//     Copyright 2020, Kay Hayen, mailto:kay.hayen@gmail.com
//
//     Part of "Nuitka", an optimizing Python compiler that is compatible and
//     integrates with CPython, but also works on its own.
//
//     Licensed under the Apache License, Version 2.0 (the "License");
//     you may not use this file except in compliance with the License.
//     You may obtain a copy of the License at
//
//        http://www.apache.org/licenses/LICENSE-2.0
//
//     Unless required by applicable law or agreed to in writing, software
//     distributed under the License is distributed on an "AS IS" BASIS,
//     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//     See the License for the specific language governing permissions and
//     limitations under the License.
//
#ifndef __NUITKA_HELPER_ITERATORS_H__
#define __NUITKA_HELPER_ITERATORS_H__

#if PYTHON_VERSION >= 270
// Initialize value for "tp_iternext" to compare with, needed by HAS_ITERNEXT
// which emulates "PyCheck_Iter" but is bug free.
extern iternextfunc default_iternext;
extern void _initSlotIternext(void);
#endif

// This is like "PyIter_Check" but without bugs due to shared library pointers.
NUITKA_MAY_BE_UNUSED static inline bool HAS_ITERNEXT(PyObject *value) {
#if PYTHON_VERSION < 300
    if (!PyType_HasFeature(Py_TYPE(value), Py_TPFLAGS_HAVE_ITER)) {
        return false;
    }
#endif

    iternextfunc tp_iternext = Py_TYPE(value)->tp_iternext;

    if (tp_iternext == NULL) {
        return false;
    }

#if PYTHON_VERSION >= 270
    return tp_iternext != default_iternext;
#else
    return true;
#endif
}

// Stolen from CPython implementation, so we can access it.
typedef struct {
    PyObject_HEAD
#if PYTHON_VERSION < 340
        long it_index;
#else
        Py_ssize_t it_index;
#endif
    PyObject *it_seq;
} seqiterobject;

NUITKA_MAY_BE_UNUSED static PyObject *MAKE_ITERATOR(PyObject *iterated) {

#if PYTHON_VERSION < 300
    getiterfunc tp_iter = NULL;
    if (PyType_HasFeature(Py_TYPE(iterated), Py_TPFLAGS_HAVE_ITER)) {
        tp_iter = Py_TYPE(iterated)->tp_iter;
    }
#else
    getiterfunc tp_iter = Py_TYPE(iterated)->tp_iter;
#endif

    if (tp_iter) {
        PyObject *result = (*tp_iter)(iterated);

        if (unlikely(result == NULL)) {
            return NULL;
        } else if (unlikely(!HAS_ITERNEXT(result))) {
            PyErr_Format(PyExc_TypeError, "iter() returned non-iterator of type '%s'", Py_TYPE(result)->tp_name);

            Py_DECREF(result);

            return NULL;
        } else {
            return result;
        }
    } else if (PySequence_Check(iterated)) {
        seqiterobject *result = PyObject_GC_New(seqiterobject, &PySeqIter_Type);
        assert(result);

        result->it_index = 0;
        Py_INCREF(iterated);
        result->it_seq = iterated;

        Nuitka_GC_Track(result);

        return (PyObject *)result;
    } else {
        PyErr_Format(PyExc_TypeError, "'%s' object is not iterable", Py_TYPE(iterated)->tp_name);

        return NULL;
    }
}

#if PYTHON_VERSION >= 370

NUITKA_MAY_BE_UNUSED static PyObject *MAKE_UNPACK_ITERATOR(PyObject *iterated) {

    getiterfunc tp_iter = Py_TYPE(iterated)->tp_iter;

    if (tp_iter) {
        PyObject *result = (*tp_iter)(iterated);

        if (unlikely(result == NULL)) {
            return NULL;
        } else if (unlikely(!HAS_ITERNEXT(result))) {
            PyErr_Format(PyExc_TypeError, "iter() returned non-iterator of type '%s'", Py_TYPE(result)->tp_name);

            Py_DECREF(result);

            return NULL;
        } else {
            return result;
        }
    } else if (PySequence_Check(iterated)) {
        seqiterobject *result = PyObject_GC_New(seqiterobject, &PySeqIter_Type);
        assert(result);

        result->it_index = 0;
        Py_INCREF(iterated);
        result->it_seq = iterated;

        Nuitka_GC_Track(result);

        return (PyObject *)result;
    } else {
        PyErr_Format(PyExc_TypeError, "cannot unpack non-iterable %s object", Py_TYPE(iterated)->tp_name);

        return NULL;
    }
}

#endif

NUITKA_MAY_BE_UNUSED static PyObject *ITERATOR_NEXT(PyObject *iterator) {
    CHECK_OBJECT(iterator);

    iternextfunc iternext = Py_TYPE(iterator)->tp_iternext;

    if (unlikely(iternext == NULL)) {
        PyErr_Format(PyExc_TypeError,
#if PYTHON_VERSION < 300 && defined(_NUITKA_FULL_COMPAT)
                     "%s object is not an iterator",
#else
                     "'%s' object is not an iterator",
#endif
                     Py_TYPE(iterator)->tp_name);

        return NULL;
    }

    PyObject *result = (*iternext)(iterator);

