#!/usr/bin/env python3
"""Check the C89 rollback index and reverse MRO restoration order."""
import re
from pathlib import Path

source = Path("cpython/Objects/typeobject.c").read_text()
match = re.search(
    r"\nstatic int\ntype_set_bases\(PyTypeObject \*type, PyObject \*new_bases, void \*context\)\n\{(.*?)\n\}",
    source,
    re.S,
)
assert match, "type_set_bases definition missing"
body = re.sub(r"/\*.*?\*/|//[^\n]*", "", match.group(1), flags=re.S)
assert not re.search(r"for\s*\(\s*Py_ssize_t\s+i\b", body), (
    "type_set_bases: C99 rollback loop index declaration remains"
)
assert re.match(r"\s*Py_ssize_t n;\s*Py_ssize_t i;", body), (
    "type_set_bases: reuse i from the opening declarations"
)
assert len(re.findall(r"\bPy_ssize_t\s+i\b", body)) == 1, (
    "type_set_bases: declare i exactly once"
)
rollback = body.split("undo:", 1)[1].split("bail:", 1)[0]
expected = '''
    n = PyList_GET_SIZE(temp);
    for (i = n - 1; i >= 0; i--) {
        PyTypeObject *cls;
        PyObject *new_mro, *old_mro = NULL;

        PyArg_UnpackTuple(PyList_GET_ITEM(temp, i),
                          "", 2, 3, &cls, &new_mro, &old_mro);
        if (cls->tp_mro == new_mro) {
            Py_XINCREF(old_mro);
            cls->tp_mro = old_mro;
            Py_DECREF(new_mro);
        }
    }
    Py_DECREF(temp);
'''
assert rollback.split() == expected.split(), (
    "type_set_bases: preserve rollback size evaluation, reverse iteration, "
    "newer-MRO guard, reference operations, and temp cleanup order"
)
print("type_set_bases rollback index C89 and unchanged restoration order: PASS")