"""

MySQL database backend for Django.

Requires MySQLdb: http://sourceforge.net/projects/mysql-python

"""

import re

try:

    import MySQLdb as Database

except ImportError, e:

    from django.core.exceptions import ImproperlyConfigured

    raise ImproperlyConfigured("Error loading MySQLdb module: %s" % e)

# We want version (1, 2, 1, 'final', 2) or later. We can't just use

# lexicographic ordering in this check because then (1, 2, 1, 'gamma')

# inadvertently passes the version test.

version = Database.version_info

if (version < (1,2,1) or (version[:3] == (1, 2, 1) and

        (len(version) < 5 or version[3] != 'final' or version[4] < 2))):

    from django.core.exceptions import ImproperlyConfigured

    raise ImproperlyConfigured("MySQLdb-1.2.1p2 or newer is required; you have %s" % Database.__version__)

from MySQLdb.converters import conversions

from MySQLdb.constants import FIELD_TYPE, FLAG, CLIENT

from django.db.backends import *

from django.db.backends.signals import connection_created

from django.db.backends.mysql.client import DatabaseClient

from django.db.backends.mysql.creation import DatabaseCreation

from django.db.backends.mysql.introspection import DatabaseIntrospection

from django.db.backends.mysql.validation import DatabaseValidation

from django.utils.safestring import SafeString, SafeUnicode

# Raise exceptions for database warnings if DEBUG is on

from django.conf import settings

if settings.DEBUG:

    from warnings import filterwarnings

    filterwarnings("error", category=Database.Warning)

DatabaseError = Database.DatabaseError

IntegrityError = Database.IntegrityError

# MySQLdb-1.2.1 returns TIME columns as timedelta -- they are more like

# timedelta in terms of actual behavior as they are signed and include days --

# and Django expects time, so we still need to override that. We also need to

# add special handling for SafeUnicode and SafeString as MySQLdb's type

# checking is too tight to catch those (see Django ticket #6052).

django_conversions = conversions.copy()

django_conversions.update({

    FIELD_TYPE.TIME: util.typecast_time,

    FIELD_TYPE.DECIMAL: util.typecast_decimal,

    FIELD_TYPE.NEWDECIMAL: util.typecast_decimal,

})

# This should match the numerical portion of the version numbers (we can treat

# versions like 5.0.24 and 5.0.24a as the same). Based on the list of version

# at http://dev.mysql.com/doc/refman/4.1/en/news.html and

# http://dev.mysql.com/doc/refman/5.0/en/news.html .

server_version_re = re.compile(r'(\d{1,2})\.(\d{1,2})\.(\d{1,2})')

# MySQLdb-1.2.1 and newer automatically makes use of SHOW WARNINGS on

# MySQL-4.1 and newer, so the MysqlDebugWrapper is unnecessary. Since the

# point is to raise Warnings as exceptions, this can be done with the Python

# warning module, and this is setup when the connection is created, and the

# standard util.CursorDebugWrapper can be used. Also, using sql_mode

# TRADITIONAL will automatically cause most warnings to be treated as errors.

class CursorWrapper(object):

    """

    A thin wrapper around MySQLdb's normal cursor class so that we can catch

    particular exception instances and reraise them with the right types.

    Implemented as a wrapper, rather than a subclass, so that we aren't stuck

    to the particular underlying representation returned by Connection.cursor().

    """

    codes_for_integrityerror = (1048,)

    def __init__(self, cursor):

        self.cursor = cursor

    def execute(self, query, args=None):

        try:

            return self.cursor.execute(query, args)

        except Database.OperationalError, e:

            # Map some error codes to IntegrityError, since they seem to be

            # misclassified and Django would prefer the more logical place.

            if e[0] in self.codes_for_integrityerror:

            raise

    def executemany(self, query, args):

        try:

            return self.cursor.executemany(query, args)

        except Database.OperationalError, e:

            # Map some error codes to IntegrityError, since they seem to be

            # misclassified and Django would prefer the more logical place.

            if e[0] in self.codes_for_integrityerror:

            raise

    def __getattr__(self, attr):

        if attr in self.__dict__:

            return self.__dict__[attr]

        else:

            return getattr(self.cursor, attr)

    def __iter__(self):

        return iter(self.cursor)

class DatabaseFeatures(BaseDatabaseFeatures):

    empty_fetchmany_value = ()

    update_can_self_select = False

    allows_group_by_pk = True

    related_fields_match_type = True

class DatabaseOperations(BaseDatabaseOperations):

    def date_extract_sql(self, lookup_type, field_name):

        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html

        if lookup_type == 'week_day':

            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.

            # Note: WEEKDAY() returns 0-6, Monday=0.

            return "DAYOFWEEK(%s)" % field_name

        else:

            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)

    def date_trunc_sql(self, lookup_type, field_name):

        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']

        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s') # Use double percents to escape.

