"""Fixer for generator.throw(E, V, T).

g.throw(E)       -> g.throw(E)

g.throw(E, V)    -> g.throw(E(V))

g.throw(E, V, T) -> g.throw(E(V).with_traceback(T))

g.throw("foo"[, V[, T]]) will warn about string exceptions."""

# Author: Collin Winter

# Local imports

from .. import pytree

from ..pgen2 import token

from .. import fixer_base

from ..fixer_util import Name, Call, ArgList, Attr, is_tuple

class FixThrow(fixer_base.BaseFix):

    PATTERN = """

    power< any trailer< '.' 'throw' >

           trailer< '(' args=arglist< exc=any ',' val=any [',' tb=any] > ')' >

    >

    |

    power< any trailer< '.' 'throw' > trailer< '(' exc=any ')' > >

    """

    def transform(self, node, results):

        syms = self.syms

        exc = results["exc"].clone()

        if exc.type is token.STRING:

            self.cannot_convert(node, "Python 3 does not support string exceptions")

            return

        # Leave "g.throw(E)" alone

        val = results.get("val")

        if val is None:

            return

        val = val.clone()

        if is_tuple(val):

            args = [c.clone() for c in val.children[1:-1]]

        else:

            val.set_prefix("")

            args = [val]

        throw_args = results["args"]

        if "tb" in results:

            tb = results["tb"].clone()

            tb.set_prefix("")

            e = Call(exc, args)

            with_tb = Attr(e, Name('with_traceback')) + [ArgList([tb])]

            throw_args.replace(pytree.Node(syms.power, with_tb))

        else:

            throw_args.replace(Call(exc, args))