#!/usr/bin/env python3
"""Check only mro_implementation's first loop index and validation semantics."""
import re
from pathlib import Path

source = Path("cpython/Objects/typeobject.c").read_text()
match = re.search(
    r"\nstatic PyObject \*\nmro_implementation\(PyTypeObject \*type\)\n\{(.*?)\n\}",
    source,
    re.S,
)
assert match, "mro_implementation definition missing"
body = re.sub(r"/\*.*?\*/", "", match.group(1), flags=re.S)
validation = body.split("if (n == 1)", 1)[0]
assert re.match(
    r"\s*PyObject \*bases;\s*Py_ssize_t n;\s*Py_ssize_t i;"
    r"\s*PyObject \*\*to_merge;\s*PyObject \*result;\s*if\b",
    validation,
), (
    "mro_implementation: first loop index must be declared in the opening block"
)
assert len(re.findall(r"\bPy_ssize_t\s+i\b", validation)) == 1, "declare first loop index exactly once"
assert len(re.findall(r"\bi\s*=(?!=)", validation)) == 1, "initialize first loop index exactly once"
expected = """
    PyObject *bases;
    Py_ssize_t n;
    Py_ssize_t i;
    PyObject **to_merge;
    PyObject *result;
    if (!_PyType_IsReady(type)) {
        if (PyType_Ready(type) < 0)
            return NULL;
    }
    bases = type->tp_bases;
    n = PyTuple_GET_SIZE(bases);
    for (i = 0; i < n; i++) {
        PyTypeObject *base = _PyType_CAST(PyTuple_GET_ITEM(bases, i));
        if (base->tp_mro == NULL) {
            PyErr_Format(PyExc_TypeError,
                         "Cannot extend an incomplete type '%.100s'",
                         base->tp_name);
            return NULL;
        }
        assert(PyTuple_Check(base->tp_mro));
    }
"""
assert validation.split() == expected.split(), (
    "mro_implementation: preserve readiness, initialization timing, loop bounds, "
    "increment, and base validation"
)
print("mro_implementation first loop index C89 declaration and unchanged validation: PASS")