#!/usr/bin/env python3
"""Check only the two static type initializer mappings at the VC6 frontier."""
import re
from pathlib import Path

source = Path('cpython/Objects/typeobject.c').read_text()
header = Path('cpython/Include/cpython/object.h').read_text()


def uncomment(text):
    return re.sub(r'/\*.*?\*/|//[^\n]*', '', text, flags=re.S)


def check(name, declaration, layout, prefix, expected, head=''):
    match = re.search(declaration + ' ' + name + r' = \{(.*?)\n\};', source, re.S)
    assert match, name + ': initializer missing'
    body = uncomment(match.group(1)).strip()
    assert not re.search(r'\.\w+\s*=', body), name + ': designated initializer is not VC6/C89 compatible'
    if head:
        assert body.startswith(head), name + ': object header changed'
        body = body[len(head):]
    fields = re.findall(r'\b(' + prefix + r'\w+)\b', uncomment(layout))
    assert len(fields) == len(set(fields)) == (36 if prefix == 'nb_' else 48)
    # Split only at top-level commas (offsetof arguments contain commas).
    values = [v.strip() for v in re.split(r',\s*(?![^()]*\))', body) if v.strip()]
    assert len(values) <= len(fields), name + ': excess initializer entries'
    values += ['0'] * (len(fields) - len(values))
    normalize = lambda value: re.sub(r'\s+', '', value)
    actual = dict(zip(fields, map(normalize, values)))
    wanted = {field: normalize(expected.get(field, '0')) for field in fields}
    assert expected.keys() <= actual.keys(), name + ': expected fields absent from header'
    assert actual == wanted, name + ': field mappings changed: ' + repr({k: (actual[k], wanted[k]) for k in fields if actual[k] != wanted[k]})
    print(f'{name}: C89 positional structure and all {len(fields)} field mappings PASS')


number_layout = re.search(r'typedef struct \{([^{}]*)\} PyNumberMethods;', header, re.S)
assert number_layout, 'PyNumberMethods layout missing'
check('type_as_number', 'static PyNumberMethods', number_layout.group(1), 'nb_', {
    'nb_or': '_Py_union_type_or',
})
type_layout = re.search(r'struct _typeobject \{(.*?)\n\};', header, re.S)
assert type_layout, 'PyTypeObject layout missing'
check('PyType_Type', 'PyTypeObject', type_layout.group(1), 'tp_', {
    'tp_name': '"type"',
    'tp_basicsize': 'sizeof(PyHeapTypeObject)',
    'tp_itemsize': 'sizeof(PyMemberDef)',
    'tp_dealloc': '(destructor)type_dealloc',
    'tp_vectorcall_offset': 'offsetof(PyTypeObject, tp_vectorcall)',
    'tp_repr': '(reprfunc)type_repr',
    'tp_as_number': '&type_as_number',
    'tp_call': '(ternaryfunc)type_call',
    'tp_getattro': '(getattrofunc)type_getattro',
    'tp_setattro': '(setattrofunc)type_setattro',
    'tp_flags': 'Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_TYPE_SUBCLASS | Py_TPFLAGS_HAVE_VECTORCALL',
    'tp_doc': 'type_doc',
    'tp_traverse': '(traverseproc)type_traverse',
    'tp_clear': '(inquiry)type_clear',
    'tp_weaklistoffset': 'offsetof(PyTypeObject, tp_weaklist)',
    'tp_methods': 'type_methods',
    'tp_members': 'type_members',
    'tp_getset': 'type_getsets',
    'tp_dictoffset': 'offsetof(PyTypeObject, tp_dict)',
    'tp_init': 'type_init',
    'tp_new': 'type_new',
    'tp_free': 'PyObject_GC_Del',
    'tp_is_gc': '(inquiry)type_is_gc',
    'tp_vectorcall': 'type_vectorcall',
}, 'PyVarObject_HEAD_INIT(&PyType_Type, 0)')