path: root/db.py

"""Wrappers to get actually replaceable DBAPI2 compliant modules and
database connection whatever the database and client lib used.

Currently support:

- postgresql (pgdb, psycopg, psycopg2, pyPgSQL)
- mysql (MySQLdb)
- sqlite (pysqlite2, sqlite, sqlite3)

just use the `get_connection` function from this module to get a
wrapped connection.  If multiple drivers for a database are available,
you can control which one you want to use using the
`set_prefered_driver` function.

Additional helpers are also provided for advanced functionalities such
as listing existing users or databases, creating database... Get the
helper for your database using the `get_adv_func_helper` function.

:copyright: 2002-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: General Public License version 2 - http://www.gnu.org/licenses
"""
__docformat__ = "restructuredtext en"

import sys
import re
from warnings import warn
import threading 
import datetime

import logilab.common as lgc
from logilab.common.deprecation import obsolete

try:
    from mx.DateTime import DateTimeType, DateTimeDeltaType, strptime
    HAS_MX_DATETIME = True
except:
    HAS_MX_DATETIME = False

__all__ = ['get_dbapi_compliant_module',
           'get_connection', 'set_prefered_driver',
           'PyConnection', 'PyCursor',
           'UnknownDriver', 'NoAdapterFound',
           ]

class UnknownDriver(Exception):
    """raised when a unknown driver is given to get connection"""

class NoAdapterFound(Exception):
    """Raised when no Adapter to DBAPI was found"""
    def __init__(self, obj, objname=None, protocol='DBAPI'):
        if objname is None:
            objname = obj.__name__
        Exception.__init__(self, "Could not adapt %s to protocol %s" %
                           (objname, protocol))
        self.adapted_obj = obj
        self.objname = objname
        self._protocol = protocol


def _import_driver_module(driver, drivers, imported_elements=None, quiet=True):
    """Imports the first module found in 'drivers' for 'driver'

    :rtype: tuple
    :returns: the tuple module_object, module_name where module_object
              is the dbapi module, and modname the module's name
    """
    if not driver in drivers:
        raise UnknownDriver(driver)
    imported_elements = imported_elements or []
    for modname in drivers[driver]:
        try:
            if not quiet:
                print >> sys.stderr, 'Trying %s' % modname
            module = __import__(modname, globals(), locals(), imported_elements)
            break
        except ImportError:
            if not quiet:
                print >> sys.stderr, '%s is not available' % modname
            continue
    else:
        raise ImportError('Unable to import a %s module' % driver)
    if not imported_elements:
        for part in modname.split('.')[1:]:
            module = getattr(module, part)
    return module, modname


## Connection and cursor wrappers #############################################

class SimpleConnectionWrapper:
    """A simple connection wrapper in python to decorated C-level connections
    with additional attributes
    """
    def __init__(self, cnx):
        """Wraps the original connection object"""
        self._cnx = cnx

    # XXX : Would it work if only __getattr__ was defined
    def cursor(self):
        """Wraps cursor()"""
        return self._cnx.cursor()

    def commit(self):
        """Wraps commit()"""
        return self._cnx.commit()

    def rollback(self):
        """Wraps rollback()"""
        return self._cnx.rollback()

    def close(self):
        """Wraps close()"""
        return self._cnx.close()

    def __getattr__(self, attrname):
        return getattr(self._cnx, attrname)

class PyConnection(SimpleConnectionWrapper):
    """A simple connection wrapper in python, generating wrapper for cursors as
    well (useful for profiling)
    """
    def __init__(self, cnx):
        """Wraps the original connection object"""
        self._cnx = cnx

    def cursor(self):
        """Wraps cursor()"""
        return PyCursor(self._cnx.cursor())



class PyCursor:
    """A simple cursor wrapper in python (useful for profiling)"""
    def __init__(self, cursor):
        self._cursor = cursor

    def close(self):
        """Wraps close()"""
        return self._cursor.close()

    def execute(self, *args, **kwargs):
        """Wraps execute()"""
        return self._cursor.execute(*args, **kwargs)

    def executemany(self, *args, **kwargs):
        """Wraps executemany()"""
        return self._cursor.executemany(*args, **kwargs)

    def fetchone(self, *args, **kwargs):
        """Wraps fetchone()"""
        return self._cursor.fetchone(*args, **kwargs)

    def fetchmany(self, *args, **kwargs):
        """Wraps execute()"""
        return self._cursor.fetchmany(*args, **kwargs)

    def fetchall(self, *args, **kwargs):
        """Wraps fetchall()"""
        return self._cursor.fetchall(*args, **kwargs)

    def __getattr__(self, attrname):
        return getattr(self._cursor, attrname)


