#!/usr/bin/env python3
"""Focused Visual C++ 6.0 C89 regression checks for methodobject.c."""

import re
import sys
from pathlib import Path

source = Path(sys.argv[1]).read_text()

match = re.search(
    r"PyObject \*\s*PyCMethod_New\(PyMethodDef \*ml, PyObject \*self, PyObject \*module, PyTypeObject \*cls\)\s*\{(?P<body>.*?)\n\}",
    source,
    re.S,
)
assert match, "PyCMethod_New definition not found"
body = match.group("body")
declarations = ("vectorcallfunc vectorcall;", "PyCFunctionObject *op;", "PyCMethodObject *om;", "switch (ml->ml_flags")
declaration_positions = [body.find(token) for token in declarations]
assert all(position >= 0 for position in declaration_positions) and declaration_positions == sorted(declaration_positions), (
    "PyCMethod_New must declare op and om at function entry before its dispatch switch"
)
ordered = (
    "switch (ml->ml_flags",
    "op = NULL;",
    "if (ml->ml_flags & METH_METHOD)",
    "om = PyObject_GC_New(PyCMethodObject, &PyCMethod_Type);",
    "op = PyObject_GC_New(PyCFunctionObject, &PyCFunction_Type);",
    "op->m_weakreflist = NULL;",
)
positions = [body.find(token) for token in ordered]
assert all(position >= 0 for position in positions) and positions == sorted(positions), (
    "PyCMethod_New must preserve flag dispatch, null initialization, allocation, and field setup order"
)
assert "PyCFunctionObject *op =" not in body and "PyCMethodObject *om =" not in body, (
    "PyCMethod_New must not introduce late C89 declarations"
)
print("methodobject PyCMethod_New C89 declarations and allocation order: PASS")

match = re.search(r"PyTypeObject PyCMethod_Type = \{(?P<body>.*?)\n\};", source, re.S)
assert match, "PyCMethod_Type initializer not found"
body = match.group("body")
assert ".tp_" not in body, "PyCMethod_Type must use positional fields instead of C99 designated initializers"
expected = (
    "PyVarObject_HEAD_INIT(&PyType_Type, 0)",
    '"builtin_method"',
    "sizeof(PyCMethodObject)",
) + ("0,",) * 27 + ("&PyCFunction_Type",)
positions = []
cursor = 0
for token in expected:
    position = body.find(token, cursor)
    positions.append(position)
    if position >= 0:
        cursor = position + len(token)
assert all(position >= 0 for position in positions), "PyCMethod_Type positional initializer must preserve the base-type slot"
print("methodobject PyCMethod_Type C89 positional initializer: PASS")


def function_body(name):
    found = re.search(
        r"static PyObject \*\s*" + re.escape(name) + r"\s*\([^;]*\)\s*\{(?P<body>.*?)\n\}",
        source,
        re.S,
    )
    assert found, name + " definition not found"
    return found.group("body")


checks = {
    "cfunction_vectorcall_FASTCALL": (
        "PyThreadState *tstate;",
        "Py_ssize_t nargs;",
        "_PyCFunctionFast meth;",
        "PyObject *result;",
        "tstate = _PyThreadState_GET();",
        "nargs = PyVectorcall_NARGS(nargsf);",
        "meth = (_PyCFunctionFast)",
        "result = meth(",
    ),
    "cfunction_vectorcall_FASTCALL_KEYWORDS": (
        "PyThreadState *tstate;",
        "Py_ssize_t nargs;",
        "_PyCFunctionFastWithKeywords meth;",
        "PyObject *result;",
        "tstate = _PyThreadState_GET();",
        "nargs = PyVectorcall_NARGS(nargsf);",
        "meth = (_PyCFunctionFastWithKeywords)",
        "result = meth(",
    ),
    "cfunction_vectorcall_NOARGS": (
        "Py_ssize_t nargs;",
        "PyCFunction meth;",
        "PyObject *result;",
        "PyThreadState *tstate = _PyThreadState_GET();",
        "if (cfunction_check_kwargs(",
        "nargs = PyVectorcall_NARGS(nargsf);",
        "meth = (PyCFunction)cfunction_enter_call(",
        "result = _PyCFunction_TrampolineCall(",
    ),
    "cfunction_vectorcall_O": (
        "Py_ssize_t nargs;",
        "PyCFunction meth;",
        "PyObject *result;",
        "PyThreadState *tstate = _PyThreadState_GET();",
        "if (cfunction_check_kwargs(",
        "nargs = PyVectorcall_NARGS(nargsf);",
        "meth = (PyCFunction)cfunction_enter_call(",
        "result = _PyCFunction_TrampolineCall(",
    ),
    "cfunction_call": (
        "PyThreadState *tstate;",
        "int flags;",
        "PyCFunction meth;",
        "PyObject *self;",
        "PyObject *result;",
        "assert(kwargs == NULL || PyDict_Check(kwargs));",
        "tstate = _PyThreadState_GET();",
        "flags = PyCFunction_GET_FLAGS(func);",
        "meth = PyCFunction_GET_FUNCTION(func);",
        "self = PyCFunction_GET_SELF(func);",
    ),
}
for name, tokens in checks.items():
    body = function_body(name)
    positions = [body.find(token) for token in tokens]
    assert all(position >= 0 for position in positions) and positions == sorted(positions), (
        name + " must keep declarations before statements and preserve evaluation order"
    )
    for declaration in tokens[:5]:
        if " = " not in declaration and declaration.endswith(";"):
            assert declaration in body, name + " is missing an opening local declaration"
print("methodobject vectorcall and call paths C89 declarations and evaluation order: PASS")