<?php
/**
 * Pimf
 *
 * @copyright Copyright (c)  Gjero Krsteski (http://krsteski.de)
 * @license   http://krsteski.de/new-bsd-license New BSD License
 */

namespace Pimf;

/**
 * @package Pimf
 * @author  Gjero Krsteski <gjero@krsteski.de>
 */
class Database extends \PDO
{
  /**
   * The current transaction level.
   *
   * @var int
   */
  protected $transLevel = 0;

  /**
   * Check database drivers that support savepoints.
   *
   * @return bool
   */
  public function nestable()
  {
    return in_array(
      $this->getAttribute(\PDO::ATTR_DRIVER_NAME), array("pgsql", "mysql")
    );
  }

  /**
   * @return bool|void
   */
  public function beginTransaction()
  {
    if ($this->transLevel == 0 || !$this->nestable()) {
      parent::beginTransaction();
    } else {
      $this->exec("SAVEPOINT LEVEL{$this->transLevel}");
    }

    $this->transLevel++;
  }

  /**
   * @return bool|void
   */
  public function commit()
  {
    $this->transLevel--;

    if ($this->transLevel == 0 || !$this->nestable()) {
      parent::commit();
    } else {
      $this->exec("RELEASE SAVEPOINT LEVEL{$this->transLevel}");
    }
  }

  /**
   * @return bool|void
   * @throws \PDOException
   */
  public function rollBack()
  {
    if ($this->transLevel == 0) {
      throw new \PDOException('trying to rollback without a transaction-start', 25000);
    }

    $this->transLevel--;

    if ($this->transLevel == 0 || !$this->nestable()) {
      parent::rollBack();
    } else {
      $this->exec("ROLLBACK TO SAVEPOINT LEVEL{$this->transLevel}");
    }
  }
}