"""Fixer that changes plain strings to bytes strings."""

import re

from lib2to3 import fixer_base

from lib2to3.pgen2 import token

from lib2to3.fixer_util import Name

from lib2to3.pygram import python_symbols as syms

_re = re.compile(r'[rR]?[\'\"]')

# XXX: Implementing a blacklist in 2to3 turned out to be more troublesome than

# blacklisting some modules inside the fixers. So, this is what I came with.

blacklist = ('mercurial/demandimport.py',

             'mercurial/py3kcompat.py', # valid python 3 already

             'mercurial/i18n.py',

            )

def isdocstring(node):

    def isclassorfunction(ancestor):

        symbols = (syms.funcdef, syms.classdef)

        # if the current node is a child of a function definition, a class

        # definition or a file, then it is a docstring

        if ancestor.type == syms.simple_stmt:

            try:

                while True:

                    if ancestor.type in symbols:

                        return True

                    ancestor = ancestor.parent

            except AttributeError:

                return False

        return False

    def ismodule(ancestor):

        # Our child is a docstring if we are a simple statement, and our

        # ancestor is file_input. In other words, our child is a lone string in

        # the source file.

        try:

            if (ancestor.type == syms.simple_stmt and

                ancestor.parent.type == syms.file_input):

                    return True

        except AttributeError:

            return False

    def isdocassignment(ancestor):

        # Assigning to __doc__, definitely a string

        try:

            while True:

                if (ancestor.type == syms.expr_stmt and

                    Name('__doc__') in ancestor.children):

                        return True

                ancestor = ancestor.parent

        except AttributeError:

            return False

    if ismodule(node.parent) or \

       isdocassignment(node.parent) or \

       isclassorfunction(node.parent):

        return True

    return False

def shouldtransform(node):

    specialnames = ['__main__']

    if node.value in specialnames:

        return False

    ggparent = node.parent.parent.parent

    sggparent = str(ggparent)

    if 'getattr' in sggparent or \

       'hasattr' in sggparent or \

       'setattr' in sggparent or \

       'encode' in sggparent or \

       'decode' in sggparent:

        return False

    return True

class FixBytes(fixer_base.BaseFix):

    PATTERN = 'STRING'

    def transform(self, node, results):

        # The filename may be prefixed with a build directory.

        if self.filename.endswith(blacklist):

            return

        if node.type == token.STRING:

            if _re.match(node.value):

                if isdocstring(node):

                    return

                if not shouldtransform(node):

                    return

                new = node.clone()

                new.value = 'b' + new.value

                return new