## Adapters list ##############################################################

class DBAPIAdapter:
    """Base class for all DBAPI adapters"""
    UNKNOWN = None

    def __init__(self, native_module, pywrap=False):
        """
        :type native_module: module
        :param native_module: the database's driver adapted module
        """
        self._native_module = native_module
        self._pywrap = pywrap
        # optimization: copy type codes from the native module to this instance
        # since the .process_value method may be heavily used
        for typecode in ('STRING', 'BOOLEAN', 'BINARY', 'DATETIME', 'NUMBER',
                         'UNKNOWN'):
            try:
                setattr(self, typecode, getattr(self, typecode))
            except AttributeError:
                print 'WARNING: %s adapter has no %s type code' % (self, typecode)

    def connect(self, host='', database='', user='', password='', port='', extra_args=None):
        """Wraps the native module connect method"""
        kwargs = {'host' : host, 'port' : port, 'database' : database,
                  'user' : user, 'password' : password}
        cnx = self._native_module.connect(**kwargs)
        return self._wrap_if_needed(cnx, user)

    def _wrap_if_needed(self, cnx, user):
        """Wraps the connection object if self._pywrap is True, and returns it
        If false, returns the original cnx object
        """
        if self._pywrap:
            cnx = PyConnection(cnx)
        try:
            cnx.logged_user = user
        except AttributeError:
            # C or __slots__ object
            cnx = SimpleConnectionWrapper(cnx)
            cnx.logged_user = user
        return cnx

    def __getattr__(self, attrname):
        return getattr(self._native_module, attrname)

    def process_value(self, value, description, encoding='utf-8', binarywrap=None):
        # if the dbapi module isn't supporting type codes, override to return value directly
        typecode = description[1]
        assert typecode is not None, self
        if typecode == self.STRING:
            if isinstance(value, str):
                return unicode(value, encoding, 'replace')
        elif typecode == self.BOOLEAN:
            return bool(value)
        elif typecode == self.BINARY and not binarywrap is None:
            return binarywrap(value)
        elif typecode == self.UNKNOWN:
            # may occurs on constant selection for instance (e.g. SELECT 'hop')
            # with postgresql at least
            if isinstance(value, str):
                return unicode(value, encoding, 'replace')

##                 elif typecode == dbapimod.DATETIME:
##                     pass
##                 elif typecode == dbapimod.NUMBER:
##                     pass
##                 else:
##                     self.warning("type -%s- unknown for %r (%s) ",
##                         typecode, value, type(value))
        return value


# Postgresql #########################################################

class _PgdbAdapter(DBAPIAdapter):
    """Simple PGDB Adapter to DBAPI (pgdb modules lacks Binary() and NUMBER)
    """
    def __init__(self, native_module, pywrap=False):
        DBAPIAdapter.__init__(self, native_module, pywrap)
        self.NUMBER = native_module.pgdbType('int2', 'int4', 'serial',
                                             'int8', 'float4', 'float8',
                                             'numeric', 'bool', 'money')

    def connect(self, host='', database='', user='', password='', port='', extra_args=None):
        """Wraps the native module connect method"""
        if port:
            warn("pgdb doesn't support 'port' parameter in connect()", UserWarning)
        kwargs = {'host' : host, 'database' : database,
                  'user' : user, 'password' : password}
        cnx = self._native_module.connect(**kwargs)
        return self._wrap_if_needed(cnx, user)


class _PsycopgAdapter(DBAPIAdapter):
    """Simple Psycopg Adapter to DBAPI (cnx_string differs from classical ones)
    """
    def connect(self, host='', database='', user='', password='', port='', extra_args=None):
        """Handles psycopg connection format"""
        if host:
            cnx_string = 'host=%s  dbname=%s  user=%s' % (host, database, user)
        else:
            cnx_string = 'dbname=%s  user=%s' % (database, user)
        if port:
            cnx_string += ' port=%s' % port
        if password:
            cnx_string = '%s password=%s' % (cnx_string, password)
        cnx = self._native_module.connect(cnx_string)
        cnx.set_isolation_level(1)
        return self._wrap_if_needed(cnx, user)


