<?php
/**
 * @file
 * Multilingual content selection module.
 *
 * Alters content queries to add language conditions.
 *
 * Queries tagged with 'i18n_select' or that already have a language condition will not be altered.
 */

// No language selection
define('I18N_SELECT_NONE', 0);
// Content with current language and undefined language
define('I18N_SELECT_NORMAL', 1);
// Select default language when current language is missing
define('I18N_SELECT_MISSING', 2);

/**
 * Enable on every page except the listed pages.
 */
define('I18N_SELECT_PAGE_NOTLISTED', 0);
/**
 * Enable on only the listed pages.
 */
define('I18N_SELECT_PAGE_LISTED', 1);
/**
 * Enable if the associated PHP code returns TRUE.
 */
define('I18N_SELECT_PAGE_PHP', 2);

/**
 * Implements hook_init().
 */
function i18n_select_init() {
  // Determine selection mode for this page
  i18n_select(i18n_select_page());
}

/**
 * Implements hook_block_list_alter().
 *
 * Dirty trick to enable selection for blocks though it may be disabled for the current page.
 */
function i18n_select_block_list_alter(&$blocks) {
  // Still, skip for form submission. There are pages like the ones produced
  // by overlay that render the blocks before the page.
  // See overlay_init(), overlay_overlay_child_initialize()
  if (empty($_POST) && !isset($_GET['token']) && variable_get('i18n_select_page_block', TRUE)) {
    i18n_select(TRUE);
  }
}

/**
 * Implements hook_menu().
 */
function i18n_select_menu() {
  $items['admin/config/regional/i18n/select'] = array(
    'title' => 'Selection',
    'description' => 'Configure extended options for multilingual content and translations.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('i18n_select_admin_settings'),
    'access arguments' => array('administer site configuration'),
    'file' => 'i18n_select.admin.inc',
    'type' => MENU_LOCAL_TASK,
  );
  return $items;
}

/**
 * Get current mode for i18n selection
 *
 * @param $type
 *   Selection type: 'nodes', 'taxonomy', etc..
 */
function i18n_select_mode($type = NULL) {
  if (i18n_select() && (!$type || variable_get('i18n_select_' . $type, TRUE))) {
    return I18N_SELECT_NORMAL;
  }
  else {
    return I18N_SELECT_NONE;
  }
}

/**
 * Check current path to enable selection.
 *
 * This works pretty much like block visibility.
 *
 * @return bool
 *   TRUE if content selection should be enabled for this page.
 */
function i18n_select_page() {
  static $mode;

  if (!isset($mode)) {
    $mode = &drupal_static(__FUNCTION__);
    $visibility = variable_get('i18n_select_page_mode', I18N_SELECT_PAGE_NOTLISTED);
    if ($pages = variable_get('i18n_select_page_list', 'admin/*')) {
      // Convert path to lowercase. This allows comparison of the same path
      // with different case. Ex: /Page, /page, /PAGE.
      $pages = drupal_strtolower($pages);
      if ($visibility < I18N_SELECT_PAGE_PHP) {
        // @see views_ajax()
        // @see I18NSelectAdminViewsAjax::testViewsAjaxWithoutSkippingTags()
        $path = isset($_REQUEST['view_path']) ? $_REQUEST['view_path'] : $_GET['q'];
        // Convert the Drupal path to lowercase.
        $path = drupal_strtolower(drupal_get_path_alias($path));
        // Compare the lowercase internal and lowercase path alias (if any).
        $page_match = drupal_match_path($path, $pages);
        if ($path != $_GET['q']) {
          $page_match = $page_match || drupal_match_path($_GET['q'], $pages);
        }
        // When $visibility has a value of 0 (I18N_SELECT_PAGE_NOTLISTED),
        // the block is displayed on all pages except those listed in $pages.
        // When set to 1 (I18N_SELECT_PAGE_LISTED), it is displayed only on
        // those pages listed in $pages.
        $mode = !($visibility xor $page_match);
      }
      elseif (module_exists('php')) {
        $mode = php_eval($pages);
      }
      else {
        $mode = FALSE;
      }
    }
    else {
      // No pages defined, still respect the setting (unlike blocks).
      $mode = $visibility == I18N_SELECT_PAGE_NOTLISTED;
    }
  }

  return $mode;
}

/**
 * Implementation of hook_query_node_access_alter().
 *
 * Rewrite node queries so language selection options are enforced.
 */
function i18n_select_query_node_access_alter(QueryAlterableInterface $query) {
  if (i18n_select_mode('nodes') && i18n_select_check_query($query, 'nid') &&
    ($table_alias = i18n_select_check_table($query, 'node', 'nid'))) {
    $query->condition($table_alias . '.language', i18n_select_langcodes());
    // Mark query as altered
    $query->addTag('i18n_select');
  }
}

