<?php

/**
 * @file
 * Contains \Drupal\Core\Database\Driver\mysql\Connection.
 */

namespace Drupal\Core\Database\Driver\mysql;

use Drupal\Core\Database\DatabaseExceptionWrapper;

use Drupal\Core\Database\Database;
use Drupal\Core\Database\DatabaseNotFoundException;
use Drupal\Core\Database\TransactionCommitFailedException;
use Drupal\Core\Database\DatabaseException;
use Drupal\Core\Database\Connection as DatabaseConnection;
use Drupal\Component\Utility\Unicode;

/**
 * @addtogroup database
 * @{
 */

/**
 * MySQL implementation of \Drupal\Core\Database\Connection.
 */
class Connection extends DatabaseConnection {

  /**
   * Error code for "Unknown database" error.
   */
  const DATABASE_NOT_FOUND = 1049;

  /**
   * Error code for "Can't initialize character set" error.
   */
  const UNSUPPORTED_CHARSET = 2019;

  /**
   * Driver-specific error code for "Unknown character set" error.
   */
  const UNKNOWN_CHARSET = 1115;

  /**
   * SQLSTATE error code for "Syntax error or access rule violation".
   */
  const SQLSTATE_SYNTAX_ERROR = 42000;

  /**
   * Flag to indicate if the cleanup function in __destruct() should run.
   *
   * @var bool
   */
  protected $needsCleanup = FALSE;

  /**
   * The minimal possible value for the max_allowed_packet setting of MySQL.
   *
   * @link https://mariadb.com/kb/en/mariadb/server-system-variables/#max_allowed_packet
   * @link https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_max_allowed_packet
   *
   * @var int
   */
  const MIN_MAX_ALLOWED_PACKET = 1024;

  /**
   * Constructs a Connection object.
   */
  public function __construct(\PDO $connection, array $connection_options = array()) {
    parent::__construct($connection, $connection_options);

    // This driver defaults to transaction support, except if explicitly passed FALSE.
    $this->transactionSupport = !isset($connection_options['transactions']) || ($connection_options['transactions'] !== FALSE);

    // MySQL never supports transactional DDL.
    $this->transactionalDDLSupport = FALSE;

    $this->connectionOptions = $connection_options;
  }

  /**
   * {@inheritdoc}
   */
  public function query($query, array $args = array(), $options = array()) {
    try {
      return parent::query($query, $args, $options);
    } catch (DatabaseException $e) {
      if ($e->getPrevious()->errorInfo[1] == 1153) {
        // If a max_allowed_packet error occurs the message length is truncated.
        // This should prevent the error from recurring if the exception is
        // logged to the database using dblog or the like.
        $message = Unicode::truncateBytes($e->getMessage(), self::MIN_MAX_ALLOWED_PACKET);
        $e = new DatabaseExceptionWrapper($message, $e->getCode(), $e->getPrevious());
      }
      throw $e;
    }
  }

  /**
   * {@inheritdoc}
   */
  public static function open(array &$connection_options = array()) {
    if (isset($connection_options['_dsn_utf8_fallback']) && $connection_options['_dsn_utf8_fallback'] === TRUE) {
      // Only used during the installer version check, as a fallback from utf8mb4.
      $charset = 'utf8';
    }
    else {
      $charset = 'utf8mb4';
    }
    // The DSN should use either a socket or a host/port.
    if (isset($connection_options['unix_socket'])) {
      $dsn = 'mysql:unix_socket=' . $connection_options['unix_socket'];
    }
    else {
      // Default to TCP connection on port 3306.
      $dsn = 'mysql:host=' . $connection_options['host'] . ';port=' . (empty($connection_options['port']) ? 3306 : $connection_options['port']);
    }
    // Character set is added to dsn to ensure PDO uses the proper character
    // set when escaping. This has security implications. See
    // https://www.drupal.org/node/1201452 for further discussion.
    $dsn .= ';charset=' . $charset;
    if (!empty($connection_options['database'])) {
      $dsn .= ';dbname=' . $connection_options['database'];
    }
    // Allow PDO options to be overridden.
    $connection_options += array(
      'pdo' => array(),
    );
    $connection_options['pdo'] += array(
      \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
      // So we don't have to mess around with cursors and unbuffered queries by default.
      \PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => TRUE,
      // Make sure MySQL returns all matched rows on update queries including
      // rows that actually didn't have to be updated because the values didn't
      // change. This matches common behavior among other database systems.
      \PDO::MYSQL_ATTR_FOUND_ROWS => TRUE,
      // Because MySQL's prepared statements skip the query cache, because it's dumb.
      \PDO::ATTR_EMULATE_PREPARES => TRUE,
    );
    if (defined('\PDO::MYSQL_ATTR_MULTI_STATEMENTS')) {
      // An added connection option in PHP 5.5.21 to optionally limit SQL to a
      // single statement like mysqli.
      $connection_options['pdo'] += [\PDO::MYSQL_ATTR_MULTI_STATEMENTS => FALSE];
    }

    $pdo = new \PDO($dsn, $connection_options['username'], $connection_options['password'], $connection_options['pdo']);

    // Force MySQL to use the UTF-8 character set. Also set the collation, if a
    // certain one has been set; otherwise, MySQL defaults to
    // 'utf8mb4_general_ci' for utf8mb4.
    if (!empty($connection_options['collation'])) {
      $pdo->exec('SET NAMES ' . $charset . ' COLLATE ' . $connection_options['collation']);
    }
    else {
      $pdo->exec('SET NAMES ' . $charset);
    }

