class Connection

class Connection extends DatabaseConnection {
    
    /**
     * Error code for "Unable to open database file" error.
     */
    const DATABASE_NOT_FOUND = 14;
    
    /**
     * Whether or not the active transaction (if any) will be rolled back.
     *
     * @var bool
     */
    protected $willRollback;
    
    /**
     * A map of condition operators to SQLite operators.
     *
     * We don't want to override any of the defaults.
     */
    protected static $sqliteConditionOperatorMap = [
        'LIKE' => [
            'postfix' => " ESCAPE '\\'",
        ],
        'NOT LIKE' => [
            'postfix' => " ESCAPE '\\'",
        ],
        'LIKE BINARY' => [
            'postfix' => " ESCAPE '\\'",
            'operator' => 'GLOB',
        ],
        'NOT LIKE BINARY' => [
            'postfix' => " ESCAPE '\\'",
            'operator' => 'NOT GLOB',
        ],
    ];
    
    /**
     * All databases attached to the current database. This is used to allow
     * prefixes to be safely handled without locking the table
     *
     * @var array
     */
    protected $attachedDatabases = [];
    
    /**
     * Whether or not a table has been dropped this request: the destructor will
     * only try to get rid of unnecessary databases if there is potential of them
     * being empty.
     *
     * This variable is set to public because Schema needs to
     * access it. However, it should not be manually set.
     *
     * @var bool
     */
    public $tableDropped = FALSE;
    
    /**
     * Constructs a \Drupal\Core\Database\Driver\sqlite\Connection object.
     */
    public function __construct(\PDO $connection, array $connection_options) {
        // We don't need a specific PDOStatement class here, we simulate it in
        // static::prepare().
        $this->statementClass = NULL;
        parent::__construct($connection, $connection_options);
        // This driver defaults to transaction support, except if explicitly passed FALSE.
        $this->transactionSupport = $this->transactionalDDLSupport = !isset($connection_options['transactions']) || $connection_options['transactions'] !== FALSE;
        $this->connectionOptions = $connection_options;
        // Attach one database for each registered prefix.
        $prefixes = $this->prefixes;
        foreach ($prefixes as &$prefix) {
            // Empty prefix means query the main database -- no need to attach anything.
            if (!empty($prefix)) {
                // Only attach the database once.
                if (!isset($this->attachedDatabases[$prefix])) {
                    $this->attachedDatabases[$prefix] = $prefix;
                    if ($connection_options['database'] === ':memory:') {
                        // In memory database use ':memory:' as database name. According to
                        // http://www.sqlite.org/inmemorydb.html it will open a unique
                        // database so attaching it twice is not a problem.
                        $this->query('ATTACH DATABASE :database AS :prefix', [
                            ':database' => $connection_options['database'],
                            ':prefix' => $prefix,
                        ]);
                    }
                    else {
                        $this->query('ATTACH DATABASE :database AS :prefix', [
                            ':database' => $connection_options['database'] . '-' . $prefix,
                            ':prefix' => $prefix,
                        ]);
                    }
                }
                // Add a ., so queries become prefix.table, which is proper syntax for
                // querying an attached database.
                $prefix .= '.';
            }
        }
        // Regenerate the prefixes replacement table.
        $this->setPrefix($prefixes);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function open(array &$connection_options = []) {
        // Allow PDO options to be overridden.
        $connection_options += [
            'pdo' => [],
        ];
        $connection_options['pdo'] += [
            \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
            // Convert numeric values to strings when fetching.
\PDO::ATTR_STRINGIFY_FETCHES => TRUE,
        ];
        try {
            $pdo = new \PDO('sqlite:' . $connection_options['database'], '', '', $connection_options['pdo']);
        } catch (\PDOException $e) {
            if ($e->getCode() == static::DATABASE_NOT_FOUND) {
                throw new DatabaseNotFoundException($e->getMessage(), $e->getCode(), $e);
            }
            // SQLite doesn't have a distinct error code for access denied, so don't
            // deal with that case.
            throw $e;
        }
        // Create functions needed by SQLite.
        $pdo->sqliteCreateFunction('if', [
            __CLASS__,
            'sqlFunctionIf',
        ]);
        $pdo->sqliteCreateFunction('greatest', [
            __CLASS__,
            'sqlFunctionGreatest',
        ]);
        $pdo->sqliteCreateFunction('pow', 'pow', 2);
        $pdo->sqliteCreateFunction('exp', 'exp', 1);
        $pdo->sqliteCreateFunction('length', 'strlen', 1);
        $pdo->sqliteCreateFunction('md5', 'md5', 1);
        $pdo->sqliteCreateFunction('concat', [
            __CLASS__,
            'sqlFunctionConcat',
        ]);
        $pdo->sqliteCreateFunction('concat_ws', [
            __CLASS__,
            'sqlFunctionConcatWs',
        ]);
        $pdo->sqliteCreateFunction('substring', [
            __CLASS__,
            'sqlFunctionSubstring',
        ], 3);
        $pdo->sqliteCreateFunction('substring_index', [
            __CLASS__,
            'sqlFunctionSubstringIndex',
        ], 3);
        $pdo->sqliteCreateFunction('rand', [
            __CLASS__,
            'sqlFunctionRand',
        ]);
        $pdo->sqliteCreateFunction('regexp', [
            __CLASS__,
            'sqlFunctionRegexp',
        ]);
        // SQLite does not support the LIKE BINARY operator, so we overload the
        // non-standard GLOB operator for case-sensitive matching. Another option
        // would have been to override another non-standard operator, MATCH, but
        // that does not support the NOT keyword prefix.
        $pdo->sqliteCreateFunction('glob', [
            __CLASS__,
            'sqlFunctionLikeBinary',
        ]);
        // Create a user-space case-insensitive collation with UTF-8 support.
        $pdo->sqliteCreateCollation('NOCASE_UTF8', [
            'Drupal\\Component\\Utility\\Unicode',
            'strcasecmp',
        ]);
        // Set SQLite init_commands if not already defined. Enable the Write-Ahead
        // Logging (WAL) for SQLite. See https://www.drupal.org/node/2348137 and
        // https://www.sqlite.org/wal.html.
        $connection_options += [
            'init_commands' => [],
        ];
        $connection_options['init_commands'] += [
            'wal' => "PRAGMA journal_mode=WAL",
        ];
        // Execute sqlite init_commands.
        if (isset($connection_options['init_commands'])) {
            $pdo->exec(implode('; ', $connection_options['init_commands']));
        }
        return $pdo;
    }
    
