"""

SQLite3 backend for django.

Python 2.3 and 2.4 require pysqlite2 (http://pysqlite.org/).

Python 2.5 and later use the sqlite3 module in the standard library.

"""

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

try:

    try:

        from sqlite3 import dbapi2 as Database

    except ImportError:

        from pysqlite2 import dbapi2 as Database

except ImportError, e:

    import sys

    from django.core.exceptions import ImproperlyConfigured

    if sys.version_info < (2, 5, 0):

        module = 'pysqlite2'

    else:

        module = 'sqlite3'

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

try:

    import decimal

except ImportError:

    from django.utils import _decimal as decimal # for Python 2.3

DatabaseError = Database.DatabaseError

IntegrityError = Database.IntegrityError

Database.register_converter("bool", lambda s: str(s) == '1')

Database.register_converter("time", util.typecast_time)

Database.register_converter("date", util.typecast_date)

Database.register_converter("datetime", util.typecast_timestamp)

Database.register_converter("timestamp", util.typecast_timestamp)

Database.register_converter("TIMESTAMP", util.typecast_timestamp)

Database.register_converter("decimal", util.typecast_decimal)

Database.register_adapter(decimal.Decimal, util.rev_typecast_decimal)

class DatabaseFeatures(BaseDatabaseFeatures):

    supports_constraints = False

class DatabaseOperations(BaseDatabaseOperations):

    def date_extract_sql(self, lookup_type, field_name):

        # sqlite doesn't support extract, so we fake it with the user-defined

        # function django_extract that's registered in connect().

        return 'django_extract("%s", %s)' % (lookup_type.lower(), field_name)

    def date_trunc_sql(self, lookup_type, field_name):

        # sqlite doesn't support DATE_TRUNC, so we fake it with a user-defined

        # function django_date_trunc that's registered in connect().

        return 'django_date_trunc("%s", %s)' % (lookup_type.lower(), field_name)

    def drop_foreignkey_sql(self):

        return ""

    def pk_default_value(self):

        return 'NULL'

    def quote_name(self, name):

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

            return name # Quoting once is enough.

        return '"%s"' % name

    def no_limit_value(self):

        return -1

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

        # NB: The generated SQL below is specific to SQLite

        # Note: The DELETE FROM... SQL generated below works for SQLite databases

        # because constraints don't exist

        sql = ['%s %s %s;' % \

                (style.SQL_KEYWORD('DELETE'),

                 style.SQL_KEYWORD('FROM'),

                 style.SQL_FIELD(self.quote_name(table))

                 ) for table in tables]

        # Note: No requirement for reset of auto-incremented indices (cf. other

        # sql_flush() implementations). Just return SQL at this point

        return sql

class DatabaseWrapper(BaseDatabaseWrapper):

    features = DatabaseFeatures()

    ops = DatabaseOperations()

    # SQLite requires LIKE statements to include an ESCAPE clause if the value

    # being escaped has a percent or underscore in it.

    # See http://www.sqlite.org/lang_expr.html for an explanation.

    operators = {

        'exact': '= %s',

        'iexact': "LIKE %s ESCAPE '\\'",

        'contains': "LIKE %s ESCAPE '\\'",

        'icontains': "LIKE %s ESCAPE '\\'",

        'regex': 'REGEXP %s',

        'iregex': "REGEXP '(?i)' || %s",

        'gt': '> %s',

        'gte': '>= %s',

        'lt': '< %s',

        'lte': '<= %s',

        'startswith': "LIKE %s ESCAPE '\\'",

        'endswith': "LIKE %s ESCAPE '\\'",

        'istartswith': "LIKE %s ESCAPE '\\'",

        'iendswith': "LIKE %s ESCAPE '\\'",

    }

    def _cursor(self, settings):

        if self.connection is None:

            kwargs = {

                'database': settings.DATABASE_NAME,

                'detect_types': Database.PARSE_DECLTYPES | Database.PARSE_COLNAMES,

            }

            kwargs.update(self.options)

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

            # Register extract, date_trunc, and regexp functions.

            self.connection.create_function("django_extract", 2, _sqlite_extract)

            self.connection.create_function("django_date_trunc", 2, _sqlite_date_trunc)

            self.connection.create_function("regexp", 2, _sqlite_regexp)

        return self.connection.cursor(factory=SQLiteCursorWrapper)

    def close(self):

        from django.conf import settings

        # If database is in memory, closing the connection destroys the

        # database. To prevent accidental data loss, ignore close requests on

        # an in-memory db.

        if settings.DATABASE_NAME != ":memory:":

            BaseDatabaseWrapper.close(self)

class SQLiteCursorWrapper(Database.Cursor):

    """

    Django uses "format" style placeholders, but pysqlite2 uses "qmark" style.

    This fixes it -- but note that if you want to use a literal "%s" in a query,

    you'll need to use "%%s".

    """

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

        query = self.convert_query(query, len(params))

        return Database.Cursor.execute(self, query, params)

    def executemany(self, query, param_list):

        try:

          query = self.convert_query(query, len(param_list[0]))

          return Database.Cursor.executemany(self, query, param_list)

        except (IndexError,TypeError):

          # No parameter list provided

          return None

    def convert_query(self, query, num_params):

        return query % tuple("?" * num_params)

def _sqlite_extract(lookup_type, dt):

    try:

        dt = util.typecast_timestamp(dt)

    except (ValueError, TypeError):

        return None

    return str(getattr(dt, lookup_type))

def _sqlite_date_trunc(lookup_type, dt):

    try:

        dt = util.typecast_timestamp(dt)

    except (ValueError, TypeError):

        return None

    if lookup_type == 'year':

        return "%i-01-01 00:00:00" % dt.year

    elif lookup_type == 'month':

        return "%i-%02i-01 00:00:00" % (dt.year, dt.month)

    elif lookup_type == 'day':

        return "%i-%02i-%02i 00:00:00" % (dt.year, dt.month, dt.day)

def _sqlite_regexp(re_pattern, re_string):

    import re

    try:

        return bool(re.search(re_pattern, re_string))

    except:

        return False