import abc
import atexit
import contextlib
import contextvars
import functools
import inspect
import os
import math
import platform
import signal
import textwrap
import threading
import typing
import warnings
from typing import Union
from rpy2.rinterface_lib import openrlib
import rpy2.rinterface_lib._rinterface_capi as _rinterface
import rpy2.rinterface_lib.embedded as embedded
import rpy2.rinterface_lib.conversion as conversion
from rpy2.rinterface_lib.conversion import _cdata_res_to_rinterface
import rpy2.rinterface_lib.memorymanagement as memorymanagement
from rpy2.rinterface_lib import na_values
from rpy2.rinterface_lib.sexp import NULL
from rpy2.rinterface_lib.sexp import NULLType
import rpy2.rinterface_lib.bufferprotocol as bufferprotocol
from rpy2.rinterface_lib import sexp
from rpy2.rinterface_lib.sexp import CharSexp  # noqa: F401
from rpy2.rinterface_lib.sexp import RTYPES
from rpy2.rinterface_lib.sexp import SexpVector
from rpy2.rinterface_lib.sexp import StrSexpVector
from rpy2.rinterface_lib.sexp import Sexp
from rpy2.rinterface_lib.sexp import SexpEnvironment
from rpy2.rinterface_lib.sexp import unserialize  # noqa: F401
from rpy2.rinterface_lib.sexp import emptyenv
from rpy2.rinterface_lib.sexp import baseenv
from rpy2.rinterface_lib.sexp import globalenv

if os.name == 'nt':
    import rpy2.rinterface_lib.embedded_mswin as embedded_mswin
    embedded._initr = embedded_mswin._initr_win32

R_NilValue = openrlib.rlib.R_NilValue

endr = embedded.endr

evaluation_context = contextvars.ContextVar('evaluation_context',
                                            default=globalenv)


def get_evaluation_context() -> SexpEnvironment:
    """Get the frame (environment) in which R code is currently evaluated."""
    warnings.warn('This function is deprecated. '
                  'Use evaluation_context directly.',
                  DeprecationWarning, stacklevel=2)
    return evaluation_context.get()


@contextlib.contextmanager
def local_context(
        env: typing.Optional[SexpEnvironment] = None,
        use_rlock: bool = True
) -> typing.Iterator[SexpEnvironment]:
    """Local context for the evaluation of R code.

    Args:
    - env: an environment to use as a context. If not specified (None, the
      default), a child environment to the current context is created.
    - use_rlock: whether to use a threading lock (see the documentation about
      "rlock". The default is True.

    Returns:
    Yield the environment (passed to env, or created).
    """

    parent_frame = evaluation_context.get()
    if env is None:
        env = baseenv['new.env'](
            baseenv['parent.frame']()
            if parent_frame is None
            else parent_frame)
    try:
        if use_rlock:
            with openrlib.rlock:
                token = evaluation_context.set(env)
                yield env
        else:
            token = evaluation_context.set(env)
            yield env
    finally:
        evaluation_context.reset(token)


def _sigint_handler(sig, frame):
    raise KeyboardInterrupt()


@_cdata_res_to_rinterface
def parse(text: str, num: int = -1):
    """Parse a string as R code.

    :param text: A string with R code to parse.
    :param num: The maximum number of lines to parse. If -1, no
      limit is applied.
    """

    if not isinstance(text, str):
        raise TypeError('text must be a string.')
    robj = StrSexpVector([text])
    with memorymanagement.rmemory() as rmemory:
        res = _rinterface._parse(robj.__sexp__._cdata, num, rmemory)
    return res


def evalr_expr(
        expr: 'ExprSexpVector',
        envir: typing.Union[
            None,
            'SexpEnvironment', 'NULLType',
            'ListSexpVector', 'PairlistSexpVector', int,
            '_MissingArgType'] = None,
        enclos: typing.Union[
            None,
            'ListSexpVector', 'PairlistSexpVector',
            'NULLType',
            '_MissingArgType'] = None
) -> sexp.Sexp:
    """Evaluate an R expression.

