"""
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 Database.IntegrityError(tuple(e))
            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 Database.IntegrityError(tuple(e))
            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)
        self.validation = DatabaseValidation()

    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
            if settings_dict['DATABASE_USER']:
                kwargs['user'] = settings_dict['DATABASE_USER']
            if settings_dict['DATABASE_NAME']:
                kwargs['db'] = settings_dict['DATABASE_NAME']
            if settings_dict['DATABASE_PASSWORD']:
                kwargs['passwd'] = settings_dict['DATABASE_PASSWORD']
            if settings_dict['DATABASE_HOST'].startswith('/'):
                kwargs['unix_socket'] = settings_dict['DATABASE_HOST']
            elif settings_dict['DATABASE_HOST']:
                kwargs['host'] = settings_dict['DATABASE_HOST']
            if settings_dict['DATABASE_PORT']:
                kwargs['port'] = int(settings_dict['DATABASE_PORT'])
            # We need the number of potentially affected rows after an
            # "UPDATE", not the number of changed rows.
            kwargs['client_flag'] = CLIENT.FOUND_ROWS
            kwargs.update(settings_dict['DATABASE_OPTIONS'])
            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