    /**
     * Destructor for the SQLite connection.
     *
     * We prune empty databases on destruct, but only if tables have been
     * dropped. This is especially needed when running the test suite, which
     * creates and destroy databases several times in a row.
     */
    public function __destruct() {
        if ($this->tableDropped && !empty($this->attachedDatabases)) {
            foreach ($this->attachedDatabases as $prefix) {
                // Check if the database is now empty, ignore the internal SQLite tables.
                try {
                    $count = $this->query('SELECT COUNT(*) FROM ' . $prefix . '.sqlite_master WHERE type = :type AND name NOT LIKE :pattern', [
                        ':type' => 'table',
                        ':pattern' => 'sqlite_%',
                    ])
                        ->fetchField();
                    // We can prune the database file if it doesn't have any tables.
                    if ($count == 0 && $this->connectionOptions['database'] != ':memory:') {
                        // Detaching the database fails at this point, but no other queries
                        // are executed after the connection is destructed so we can simply
                        // remove the database file.
                        unlink($this->connectionOptions['database'] . '-' . $prefix);
                    }
                } catch (\Exception $e) {
                    // Ignore the exception and continue. There is nothing we can do here
                    // to report the error or fail safe.
                }
            }
        }
    }
    
    /**
     * Gets all the attached databases.
     *
     * @return array
     *   An array of attached database names.
     *
     * @see \Drupal\Core\Database\Driver\sqlite\Connection::__construct()
     */
    public function getAttachedDatabases() {
        return $this->attachedDatabases;
    }
    
    /**
     * SQLite compatibility implementation for the IF() SQL function.
     */
    public static function sqlFunctionIf($condition, $expr1, $expr2 = NULL) {
        return $condition ? $expr1 : $expr2;
    }
    