    // Set MySQL init_commands if not already defined.  Default Drupal's MySQL
    // behavior to conform more closely to SQL standards.  This allows Drupal
    // to run almost seamlessly on many different kinds of database systems.
    // These settings force MySQL to behave the same as postgresql, or sqlite
    // in regards to syntax interpretation and invalid data handling.  See
    // https://www.drupal.org/node/344575 for further discussion. Also, as MySQL
    // 5.5 changed the meaning of TRADITIONAL we need to spell out the modes one
    // by one.
    $connection_options += array(
      'init_commands' => array(),
    );
    $connection_options['init_commands'] += array(
      'sql_mode' => "SET sql_mode = 'ANSI,STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,ONLY_FULL_GROUP_BY'",
    );
    // Execute initial commands.
    foreach ($connection_options['init_commands'] as $sql) {
      $pdo->exec($sql);
    }

    return $pdo;
  }

  /**
   * {@inheritdoc}
   */
  public function serialize() {
    // Cleanup the connection, much like __destruct() does it as well.
    if ($this->needsCleanup) {
      $this->nextIdDelete();
    }
    $this->needsCleanup = FALSE;

    return parent::serialize();
  }

  /**
   * {@inheritdoc}
   */
  public function __destruct() {
    if ($this->needsCleanup) {
      $this->nextIdDelete();
    }
  }

  public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
    return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);
  }

  public function queryTemporary($query, array $args = array(), array $options = array()) {
    $tablename = $this->generateTemporaryTableName();
    $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY ' . $query, $args, $options);
    return $tablename;
  }

  public function driver() {
    return 'mysql';
  }

  public function databaseType() {
    return 'mysql';
  }

  /**
   * Overrides \Drupal\Core\Database\Connection::createDatabase().
   *
   * @param string $database
   *   The name of the database to create.
   *
   * @throws \Drupal\Core\Database\DatabaseNotFoundException
   */
  public function createDatabase($database) {
    // Escape the database name.
    $database = Database::getConnection()->escapeDatabase($database);

    try {
      // Create the database and set it as active.
      $this->connection->exec("CREATE DATABASE $database");
      $this->connection->exec("USE $database");
    }
    catch (\Exception $e) {
      throw new DatabaseNotFoundException($e->getMessage());
    }
  }

  public function mapConditionOperator($operator) {
    // We don't want to override any of the defaults.
    return NULL;
  }

  public function nextId($existing_id = 0) {
    $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
    // This should only happen after an import or similar event.
    if ($existing_id >= $new_id) {
      // If we INSERT a value manually into the sequences table, on the next
      // INSERT, MySQL will generate a larger value. However, there is no way
      // of knowing whether this value already exists in the table. MySQL
      // provides an INSERT IGNORE which would work, but that can mask problems
      // other than duplicate keys. Instead, we use INSERT ... ON DUPLICATE KEY
      // UPDATE in such a way that the UPDATE does not do anything. This way,
      // duplicate keys do not generate errors but everything else does.
      $this->query('INSERT INTO {sequences} (value) VALUES (:value) ON DUPLICATE KEY UPDATE value = value', array(':value' => $existing_id));
      $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
    }
    $this->needsCleanup = TRUE;
    return $new_id;
  }

  public function nextIdDelete() {
    // While we want to clean up the table to keep it up from occupying too
    // much storage and memory, we must keep the highest value in the table
    // because InnoDB uses an in-memory auto-increment counter as long as the
    // server runs. When the server is stopped and restarted, InnoDB
    // reinitializes the counter for each table for the first INSERT to the
    // table based solely on values from the table so deleting all values would
    // be a problem in this case. Also, TRUNCATE resets the auto increment
    // counter.
    try {
      $max_id = $this->query('SELECT MAX(value) FROM {sequences}')->fetchField();
      // We know we are using MySQL here, no need for the slower db_delete().
      $this->query('DELETE FROM {sequences} WHERE value < :value', array(':value' => $max_id));
    }
    // During testing, this function is called from shutdown with the
    // simpletest prefix stored in $this->connection, and those tables are gone
    // by the time shutdown is called so we need to ignore the database
    // errors. There is no problem with completely ignoring errors here: if
    // these queries fail, the sequence will work just fine, just use a bit
    // more database storage and memory.
    catch (DatabaseException $e) {
    }
  }

  /**
   * Overridden to work around issues to MySQL not supporting transactional DDL.
   */
  protected function popCommittableTransactions() {
    // Commit all the committable layers.
    foreach (array_reverse($this->transactionLayers) as $name => $active) {
      // Stop once we found an active transaction.
      if ($active) {
        break;
      }

      // If there are no more layers left then we should commit.
      unset($this->transactionLayers[$name]);
      if (empty($this->transactionLayers)) {
        if (!$this->connection->commit()) {
          throw new TransactionCommitFailedException();
        }
      }
      else {
        // Attempt to release this savepoint in the standard way.
        try {
          $this->query('RELEASE SAVEPOINT ' . $name);
        }
        catch (DatabaseExceptionWrapper $e) {
          // However, in MySQL (InnoDB), savepoints are automatically committed
          // when tables are altered or created (DDL transactions are not
          // supported). This can cause exceptions due to trying to release
          // savepoints which no longer exist.
          //
          // To avoid exceptions when no actual error has occurred, we silently
          // succeed for MySQL error code 1305 ("SAVEPOINT does not exist").
          if ($e->getPrevious()->errorInfo[1] == '1305') {
            // If one SAVEPOINT was released automatically, then all were.
            // Therefore, clean the transaction stack.
            $this->transactionLayers = array();
            // We also have to explain to PDO that the transaction stack has
            // been cleaned-up.
            $this->connection->commit();
          }
          else {
            throw $e;
          }
        }
      }
    }
  }

}


/**
 * @} End of "addtogroup database".
 */
