"""
SQLite3 backend for django.  Requires pysqlite2 (http://pysqlite.org/).
"""

from django.db.backends import 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)

DatabaseError = Database.DatabaseError

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)

def utf8rowFactory(cursor, row):
    def utf8(s):
        if type(s) == unicode:
            return s.encode("utf-8")
        else:
            return s
    return [utf8(r) for r in row]

try:
    # Only exists in Python 2.4+
    from threading import local
except ImportError:
    # Import copy of _thread_local.py from Python 2.4
    from django.utils._threading_local import local

class DatabaseWrapper(local):
    def __init__(self, **kwargs):
        self.connection = None
        self.queries = []
        self.options = kwargs

    def cursor(self):
        from django.conf import 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 and date_trunc functions.
            self.connection.create_function("django_extract", 2, _sqlite_extract)
            self.connection.create_function("django_date_trunc", 2, _sqlite_date_trunc)
        cursor = self.connection.cursor(factory=SQLiteCursorWrapper)
        cursor.row_factory = utf8rowFactory
        if settings.DEBUG:
            return util.CursorDebugWrapper(cursor, self)
        else:
            return cursor

    def _commit(self):
        if self.connection is not None:
            self.connection.commit()

    def _rollback(self):
        if self.connection is not None:
            self.connection.rollback()

    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 self.connection is not None and settings.DATABASE_NAME != ":memory:":
            self.connection.close()
            self.connection = None

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):
        query = self.convert_query(query, len(param_list[0]))
        return Database.Cursor.executemany(self, query, param_list)

    def convert_query(self, query, num_params):
        return query % tuple("?" * num_params)

supports_constraints = False

def quote_name(name):
    if name.startswith('"') and name.endswith('"'):
        return name # Quoting once is enough.
    return '"%s"' % name

dictfetchone = util.dictfetchone
dictfetchmany = util.dictfetchmany
dictfetchall  = util.dictfetchall

def get_last_insert_id(cursor, table_name, pk_name):
    return cursor.lastrowid

def get_date_extract_sql(lookup_type, table_name):
    # lookup_type is 'year', 'month', 'day'
    # sqlite doesn't support extract, so we fake it with the user-defined
    # function _sqlite_extract that's registered in connect(), above.
    return 'django_extract("%s", %s)' % (lookup_type.lower(), table_name)

def _sqlite_extract(lookup_type, dt):
    try:
        dt = util.typecast_timestamp(dt)
    except (ValueError, TypeError):
        return None
    return str(getattr(dt, lookup_type))

def get_date_trunc_sql(lookup_type, field_name):
    # lookup_type is 'year', 'month', 'day'
    # sqlite doesn't support DATE_TRUNC, so we fake it as above.
    return 'django_date_trunc("%s", %s)' % (lookup_type.lower(), field_name)

def get_limit_offset_sql(limit, offset=None):
    sql = "LIMIT %s" % limit
    if offset and offset != 0:
        sql += " OFFSET %s" % offset
    return sql

def get_random_function_sql():
    return "RANDOM()"

def get_deferrable_sql():
    return ""

def get_fulltext_search_sql(field_name):
    raise NotImplementedError

def get_drop_foreignkey_sql():
    return ""

def get_pk_default_value():
    return "NULL"

def get_sql_flush(style, tables, sequences):
    """Return a list of SQL statements required to remove all data from
    all tables in the database (without actually removing the tables
    themselves) and put the database in an empty 'initial' state
    
    """
    # 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(quote_name(table))
             ) for table in tables]
    # Note: No requirement for reset of auto-incremented indices (cf. other
    # get_sql_flush() implementations). Just return SQL at this point
    return sql

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)

# 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.
OPERATOR_MAPPING = {
    'exact': '= %s',
    'iexact': "LIKE %s ESCAPE '\\'",
    'contains': "LIKE %s ESCAPE '\\'",
    'icontains': "LIKE %s ESCAPE '\\'",
    'gt': '> %s',
    'gte': '>= %s',
    'lt': '< %s',
    'lte': '<= %s',
    'startswith': "LIKE %s ESCAPE '\\'",
    'endswith': "LIKE %s ESCAPE '\\'",
    'istartswith': "LIKE %s ESCAPE '\\'",
    'iendswith': "LIKE %s ESCAPE '\\'",
}
