class Connection

class Connection extends DatabaseConnection {
    
    /**
     * The name by which to obtain a lock for retrieve the next insert id.
     */
    const POSTGRESQL_NEXTID_LOCK = 1000;
    
    /**
     * Error code for "Unknown database" error.
     */
    const DATABASE_NOT_FOUND = 7;
    
    /**
     * Error code for "Connection failure" errors.
     *
     * Technically this is an internal error code that will only be shown in the
     * PDOException message. It will need to get extracted.
     */
    const CONNECTION_FAILURE = '08006';
    
    /**
     * {@inheritdoc}
     */
    protected $statementClass = NULL;
    
    /**
     * {@inheritdoc}
     */
    protected $statementWrapperClass = StatementWrapper::class;
    
    /**
     * A map of condition operators to PostgreSQL operators.
     *
     * In PostgreSQL, 'LIKE' is case-sensitive. ILIKE should be used for
     * case-insensitive statements.
     */
    protected static $postgresqlConditionOperatorMap = [
        'LIKE' => [
            'operator' => 'ILIKE',
        ],
        'LIKE BINARY' => [
            'operator' => 'LIKE',
        ],
        'NOT LIKE' => [
            'operator' => 'NOT ILIKE',
        ],
        'REGEXP' => [
            'operator' => '~*',
        ],
        'NOT REGEXP' => [
            'operator' => '!~*',
        ],
    ];
    
    /**
     * {@inheritdoc}
     */
    protected $transactionalDDLSupport = TRUE;
    
    /**
     * {@inheritdoc}
     */
    protected $identifierQuotes = [
        '"',
        '"',
    ];
    
    /**
     * Constructs a connection object.
     */
    public function __construct(\PDO $connection, array $connection_options) {
        parent::__construct($connection, $connection_options);
        // Force PostgreSQL to use the UTF-8 character set by default.
        $this->connection
            ->exec("SET NAMES 'UTF8'");
        // Execute PostgreSQL init_commands.
        if (isset($connection_options['init_commands'])) {
            $this->connection
                ->exec(implode('; ', $connection_options['init_commands']));
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function open(array &$connection_options = []) {
        // Default to TCP connection on port 5432.
        if (empty($connection_options['port'])) {
            $connection_options['port'] = 5432;
        }
        // PostgreSQL in trust mode doesn't require a password to be supplied.
        if (empty($connection_options['password'])) {
            $connection_options['password'] = NULL;
        }
        else {
            $connection_options['password'] = str_replace('\\', '\\\\', $connection_options['password']);
        }
        $connection_options['database'] = !empty($connection_options['database']) ? $connection_options['database'] : 'template1';
        $dsn = 'pgsql:host=' . $connection_options['host'] . ' dbname=' . $connection_options['database'] . ' port=' . $connection_options['port'];
        // Allow PDO options to be overridden.
        $connection_options += [
            'pdo' => [],
        ];
        $connection_options['pdo'] += [
            \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
            // Prepared statements are most effective for performance when queries
            // are recycled (used several times). However, if they are not re-used,
            // prepared statements become inefficient. Since most of Drupal's
            // prepared queries are not re-used, it should be faster to emulate
            // the preparation than to actually ready statements for re-use. If in
            // doubt, reset to FALSE and measure performance.
\PDO::ATTR_EMULATE_PREPARES => TRUE,
            // Convert numeric values to strings when fetching.
\PDO::ATTR_STRINGIFY_FETCHES => TRUE,
        ];
        try {
            $pdo = new \PDO($dsn, $connection_options['username'], $connection_options['password'], $connection_options['pdo']);
        } catch (\PDOException $e) {
            if (static::getSQLState($e) == static::CONNECTION_FAILURE) {
                if (strpos($e->getMessage(), 'password authentication failed for user') !== FALSE) {
                    throw new DatabaseAccessDeniedException($e->getMessage(), $e->getCode(), $e);
                }
                elseif (strpos($e->getMessage(), 'database') !== FALSE && strpos($e->getMessage(), 'does not exist') !== FALSE) {
                    throw new DatabaseNotFoundException($e->getMessage(), $e->getCode(), $e);
                }
            }
            throw $e;
        }
        return $pdo;
    }
    
    /**
     * {@inheritdoc}
     */
    public function query($query, array $args = [], $options = []) {
        $options += $this->defaultOptions();
        // The PDO PostgreSQL driver has a bug which doesn't type cast booleans
        // correctly when parameters are bound using associative arrays.
        // @see http://bugs.php.net/bug.php?id=48383
        foreach ($args as &$value) {
            if (is_bool($value)) {
                $value = (int) $value;
            }
        }
        // We need to wrap queries with a savepoint if:
        // - Currently in a transaction.
        // - A 'mimic_implicit_commit' does not exist already.
        // - The query is not a savepoint query.
        $wrap_with_savepoint = $this->inTransaction() && !isset($this->transactionLayers['mimic_implicit_commit']) && !(is_string($query) && (stripos($query, 'ROLLBACK TO SAVEPOINT ') === 0 || stripos($query, 'RELEASE SAVEPOINT ') === 0 || stripos($query, 'SAVEPOINT ') === 0));
        if ($wrap_with_savepoint) {
            // Create a savepoint so we can rollback a failed query. This is so we can
            // mimic MySQL and SQLite transactions which don't fail if a single query
            // fails. This is important for tables that are created on demand. For
            // example, \Drupal\Core\Cache\DatabaseBackend.
            $this->addSavepoint();
            try {
                $return = parent::query($query, $args, $options);
                $this->releaseSavepoint();
            } catch (\Exception $e) {
                $this->rollbackSavepoint();
                throw $e;
            }
        }
        else {
            $return = parent::query($query, $args, $options);
        }
        return $return;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareStatement(string $query, array $options, bool $allow_row_count = FALSE) : StatementInterface {
        // mapConditionOperator converts some operations (LIKE, REGEXP, etc.) to
        // PostgreSQL equivalents (ILIKE, ~*, etc.). However PostgreSQL doesn't
        // automatically cast the fields to the right type for these operators,
        // so we need to alter the query and add the type-cast.
        $query = preg_replace('/ ([^ ]+) +(I*LIKE|NOT +I*LIKE|~\\*|!~\\*) /i', ' ${1}::text ${2} ', $query);
        return parent::prepareStatement($query, $options, $allow_row_count);
    }
    public function queryRange($query, $from, $count, array $args = [], array $options = []) {
        return $this->query($query . ' LIMIT ' . (int) $count . ' OFFSET ' . (int) $from, $args, $options);
    }
    