class _Psycopg2Adapter(_PsycopgAdapter):
    """Simple Psycopg2 Adapter to DBAPI (cnx_string differs from classical ones)
    """
    # not defined in psycopg2.extensions
    # "select typname from pg_type where oid=705";
    UNKNOWN = 705

    def __init__(self, native_module, pywrap=False):
        from psycopg2 import extensions
        self.BOOLEAN = extensions.BOOLEAN
        DBAPIAdapter.__init__(self, native_module, pywrap)
        self._init_psycopg2()

    def _init_psycopg2(self):
        """initialize psycopg2 to use mx.DateTime for date and timestamps
        instead for datetime.datetime"""
        psycopg2 = self._native_module
        if hasattr(psycopg2, '_lc_initialized'):
            return
        psycopg2._lc_initialized = 1
        # use mxDateTime instead of datetime if available
        if HAS_MX_DATETIME and lgc.USE_MX_DATETIME:
            from psycopg2 import extensions
            extensions.register_type(psycopg2._psycopg.MXDATETIME)
            extensions.register_type(psycopg2._psycopg.MXINTERVAL)
            extensions.register_type(psycopg2._psycopg.MXDATE)
            extensions.register_type(psycopg2._psycopg.MXTIME)
            # StringIO/cStringIO adaptation
            # XXX (syt) todo, see my december discussion on the psycopg2 list
            # for a working solution
            #def adapt_stringio(stringio):
            #    print 'ADAPTING', stringio
            #    return psycopg2.Binary(stringio.getvalue())
            #import StringIO
            #extensions.register_adapter(StringIO.StringIO, adapt_stringio)
            #import cStringIO
            #extensions.register_adapter(cStringIO.StringIO, adapt_stringio)


class _PgsqlAdapter(DBAPIAdapter):
    """Simple pyPgSQL Adapter to DBAPI
    """
    def connect(self, host='', database='', user='', password='', port='', extra_args=None):
        """Handles psycopg connection format"""
        kwargs = {'host' : host, 'port': port or None,
                  'database' : database,
                  'user' : user, 'password' : password or None}
        cnx = self._native_module.connect(**kwargs)
        return self._wrap_if_needed(cnx, user)


    def Binary(self, string):
        """Emulates the Binary (cf. DB-API) function"""
        return str

    def __getattr__(self, attrname):
        # __import__('pyPgSQL.PgSQL', ...) imports the toplevel package
        return getattr(self._native_module, attrname)


# Sqlite #############################################################

class _PySqlite2Adapter(DBAPIAdapter):
    """Simple pysqlite2 Adapter to DBAPI
    """
    # no type code in pysqlite2
    BINARY = 'XXX'
    STRING = 'XXX'
    DATETIME = 'XXX'
    NUMBER = 'XXX'
    BOOLEAN = 'XXX'

    def __init__(self, native_module, pywrap=False):
        DBAPIAdapter.__init__(self, native_module, pywrap)
        self._init_pysqlite2()

    def _init_pysqlite2(self):
        """initialize pysqlite2 to use mx.DateTime for date and timestamps"""
        sqlite = self._native_module
        if hasattr(sqlite, '_lc_initialized'):
            return
        sqlite._lc_initialized = 1

        # bytea type handling
        from StringIO import StringIO
        def adapt_bytea(data):
            return data.getvalue()
        sqlite.register_adapter(StringIO, adapt_bytea)
        def convert_bytea(data, Binary=sqlite.Binary):
            return Binary(data)
        sqlite.register_converter('bytea', convert_bytea)

        # boolean type handling
        def adapt_boolean(bval):
            return str(bval).upper()
        sqlite.register_adapter(bool, adapt_boolean)
        def convert_boolean(ustr):
            if ustr.upper() in ('F', 'FALSE'):
                return False
            return True
        sqlite.register_converter('boolean', convert_boolean)


