from __future__ import absolute_import

from django.db.models.lookups import Exact

from bitfield.types import Bit, BitHandler


class BitQueryLookupWrapper(Exact):  # NOQA
    def process_lhs(self, compiler, connection, lhs=None):
        lhs_sql, lhs_params = super(BitQueryLookupWrapper, self).process_lhs(
            compiler, connection, lhs
        )

        if not isinstance(self.rhs, (BitHandler, Bit)):
            return lhs_sql, lhs_params

        op = " & " if self.rhs else " | "
        rhs_sql, rhs_params = self.process_rhs(compiler, connection)
        params = list(lhs_params)
        params.extend(rhs_params)

        return op.join((lhs_sql, rhs_sql)), params

    def get_db_prep_lookup(self, value, connection):
        v = value.mask if isinstance(value, (BitHandler, Bit)) else value
        return super(BitQueryLookupWrapper, self).get_db_prep_lookup(v, connection)

    def get_prep_lookup(self):
        if isinstance(self.rhs, (BitHandler, Bit)):
            return self.rhs  # resolve at later stage, in get_db_prep_lookup
        return super(BitQueryLookupWrapper, self).get_prep_lookup()


class BitQuerySaveWrapper(BitQueryLookupWrapper):
    def as_sql(self, qn, connection):
        """
        Create the proper SQL fragment. This inserts something like
        "(T0.flags & value) != 0".

        This will be called by Where.as_sql()
        """
        engine = connection.settings_dict["ENGINE"].rsplit(".", -1)[-1]
        if engine.startswith("postgres"):
            XOR_OPERATOR = "#"
        elif engine.startswith("sqlite"):
            raise NotImplementedError
        else:
            XOR_OPERATOR = "^"

        if self.bit:
            return (
                "%s.%s | %d" % (qn(self.table_alias), qn(self.column), self.bit.mask),
                [],
            )
        return (
            "%s.%s %s %d"
            % (qn(self.table_alias), qn(self.column), XOR_OPERATOR, self.bit.mask),
            [],
        )