"""Fixer for it.next() -> next(it), per PEP 3114."""

# Author: Collin Winter

# Things that currently aren't covered:

#   - listcomp "next" names aren't warned

#   - "with" statement targets aren't checked

# Local imports

from ..pgen2 import token

from ..pygram import python_symbols as syms

from .. import fixer_base

from ..fixer_util import Name, Call, find_binding

bind_warning = "Calls to builtin next() possibly shadowed by global binding"

class FixNext(fixer_base.BaseFix):

    PATTERN = """

    power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >

    |

    power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >

    |

    classdef< 'class' any+ ':'

              suite< any*

                     funcdef< 'def'

                              name='next'

                              parameters< '(' NAME ')' > any+ >

                     any* > >

    |

    global=global_stmt< 'global' any* 'next' any* >

    """

    order = "pre" # Pre-order tree traversal

    def start_tree(self, tree, filename):

        super(FixNext, self).start_tree(tree, filename)

        n = find_binding('next', tree)

        if n:

            self.warning(n, bind_warning)

            self.shadowed_next = True

        else:

            self.shadowed_next = False

    def transform(self, node, results):

        assert results

        base = results.get("base")

        attr = results.get("attr")

        name = results.get("name")

        mod = results.get("mod")

        if base:

            if self.shadowed_next:

                attr.replace(Name("__next__", prefix=attr.get_prefix()))

            else:

                base = [n.clone() for n in base]

                base[0].set_prefix("")

                node.replace(Call(Name("next", prefix=node.get_prefix()), base))

        elif name:

            n = Name("__next__", prefix=name.get_prefix())

            name.replace(n)

        elif attr:

            # We don't do this transformation if we're assigning to "x.next".

            # Unfortunately, it doesn't seem possible to do this in PATTERN,

            #  so it's being done here.

            if is_assign_target(node):

                head = results["head"]

                if "".join([str(n) for n in head]).strip() == '__builtin__':

                    self.warning(node, bind_warning)

                return

            attr.replace(Name("__next__"))

        elif "global" in results:

            self.warning(node, bind_warning)

            self.shadowed_next = True

### The following functions help test if node is part of an assignment

###  target.

def is_assign_target(node):

    assign = find_assign(node)

    if assign is None:

        return False

    for child in assign.children:

        if child.type == token.EQUAL:

            return False

        elif is_subtree(child, node):

            return True

    return False

def find_assign(node):

    if node.type == syms.expr_stmt:

        return node

    if node.type == syms.simple_stmt or node.parent is None:

        return None

    return find_assign(node.parent)

def is_subtree(root, node):

    if root == node:

        return True

    return any([is_subtree(c, node) for c in root.children])