"""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):
BM_compatible = True
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")

if base:
if self.shadowed_next:
attr.replace(Name("__next__", prefix=attr.prefix))
else:
base = [n.clone() for n in base]
base[0].prefix = ""
node.replace(Call(Name("next", prefix=node.prefix), base))
elif name:
n = Name("__next__", prefix=name.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)