    :param expr: An R expression.
    :param envir: An optional R environment in which the evaluation
      will happen. If None, which is the default, the environment in
     the context variable `evaluation_context` is used.
    :param enclos: An enclosure. This is only relevant when envir
      is a list, a pairlist, or a data.frame. It specifies where to
    look for objects not found in envir.
    :return: The R objects resulting from the evaluation of the code"""

    if envir is None:
        envir = evaluation_context.get()
    if enclos is None:
        enclos = MissingArg
    res = baseenv['eval'](expr, envir=envir, enclos=enclos)
    return res


def evalr_expr_with_visible(
        expr: 'ExprSexpVector',
        envir: typing.Union[
            None,
            'SexpEnvironment'] = None
) -> 'ListSexpVector':
    """Evaluate an R expression and return value and visibility flag.

    :param expr: An R expression.
    :param envir: An environment in which the expression will be evaluated.

    :return: An R list with (value, visibility) where visibility is
    an R boolean.
    """
    if envir is None:
        envir = evaluation_context.get()
    assert isinstance(envir, SexpEnvironment)

    error_occured = _rinterface.ffi.new('int *', 0)
    with memorymanagement.rmemory() as rmemory:
        r_call_nested = rmemory.protect(
            openrlib.rlib.Rf_lang2(
                baseenv['eval'].__sexp__._cdata,
                expr.__sexp__._cdata)
        )
        r_call = rmemory.protect(
            openrlib.rlib.Rf_lang2(
                baseenv['withVisible'].__sexp__._cdata,
                r_call_nested)
        )
        r_res = rmemory.protect(
                openrlib.rlib.R_tryEval(
                    r_call,
                    envir.__sexp__._cdata,  # call context.
                    error_occured)
        )
        if error_occured[0]:
            raise embedded.RRuntimeError(_rinterface._geterrmessage())
        res = conversion._cdata_to_rinterface(r_res)
        assert isinstance(res, ListSexpVector)
    return res


def evalr(
        source: str,
        maxlines: int = -1,
        envir: typing.Union[
            None,
            'SexpEnvironment', 'NULLType',
            'ListSexpVector', 'PairlistSexpVector', int,
            '_MissingArgType'] = None,
        enclos: typing.Union[
            None,
            'ListSexpVector', 'PairlistSexpVector',
            'NULLType', '_MissingArgType'] = None
) -> sexp.Sexp:
    """Evaluate a string as R code.

    Evaluate a string as R just as it would happen when writing
    code in an R terminal.

    :param str text: A string to be evaluated as R code,
    or an R expression.
    :param int maxlines: The maximum number of lines to parse. If -1, no
      limit is applied.
    :param envir: An optional R environment in which the evaluation
      will happen.
    :param enclos: An enclosure. This is only relevant when envir
      is a list, a pairlist, or a data.frame. It specifies where to
    look for objects not found in envir.
    :return: The R objects resulting from the evaluation of the code"""

    expr = parse(source, num=maxlines)
    res = evalr_expr(expr, envir=envir, enclos=enclos)
    return res


def vector_memoryview(obj: sexp.SexpVector,
                      sizeof_str: str, cast_str: str) -> memoryview:
    """
    :param obj: R vector
    :param str sizeof_str: Type in a string to use with ffi.sizeof()
        (for example "int")
    :param str cast_str: Type in a string to use with memoryview.cast()
        (for example "i")
    """
    b = openrlib.ffi.buffer(
        obj._R_GET_PTR(obj.__sexp__._cdata),
        openrlib.ffi.sizeof(sizeof_str) * len(obj))
    shape = bufferprotocol.getshape(obj.__sexp__._cdata)
    # One could have expected to only need builtin Python
    # and do something like
    # ```
    # mv = memoryview(b).cast(cast_str, shape, order='F')
    # ```
    # but Python does not handle FORTRAN-ordered arrays without having
    # to write C extensions (see
    # https://bugs.python.org/issue34778 is not resolved).
    # Having numpy a requirement just for this is a problem so a
    # C function to swap the strides in place was written
    try:
        import rpy2.rinterface_lib._bufferprotocol as bp   # type: ignore
        mv = memoryview(b).cast(cast_str, shape)
        bp.memoryview_swapstrides(mv)
    except ImportError:
        import numpy  # type: ignore
        a = numpy.frombuffer(b, dtype=cast_str).reshape(shape, order='F')
        # The typed signature for memoryview does not help the static
        # type checker verify that a numpy.ndarray implement the buffer
        # protocol. Type checking is ignored to avoid a check error.
        mv = memoryview(a)  # type: ignore
    return mv


class SexpSymbol(sexp.Sexp):
    """An unevaluated R symbol."""