        # decimal type handling
        from decimal import Decimal
        def adapt_decimal(data):
            return str(data)
        sqlite.register_adapter(Decimal, adapt_decimal)

        def convert_decimal(data):
            return Decimal(data)
        sqlite.register_converter('decimal', convert_decimal)

        # date/time types handling
        if HAS_MX_DATETIME and lgc.USE_MX_DATETIME:
            def adapt_mxdatetime(mxd):
                return mxd.strftime('%Y-%m-%d %H:%M:%S')
            sqlite.register_adapter(DateTimeType, adapt_mxdatetime)
            def adapt_mxdatetimedelta(mxd):
                return mxd.strftime('%H:%M:%S')
            sqlite.register_adapter(DateTimeDeltaType, adapt_mxdatetimedelta)

            def convert_mxdate(ustr):
                return strptime(ustr, '%Y-%m-%d %H:%M:%S')
            sqlite.register_converter('date', convert_mxdate)
            def convert_mxdatetime(ustr):
                return strptime(ustr, '%Y-%m-%d %H:%M:%S')
            sqlite.register_converter('timestamp', convert_mxdatetime)
            def convert_mxtime(ustr):
                try:
                    return strptime(ustr, '%H:%M:%S')
                except:
                    # DateTime used as Time?
                    return strptime(ustr, '%Y-%m-%d %H:%M:%S')
            sqlite.register_converter('time', convert_mxtime)
        # else use datetime.datetime
        else:
            from datetime import time, timedelta
            # datetime.time
            def adapt_time(data):
                return data.strftime('%H:%M:%S')
            sqlite.register_adapter(time, adapt_time)
            def convert_time(data):
               return time(*[int(i) for i in data.split(':')])
            sqlite.register_converter('time', convert_time)
            # datetime.timedelta
            def adapt_timedelta(data):
                '''the sign in the result only refers to the number of days.  day
                fractions always indicate a positive offset.  this may seem strange,
                but it is the same that is done by the default __str__ method.  we
                redefine it here anyways (instead of simply doing "str") because we
                do not want any "days," string within the representation.
                '''
                days = data.days
                frac = data - timedelta(days)
                return "%d %s" % (data.days, frac)
            sqlite.register_adapter(timedelta, adapt_timedelta)
            def convert_timedelta(data):
                parts = data.split(" ")
                if len(parts) == 2:
                    daypart, timepart = parts
                    days = int(daypart)
                else:
                    days = 0
                    timepart = parts[-1]
                timepart_full = timepart.split(".")
                hours, minutes, seconds = map(int, timepart_full[0].split(":"))
                if len(timepart_full) == 2:
                    microseconds = int(float("0." + timepart_full[1]) * 1000000)
                else:
                    microseconds = 0
                data = timedelta(days,
                                 hours*3600 + minutes*60 + seconds,
                                 microseconds)
                return data
            sqlite.register_converter('interval', convert_timedelta)


    def connect(self, host='', database='', user='', password='', port=None, extra_args=None):
        """Handles sqlite connection format"""
        sqlite = self._native_module

        class PySqlite2Cursor(sqlite.Cursor):
            """cursor adapting usual dict format to pysqlite named format
            in SQL queries
            """
            def _replace_parameters(self, sql, kwargs):
                if isinstance(kwargs, dict):
                    return re.sub(r'%\(([^\)]+)\)s', r':\1', sql)
                # XXX dumb
                return re.sub(r'%s', r'?', sql)

            def execute(self, sql, kwargs=None):
                if kwargs is None:
                    self.__class__.__bases__[0].execute(self, sql)
                else:
                    final_sql = self._replace_parameters(sql, kwargs)
                    self.__class__.__bases__[0].execute(self, final_sql , kwargs)

            def executemany(self, sql, kwargss):
                if not isinstance(kwargss, (list, tuple)):
                    kwargss = tuple(kwargss)
                self.__class__.__bases__[0].executemany(self, self._replace_parameters(sql, kwargss[0]), kwargss)

        class PySqlite2CnxWrapper:
            def __init__(self, cnx):
                self._cnx = cnx

