<?php
// $Id: i18n_select.module,v 1.1.2.5 2011-02-24 09:09:00 jareyero Exp $
/**
 * @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) {
  if (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 variable_get('i18n_select_missing_translation', FALSE) ? I18N_SELECT_MISSING : I18N_SELECT_NORMAL;
  }
  else {
    return I18N_SELECT_NONE;
  }
}

/**
 * Check current path to enable selection
 * 
 * This works pretty much like block visibility
 */
function i18n_select_page() {
  $visibility = variable_get('i18n_select_page_mode', I18N_SELECT_PAGE_NOTLISTED);
  if ($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) {
      // Convert the Drupal path to lowercase
      $path = drupal_strtolower(drupal_get_path_alias($_GET['q']));
      // 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 $pages.
      return !($visibility xor $page_match);
    }
    elseif (module_exists('php')) {
      return php_eval($pages);
    }
    else {
      return FALSE;
    }
  }
  else {
    // No pages defined, still respect the setting (unlike blocks)
    return $visibility == I18N_SELECT_PAGE_NOTLISTED;
  }
}

/**
 * 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) {
  $mode = i18n_select_mode('nodes');

  if ($mode && ($table_alias = i18n_select_check_table($query, 'node'))  && i18n_select_check_query($query, $table_alias)) {
    // if the language field is present we don't want to do any filtering.
    $fields = $query->getFields();
    if (isset($fields['language'])) {
      return;
    }

    $language = i18n_select_language();
    $default_lang = language_default('language');

    if (($mode & I18N_SELECT_MISSING) && $language != $default_lang) {        
      // we want to include nodes from the default language that haven't been
      // translated to the current language
      // SELECT * FROM node n
      //   LEFT JOIN node i18n ON n.tnid > 0 AND n.tnid = i18n.tnid AND i18n.language = 'es'
      //   WHERE n.language='es' OR (n.language='en' AND i18n.nid IS NULL)

      // Make sure the conditions refer to the node table. eg using 'n.promote' instead of 'promote'
      i18n_select_check_conditions($query, $table_alias);

      $query->leftjoin('node', 'i18n', $table_alias . '.tnid > 0 AND ' . $table_alias . '.tnid = i18n.tnid AND i18n.language = :lang', array(':lang' => $language));
      $query->where($table_alias . '.language=:lang OR (' . $table_alias . '.language=:default_lang AND i18n.nid IS NULL)', array(':lang' => $language, ':default_lang' => $default_lang));
    } else {
      $query->condition($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) {
  $mode = i18n_select_mode('taxonomy');
  if (module_exists('i18n_taxonomy') && $mode && ($table_alias = i18n_select_check_table($query, 'taxonomy_term_data')) && i18n_select_check_query($query, $table_alias)) {
    $query->condition($table_alias . '.language', i18n_select_langcodes());
    // Mark query as altered
    $query->addTag('i18n_select');
  }
}

/**
 * Check table exists in query and get alias for it
 * 
 * @todo Should we add the table if not there?
 */
function i18n_select_check_table($query, $table_name) {
  foreach ($query->getTables() as $table) {
    if ($table['table'] == $table_name) {
      return !empty($table['alias']) ? $table['alias'] : $table_name;
    }
  }
}

/**
 * Check all query conditions have a table alias
 */
function i18n_select_check_conditions($query, $table_alias) {
  $conditions =& $query->conditions();
  foreach ($conditions as $index => $condition) {
    if (is_array($condition) && isset($condition['field'])) {
      if (strpos($condition['field'], '.') === FALSE) {
        $conditions[$index]['field'] = $table_alias . '.' . $condition['field'];
      }
    }
  }
}

/**
 * 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
 */
function i18n_select_check_query($query, $table_alias, $field_name = 'language') {
  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;
    }
  }
  $fields = $query->getFields();
  $table_field = $table_alias . '.' . $field_name;
  foreach ($query->conditions() as $condition) {
    // @todo Research under which conditions field is not string, see http://drupal.org/node/1062054
    if (is_array($condition) && isset($condition['field']) && is_string($condition['field']) && ($condition['field'] == $field_name || $condition['field'] == $table_field)) {
      return FALSE;
    }
  }
  return TRUE;
}

/**
 * Get main language code for content selection
 */
function i18n_select_language() {
  return $GLOBALS['language_content']->language;
}

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