    def __init__(
            self,
            obj: Union[Sexp,
                       _rinterface.SexpCapsule,
                       _rinterface.UninitializedRCapsule,
                       str]
    ):
        if isinstance(obj, Sexp) or isinstance(obj, _rinterface.CapsuleBase):
            super().__init__(obj)
        elif isinstance(obj, str):
            name_cdata = _rinterface.ffi.new('char []', obj.encode('utf-8'))
            sexp = _rinterface.SexpCapsule(
                openrlib.rlib.Rf_install(name_cdata))
            super().__init__(sexp)
        else:
            raise TypeError(
                'The constructor must be called '
                'with that is an instance of rpy2.rinterface.sexp.Sexp '
                'or an instance of rpy2.rinterface._rinterface.SexpCapsule')

    def __str__(self) -> str:
        return conversion._cchar_to_str(
            openrlib._STRING_VALUE(
                self._sexpobject._cdata
            ), 'utf-8'
        )


class _MissingArgType(SexpSymbol, metaclass=sexp.SingletonABC):
    """Missing argument in a call to an R function.

    When evaluating a function, arguments that are not specified
    can take a default value when named, otherwise they will
    take a special value that indicates that they are missing."""

    def __init__(self):
        if embedded.isready():
            tmp = sexp.Sexp(
                _rinterface.UnmanagedSexpCapsule(
                    openrlib.rlib.R_MissingArg
                )
            )
        else:
            tmp = sexp.Sexp(
                _rinterface.UninitializedRCapsule(RTYPES.SYMSXP.value)
            )
        super().__init__(tmp)

    def __bool__(self) -> bool:
        """This is always False."""
        return False

    @property
    def __sexp__(self) -> typing.Union['_rinterface.SexpCapsule',
                                       '_rinterface.UninitializedRCapsule']:
        return self._sexpobject

    @__sexp__.setter
    def __sexp__(self, value: typing.Union['_rinterface.SexpCapsule',
                                           '_rinterface.UninitializedRCapsule']) -> None:
        raise TypeError('The capsule for the R object cannot be modified.')


MissingArg = _MissingArgType()


class SexpPromise(Sexp):

    @_cdata_res_to_rinterface
    def eval(self, env: typing.Optional[SexpEnvironment] = None) -> sexp.Sexp:
        """"Evalute the R "promise".

        :param env: The environment in which to evaluate the
          promise.
        """
        if env is None:
            env = globalenv
        return openrlib.rlib.Rf_eval(self.__sexp__._cdata, env)


class SexpVectorWithNumpyInterface(SexpVector):
    """Numpy-specific API for accessing the content of a numpy array.

    This interface implements version 3 of Numpy's `__array_interface__`
    and is only available / possible for some of the R vectors."""

    @property
    @abc.abstractmethod
    def _NP_TYPESTR(self) -> str:
        pass

    @property
    def __array_interface__(
            self
    ) -> dict:
        """Return an `__array_interface__` version 3.

        Note that the pointer returned in the items 'data' corresponds to
        a memory area under R's memory management and that it will become
        invalid once the area once R frees the object. It is safer to keep
        the rpy2 object proxying the R object alive for the duration the
        pointer is used in Python / numpy."""
        shape = bufferprotocol.getshape(self.__sexp__._cdata)
        data = openrlib.ffi.buffer(self._R_GET_PTR(self.__sexp__._cdata))
        strides = bufferprotocol.getstrides(self.__sexp__._cdata,
                                            shape,
                                            self._R_SIZEOF_ELT)
        return {'shape': shape,
                'typestr': self._NP_TYPESTR,
                'strides': strides,
                'data': data,
                'version': 3}

    @classmethod
    def _check_C_compatible(cls, mview):
        return (
            mview.itemsize == cls._R_SIZEOF_ELT
            and
            (
                cls._NP_TYPESTR == '|u1'
                or
                cls._NP_TYPESTR.endswith(mview.format)
            )
        )


class ByteSexpVector(SexpVectorWithNumpyInterface):
    """Array of bytes.

