<?php

namespace Drupal\mysql\Driver\Database\mysql;

use Drupal\Core\Database\DatabaseAccessDeniedException;
use Drupal\Core\Database\DatabaseExceptionWrapper;
use Drupal\Core\Database\StatementWrapper;
use Drupal\Core\Database\Database;
use Drupal\Core\Database\DatabaseNotFoundException;
use Drupal\Core\Database\DatabaseException;
use Drupal\Core\Database\Connection as DatabaseConnection;
use Drupal\Core\Database\SupportsTemporaryTablesInterface;
use Drupal\Core\Database\TransactionNoActiveException;

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

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

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

  /**
   * Error code for "Access denied" error.
   */
  const ACCESS_DENIED = 1045;

  /**
   * 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;

  /**
   * {@inheritdoc}
   */
  protected $statementWrapperClass = StatementWrapper::class;

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

  /**
   * Stores the server version after it has been retrieved from the database.
   *
   * @var string
   *
   * @see \Drupal\mysql\Driver\Database\mysql\Connection::version
   */
  private $serverVersion;

  /**
   * 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;

  /**
   * {@inheritdoc}
   */
  protected $identifierQuotes = ['"', '"'];

  /**
   * {@inheritdoc}
   */
  public function __construct(\PDO $connection, array $connection_options) {
    // If the SQL mode doesn't include 'ANSI_QUOTES' (explicitly or via a
    // combination mode), then MySQL doesn't interpret a double quote as an
    // identifier quote, in which case use the non-ANSI-standard backtick.
    //
    // Because we still support MySQL 5.7, check for the deprecated combination
    // modes as well.
    //
    // @see https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_ansi_quotes
    $ansi_quotes_modes = ['ANSI_QUOTES', 'ANSI', 'DB2', 'MAXDB', 'MSSQL', 'ORACLE', 'POSTGRESQL'];
    $is_ansi_quotes_mode = FALSE;
    foreach ($ansi_quotes_modes as $mode) {
      // None of the modes in $ansi_quotes_modes are substrings of other modes
      // that are not in $ansi_quotes_modes, so a simple stripos() does not
      // return false positives.
      if (stripos($connection_options['init_commands']['sql_mode'], $mode) !== FALSE) {
        $is_ansi_quotes_mode = TRUE;
        break;
      }
    }
    if ($this->identifierQuotes === ['"', '"'] && !$is_ansi_quotes_mode) {
      $this->identifierQuotes = ['`', '`'];
    }
    parent::__construct($connection, $connection_options);
  }

  /**
   * {@inheritdoc}
   */
  public static function open(array &$connection_options = []) {
    if (isset($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 += [
      'pdo' => [],
    ];
    $connection_options['pdo'] += [
      \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,
      // Limit SQL to a single statement like mysqli.
      \PDO::MYSQL_ATTR_MULTI_STATEMENTS => FALSE,
      // Convert numeric values to strings when fetching. In PHP 8.1,
      // \PDO::ATTR_EMULATE_PREPARES now behaves the same way as non emulated
      // prepares and returns integers. See https://externals.io/message/113294
      // for further discussion.
      \PDO::ATTR_STRINGIFY_FETCHES => TRUE,
    ];

    try {
      $pdo = new \PDO($dsn, $connection_options['username'], $connection_options['password'], $connection_options['pdo']);
    }
    catch (\PDOException $e) {
      if ($e->getCode() == static::DATABASE_NOT_FOUND) {
        throw new DatabaseNotFoundException($e->getMessage(), $e->getCode(), $e);
      }
      if ($e->getCode() == static::ACCESS_DENIED) {
        throw new DatabaseAccessDeniedException($e->getMessage(), $e->getCode(), $e);
      }
      throw $e;
    }

    // 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' (MySQL 5) or 'utf8mb4_0900_ai_ci' (MySQL 8) 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 += [
      'init_commands' => [],
    ];

    $connection_options['init_commands'] += [
      'sql_mode' => "SET sql_mode = 'ANSI,TRADITIONAL'",
    ];

    // Execute initial commands.
    foreach ($connection_options['init_commands'] as $sql) {
      $pdo->exec($sql);
    }

    return $pdo;
  }

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

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

  /**
   * {@inheritdoc}
   */
  public function queryTemporary($query, array $args = [], array $options = []) {
    $tablename = 'db_temporary_' . uniqid();
    $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY ' . $query, $args, $options);
    return $tablename;
  }

