"""Fixer that changes 'a ,b' into 'a, b'.

This also changes '{a :b}' into '{a: b}', but does not touch other

uses of colons.  It does not touch other uses of whitespace.

"""

from .. import pytree

from ..pgen2 import token

from .. import fixer_base

class FixWsComma(fixer_base.BaseFix):

    explicit = True # The user must ask for this fixers

    PATTERN = """

    any<(not(',') any)+ ',' ((not(',') any)+ ',')* [not(',') any]>

    """

    COMMA = pytree.Leaf(token.COMMA, ",")

    COLON = pytree.Leaf(token.COLON, ":")

    SEPS = (COMMA, COLON)

    def transform(self, node, results):

        new = node.clone()

        comma = False

        for child in new.children:

            if child in self.SEPS:

                prefix = child.get_prefix()

                if prefix.isspace() and "\n" not in prefix:

                    child.set_prefix("")

                comma = True

            else:

                if comma:

                    prefix = child.get_prefix()

                    if not prefix:

                        child.set_prefix(" ")

                comma = False

        return new