    This is the R equivalent to a Python :class:`bytesarray`.
    """

    _R_TYPE = openrlib.rlib.RAWSXP
    _R_SIZEOF_ELT = _rinterface.ffi.sizeof('char')
    _NP_TYPESTR = '|u1'

    _R_GET_PTR = staticmethod(openrlib.RAW)

    @staticmethod
    def _CAST_IN(x: typing.Any) -> int:
        if isinstance(x, int):
            if x > 255:
                raise ValueError('byte must be in range(0, 256)')
            res = x
        elif isinstance(x, (bytes, bytearray)):
            if len(x) != 1:
                raise ValueError('byte must be a single character')
            res = ord(x)
        else:
            raise ValueError('byte must be an integer [0, 255] or a '
                             'single byte character')
        return res

    @staticmethod
    def _R_VECTOR_ELT(x, i: int) -> None:
        return openrlib.RAW(x)[i]

    @staticmethod
    def _R_SET_VECTOR_ELT(x, i: int, val) -> None:
        openrlib.RAW(x)[i] = val

    def __getitem__(self,
                    i: Union[int, slice]) -> Union[int, 'ByteSexpVector']:

        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            res = openrlib.RAW_ELT(cdata, i_c)
        elif isinstance(i, slice):
            res = type(self).from_iterable(
                [openrlib.RAW_ELT(
                    cdata, i_c
                ) for i_c in range(*i.indices(len(self)))
                ]
            )
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))
        return res

    def __setitem__(self, i: Union[int, slice], value) -> None:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            openrlib.RAW(cdata)[i_c] = self._CAST_IN(value)
        elif isinstance(i, slice):
            for i_c, v in zip(range(*i.indices(len(self))), value):
                if v > 255:
                    raise ValueError('byte must be in range(0, 256)')
                openrlib.RAW(cdata)[i_c] = self._CAST_IN(v)
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))


class BoolSexpVector(SexpVectorWithNumpyInterface):
    """Array of booleans.

    Note that R is internally storing booleans as integers to
    allow an additional "NA" value to represent missingness."""

    _R_TYPE = openrlib.rlib.LGLSXP
    _R_SIZEOF_ELT = _rinterface.ffi.sizeof('Rboolean')
    _NP_TYPESTR = '|i'
    _R_VECTOR_ELT = openrlib.LOGICAL_ELT
    _R_SET_VECTOR_ELT = openrlib.SET_LOGICAL_ELT
    _R_GET_PTR = staticmethod(openrlib.LOGICAL)

    @staticmethod
    def _CAST_IN(x):
        if x is None or x == openrlib.rlib.R_NaInt:
            return NA_Logical
        else:
            return bool(x)

    def __getitem__(self, i: Union[int, slice]) -> Union[bool,
                                                         'sexp.NALogicalType',
                                                         'BoolSexpVector']:
        res: Union[bool,
                   'sexp.NALogicalType',
                   'BoolSexpVector']
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            elt = openrlib.LOGICAL_ELT(cdata, i_c)
            res = (na_values.NA_Logical  # type: ignore
                   if elt == NA_Logical else bool(elt))
        elif isinstance(i, slice):
            res = type(self).from_iterable(
                [openrlib.LOGICAL_ELT(cdata, i_c)
                 for i_c in range(*i.indices(len(self)))]
            )
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))
        return res

    def __setitem__(self, i: Union[int, slice], value) -> None:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            openrlib.SET_LOGICAL_ELT(cdata, i_c,
                                     int(value))
        elif isinstance(i, slice):
            for i_c, v in zip(range(*i.indices(len(self))), value):
                openrlib.SET_LOGICAL_ELT(cdata, i_c,
                                         int(v))
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))

    def memoryview(self) -> memoryview:
        return vector_memoryview(self, 'int', 'i')


def nullable_int(v):
    if type(v) is float and math.isnan(v):
        return openrlib.rlib.R_NaInt
    else:
        return int(v)


class IntSexpVector(SexpVectorWithNumpyInterface):

