"""
This module implements connections for MySQLdb. Presently there is
only one class: Connection. Others are unlikely. However, you might
want to make your own subclasses. In most cases, you will probably
override Connection.default_cursor with a non-standard Cursor class.
"""
import re
import sys

from MySQLdb import cursors
from MySQLdb.compat import unicode, PY2
from _mysql_exceptions import (
    Warning, Error, InterfaceError, DataError,
    DatabaseError, OperationalError, IntegrityError, InternalError,
    NotSupportedError, ProgrammingError,
)
import _mysql


if not PY2:
    if sys.version_info[:2] < (3, 6):
        # See http://bugs.python.org/issue24870
        _surrogateescape_table = [chr(i) if i < 0x80 else chr(i + 0xdc00) for i in range(256)]

        def _fast_surrogateescape(s):
            return s.decode('latin1').translate(_surrogateescape_table)
    else:
        def _fast_surrogateescape(s):
            return s.decode('ascii', 'surrogateescape')


def defaulterrorhandler(connection, cursor, errorclass, errorvalue):
    """
    If cursor is not None, (errorclass, errorvalue) is appended to
    cursor.messages; otherwise it is appended to
    connection.messages. Then errorclass is raised with errorvalue as
    the value.

    You can override this with your own error handler by assigning it
    to the instance.
    """
    error = errorclass, errorvalue
    if cursor:
        cursor.messages.append(error)
    else:
        connection.messages.append(error)
    del cursor
    del connection
    if isinstance(errorvalue, BaseException):
        raise errorvalue
    if errorclass is not None:
        raise errorclass(errorvalue)
    else:
        raise Exception(errorvalue)


re_numeric_part = re.compile(r"^(\d+)")

def numeric_part(s):
    """Returns the leading numeric part of a string.

    >>> numeric_part("20-alpha")
    20
    >>> numeric_part("foo")
    >>> numeric_part("16b")
    16
    """

    m = re_numeric_part.match(s)
    if m:
        return int(m.group(1))
    return None


class Connection(_mysql.connection):
    """MySQL Database Connection Object"""

    default_cursor = cursors.Cursor
    waiter = None

    def __init__(self, *args, **kwargs):
        """
        Create a connection to the database. It is strongly recommended
        that you only use keyword parameters. Consult the MySQL C API
        documentation for more information.

        :param str host:        host to connect
        :param str user:        user to connect as
        :param str password:    password to use
        :param str passwd:      alias of password, for backward compatibility
        :param str database:    database to use
        :param str db:          alias of database, for backward compatibility
        :param int port:        TCP/IP port to connect to
        :param str unix_socket: location of unix_socket to use
        :param dict conv:       conversion dictionary, see MySQLdb.converters
        :param int connect_timeout:
            number of seconds to wait before the connection attempt fails.

        :param bool compress:   if set, compression is enabled
        :param str named_pipe:  if set, a named pipe is used to connect (Windows only)
        :param str init_command:
            command which is run once the connection is created

        :param str read_default_file:
            file from which default client values are read

        :param str read_default_group:
            configuration group to use from the default file

        :param type cursorclass:
            class object, used to create cursors (keyword only)

        :param str use_unicode:
            If True, text-like columns are returned as unicode objects
            using the connection's character set.  Otherwise, text-like
            columns are returned as strings.  columns are returned as
            normal strings. Unicode objects will always be encoded to
            the connection's character set regardless of this setting.
            Default to False on Python 2 and True on Python 3.

        :param str charset:
            If supplied, the connection character set will be changed
            to this character set (MySQL-4.1 and newer). This implies
            use_unicode=True.

        :param str sql_mode:
            If supplied, the session SQL mode will be changed to this
            setting (MySQL-4.1 and newer). For more details and legal
            values, see the MySQL documentation.

        :param int client_flag:
            flags to use or 0 (see MySQL docs or constants/CLIENTS.py)

        :param dict ssl:
            dictionary or mapping contains SSL connection parameters;
            see the MySQL documentation for more details
            (mysql_ssl_set()).  If this is set, and the client does not
            support SSL, NotSupportedError will be raised.

        :param bool local_infile:
            enables LOAD LOCAL INFILE; zero disables

        :param bool autocommit:
            If False (default), autocommit is disabled.
            If True, autocommit is enabled.
            If None, autocommit isn't set and server default is used.