            def cursor(self):
                return self._cnx.cursor(PySqlite2Cursor)
            def __getattr__(self, attrname):
                return getattr(self._cnx, attrname)
        cnx = sqlite.connect(database, detect_types=sqlite.PARSE_DECLTYPES)
        return self._wrap_if_needed(PySqlite2CnxWrapper(cnx), user)

    def process_value(self, value, description, encoding='utf-8', binarywrap=None):
        if binarywrap is not None and isinstance(value, self._native_module.Binary):
            return binarywrap(value)
        return value # no type code support, can't do anything


class _SqliteAdapter(DBAPIAdapter):
    """Simple sqlite Adapter to DBAPI
    """
    def __init__(self, native_module, pywrap=False):
        DBAPIAdapter.__init__(self, native_module, pywrap)
        self.DATETIME = native_module.TIMESTAMP

    def connect(self, host='', database='', user='', password='', port='', extra_args=None):
        """Handles sqlite connection format"""
        cnx = self._native_module.connect(database)
        return self._wrap_if_needed(cnx, user)


# Mysql ##############################################################

class _MySqlDBAdapter(DBAPIAdapter):
    """Simple mysql Adapter to DBAPI
    """
    BOOLEAN = 'XXX' # no specific type code for boolean

    def __init__(self, native_module, pywrap=False):
        DBAPIAdapter.__init__(self, native_module, pywrap)
        self._init_module()

    def _init_module(self):
        """initialize mysqldb to use mx.DateTime for date and timestamps"""
        natmod = self._native_module
        if hasattr(natmod, '_lc_initialized'):
            return
        natmod._lc_initialized = 1
        # date/time types handling
        if HAS_MX_DATETIME and lgc.USE_MX_DATETIME:
            from MySQLdb import times
            from mx import DateTime as mxdt
            times.Date = times.date = mxdt.Date
            times.Time = times.time = mxdt.Time
            times.Timestamp = times.datetime = mxdt.DateTime
            times.TimeDelta = times.timedelta = mxdt.TimeDelta
            times.DateTimeType = mxdt.DateTimeType
            times.DateTimeDeltaType = mxdt.DateTimeDeltaType

    def connect(self, host='', database='', user='', password='', port=None,
                unicode=True, charset='utf8', extra_args=None):
        """Handles mysqldb connection format
        the unicode named argument asks to use Unicode objects for strings
        in result sets and query parameters
        """
        kwargs = {'host' : host or '', 'db' : database,
                  'user' : user, 'passwd' : password,
                  'use_unicode' : unicode}
        # MySQLdb doesn't support None port
        if port:
            kwargs['port'] = int(port)
        cnx = self._native_module.connect(**kwargs)
        if unicode:
            if charset.lower() == 'utf-8':
                charset = 'utf8'
            cnx.set_character_set(charset)
        return self._wrap_if_needed(cnx, user)

    def process_value(self, value, description, encoding='utf-8', binarywrap=None):
        typecode = description[1]
        # hack to differentiate mediumtext (String) and tinyblob/longblog
        # (Password/Bytes) which are all sharing the same type code :(
        if typecode == self.BINARY:
            if hasattr(value, 'tostring'): # may be an array
                value = value.tostring()
            maxsize = description[3]
            # mediumtext can hold up to (2**24 - 1) characters (16777215)
            # but if utf8 is set, each character is stored on 3 bytes words,
            # so we have to test for 3 * (2**24 - 1)  (i.e. 50331645)
            # XXX: what about other encodings ??
            if maxsize in (16777215, 50331645): # mediumtext (2**24 - 1)
                if isinstance(value, str):
                    return unicode(value, encoding, 'replace')
                return value
            #if maxsize == 255: # tinyblob (2**8 - 1)
            #    return value
            if binarywrap is None:
                return value
            return binarywrap(value)
        return DBAPIAdapter.process_value(self, value, description, encoding, binarywrap)

    def type_code_test(self, cursor):
        for typename in ('STRING', 'BOOLEAN', 'BINARY', 'DATETIME', 'NUMBER'):
            print typename, getattr(self, typename)
        try:
            cursor.execute("""CREATE TABLE _type_code_test(
            varchar_field varchar(50),
            text_field text unicode,
            mtext_field mediumtext,
            binary_field tinyblob,
            blob_field blob,
            lblob_field longblob
            )""")
            cursor.execute("INSERT INTO _type_code_test VALUES ('1','2','3','4', '5', '6')")
            cursor.execute("SELECT * FROM _type_code_test")
            descr = cursor.description
            print 'db fields type codes'
            for i, name in enumerate(('varchar', 'text', 'mediumtext',
                                      'binary', 'blob', 'longblob')):
                print name, descr[i]
        finally:
            cursor.execute("DROP TABLE _type_code_test")

class _BaseSqlServerAdapter(DBAPIAdapter):
    driver = 'Override in subclass'
    _use_trusted_connection = False
    _use_autocommit = False
    _fetch_lock = threading.Lock()