    _R_TYPE = openrlib.rlib.INTSXP
    _R_SET_VECTOR_ELT = openrlib.SET_INTEGER_ELT
    _R_VECTOR_ELT = openrlib.INTEGER_ELT
    _R_SIZEOF_ELT = _rinterface.ffi.sizeof('int')
    _NP_TYPESTR = '|i'

    _R_GET_PTR = staticmethod(openrlib.INTEGER)
    _CAST_IN = staticmethod(nullable_int)

    def __getitem__(self, i: Union[int, slice]) -> Union[int, 'IntSexpVector']:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            res = openrlib.INTEGER_ELT(cdata, i_c)
            if res == NA_Integer:
                res = NA_Integer
        elif isinstance(i, slice):
            res = type(self).from_iterable(
                [openrlib.INTEGER_ELT(
                    cdata, i_c
                ) for i_c in range(*i.indices(len(self)))]
            )
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))
        return res

    def __setitem__(self, i: Union[int, slice], value) -> None:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            openrlib.SET_INTEGER_ELT(cdata, i_c,
                                     int(value))
        elif isinstance(i, slice):
            for i_c, v in zip(range(*i.indices(len(self))), value):
                openrlib.SET_INTEGER_ELT(cdata, i_c,
                                         int(v))
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))

    def memoryview(self) -> memoryview:
        return vector_memoryview(self, 'int', 'i')


class FloatSexpVector(SexpVectorWithNumpyInterface):

    _R_TYPE = openrlib.rlib.REALSXP
    _R_VECTOR_ELT = openrlib.REAL_ELT
    _R_SET_VECTOR_ELT = openrlib.SET_REAL_ELT
    _R_SIZEOF_ELT = _rinterface.ffi.sizeof('double')
    _NP_TYPESTR = '|d'

    _CAST_IN = staticmethod(float)
    _R_GET_PTR = staticmethod(openrlib.REAL)

    def __getitem__(
            self, i: Union[int, slice]
    ) -> Union[float, 'FloatSexpVector']:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            res = openrlib.REAL_ELT(cdata, i_c)
        elif isinstance(i, slice):
            res = type(self).from_iterable(
                [openrlib.REAL_ELT(
                    cdata, i_c) for i_c in range(*i.indices(len(self)))]
            )
        else:
            raise TypeError('Indices must be integers or slices, not %s' %
                            type(i))
        return res

    def __setitem__(self, i: Union[int, slice], value) -> None:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            openrlib.SET_REAL_ELT(cdata, i_c,
                                  float(value))
        elif isinstance(i, slice):
            for i_c, v in zip(range(*i.indices(len(self))), value):
                openrlib.SET_REAL_ELT(cdata, i_c,
                                      float(v))
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))

    def memoryview(self) -> memoryview:
        return vector_memoryview(self, 'double', 'd')


class ComplexSexpVector(SexpVector):

    _R_TYPE = openrlib.rlib.CPLXSXP
    _R_GET_PTR = staticmethod(openrlib.COMPLEX)
    _R_SIZEOF_ELT = _rinterface.ffi.sizeof('Rcomplex')

    @staticmethod
    def _R_VECTOR_ELT(x, i):
        return openrlib.COMPLEX(x)[i]

    @staticmethod
    def _R_SET_VECTOR_ELT(x, i, v):
        openrlib.COMPLEX(x).__setitem__(i, v)

