"""

MySQL database backend for Django.

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

"""

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

from django.utils.encoding import force_unicode

try:

    import MySQLdb as Database

except ImportError, e:

    from django.core.exceptions import ImproperlyConfigured

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

from MySQLdb.converters import conversions

from MySQLdb.constants import FIELD_TYPE

import types

import re

DatabaseError = Database.DatabaseError

IntegrityError = Database.IntegrityError

django_conversions = conversions.copy()

django_conversions.update({

    types.BooleanType: util.rev_typecast_boolean,

    FIELD_TYPE.DATETIME: util.typecast_timestamp,

    FIELD_TYPE.DATE: util.typecast_date,

    FIELD_TYPE.TIME: util.typecast_time,

    FIELD_TYPE.DECIMAL: util.typecast_decimal,

    FIELD_TYPE.STRING: force_unicode,

    FIELD_TYPE.VAR_STRING: force_unicode,

    # Note: We don't add a convertor for BLOB here. Doesn't seem to be required.

})

# 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})')

# This is an extra debug layer over MySQL queries, to display warnings.

# It's only used when DEBUG=True.

class MysqlDebugWrapper:

    def __init__(self, cursor):

        self.cursor = cursor

    def execute(self, sql, params=()):

        try:

            return self.cursor.execute(sql, params)

        except Database.Warning, w:

            self.cursor.execute("SHOW WARNINGS")

            raise Database.Warning("%s: %s" % (w, self.cursor.fetchall()))

    def executemany(self, sql, param_list):

        try:

            return self.cursor.executemany(sql, param_list)

        except Database.Warning, w:

            self.cursor.execute("SHOW WARNINGS")

            raise Database.Warning("%s: %s" % (w, self.cursor.fetchall()))

    def __getattr__(self, attr):

        if attr in self.__dict__:

            return self.__dict__[attr]

        else:

            return getattr(self.cursor, attr)

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 = {

                # Note: use_unicode intentonally not set to work around some

                # backwards-compat issues. We do it manually.

                'user': settings.DATABASE_USER,

                'db': settings.DATABASE_NAME,

                'passwd': settings.DATABASE_PASSWORD,

                'conv': django_conversions,

            }

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

                kwargs['unix_socket'] = settings.DATABASE_HOST

            else:

                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()

            if self.connection.get_server_info() >= '4.1' and not self.connection.character_set_name().startswith('utf8'):

                if hasattr(self.connection, 'charset'):

                    # MySQLdb < 1.2.1 backwards-compat hacks.

                    conn = self.connection

                    cursor.execute("SET NAMES 'utf8'")

                    cursor.execute("SET CHARACTER SET 'utf8'")

                    to_str = lambda u, dummy=None, c=conn: c.literal(u.encode('utf-8'))

                    conn.converter[unicode] = to_str

                else:

                    self.connection.set_character_set('utf8')

        else:

            cursor = self.connection.cursor()

        return cursor

    def make_debug_cursor(self, cursor):

        return BaseDatabaseWrapper.make_debug_cursor(self, MysqlDebugWrapper(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