"""
Support for the pymssql dialect.

This dialect supports pymssql 1.0 and greater.

pymssql is available at:

    http://pymssql.sourceforge.net/
    
Connecting
^^^^^^^^^^
    
Sample connect string::

    mssql+pymssql://<username>:<password>@<freetds_name>

Adding "?charset=utf8" or similar will cause pymssql to return
strings as Python unicode objects.   This can potentially improve 
performance in some scenarios as decoding of strings is 
handled natively.

Limitations
^^^^^^^^^^^

pymssql inherits a lot of limitations from FreeTDS, including:

* no support for multibyte schema identifiers
* poor support for large decimals
* poor support for binary fields
* poor support for VARCHAR/CHAR fields over 255 characters

Please consult the pymssql documentation for further information.

"""
from sqlalchemy.dialects.mssql.base import MSDialect
from sqlalchemy import types as sqltypes, util, processors
import re
import decimal

class _MSNumeric_pymssql(sqltypes.Numeric):
    def result_processor(self, dialect, type_):
        if not self.asdecimal:
            return processors.to_float
        else:
            return sqltypes.Numeric.result_processor(self, dialect, type_)

class MSDialect_pymssql(MSDialect):
    supports_sane_rowcount = False
    max_identifier_length = 30
    driver = 'pymssql'
    
    colspecs = util.update_copy(
        MSDialect.colspecs,
        {
            sqltypes.Numeric:_MSNumeric_pymssql,
            sqltypes.Float:sqltypes.Float,
        }
    )
    @classmethod
    def dbapi(cls):
        module = __import__('pymssql')
        # pymmsql doesn't have a Binary method.  we use string
        # TODO: monkeypatching here is less than ideal
        module.Binary = str
        
        client_ver = tuple(int(x) for x in module.__version__.split("."))
        if client_ver < (1, ):
            util.warn("The pymssql dialect expects at least "
                            "the 1.0 series of the pymssql DBAPI.")
        return module

    def __init__(self, **params):
        super(MSDialect_pymssql, self).__init__(**params)
        self.use_scope_identity = True

    def _get_server_version_info(self, connection):
        vers = connection.scalar("select @@version")
        m = re.match(r"Microsoft SQL Server.*? - (\d+).(\d+).(\d+).(\d+)", vers)
        if m:
            return tuple(int(x) for x in m.group(1, 2, 3, 4))
        else:
            return None

    def create_connect_args(self, url):
        opts = url.translate_connect_args(username='user')
        opts.update(url.query)
        opts.pop('port', None)
        return [[], opts]

    def is_disconnect(self, e):
        for msg in (
            "Error 10054",
            "Not connected to any MS SQL server",
            "Connection is closed"
        ):
            if msg in str(e):
                return True
        else:
            return False

dialect = MSDialect_pymssql