        :param bool binary_prefix:
            If set, the '_binary' prefix will be used for raw byte query
            arguments (e.g. Binary). This is disabled by default.

        There are a number of undocumented, non-standard methods. See the
        documentation for the MySQL C API for some hints on what they do.
        """
        from MySQLdb.constants import CLIENT, FIELD_TYPE
        from MySQLdb.converters import conversions
        from weakref import proxy

        kwargs2 = kwargs.copy()

        if 'database' in kwargs2:
            kwargs2['db'] = kwargs2.pop('database')
        if 'password' in kwargs2:
            kwargs2['passwd'] = kwargs2.pop('password')

        if 'conv' in kwargs:
            conv = kwargs['conv']
        else:
            conv = conversions

        conv2 = {}
        for k, v in conv.items():
            if isinstance(k, int) and isinstance(v, list):
                conv2[k] = v[:]
            else:
                conv2[k] = v
        kwargs2['conv'] = conv2

        cursorclass = kwargs2.pop('cursorclass', self.default_cursor)
        charset = kwargs2.pop('charset', '')

        if charset or not PY2:
            use_unicode = True
        else:
            use_unicode = False

        use_unicode = kwargs2.pop('use_unicode', use_unicode)
        sql_mode = kwargs2.pop('sql_mode', '')
        binary_prefix = kwargs2.pop('binary_prefix', False)

        client_flag = kwargs.get('client_flag', 0)
        client_version = tuple([ numeric_part(n) for n in _mysql.get_client_info().split('.')[:2] ])
        if client_version >= (4, 1):
            client_flag |= CLIENT.MULTI_STATEMENTS
        if client_version >= (5, 0):
            client_flag |= CLIENT.MULTI_RESULTS

        kwargs2['client_flag'] = client_flag

        # PEP-249 requires autocommit to be initially off
        autocommit = kwargs2.pop('autocommit', False)
        self.waiter = kwargs2.pop('waiter', None)

        super(Connection, self).__init__(*args, **kwargs2)
        self.cursorclass = cursorclass
        self.encoders = dict([ (k, v) for k, v in conv.items()
                               if type(k) is not int ])

        self._server_version = tuple([ numeric_part(n) for n in self.get_server_info().split('.')[:2] ])

        db = proxy(self)
        def _get_string_literal():
            # Note: string_literal() is called for bytes object on Python 3 (via bytes_literal)
            def string_literal(obj, dummy=None):
                return db.string_literal(obj)
            return string_literal

        def _get_unicode_literal():
            if PY2:
                # unicode_literal is called for only unicode object.
                def unicode_literal(u, dummy=None):
                    return db.string_literal(u.encode(unicode_literal.charset))
            else:
                # unicode_literal() is called for arbitrary object.
                def unicode_literal(u, dummy=None):
                    return db.string_literal(str(u).encode(unicode_literal.charset))
            return unicode_literal

        def _get_bytes_literal():
            def bytes_literal(obj, dummy=None):
                return b'_binary' + db.string_literal(obj)
            return bytes_literal

        def _get_string_decoder():
            def string_decoder(s):
                return s.decode(string_decoder.charset)
            return string_decoder

        string_literal = _get_string_literal()
        self.unicode_literal = unicode_literal = _get_unicode_literal()
        bytes_literal = _get_bytes_literal()
        self.string_decoder = string_decoder = _get_string_decoder()
        if not charset:
            charset = self.character_set_name()
        self.set_character_set(charset)

        if sql_mode:
            self.set_sql_mode(sql_mode)

        if use_unicode:
            self.converter[FIELD_TYPE.STRING].append((None, string_decoder))
            self.converter[FIELD_TYPE.VAR_STRING].append((None, string_decoder))
            self.converter[FIELD_TYPE.VARCHAR].append((None, string_decoder))
            self.converter[FIELD_TYPE.BLOB].append((None, string_decoder))

        if binary_prefix:
            self.encoders[bytes] = string_literal if PY2 else bytes_literal
            self.encoders[bytearray] = bytes_literal
        else:
            self.encoders[bytes] = string_literal