#if PYTHON_VERSION < 300
    if (result == NULL) {
        PyObject *error = GET_ERROR_OCCURRED();
        if (error) {
            if (likely(EXCEPTION_MATCH_BOOL_SINGLE(error, PyExc_StopIteration))) {
                CLEAR_ERROR_OCCURRED();
            }
        }
    }
#endif

    return result;
}

NUITKA_MAY_BE_UNUSED static PyObject *BUILTIN_NEXT1(PyObject *iterator) {
    CHECK_OBJECT(iterator);

    iternextfunc iternext = Py_TYPE(iterator)->tp_iternext;

    if (unlikely(iternext == NULL)) {
        PyErr_Format(PyExc_TypeError,
#if PYTHON_VERSION < 300 && defined(_NUITKA_FULL_COMPAT)
                     "%s object is not an iterator",
#else
                     "'%s' object is not an iterator",
#endif
                     Py_TYPE(iterator)->tp_name);

        return NULL;
    }

    PyObject *result = (*iternext)(iterator);

    if (unlikely(result == NULL)) {
        // The iteration can return NULL with no error, which means
        // StopIteration.
        if (!ERROR_OCCURRED()) {
            SET_CURRENT_EXCEPTION_TYPE0(PyExc_StopIteration);
        }

        return NULL;
    } else {
        CHECK_OBJECT(result);
    }

    return result;
}

NUITKA_MAY_BE_UNUSED static PyObject *BUILTIN_NEXT2(PyObject *iterator, PyObject *default_value) {
    CHECK_OBJECT(iterator);
    CHECK_OBJECT(default_value);

    PyObject *result = (*Py_TYPE(iterator)->tp_iternext)(iterator);

    if (unlikely(result == NULL)) {
        PyObject *error = GET_ERROR_OCCURRED();

        if (error != NULL) {
            if (EXCEPTION_MATCH_BOOL_SINGLE(error, PyExc_StopIteration)) {
                DROP_ERROR_OCCURRED();

                Py_INCREF(default_value);
                return default_value;
            } else {
                return NULL;
            }
        } else {
            Py_INCREF(default_value);
            return default_value;
        }
    } else {
        CHECK_OBJECT(result);
    }

    return result;
}

#if PYTHON_VERSION < 350
NUITKA_MAY_BE_UNUSED static PyObject *UNPACK_NEXT(PyObject *iterator, int seq_size_so_far)
#else
NUITKA_MAY_BE_UNUSED static PyObject *UNPACK_NEXT(PyObject *iterator, int seq_size_so_far, int expected)
#endif
{
    CHECK_OBJECT(iterator);
    assert(HAS_ITERNEXT(iterator));

    PyObject *result = (*Py_TYPE(iterator)->tp_iternext)(iterator);

    if (unlikely(result == NULL)) {
#if PYTHON_VERSION < 300
        if (unlikely(!ERROR_OCCURRED()))
#else
        if (unlikely(!ERROR_OCCURRED() || EXCEPTION_MATCH_BOOL_SINGLE(GET_ERROR_OCCURRED(), PyExc_StopIteration)))
#endif
        {
#if PYTHON_VERSION < 350
            if (seq_size_so_far == 1) {
                SET_CURRENT_EXCEPTION_TYPE0_STR(PyExc_ValueError, "need more than 1 value to unpack");
            } else {
                PyErr_Format(PyExc_ValueError, "need more than %d values to unpack", seq_size_so_far);
            }
#else
            PyErr_Format(PyExc_ValueError, "not enough values to unpack (expected %d, got %d)", expected,
                         seq_size_so_far);
#endif
        }

        return NULL;
    }

    CHECK_OBJECT(result);

    return result;
}

#if PYTHON_VERSION >= 350
NUITKA_MAY_BE_UNUSED static PyObject *UNPACK_NEXT_STARRED(PyObject *iterator, int seq_size_so_far, int expected) {
    CHECK_OBJECT(iterator);
    assert(HAS_ITERNEXT(iterator));

    PyObject *result = (*Py_TYPE(iterator)->tp_iternext)(iterator);

    if (unlikely(result == NULL)) {
        if (unlikely(!ERROR_OCCURRED() || EXCEPTION_MATCH_BOOL_SINGLE(GET_ERROR_OCCURRED(), PyExc_StopIteration))) {
            PyErr_Format(PyExc_ValueError, "not enough values to unpack (expected at least %d, got %d)", expected,
                         seq_size_so_far);
        }

        return NULL;
    }

    CHECK_OBJECT(result);

    return result;
}
#endif

NUITKA_MAY_BE_UNUSED static bool UNPACK_ITERATOR_CHECK(PyObject *iterator) {
    CHECK_OBJECT(iterator);
    assert(HAS_ITERNEXT(iterator));

    PyObject *attempt = (*Py_TYPE(iterator)->tp_iternext)(iterator);

    if (likely(attempt == NULL)) {
        return CHECK_AND_CLEAR_STOP_ITERATION_OCCURRED();
    } else {
        Py_DECREF(attempt);

        SET_CURRENT_EXCEPTION_TYPE0_STR(PyExc_ValueError, "too many values to unpack");
        return false;
    }
}

#endif
