$synonym_term->tid] = array('name' => $synonym_term->name);
        // Additionally we have to find out which synonym triggered inclusion
        // of this term.
        $synonyms = synonyms_get_term_synonyms($synonym_term);
        foreach ($synonyms as $item) {
          if (strpos(mb_strtoupper($item['value'], 'UTF-8'), mb_strtoupper($tag_last, 'UTF-8')) !== FALSE) {
            $tags_return[$synonym_term->tid]['synonym'] = $item['value'];
            break;
          }
        }
      }
    }
    $prefix = count($tags_typed) ? drupal_implode_tags($tags_typed) . ', ' : '';

    // Now formatting the results.
    foreach ($tags_return as $tid => $info) {
      $n = $info['name'];
      // Term names containing commas or quotes must be wrapped in quotes.
      if (strpos($info['name'], ',') !== FALSE || strpos($info['name'], '"') !== FALSE) {
        $n = '"' . str_replace('"', '""', $info['name']) . '"';
      }

      if (isset($info['synonym'])) {
        $display_name = t('@synonym, synonym of %term', array('@synonym' => $info['synonym'], '%term' => $info['name']));
      }
      else {
        $display_name = check_plain($info['name']);
      }
      $term_matches[$prefix . $n] = $display_name;
    }
  }
  drupal_json_output($term_matches);
}

/**
 * Try to find a term by its name or synonym.
 *
 * To maximize the match trimming and case-insensetive comparison is used.
 *
 * @param string $name
 *   The string to be searched for its {taxonomy_term}.tid
 * @param object $vocabulary
 *   Fully loaded vocabulary object in which you wish to search
 * @param int $parent
 *   Optional. In case you want to narrow your search scope, this parameter
 *   takes in the {taxonomy_term}.tid of the parent term, letting you search
 *   only among its children
 *
 * @return int
 *   If the look up was successfull returns the {taxonomy_term}.tid of the
 *   found term, otherwise returns 0
 */
function synonyms_get_term_by_synonym($name, $vocabulary, $parent = 0) {
  $name = mb_strtoupper(trim($name), 'UTF-8');

  $tree = taxonomy_get_tree($vocabulary->vid, $parent, NULL, TRUE);
  foreach ($tree as $term) {
    if (mb_strtoupper($term->name, 'UTF-8') == $name) {
      return $term->tid;
    }

    // We additionally scan through the synonyms.
    $synonyms = synonyms_get_term_synonyms($term);
    foreach ($synonyms as $item) {
      if (mb_strtoupper($item['safe_value'], 'UTF-8') == $name) {
        return $term->tid;
      }
    }
  }

  // If we have reached down here, this means we haven't got any match
  // as fallback we return 0.
  return 0;
}

/**
 * Look up a term considering synonyms and if nothing found add one.
 *
 * This function is useful for automated creation of new terms
 * as it won't generate the same terms over and over again.
 *
 * @param string $name
 *   The string to be searched for its {taxonomy_term}.tid
 * @param object $vocabulary
 *   Fully loaded vocabulary object in which you wish to search
 * @param int $parent
 *   Optional. In case you want to narrow your search scope, this parameter
 *   takes in the {taxonomy_term}.tid of the parent term, letting you search
 *   only among its children
 *
 * @return int
 *   If a term already exists, its {taxonomy_term}.tid is returned,
 *   otherwise it creates a new term and returns its {taxonomy_term}.tid
 */
function synonyms_add_term_by_synonym($name, $vocabulary, $parent = 0) {
  $tid = synonyms_get_term_by_synonym($name, $vocabulary, $parent);
  if ($tid) {
    // We found some term, returning its tid.
    return $tid;
  }

  // We haven't found any term, so we create one.
  $term = (object) array(
    'name' => $name,
    'vid' => $vocabulary->vid,
    'parent' => array($parent),
  );
  taxonomy_term_save($term);

  if (isset($term->tid)) {
    return $term->tid;
  }

  // Normally we shouldn't reach up to here, because a term would have got
  // created and the just created tid would have been returned. Nevertheless,
  // as a fallback in case of any error we return 0.
  return 0;
}