    @classmethod
    def use_trusted_connection(klass, use_trusted=False):
        """
        pass True to this class method to enable Windows
        Authentication (i.e. passwordless auth)
        """
        klass._use_trusted_connection = use_trusted

    @classmethod
    def use_autocommit(klass, use_autocommit=False):
        """
        pass True to this class method to enable autocommit (required
        for backup and restore)
        """
        klass._use_autocommit = use_autocommit

    @classmethod
    def _process_extra_args(klass, arguments):
        arguments = arguments.lower().split(';')
        if 'trusted_connection' in arguments:
            klass.use_trusted_connection(True)
        if 'autocommit' in arguments:
            klass.use_autocommit(True)

    def connect(self, host='', database='', user='', password='', port=None, extra_args=None):
        """Handles pyodbc connection format
        
        If extra_args is not None, it is expected to be a string
        containing a list of semicolon separated keywords. The only
        keyword currently supported is Trusted_Connection : if found
        the connection string to the database will include
        Trusted_Connection=yes (which for SqlServer will trigger using
        Windows Authentication, and therefore no login/password is
        required.
        """
        lock = self._fetch_lock
        class SqlServerCursor(object):
            """cursor adapting usual dict format to pyodbc/adobdapi format
            in SQL queries
            """
            def __init__(self, cursor):
                self._cursor = cursor
                self._fetch_lock = lock
            def _replace_parameters(self, sql, kwargs, _date_class=datetime.date):
                if isinstance(kwargs, dict):
                    new_sql = re.sub(r'%\(([^\)]+)\)s', r'?', sql)
                    key_order = re.findall(r'%\(([^\)]+)\)s', sql)
                    args = []
                    for key in key_order:
                        arg = kwargs[key]
                        if isinstance(arg, _date_class):
                            arg = datetime.datetime.combine(arg, datetime.time(0))
                        args.append(arg)

                    return new_sql, tuple(args)
                        
                # XXX dumb
                return re.sub(r'%s', r'?', sql), kwargs

            def execute(self, sql, kwargs=None):
                if kwargs is None:
                    self._cursor.execute(sql)
                else:
                    final_sql, args = self._replace_parameters(sql, kwargs)
                    self._cursor.execute(final_sql , args)
            def executemany(self, sql, kwargss):
                if not isinstance(kwargss, (list, tuple)):
                    kwargss = tuple(kwargss)
                self._cursor.executemany(self, self._replace_parameters(sql, kwargss[0]), kwargss)

            def _get_smalldate_columns(self):
                cols = []
                for i, coldef in enumerate(self._cursor.description):
                    if coldef[1] is datetime.datetime and coldef[3] == 16:
                        cols.append(i)
                return cols

            def fetchone(self):
                smalldate_cols = self._get_smalldate_columns()
                self._fetch_lock.acquire()
                try:
                    row = self._cursor.fetchone()
                finally:
                    self._fetch_lock.release()
                return self._replace_smalldate(row, smalldate_cols)

            def fetchall (self):
                smalldate_cols = self._get_smalldate_columns()
                rows = []
                while True:
                    self._fetch_lock.acquire()
                    try:
                        batch = self._cursor.fetchmany(1024)
                    finally:
                        self._fetch_lock.release()
                    if not batch:
                        break
                    for row in batch:
                        rows.append(self._replace_smalldate(row, smalldate_cols))
                return rows

            def _replace_smalldate(self, row, smalldate_cols):
                if smalldate_cols:
                    new_row = row[:]
                    for col in smalldate_cols:
                        new_row[col] = new_row[col].date()
                    return new_row
                else:
                    return row
            def __getattr__(self, attrname):
                return getattr(self._cursor, attrname)

