"""Fixer for sys.exc_{type, value, traceback}

sys.exc_type -> sys.exc_info()[0]
sys.exc_value -> sys.exc_info()[1]
sys.exc_traceback -> sys.exc_info()[2]
"""

# By Jeff Balogh and Benjamin Peterson

# Local imports
from .. import fixer_base
from ..fixer_util import Attr, Call, Name, Number, Subscript, Node, syms

class FixSysExc(fixer_base.BaseFix):
# This order matches the ordering of sys.exc_info().
exc_info = [u"exc_type", u"exc_value", u"exc_traceback"]
BM_compatible = True
PATTERN = """
power< 'sys' trailer< dot='.' attribute=(%s) > >
""" % '|'.join("'%s'" % e for e in exc_info)

def transform(self, node, results):
sys_attr = results["attribute"][0]
index = Number(self.exc_info.index(sys_attr.value))

call = Call(Name(u"exc_info"), prefix=sys_attr.prefix)
attr = Attr(Name(u"sys"), call)
attr[1].children[0].prefix = results["dot"].prefix
attr.append(Subscript(index))
return Node(syms.power, attr, prefix=node.prefix)