/**
 * Implementation of hook_query_term_access_alter().
 *
 * Rewrite taxonomy term queries so language selection options are enforced.
 */
function i18n_select_query_term_access_alter(QueryAlterableInterface $query) {
  if (module_exists('i18n_taxonomy') && i18n_select_mode('taxonomy') && i18n_select_check_query($query, 'tid') &&
    ($table_alias = i18n_select_check_table($query, 'taxonomy_term_data', 'tid'))) {
    $query->condition($table_alias . '.language', i18n_select_langcodes());
    // Mark query as altered
    $query->addTag('i18n_select');
  }
}

/**
 * Check table exists in query and get alias for it.
 *
 * @param $query
 *   Query object
 * @param $table_name
 *   Table name to find.
 * @param $field_name
 *   field to join the table if needed.
 *
 * @return
 *   Table alias if found, none if not.
 */
function i18n_select_check_table($query, $table_name, $field_name) {
  $tables = $query->getTables();
  foreach ($tables as $table) {
    if (!($table instanceof SelectQueryInterface) && $table['table'] == $table_name) {
      return _i18n_select_table_alias($table);
    }
  }
  // Join the table if we can find the key field on any of the tables
  // And all the conditions have a table alias (or there's a unique table).
  if (count($tables) == 1) {
    $table = reset($tables);
    $table_alias = _i18n_select_table_alias($table);
    if (i18n_select_check_conditions($query, $table_alias)) {
      $join_table = $table_alias;
    }
  }
  elseif (i18n_select_check_conditions($query)) {
    // Try to find the right field in the table schema.
    foreach ($tables as $table) {
      $schema = drupal_get_schema($table['table']);
      if ($schema && !empty($schema['fields'][$field_name])) {
        $join_table = _i18n_select_table_alias($table);
        break;
      }
    }
  }
  if (!empty($join_table)) {
    return $query->join($table_name, $table_name, $join_table . '.' . $field_name . ' = %alias.' . $field_name);
  }
  else {
    return FALSE;
  }
}

/**
 * Get table alias
 */
function _i18n_select_table_alias($table) {
  return !empty($table['alias']) ? $table['alias'] : $table['table'];
}

/**
 * Check all query conditions have a table alias.
 *
 * @param $table_alias
 *   Optional table alias for fields without table.
 *
 * @return boolean
 *   TRUE if table conditions are ok, FALSE otherwise.
 */
function i18n_select_check_conditions($query, $table_alias = NULL) {
  $conditions =& $query->conditions();
  foreach ($conditions as $index => $condition) {
    if (is_array($condition) && !empty($condition['field'])) {
      if (strpos($condition['field'], '.') === FALSE) {
        if ($table_alias) {
          // Change the condition to include a table alias.
          $conditions[$index]['field'] = $table_alias . '.' . $condition['field'];
        }
        else {
          // We won't risk joining anything here.
          return FALSE;
        }
      }
    }
  }
  return TRUE;
}

/**
 * Check whether we should apply language conditions here:
 * - The query has not been tagged with 'i18n_select'
 * - The query doesn't have already a language condition
 * - All the conditions have a table alias or there's only one table.
 * - We are not loading specific objects (no condition for index field).
 *
 * @param $query
 *   Query object.
 * @param $index_field
 *   Object index field to check we don't have 'IN' conditions for it.
 */
function i18n_select_check_query($query, $index_field = NULL) {
  static $tags;
  // Skip queries with certain tags
  if (!isset($tags)) {
    $tags = ($skip = variable_get('i18n_select_skip_tags', 'views')) ? array_map('trim', explode(',', $skip)) : array();
    $tags[] = 'i18n_select';
  }
  foreach ($tags as $tag) {
    if ($query->hasTag($tag)) {
      return FALSE;
    }
  }
  // Check all the conditions to see whether the query is suitable for altering.
  foreach ($query->conditions() as $condition) {
    if (is_array($condition)) {
      // @todo For some complex queries, like search ones, field is a DatabaseCondition object
      if (!isset($condition['field']) || !is_string($condition['field'])) {
        // There's a weird condition field, we won't take any chances.
        return FALSE;
      }
      else {
        // Just check the condition doesn't include the language field
        if (strpos($condition['field'], '.') === FALSE) {
          $field = $condition['field'];
        }
        else {
          list($table, $field) = explode('.', $condition['field']);
        }
        if ($field == 'language') {
          return FALSE;
        }
        // Check 'IN' conditions for index field, usually entity loading for specific objects.
        if ($field == $index_field && $condition['operator'] == 'IN') {
          return FALSE;
        }
      }
    }
  }
  // If the language field is present we don't want to do any filtering.
  $fields = $query->getFields();
  if (isset($fields['language'])) {
    return FALSE;
  }

  return TRUE;
}

/**
 * Get main language for content selection
 */
function i18n_select_language() {
  return $GLOBALS[LANGUAGE_TYPE_CONTENT];
}

/**
 * Get language codes for content selection to use in query conditions
 */
function i18n_select_langcodes() {
  return array(i18n_select_language()->language, LANGUAGE_NONE);
}