        class SqlServerCnxWrapper:
            def __init__(self, cnx):
                self._cnx = cnx
            def cursor(self):
                return SqlServerCursor(self._cnx.cursor())
            def __getattr__(self, attrname):
                return getattr(self._cnx, attrname)
        cnx = self._connect(host=host, database=database, user=user, password=password, port=port, extra_args=extra_args)
        return self._wrap_if_needed(SqlServerCnxWrapper(cnx), user)

    def process_value(self, value, description, encoding='utf-8', binarywrap=None):
        # if the dbapi module isn't supporting type codes, override to return value directly
        typecode = description[1]
        assert typecode is not None, self
        if typecode == self.STRING:
            if isinstance(value, str):
                return unicode(value, encoding, 'replace')
        elif typecode == self.BINARY:  # value is a python buffer
            if binarywrap is not None:
                return binarywrap(value[:])
            else:
                return value[:]
        elif typecode == self.UNKNOWN:
            # may occurs on constant selection for instance (e.g. SELECT 'hop')
            # with postgresql at least
            if isinstance(value, str):
                return unicode(value, encoding, 'replace')

        return value

class _PyodbcAdapter(_BaseSqlServerAdapter):
    def _connect(self, host='', database='', user='', password='', port=None, extra_args=None):
        if extra_args is not None:
            self._process_extra_args(extra_args)
        cnx_string_bits = ['DRIVER={%(driver)s}']
        variables = {'host' : host,
                     'database' : database,
                     'user' : user, 'password' : password,
                     'driver': self.driver}
        if self._use_trusted_connection:
            variables['Trusted_Connection'] = 'yes'
            del variables['user']
            del variables['password']
        if self._use_autocommit:
            variables['autocommit'] = True
        return self._native_module.connect(**variables)

class _PyodbcSqlServer2000Adapter(_PyodbcAdapter):
    driver = "SQL Server"
    
class _PyodbcSqlServer2005Adapter(_PyodbcAdapter):
    driver = "SQL Server Native Client 10.0"

class _PyodbcSqlServer2008Adapter(_PyodbcAdapter):
    driver = "SQL Server Native Client 10.0"

class _AdodbapiAdapter(_BaseSqlServerAdapter):
   
    def _connect(self, host='', database='', user='', password='', port=None, extra_args=None):
        if extra_args is not None:
            self._process_extra_args(extra_args)
        if self._use_trusted_connection:
            # this will open a MS-SQL table with Windows authentication
            auth = 'Integrated Security=SSPI'
        else:
            # this set opens a MS-SQL table with SQL authentication 
            auth = 'user ID=%s; Password=%s;' % (user, password)
        constr = r"Initial Catalog=%s; Data Source=%s; Provider=SQLOLEDB.1; %s"  %(database, host, auth)
        return self._native_module.connect(constr)

class _AdodbapiSqlServer2000Adapter(_AdodbapiAdapter):
    driver = "SQL Server"
    
class _AdodbapiSqlServer2005Adapter(_AdodbapiAdapter):
    driver = "SQL Server Native Client 10.0"

class _AdodbapiSqlServer2008Adapter(_AdodbapiAdapter):
    driver = "SQL Server Native Client 10.0"

## Drivers, Adapters and helpers registries ###################################


PREFERED_DRIVERS = {
    "postgres" : [ 'psycopg2', 'psycopg', 'pgdb', 'pyPgSQL.PgSQL', ],
    "mysql" : [ 'MySQLdb', ], # 'pyMySQL.MySQL, ],
    "sqlite" : ['pysqlite2.dbapi2', 'sqlite', 'sqlite3',],
    "sqlserver2000" : ['pyodbc', 'adodbapi', ],
    "sqlserver2005" : ['pyodbc', 'adodbapi', ],
    "sqlserver2008" : ['pyodbc', 'adodbapi', ],
    }