    /**
     * SQLite compatibility implementation for the GREATEST() SQL function.
     */
    public static function sqlFunctionGreatest() {
        $args = func_get_args();
        foreach ($args as $v) {
            if (!isset($v)) {
                unset($args);
            }
        }
        if (count($args)) {
            return max($args);
        }
        else {
            return NULL;
        }
    }
    
    /**
     * SQLite compatibility implementation for the CONCAT() SQL function.
     */
    public static function sqlFunctionConcat() {
        $args = func_get_args();
        return implode('', $args);
    }
    
    /**
     * SQLite compatibility implementation for the CONCAT_WS() SQL function.
     *
     * @see http://dev.mysql.com/doc/refman/5.6/en/string-functions.html#function_concat-ws
     */
    public static function sqlFunctionConcatWs() {
        $args = func_get_args();
        $separator = array_shift($args);
        // If the separator is NULL, the result is NULL.
        if ($separator === FALSE || is_null($separator)) {
            return NULL;
        }
        // Skip any NULL values after the separator argument.
        $args = array_filter($args, function ($value) {
            return !is_null($value);
        });
        return implode($separator, $args);
    }
    
    /**
     * SQLite compatibility implementation for the SUBSTRING() SQL function.
     */
    public static function sqlFunctionSubstring($string, $from, $length) {
        return substr($string, $from - 1, $length);
    }
    
    /**
     * SQLite compatibility implementation for the SUBSTRING_INDEX() SQL function.
     */
    public static function sqlFunctionSubstringIndex($string, $delimiter, $count) {
        // If string is empty, simply return an empty string.
        if (empty($string)) {
            return '';
        }
        $end = 0;
        for ($i = 0; $i < $count; $i++) {
            $end = strpos($string, $delimiter, $end + 1);
            if ($end === FALSE) {
                $end = strlen($string);
            }
        }
        return substr($string, 0, $end);
    }
    
    /**
     * SQLite compatibility implementation for the RAND() SQL function.
     */
    public static function sqlFunctionRand($seed = NULL) {
        if (isset($seed)) {
            mt_srand($seed);
        }
        return mt_rand() / mt_getrandmax();
    }
    
    /**
     * SQLite compatibility implementation for the REGEXP SQL operator.
     *
     * The REGEXP operator is natively known, but not implemented by default.
     *
     * @see http://www.sqlite.org/lang_expr.html#regexp
     */
    public static function sqlFunctionRegexp($pattern, $subject) {
        // preg_quote() cannot be used here, since $pattern may contain reserved
        // regular expression characters already (such as ^, $, etc). Therefore,
        // use a rare character as PCRE delimiter.
        $pattern = '#' . addcslashes($pattern, '#') . '#i';
        return preg_match($pattern, $subject);
    }
    
    /**
     * SQLite compatibility implementation for the LIKE BINARY SQL operator.
     *
     * SQLite supports case-sensitive LIKE operations through the
     * 'case_sensitive_like' PRAGMA statement, but only for ASCII characters, so
     * we have to provide our own implementation with UTF-8 support.
     *
     * @see https://sqlite.org/pragma.html#pragma_case_sensitive_like
     * @see https://sqlite.org/lang_expr.html#like
     */
    public static function sqlFunctionLikeBinary($pattern, $subject) {
        // Replace the SQL LIKE wildcard meta-characters with the equivalent regular
        // expression meta-characters and escape the delimiter that will be used for
        // matching.
        $pattern = str_replace([
            '%',
            '_',
        ], [
            '.*?',
            '.',
        ], preg_quote($pattern, '/'));
        return preg_match('/^' . $pattern . '$/', $subject);
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepare($statement, array $driver_options = []) {
        return new Statement($this->connection, $this, $statement, $driver_options);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function handleQueryException(\PDOException $e, $query, array $args = [], $options = []) {
        // The database schema might be changed by another process in between the
        // time that the statement was prepared and the time the statement was run
        // (e.g. usually happens when running tests). In this case, we need to
        // re-run the query.
        // @see http://www.sqlite.org/faq.html#q15
        // @see http://www.sqlite.org/rescode.html#schema
        if (!empty($e->errorInfo[1]) && $e->errorInfo[1] === 17) {
            return $this->query($query, $args, $options);
        }
        parent::handleQueryException($e, $query, $args, $options);
    }
    public function queryRange($query, $from, $count, array $args = [], array $options = []) {
        return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);
    }
    public function queryTemporary($query, array $args = [], array $options = []) {
        // Generate a new temporary table name and protect it from prefixing.
        // SQLite requires that temporary tables to be non-qualified.
        $tablename = $this->generateTemporaryTableName();
        $prefixes = $this->prefixes;
        $prefixes[$tablename] = '';
        $this->setPrefix($prefixes);
        $this->query('CREATE TEMPORARY TABLE ' . $tablename . ' AS ' . $query, $args, $options);
        return $tablename;
    }
    public function driver() {
        return 'sqlite';
    }
    public function databaseType() {
        return 'sqlite';
    }
    