/**
 * Public function for retrieving synonyms of a taxonomy term.
 *
 * @param object $term
 *   Fully loaded taxonomy term for which the synonyms are desired
 *
 * @return array
 *   Array of synonyms, if synonyms are disabled for the taxonomy term's
 *   vocabulary, an empty array is returned. Each synonyms array consists of the
 *   following keys:
 *     value - the value of a synonym as it was input by user
 *     safe_value - a sanitized value of a synonym
 */
function synonyms_get_term_synonyms($term) {
  $synonyms = array();
  $vocabulary = taxonomy_vocabulary_load($term->vid);
  foreach (synonyms_synonyms_fields($vocabulary) as $field) {
    $bundle = field_extract_bundle('taxonomy_term', $vocabulary);
    $instance = field_info_instance('taxonomy_term', $field, $bundle);
    $field = field_info_field($field);
    $items = field_get_items('taxonomy_term', $term, $field['field_name']);

    if (is_array($items) && !empty($items)) {
      $class = synonyms_extractor_info($field['type']);
      $synonyms = array_merge($synonyms, $class::synonymsExtract($items, $field, $instance, $term, 'taxonomy_term'));
    }
  }

  // Applying sanitization to the extracted synonyms.
  foreach ($synonyms as $k => $v) {
    $synonyms[$k] = array(
      'value' => $v,
      'safe_value' => check_plain($v),
    );
  }

  return $synonyms;
}

/**
 * Allow to merge $synonym_entity as a synonym into $trunk_entity.
 *
 * Helpful function during various merging operations. It allows you to add a
 * synonym (where possible) into one entity, which will represent another entity
 * in the format expected by the field in which the synonym is being added.
 * Important note: if the cardinality limit of the field into which you are
 * adding synonym has been reached, calling to this function will take no
 * effect.
 *
 * @param object $trunk_entity
 *   Fully loaded entity object in which the synonym is being added
 * @param string $trunk_entity_type
 *   Entity type of $trunk_entity
 * @param string $field
 *   Field name that should exist in $trunk_entity and be enabled as a synonym
 *   source. Into this field synonym will be added
 * @param object $synonym_entity
 *   Fully loaded entity object which will be added as a synonym
 * @param string $synonym_entity_type
 *   Entity type of $synonym_entity
 *
 * @return bool
 *   Whether synonym has been successfully added
 */
function synonyms_add_entity_as_synonym($trunk_entity, $trunk_entity_type, $field, $synonym_entity, $synonym_entity_type) {
  if ($trunk_entity_type != 'taxonomy_term') {
    // Currently synonyms module only operates on taxonomy terms.
    return FALSE;
  }
  if (!in_array($field, synonyms_synonyms_fields(taxonomy_vocabulary_load($trunk_entity->vid)))) {
    // $field either doesn't exist in the $trunk_entity or it's not enabled as
    // a source of synonyms.
    return FALSE;
  }
  // Preparing arguments for calling a method of Extractor class.
  $field = field_info_field($field);
  $extractor = synonyms_extractor_info($field['type']);
  $items = field_get_items($trunk_entity_type, $trunk_entity, $field['field_name']);
  $items = is_array($items) ? $items : array();
  $trunk_entity_ids = entity_extract_ids($trunk_entity_type, $trunk_entity);
  $instance = field_info_instance($trunk_entity_type, $field['field_name'], $trunk_entity_ids[2]);

  $extra_items = $extractor::mergeEntityAsSynonym($items, $field, $instance, $synonym_entity, $synonym_entity_type);

  // Merging extracted synonym items into the values of the field that already
  // exist.
  // @todo: Currently we hardcode to LANGUAGE_NONE, but in future it would be
  // nice to have multilanguage support.
  $items = array_merge($items, $extra_items);
  $trunk_entity->{$field['field_name']}[LANGUAGE_NONE] = $items;
  // In future if this module eventually becomes a gateway for synonyms for any
  // entity types, we'll substitute it with entity_save().
  taxonomy_term_save($trunk_entity);
  return TRUE;
}

/**
 * Return array of field names that are sources of synonyms.
 *
 * Return array of field names that are currently enabled as source of
 * synonyms in the supplied vocabulary.
 *
 * @param object $vocabulary
 *   Fully loaded taxonomy vocabulary object
 *
 * @return array
 *   Array of field names
 */
function synonyms_synonyms_fields($vocabulary) {
  $settings = synonyms_vocabulary_settings($vocabulary);
  if (!isset($settings['synonyms']) || !is_array($settings['synonyms'])) {
    // Wierd as normally we expect to see here at least an empty array but
    // no problem. We simply initialize it.
    $settings['synonyms'] = array();
  }

