"""
Convert use of sys.exitfunc to use the atexit module.
"""

# Author: Benjamin Peterson

from lib2to3 import pytree, fixer_base
from lib2to3.fixer_util import Name, Attr, Call, Comma, Newline, syms


class FixExitfunc(fixer_base.BaseFix):
keep_line_order = True
BM_compatible = True

PATTERN = """
(
sys_import=import_name<'import'
('sys'
|
dotted_as_names< (any ',')* 'sys' (',' any)* >
)
>
|
expr_stmt<
power< 'sys' trailer< '.' 'exitfunc' > >
'=' func=any >
)
"""

def __init__(self, *args):
super(FixExitfunc, self).__init__(*args)

def start_tree(self, tree, filename):
super(FixExitfunc, self).start_tree(tree, filename)
self.sys_import = None

def transform(self, node, results):
# First, find a the sys import. We'll just hope it's global scope.
if "sys_import" in results:
if self.sys_import is None:
self.sys_import = results["sys_import"]
return

func = results["func"].clone()
func.prefix = u""
register = pytree.Node(syms.power,
Attr(Name(u"atexit"), Name(u"register"))
)
call = Call(register, [func], node.prefix)
node.replace(call)

if self.sys_import is None:
# That's interesting.
self.warning(node, "Can't find sys import; Please add an atexit "
"import at the top of your file.")
return

# Now add an atexit import after the sys import.
names = self.sys_import.children[1]
if names.type == syms.dotted_as_names:
names.append_child(Comma())
names.append_child(Name(u"atexit", u" "))
else:
containing_stmt = self.sys_import.parent
position = containing_stmt.children.index(self.sys_import)
stmt_container = containing_stmt.parent
new_import = pytree.Node(syms.import_name,
[Name(u"import"), Name(u"atexit", u" ")]
)
new = pytree.Node(syms.simple_stmt, [new_import])
containing_stmt.insert_child(position + 1, Newline())
containing_stmt.insert_child(position + 2, new)