    @staticmethod
    def _CAST_IN(x):
        if isinstance(x, complex):
            res = (x.real, x.imag)
        else:
            try:
                res = (x.r, x.i)
            except AttributeError:
                raise TypeError(
                    'Unable to turn value into an R complex number.'
                )
        return res

    def __getitem__(
            self, i: Union[int, slice]
    ) -> Union[complex, 'ComplexSexpVector']:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            _ = openrlib.COMPLEX_ELT(cdata, i_c)
            res = complex(_.r, _.i)
        elif isinstance(i, slice):
            res = type(self).from_iterable(
                [openrlib.COMPLEX_ELT(
                    cdata, i_c) for i_c in range(*i.indices(len(self)))]
            )
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))
        return res

    def __setitem__(self, i: Union[int, slice], value) -> None:
        cdata = self.__sexp__._cdata
        if isinstance(i, int):
            i_c = _rinterface._python_index_to_c(cdata, i)
            openrlib.COMPLEX(cdata)[i_c] = self._CAST_IN(value)
        elif isinstance(i, slice):
            for i_c, v in zip(range(*i.indices(len(self))), value):
                openrlib.COMPLEX(cdata)[i_c] = self._CAST_IN(v)
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))


class ListSexpVector(SexpVector):
    """R list.

    An R list an R vector (array) that is similar to a Python list in
    the sense that items in the list can be of any type, whereas most
    other R vectors are homogeneous (all items are of the same type).
    """
    _R_TYPE = openrlib.rlib.VECSXP
    _R_GET_PTR = staticmethod(openrlib._VECTOR_PTR)
    _R_SIZEOF_ELT = None
    _R_VECTOR_ELT = openrlib.rlib.VECTOR_ELT
    _R_SET_VECTOR_ELT = openrlib.rlib.SET_VECTOR_ELT
    _CAST_IN = staticmethod(conversion._get_cdata)


class PairlistSexpVector(SexpVector):
    """R pairlist.

    A R pairlist is rarely used outside of R's internal libraries and
    a relatively small number of use cases. It is essentially a LISP-like
    list of (name, value) pairs.
    """
    _R_TYPE = openrlib.rlib.LISTSXP
    _R_GET_PTR = None
    _R_SIZEOF_ELT = None
    _R_VECTOR_ELT = None
    _R_SET_VECTOR_ELT = None
    _CAST_IN = staticmethod(conversion._get_cdata)

    def __getitem__(self, i: Union[int, slice]) -> Sexp:
        cdata = self.__sexp__._cdata
        rlib = openrlib.rlib
        if isinstance(i, int):
            # R-exts says that it is converted to a VECSXP when subsetted.
            i_c = _rinterface._python_index_to_c(cdata, i)
            item_cdata = rlib.Rf_nthcdr(cdata, i_c)
            with memorymanagement.rmemory() as rmemory:
                res_cdata = rmemory.protect(
                    rlib.Rf_allocVector(RTYPES.VECSXP, 1))
                rlib.SET_VECTOR_ELT(
                    res_cdata,
                    0,
                    rlib.CAR(
                        item_cdata
                    ))
                res_name = rmemory.protect(
                    rlib.Rf_allocVector(RTYPES.STRSXP, 1))
                item_cdata_name = rlib.PRINTNAME(rlib.TAG(item_cdata))
                if _rinterface._TYPEOF(item_cdata_name) != rlib.NILSXP:
                    rlib.SET_STRING_ELT(
                        res_name,
                        0,
                        item_cdata_name)
                    rlib.Rf_namesgets(res_cdata, res_name)
                res = conversion._cdata_to_rinterface(res_cdata)
        elif isinstance(i, slice):
            iter_indices = range(*i.indices(len(self)))
            n = len(iter_indices)
            with memorymanagement.rmemory() as rmemory:
                res_cdata = rmemory.protect(
                    rlib.Rf_allocVector(
                        self._R_TYPE, n)
                )
                iter_res_cdata = res_cdata
                prev_i = 0
                lst_cdata = self.__sexp__._cdata
                for i in iter_indices:
                    if i >= len(self):
                        raise IndexError('index out of range')
                    lst_cdata = rlib.Rf_nthcdr(lst_cdata, i - prev_i)
                    prev_i = i
                    rlib.SETCAR(iter_res_cdata,
                                rlib.CAR(lst_cdata))
                    rlib.SET_TAG(iter_res_cdata,
                                 rlib.TAG(lst_cdata))
                    iter_res_cdata = rlib.CDR(iter_res_cdata)
                res = conversion._cdata_to_rinterface(res_cdata)
        else:
            raise TypeError(
                'Indices must be integers or slices, not %s' % type(i))
        return res

