<?php
/*
 +--------------------------------------------------------------------+
 | Copyright CiviCRM LLC. All rights reserved.                        |
 |                                                                    |
 | This work is published under the GNU AGPLv3 license with some      |
 | permitted exceptions and without any warranty. For full license    |
 | and copyright information, see https://civicrm.org/licensing       |
 +--------------------------------------------------------------------+
 */

/**
 * Just another collection of static utils functions.
 *
 * @package CRM
 * @copyright CiviCRM LLC https://civicrm.org/licensing
 */
class CRM_Utils_SQL {

  /**
   * Helper function for adding the permissioned subquery from one entity onto another
   *
   * @param string $entity
   * @param string $joinColumn
   * @return array
   */
  public static function mergeSubquery($entity, $joinColumn = 'id') {
    require_once 'api/v3/utils.php';
    $baoName = _civicrm_api3_get_BAO($entity);
    $bao = new $baoName();
    $clauses = $subclauses = [];
    foreach ((array) $bao->addSelectWhereClause() as $field => $vals) {
      if ($vals && $field == $joinColumn) {
        $clauses = array_merge($clauses, (array) $vals);
      }
      elseif ($vals) {
        $subclauses[] = "$field " . implode(" AND $field ", (array) $vals);
      }
    }
    if ($subclauses) {
      $clauses[] = "IN (SELECT `$joinColumn` FROM `" . $bao->tableName() . "` WHERE " . implode(' AND ', $subclauses) . ")";
    }
    return $clauses;
  }

  /**
   * Get current sqlModes of the session
   * @return array
   */
  public static function getSqlModes() {
    $sqlModes = explode(',', CRM_Core_DAO::singleValueQuery('SELECT @@sql_mode'));
    return $sqlModes;
  }

  /**
   * Checks if this system enforce the MYSQL mode ONLY_FULL_GROUP_BY.
   * This function should be named supportsAnyValueAndEnforcesFullGroupBY(),
   * but should be deprecated instead.
   *
   * @return mixed
   * @deprecated
   */
  public static function supportsFullGroupBy() {
    // CRM-21455 MariaDB 10.2 does not support ANY_VALUE
    $version = self::getDatabaseVersion();

    if (stripos($version, 'mariadb') !== FALSE) {
      return FALSE;
    }

    return version_compare($version, '5.7', '>=');
  }

  /**
   * Disable ONLY_FULL_GROUP_BY for MySQL versions lower then 5.7
   *
   * @return bool
   */
  public static function disableFullGroupByMode() {
    $sqlModes = self::getSqlModes();

    // Disable only_full_group_by mode for lower sql versions.
    if (!self::supportsFullGroupBy() || (!empty($sqlModes) && !in_array('ONLY_FULL_GROUP_BY', $sqlModes))) {
      if ($key = array_search('ONLY_FULL_GROUP_BY', $sqlModes)) {
        unset($sqlModes[$key]);
        CRM_Core_DAO::executeQuery("SET SESSION sql_mode = '" . implode(',', $sqlModes) . "'");
      }
      return TRUE;
    }

    return FALSE;
  }

  /**
   * CHeck if ONLY_FULL_GROUP_BY is in the global sql_modes
   * @return bool
   */
  public static function isGroupByModeInDefault() {
    $sqlModes = explode(',', CRM_Core_DAO::singleValueQuery('SELECT @@global.sql_mode'));
    if (!in_array('ONLY_FULL_GROUP_BY', $sqlModes)) {
      return FALSE;
    }
    return TRUE;
  }

  /**
   * Does the DB version support mutliple locks per
   *
   * https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
   *
   * This is a conservative measure to introduce the change which we expect to deprecate later.
   *
   * @todo we only check mariadb & mysql right now but maybe can add percona.
   */
  public static function supportsMultipleLocks() {
    static $isSupportLocks = NULL;
    if (!isset($isSupportLocks)) {
      $version = self::getDatabaseVersion();
      if (stripos($version, 'mariadb') !== FALSE) {
        $isSupportLocks = version_compare($version, '10.0.2', '>=');
      }
      else {
        $isSupportLocks = version_compare($version, '5.7.5', '>=');
      }
    }

    return $isSupportLocks;
  }

  /**
   * Get the version string for the database.
   *
   * @return string
   */
  public static function getDatabaseVersion() {
    return CRM_Core_DAO::singleValueQuery('SELECT VERSION()');
  }

}