"""

MySQL database backend for Django.

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

"""

from django.db.backends import BaseDatabaseWrapper, BaseDatabaseFeatures, BaseDatabaseOperations, util

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

import re

# 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 supports the Python boolean type, and only uses datetime

# module for time-related columns; older versions could have used mx.DateTime

# or strings if there were no datetime module. However, MySQLdb still 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.

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 DatabaseFeatures(BaseDatabaseFeatures):

    autoindexes_primary_keys = False

    inline_fk_references = False

    empty_fetchmany_value = ()

    update_can_self_select = False

class DatabaseOperations(BaseDatabaseOperations):

    def date_extract_sql(self, lookup_type, field_name):

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

        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 fulltext_search_sql(self, field_name):

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

    def limit_offset_sql(self, limit, offset=None):

        # 'LIMIT 20,40'

        sql = "LIMIT "

        if offset and offset != 0:

            sql += "%s," % offset

        return sql + str(limit)

    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 []

class DatabaseWrapper(BaseDatabaseWrapper):

    features = DatabaseFeatures()

    ops = DatabaseOperations()

    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, **kwargs):

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

        self.server_version = None

    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, settings):

        if not self._valid_connection():

            kwargs = {

                'conv': django_conversions,

                'charset': 'utf8',

                'use_unicode': True,

            }

            if settings.DATABASE_USER:

                kwargs['user'] = settings.DATABASE_USER

            if settings.DATABASE_NAME:

                kwargs['db'] = settings.DATABASE_NAME

            if settings.DATABASE_PASSWORD:

                kwargs['passwd'] = settings.DATABASE_PASSWORD

            if settings.DATABASE_HOST.startswith('/'):

                kwargs['unix_socket'] = settings.DATABASE_HOST

            elif settings.DATABASE_HOST:

                kwargs['host'] = settings.DATABASE_HOST

            if settings.DATABASE_PORT:

                kwargs['port'] = int(settings.DATABASE_PORT)

            kwargs.update(self.options)

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

        cursor = 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