    /**
     * 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) {
        // Verify the database is writable.
        $db_directory = new \SplFileInfo(dirname($database));
        if (!$db_directory->isDir() && !\Drupal::service('file_system')->mkdir($db_directory->getPathName(), 0755, TRUE)) {
            throw new DatabaseNotFoundException('Unable to create database directory ' . $db_directory->getPathName());
        }
    }
    public function mapConditionOperator($operator) {
        return isset(static::$sqliteConditionOperatorMap[$operator]) ? static::$sqliteConditionOperatorMap[$operator] : NULL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareQuery($query) {
        return $this->prepare($this->prefixTables($query));
    }
    public function nextId($existing_id = 0) {
        $this->startTransaction();
        // We can safely use literal queries here instead of the slower query
        // builder because if a given database breaks here then it can simply
        // override nextId. However, this is unlikely as we deal with short strings
        // and integers and no known databases require special handling for those
        // simple cases. If another transaction wants to write the same row, it will
        // wait until this transaction commits. Also, the return value needs to be
        // set to RETURN_AFFECTED as if it were a real update() query otherwise it
        // is not possible to get the row count properly.
        $affected = $this->query('UPDATE {sequences} SET value = GREATEST(value, :existing_id) + 1', [
            ':existing_id' => $existing_id,
        ], [
            'return' => Database::RETURN_AFFECTED,
        ]);
        if (!$affected) {
            $this->query('INSERT INTO {sequences} (value) VALUES (:existing_id + 1)', [
                ':existing_id' => $existing_id,
            ]);
        }
        // The transaction gets committed when the transaction object gets destroyed
        // because it gets out of scope.
        return $this->query('SELECT value FROM {sequences}')
            ->fetchField();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFullQualifiedTableName($table) {
        $prefix = $this->tablePrefix($table);
        // Don't include the SQLite database file name as part of the table name.
        return $prefix . $table;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createConnectionOptionsFromUrl($url, $root) {
        $database = parent::createConnectionOptionsFromUrl($url, $root);
        // A SQLite database path with two leading slashes indicates a system path.
        // Otherwise the path is relative to the Drupal root.
        $url_components = parse_url($url);
        if ($url_components['path'][0] === '/') {
            $url_components['path'] = substr($url_components['path'], 1);
        }
        if ($url_components['path'][0] === '/' || $url_components['path'] === ':memory:') {
            $database['database'] = $url_components['path'];
        }
        else {
            $database['database'] = $root . '/' . $url_components['path'];
        }
        // User credentials and system port are irrelevant for SQLite.
        unset($database['username'], $database['password'], $database['port']);
        return $database;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createUrlFromConnectionOptions(array $connection_options) {
        if (!isset($connection_options['driver'], $connection_options['database'])) {
            throw new \InvalidArgumentException("As a minimum, the connection options array must contain at least the 'driver' and 'database' keys");
        }
        $db_url = 'sqlite://localhost/' . $connection_options['database'];
        if (isset($connection_options['prefix']['default']) && $connection_options['prefix']['default'] !== NULL && $connection_options['prefix']['default'] !== '') {
            $db_url .= '#' . $connection_options['prefix']['default'];
        }
        return $db_url;
    }

}