    /**
     * {@inheritdoc}
     */
    public function queryTemporary($query, array $args = [], array $options = []) {
        $tablename = $this->generateTemporaryTableName();
        $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} AS ' . $query, $args, $options);
        return $tablename;
    }
    public function driver() {
        return 'pgsql';
    }
    public function databaseType() {
        return 'pgsql';
    }
    
    /**
     * 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);
        // If the PECL intl extension is installed, use it to determine the proper
        // locale.  Otherwise, fall back to en_US.
        if (class_exists('Locale')) {
            $locale = \Locale::getDefault();
        }
        else {
            $locale = 'en_US';
        }
        try {
            // Create the database and set it as active.
            $this->connection
                ->exec("CREATE DATABASE {$database} WITH TEMPLATE template0 ENCODING='utf8' LC_CTYPE='{$locale}.utf8' LC_COLLATE='{$locale}.utf8'");
        } catch (\Exception $e) {
            throw new DatabaseNotFoundException($e->getMessage());
        }
    }
    public function mapConditionOperator($operator) {
        return static::$postgresqlConditionOperatorMap[$operator] ?? NULL;
    }
    
    /**
     * Retrieve a the next id in a sequence.
     *
     * PostgreSQL has built in sequences. We'll use these instead of inserting
     * and updating a sequences table.
     */
    public function nextId($existing = 0) {
        // Retrieve the name of the sequence. This information cannot be cached
        // because the prefix may change, for example, like it does in tests.
        $sequence_name = $this->makeSequenceName('sequences', 'value');
        // When PostgreSQL gets a value too small then it will lock the table,
        // retry the INSERT and if it's still too small then alter the sequence.
        $id = $this->query("SELECT nextval('" . $sequence_name . "')")
            ->fetchField();
        if ($id > $existing) {
            return $id;
        }
        // PostgreSQL advisory locks are simply locks to be used by an
        // application such as Drupal. This will prevent other Drupal processes
        // from altering the sequence while we are.
        $this->query("SELECT pg_advisory_lock(" . self::POSTGRESQL_NEXTID_LOCK . ")");
        // While waiting to obtain the lock, the sequence may have been altered
        // so lets try again to obtain an adequate value.
        $id = $this->query("SELECT nextval('" . $sequence_name . "')")
            ->fetchField();
        if ($id > $existing) {
            $this->query("SELECT pg_advisory_unlock(" . self::POSTGRESQL_NEXTID_LOCK . ")");
            return $id;
        }
        // Reset the sequence to a higher value than the existing id.
        $this->query("ALTER SEQUENCE " . $sequence_name . " RESTART WITH " . ($existing + 1));
        // Retrieve the next id. We know this will be as high as we want it.
        $id = $this->query("SELECT nextval('" . $sequence_name . "')")
            ->fetchField();
        $this->query("SELECT pg_advisory_unlock(" . self::POSTGRESQL_NEXTID_LOCK . ")");
        return $id;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFullQualifiedTableName($table) {
        $options = $this->getConnectionOptions();
        $prefix = $this->tablePrefix($table);
        // The fully qualified table name in PostgreSQL is in the form of
        // <database>.<schema>.<table>, so we have to include the 'public' schema in
        // the return value.
        return $options['database'] . '.public.' . $prefix . $table;
    }
    
    /**
     * Add a new savepoint with a unique name.
     *
     * The main use for this method is to mimic InnoDB functionality, which
     * provides an inherent savepoint before any query in a transaction.
     *
     * @param $savepoint_name
     *   A string representing the savepoint name. By default,
     *   "mimic_implicit_commit" is used.
     *
     * @see Drupal\Core\Database\Connection::pushTransaction()
     */
    public function addSavepoint($savepoint_name = 'mimic_implicit_commit') {
        if ($this->inTransaction()) {
            $this->pushTransaction($savepoint_name);
        }
    }
    
    /**
     * Release a savepoint by name.
     *
     * @param $savepoint_name
     *   A string representing the savepoint name. By default,
     *   "mimic_implicit_commit" is used.
     *
     * @see Drupal\Core\Database\Connection::popTransaction()
     */
    public function releaseSavepoint($savepoint_name = 'mimic_implicit_commit') {
        if (isset($this->transactionLayers[$savepoint_name])) {
            $this->popTransaction($savepoint_name);
        }
    }
    
    /**
     * Rollback a savepoint by name if it exists.
     *
     * @param $savepoint_name
     *   A string representing the savepoint name. By default,
     *   "mimic_implicit_commit" is used.
     */
    public function rollbackSavepoint($savepoint_name = 'mimic_implicit_commit') {
        if (isset($this->transactionLayers[$savepoint_name])) {
            $this->rollBack($savepoint_name);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasJson() : bool {
        try {
            return (bool) $this->query('SELECT JSON_TYPEOF(\'1\')');
        } catch (\Exception $e) {
            return FALSE;
        }
    }

}