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

  /**
   * {@inheritdoc}
   */
  public function version() {
    if ($this->isMariaDb()) {
      return $this->getMariaDbVersionMatch();
    }

    return $this->getServerVersion();
  }

  /**
   * Determines whether the MySQL distribution is MariaDB or not.
   *
   * @return bool
   *   Returns TRUE if the distribution is MariaDB, or FALSE if not.
   */
  public function isMariaDb(): bool {
    return (bool) $this->getMariaDbVersionMatch();
  }

  /**
   * Gets the MariaDB portion of the server version.
   *
   * @return string
   *   The MariaDB portion of the server version if present, or NULL if not.
   */
  protected function getMariaDbVersionMatch(): ?string {
    // MariaDB may prefix its version string with '5.5.5-', which should be
    // ignored.
    // @see https://github.com/MariaDB/server/blob/f6633bf058802ad7da8196d01fd19d75c53f7274/include/mysql_com.h#L42.
    $regex = '/^(?:5\.5\.5-)?(\d+\.\d+\.\d+.*-mariadb.*)/i';

    preg_match($regex, $this->getServerVersion(), $matches);
    return (empty($matches[1])) ? NULL : $matches[1];
  }

  /**
   * Gets the server version.
   *
   * @return string
   *   The PDO server version.
   */
  protected function getServerVersion(): string {
    if (!$this->serverVersion) {
      $this->serverVersion = $this->query('SELECT VERSION()')->fetchField();
    }
    return $this->serverVersion;
  }

  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) {
    $this->query('INSERT INTO {sequences} () VALUES ()');
    $new_id = $this->lastInsertId();
    // This should only happen after an import or similar event.
    if ($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', [':value' => $existing_id]);
      $this->query('INSERT INTO {sequences} () VALUES ()');
      $new_id = $this->lastInsertId();
    }
    $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
    // re-initializes 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 ::delete().
      $this->query('DELETE FROM {sequences} WHERE value < :value', [':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)) {
        $this->doCommit();
      }
      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 = [];
            // We also have to explain to PDO that the transaction stack has
            // been cleaned-up.
            $this->doCommit();
          }
          else {
            throw $e;
          }
        }
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public function rollBack($savepoint_name = 'drupal_transaction') {
    // MySQL will automatically commit transactions when tables are altered or
    // created (DDL transactions are not supported). Prevent triggering an
    // exception to ensure that the error that has caused the rollback is
    // properly reported.
    if (!$this->connection->inTransaction()) {
      // On PHP 7 $this->connection->inTransaction() will return TRUE and
      // $this->connection->rollback() does not throw an exception; the
      // following code is unreachable.

      // If \Drupal\Core\Database\Connection::rollBack() would throw an
      // exception then continue to throw an exception.
      if (!$this->inTransaction()) {
        throw new TransactionNoActiveException();
      }
      // A previous rollback to an earlier savepoint may mean that the savepoint
      // in question has already been accidentally committed.
      if (!isset($this->transactionLayers[$savepoint_name])) {
        throw new TransactionNoActiveException();
      }

      trigger_error('Rollback attempted when there is no active transaction. This can cause data integrity issues.', E_USER_WARNING);
      return;
    }
    return parent::rollBack($savepoint_name);
  }

  /**
   * {@inheritdoc}
   */
  protected function doCommit() {
    // MySQL will automatically commit transactions when tables are altered or
    // created (DDL transactions are not supported). Prevent triggering an
    // exception in this case as all statements have been committed.
    if ($this->connection->inTransaction()) {
      // On PHP 7 $this->connection->inTransaction() will return TRUE and
      // $this->connection->commit() does not throw an exception.
      $success = parent::doCommit();
    }
    else {
      // Process the post-root (non-nested) transaction commit callbacks. The
      // following code is copied from
      // \Drupal\Core\Database\Connection::doCommit()
      $success = TRUE;
      if (!empty($this->rootTransactionEndCallbacks)) {
        $callbacks = $this->rootTransactionEndCallbacks;
        $this->rootTransactionEndCallbacks = [];
        foreach ($callbacks as $callback) {
          call_user_func($callback, $success);
        }
      }
    }
    return $success;
  }

}


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