  // It's not just as easy as pulling up already saved value. After this
  // we have to make sure that all the fields are still present and have not
  // been deleted from the vocabulary.
  $bundle = field_extract_bundle('taxonomy_term', $vocabulary);
  $instances = field_info_instances('taxonomy_term', $bundle);
  $settings['synonyms'] = array_intersect($settings['synonyms'], array_keys($instances));

  return $settings['synonyms'];
}

/**
 * Enforce the setting "synonyms".
 *
 * @param object $vocabulary
 *   Fully loaded entity of a taxonomy vocabulary
 * @param array $fields
 *   Array of fields that are enabled as a source of synonyms
 */
function synonyms_synonyms_enforce($vocabulary, $fields) {
  $bundle = field_extract_bundle('taxonomy_term', $vocabulary);

  // Normally all the fields already exist, we just need to assure that
  // default synonyms field exists if it is enabled as a source of synonyms.
  // Otherwise we make sure we delete instance of the default field in the
  // vocabulary.
  $instance = field_info_instance('taxonomy_term', SYNONYMS_DEFAULT_FIELD_NAME, $bundle);
  if (in_array(SYNONYMS_DEFAULT_FIELD_NAME, $fields)) {
    if (is_null($instance)) {
      // Make sure the field exists.
      synonyms_default_field_ensure();

      field_create_instance(array(
        'field_name' => SYNONYMS_DEFAULT_FIELD_NAME,
        'entity_type' => 'taxonomy_term',
        'bundle' => $bundle,
        'label' => t('Synonyms'),
        'description' => t('Please, enter the synonyms which should be related to this term.'),
      ));
    }

  }
  elseif (!is_null($instance)) {
    // Deleting the instance, we will delete the field separately when the
    // module gets uninstalled.
    field_delete_instance($instance, FALSE);
  }
}

/**
 * Return the current settings for the supplied $vocabulary.
 *
 * @param object $vocabulary
 *   Fully loaded entity of a taxonomy vocabulary
 *
 * @return array
 *   Array of current synonyms settings for the supplied vocabulary.
 *   Should include the following keys:
 *     synonyms - array of field names that are enabled as source of synonyms
 */
function synonyms_vocabulary_settings($vocabulary) {
  $settings = array();

  if (isset($vocabulary->vid)) {
    $settings = variable_get('synonyms_settings_' . $vocabulary->vid, array());
  }

  return $settings;
}

/**
 * Save the current settings for the supplied $vocabulary.
 *
 * @param object $vocabulary
 *   Fully loaded entity of a taxonomy vocabulary
 * @param array $settings
 *   Settings the have to be stored. The structure of this array has to be
 *   identical to the output array of the function
 *   synonyms_vocabulary_settings()
 */
function synonyms_vocabulary_settings_save($vocabulary, $settings) {
  variable_set('synonyms_settings_' . $vocabulary->vid, $settings);

  // Now enforcing each setting.
  foreach ($settings as $k => $v) {
    switch ($k) {
      case 'synonyms':
        synonyms_synonyms_enforce($vocabulary, $v);
        break;
    }
  }
}

/**
 * Make sure the default synonyms field exists.
 *
 * If the field doesn't exist function creates one, if the field exists,
 * the function does nothing.
 */
function synonyms_default_field_ensure() {
  $field = field_info_field(SYNONYMS_DEFAULT_FIELD_NAME);
  if (is_null($field)) {
    $field = array(
      'field_name' => SYNONYMS_DEFAULT_FIELD_NAME,
      'cardinality' => FIELD_CARDINALITY_UNLIMITED,
      'locked' => TRUE,
      'type' => 'text',
    );
    field_create_field($field);
  }
}

/**
 * Extract instances that are applicapable for being source of synonyms.
 *
 * Walk through all instances of a vocabulary and extract only valid candidates
 * for becoming a source of synonyms for the vocabulary terms.
 *
 * @param object $vocabulary
 *   Fully loaded vocabulary object
 *
 * @return array
 *   Array of instance arrays
 */
function synonyms_instances_extract_applicapable($vocabulary) {
  $applicapable_field_types = array_keys(synonyms_extractor_info());
  $applicapable = array();
  $bundle = field_extract_bundle('taxonomy_term', $vocabulary);
  foreach (field_info_instances('taxonomy_term', $bundle) as $instance) {
    $field = field_info_field($instance['field_name']);
    if (in_array($field['type'], $applicapable_field_types)) {
      $applicapable[] = $instance;
    }
  }
  return $applicapable;
}