        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')

        try:

            i = fields.index(lookup_type) + 1

        except ValueError:

            sql = field_name

        else:

            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])

            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)

        return sql

    def drop_foreignkey_sql(self):

        return "DROP FOREIGN KEY"

    def force_no_ordering(self):

        """

        "ORDER BY NULL" prevents MySQL from implicitly ordering by grouped

        columns. If no ordering would otherwise be applied, we don't want any

        implicit sorting going on.

        """

        return ["NULL"]

    def fulltext_search_sql(self, field_name):

        return 'MATCH (%s) AGAINST (%%s IN BOOLEAN MODE)' % field_name

    def no_limit_value(self):

        # 2**64 - 1, as recommended by the MySQL documentation

        return 18446744073709551615L

    def quote_name(self, name):

        if name.startswith("`") and name.endswith("`"):

            return name # Quoting once is enough.

        return "`%s`" % name

    def random_function_sql(self):

        return 'RAND()'

    def sql_flush(self, style, tables, sequences):

        # NB: The generated SQL below is specific to MySQL

        # 'TRUNCATE x;', 'TRUNCATE y;', 'TRUNCATE z;'... style SQL statements

        # to clear all tables of all data

        if tables:

            sql = ['SET FOREIGN_KEY_CHECKS = 0;']

            for table in tables:

                sql.append('%s %s;' % (style.SQL_KEYWORD('TRUNCATE'), style.SQL_FIELD(self.quote_name(table))))

            sql.append('SET FOREIGN_KEY_CHECKS = 1;')

            # 'ALTER TABLE table AUTO_INCREMENT = 1;'... style SQL statements

            # to reset sequence indices

            sql.extend(["%s %s %s %s %s;" % \

                (style.SQL_KEYWORD('ALTER'),

                 style.SQL_KEYWORD('TABLE'),

                 style.SQL_TABLE(self.quote_name(sequence['table'])),

                 style.SQL_KEYWORD('AUTO_INCREMENT'),

                 style.SQL_FIELD('= 1'),

                ) for sequence in sequences])

            return sql

        else:

            return []

    def value_to_db_datetime(self, value):

        if value is None:

            return None

        # MySQL doesn't support tz-aware datetimes

        if value.tzinfo is not None:

            raise ValueError("MySQL backend does not support timezone-aware datetimes.")

        # MySQL doesn't support microseconds

        return unicode(value.replace(microsecond=0))

    def value_to_db_time(self, value):

        if value is None:

            return None

        # MySQL doesn't support tz-aware datetimes

        if value.tzinfo is not None:

            raise ValueError("MySQL backend does not support timezone-aware datetimes.")

        # MySQL doesn't support microseconds

        return unicode(value.replace(microsecond=0))

    def year_lookup_bounds(self, value):

        # Again, no microseconds

        first = '%s-01-01 00:00:00'

        second = '%s-12-31 23:59:59.99'

        return [first % value, second % value]

class DatabaseWrapper(BaseDatabaseWrapper):

    operators = {

        'exact': '= %s',

        'iexact': 'LIKE %s',

        'contains': 'LIKE BINARY %s',

        'icontains': 'LIKE %s',

        'regex': 'REGEXP BINARY %s',

        'iregex': 'REGEXP %s',

        'gt': '> %s',

        'gte': '>= %s',

        'lt': '< %s',

        'lte': '<= %s',

        'startswith': 'LIKE BINARY %s',

        'endswith': 'LIKE BINARY %s',

        'istartswith': 'LIKE %s',

        'iendswith': 'LIKE %s',

    }

    def __init__(self, *args, **kwargs):

        super(DatabaseWrapper, self).__init__(*args, **kwargs)

        self.server_version = None

        self.features = DatabaseFeatures()

        self.ops = DatabaseOperations()

        self.client = DatabaseClient(self)

        self.creation = DatabaseCreation(self)

        self.introspection = DatabaseIntrospection(self)

    def _valid_connection(self):

        if self.connection is not None:

            try:

                self.connection.ping()

                return True

            except DatabaseError:

                self.connection.close()

                self.connection = None

        return False

    def _cursor(self):

        if not self._valid_connection():

            kwargs = {

                'conv': django_conversions,

                'charset': 'utf8',

                'use_unicode': True,

            }

            settings_dict = self.settings_dict

            # We need the number of potentially affected rows after an

            # "UPDATE", not the number of changed rows.

            kwargs['client_flag'] = CLIENT.FOUND_ROWS

            self.connection = Database.connect(**kwargs)

            self.connection.encoders[SafeUnicode] = self.connection.encoders[unicode]

            self.connection.encoders[SafeString] = self.connection.encoders[str]

            connection_created.send(sender=self.__class__)

        cursor = CursorWrapper(self.connection.cursor())

        return cursor

    def _rollback(self):

        try:

            BaseDatabaseWrapper._rollback(self)

        except Database.NotSupportedError:

            pass

    def get_server_version(self):

        if not self.server_version:

            if not self._valid_connection():

                self.cursor()

            m = server_version_re.match(self.connection.get_server_info())

            if not m:

                raise Exception('Unable to determine MySQL version from version string %r' % self.connection.get_server_info())

            self.server_version = tuple([int(x) for x in m.groups()])

        return self.server_version