        self.encoders[unicode] = unicode_literal
        self._transactional = self.server_capabilities & CLIENT.TRANSACTIONS
        if self._transactional:
            if autocommit is not None:
                self.autocommit(autocommit)
        self.messages = []

    def autocommit(self, on):
        on = bool(on)
        if self.get_autocommit() != on:
            _mysql.connection.autocommit(self, on)

    def cursor(self, cursorclass=None):
        """
        Create a cursor on which queries may be performed. The
        optional cursorclass parameter is used to create the
        Cursor. By default, self.cursorclass=cursors.Cursor is
        used.
        """
        return (cursorclass or self.cursorclass)(self)

    def query(self, query):
        # Since _mysql releases GIL while querying, we need immutable buffer.
        if isinstance(query, bytearray):
            query = bytes(query)
        if self.waiter is not None:
            self.send_query(query)
            self.waiter(self.fileno())
            self.read_query_result()
        else:
            _mysql.connection.query(self, query)

    def __enter__(self):
        from warnings import warn
        warn("context interface will be changed.  Use explicit conn.commit() or conn.rollback().",
             DeprecationWarning, 2)
        if self.get_autocommit():
            self.query("BEGIN")
        return self.cursor()

    def __exit__(self, exc, value, tb):
        if exc:
            self.rollback()
        else:
            self.commit()

    def literal(self, o):
        """If o is a single object, returns an SQL literal as a string.
        If o is a non-string sequence, the items of the sequence are
        converted and returned as a sequence.

        Non-standard. For internal use; do not use this in your
        applications.
        """
        s = self.escape(o, self.encoders)
        # Python 3(~3.4) doesn't support % operation for bytes object.
        # We should decode it before using %.
        # Decoding with ascii and surrogateescape allows convert arbitrary
        # bytes to unicode and back again.
        # See http://python.org/dev/peps/pep-0383/
        if not PY2 and isinstance(s, (bytes, bytearray)):
            return _fast_surrogateescape(s)
        return s

    def begin(self):
        """Explicitly begin a connection. Non-standard.
        DEPRECATED: Will be removed in 1.3.
        Use an SQL BEGIN statement instead."""
        from warnings import warn
        warn("begin() is non-standard and will be removed in 1.4",
             DeprecationWarning, 2)
        self.query("BEGIN")

    if not hasattr(_mysql.connection, 'warning_count'):

        def warning_count(self):
            """Return the number of warnings generated from the
            last query. This is derived from the info() method."""
            info = self.info()
            if info:
                return int(info.split()[-1])
            else:
                return 0

    def set_character_set(self, charset):
        """Set the connection character set to charset. The character
        set can only be changed in MySQL-4.1 and newer. If you try
        to change the character set from the current value in an
        older version, NotSupportedError will be raised."""
        if charset == "utf8mb4":
            py_charset = "utf8"
        else:
            py_charset = charset
        if self.character_set_name() != charset:
            try:
                super(Connection, self).set_character_set(charset)
            except AttributeError:
                if self._server_version < (4, 1):
                    raise NotSupportedError("server is too old to set charset")
                self.query('SET NAMES %s' % charset)
                self.store_result()
        self.string_decoder.charset = py_charset
        self.unicode_literal.charset = py_charset
        self.encoding = py_charset

    def set_sql_mode(self, sql_mode):
        """Set the connection sql_mode. See MySQL documentation for
        legal values."""
        if self._server_version < (4, 1):
            raise NotSupportedError("server is too old to set sql_mode")
        self.query("SET SESSION sql_mode='%s'" % sql_mode)
        self.store_result()

    def show_warnings(self):
        """Return detailed information about warnings as a
        sequence of tuples of (Level, Code, Message). This
        is only supported in MySQL-4.1 and up. If your server
        is an earlier version, an empty sequence is returned."""
        if self._server_version < (4,1): return ()
        self.query("SHOW WARNINGS")
        r = self.store_result()
        warnings = r.fetch_row(0)
        return warnings

    Warning = Warning
    Error = Error
    InterfaceError = InterfaceError
    DatabaseError = DatabaseError
    DataError = DataError
    OperationalError = OperationalError
    IntegrityError = IntegrityError
    InternalError = InternalError
    ProgrammingError = ProgrammingError
    NotSupportedError = NotSupportedError

    errorhandler = defaulterrorhandler

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