_ADAPTERS = {
    'postgres' : { 'pgdb' : _PgdbAdapter,
                   'psycopg' : _PsycopgAdapter,
                   'psycopg2' : _Psycopg2Adapter,
                   'pyPgSQL.PgSQL' : _PgsqlAdapter,
                   },
    'mysql' : { 'MySQLdb' : _MySqlDBAdapter, },
    'sqlite' : { 'pysqlite2.dbapi2' : _PySqlite2Adapter,
                 'sqlite' : _SqliteAdapter,
                 'sqlite3' : _PySqlite2Adapter, },
    "sqlserver2000" : {'adodbapi': _AdodbapiSqlServer2000Adapter,
                       'pyodbc': _PyodbcSqlServer2000Adapter},
    "sqlserver2005" : {'adodbapi': _AdodbapiSqlServer2005Adapter,
                       'pyodbc': _PyodbcSqlServer2005Adapter},
    "sqlserver2008" : {'adodbapi': _AdodbapiSqlServer2008Adapter,
                       'pyodbc': _PyodbcSqlServer2008Adapter},
    }

# _AdapterDirectory could be more generic by adding a 'protocol' parameter
# This one would become an adapter for 'DBAPI' protocol
class _AdapterDirectory(dict):
    """A simple dict that registers all adapters"""
    def register_adapter(self, adapter, driver, modname):
        """Registers 'adapter' in directory as adapting 'mod'"""
        try:
            driver_dict = self[driver]
        except KeyError:
            self[driver] = {}

        # XXX Should we have a list of adapters ?
        driver_dict[modname] = adapter

    def adapt(self, database, prefered_drivers = None, pywrap = False):
        """Returns an dbapi-compliant object based for database"""
        prefered_drivers = prefered_drivers or PREFERED_DRIVERS
        module, modname = _import_driver_module(database, prefered_drivers)
        try:
            return self[database][modname](module, pywrap=pywrap)
        except KeyError:
            raise NoAdapterFound(obj=module)

    def get_adapter(self, database, modname):
        try:
            return self[database][modname]
        except KeyError:
            raise NoAdapterFound(None, modname)

ADAPTER_DIRECTORY = _AdapterDirectory(_ADAPTERS)
del _AdapterDirectory


## Main functions #############################################################

def set_prefered_driver(database, module, _drivers=PREFERED_DRIVERS):
    """sets the preferred driver module for database
    database is the name of the db engine (postgresql, mysql...)
    module is the name of the module providing the connect function
    syntax is (params_func, post_process_func_or_None)
    _drivers is a optional dictionary of drivers
    """
    try:
        modules = _drivers[database]
    except KeyError:
        raise UnknownDriver('Unknown database %s' % database)
    # Remove module from modules list, and re-insert it in first position
    try:
        modules.remove(module)
    except ValueError:
        raise UnknownDriver('Unknown module %s for %s' % (module, database))
    modules.insert(0, module)

def get_dbapi_compliant_module(driver, prefered_drivers = None, quiet = False,
                               pywrap = False):
    """returns a fully dbapi compliant module"""
    try:
        mod = ADAPTER_DIRECTORY.adapt(driver, prefered_drivers, pywrap=pywrap)
    except NoAdapterFound, err:
        if not quiet:
            msg = 'No Adapter found for %s, returning native module'
            print >> sys.stderr, msg % err.objname
        mod = err.adapted_obj
    from logilab.common.adbh import get_adv_func_helper
    mod.adv_func_helper = get_adv_func_helper(driver)
    return mod

def get_connection(driver='postgres', host='', database='', user='',
                  password='', port='', quiet=False, drivers=PREFERED_DRIVERS,
                  pywrap=False, extra_args=None):
    """return a db connection according to given arguments"""
    module, modname = _import_driver_module(driver, drivers, ['connect'])
    try:
        adapter = ADAPTER_DIRECTORY.get_adapter(driver, modname)
    except NoAdapterFound, err:
        if not quiet:
            msg = 'No Adapter found for %s, using default one' % err.objname
            print >> sys.stderr, msg
        adapted_module = DBAPIAdapter(module, pywrap)
    else:
        adapted_module = adapter(module, pywrap)
    if host and not port:
        try:
            host, port = host.split(':', 1)
        except ValueError:
            pass
    if port:
        port = int(port)
    return adapted_module.connect(host, database, user, password, port=port, extra_args=extra_args)


from logilab.common.deprecation import moved
get_adv_func_helper = moved('logilab.common.adbh', 'get_adv_func_helper')