    @classmethod
    @_cdata_res_to_rinterface
    def from_iterable(cls, iterable, cast_in=None):
        raise NotImplementedError()


class ExprSexpVector(SexpVector):
    _R_TYPE = openrlib.rlib.EXPRSXP
    _R_GET_PTR = None
    _CAST_IN = None
    _R_SIZEOF_ELT = None
    _R_VECTOR_ELT = openrlib.rlib.VECTOR_ELT
    _R_SET_VECTOR_ELT = None


_str2lang = None


def _get_str2lang():
    global _str2lang
    if _str2lang is None:
        try:
            _str2lang = baseenv['str2lang']
        except KeyError:
            # TODO: This exists to ensure compatibility with
            # older versions of R. If should be removed when
            # older versions of R are no longer supported.
            _str2lang = evalr('function(s) '
                              'base::parse(text=s, keep.source=FALSE)[[1]]')
    return _str2lang


LangSexpVector_VT = typing.TypeVar('LangSexpVector_VT', bound='LangSexpVector')


class LangSexpVector(SexpVector):
    """An R language object.

    To create from a (Python) string containing R code
    use the classmethod `from_string`."""
    _R_TYPE = openrlib.rlib.LANGSXP
    _R_GET_PTR = None
    _CAST_IN = None
    _R_SIZEOF_ELT = None
    _R_VECTOR_ELT = None
    _R_SET_VECTOR_ELT = None

    @_cdata_res_to_rinterface
    def __getitem__(self, i: int):
        cdata = self.__sexp__._cdata
        i_c = _rinterface._python_index_to_c(cdata, i)
        return openrlib.rlib.CAR(
            openrlib.rlib.Rf_nthcdr(cdata, i_c)
        )

    def __setitem__(self, i: typing.Union[int, slice],
                    value: sexp.SupportsSEXP) -> None:
        if isinstance(i, slice):
            raise NotImplementedError(
                'Assigning slices to LangSexpVectors is not yet implemented.'
            )
        cdata = self.__sexp__._cdata
        i_c = _rinterface._python_index_to_c(cdata, i)
        openrlib.rlib.SETCAR(
            openrlib.rlib.Rf_nthcdr(cdata, i_c),
            value.__sexp__._cdata
        )

    @classmethod
    def from_string(
            cls: typing.Type[LangSexpVector_VT], s: str
    ) -> LangSexpVector_VT:
        """Create an R language object from a string.

        This creates an unevaluated R language object.

        Args:
            s: R source code in a string.

        Returns:
            An instance of the class the method is called from.
        """
        return cls(_get_str2lang()(s))


class SexpClosure(Sexp):

    @_cdata_res_to_rinterface
    def __call__(self, *args, **kwargs) -> Sexp:
        error_occured = _rinterface.ffi.new('int *', 0)
        with memorymanagement.rmemory() as rmemory:
            call_r = rmemory.protect(
                _rinterface.build_rcall(self.__sexp__._cdata, args,
                                        kwargs.items()))
            call_context = evaluation_context.get()
            res = rmemory.protect(
                openrlib.rlib.R_tryEval(
                    call_r,
                    call_context.__sexp__._cdata,
                    error_occured)
            )
            if error_occured[0]:
                raise embedded.RRuntimeError(_rinterface._geterrmessage())
        return res

    @_cdata_res_to_rinterface
    def rcall(self, keyvals,
              environment: typing.Optional[SexpEnvironment] = None):
        """Call/evaluate an R function.

        Args:
        - keyvals: a sequence of key/value (name/parameter) pairs. A
          name/parameter that is None will indicated an unnamed parameter.
          Like in R, keys/names do not have to be unique, partial matching
          can be used, and named/unnamed parameters can occur at any position
          in the sequence.
        - environment: an optional R environment to evaluate the function.
        """
        # TODO: check keyvals are pairs ?
        if environment is None:
            environment = evaluation_context.get()
        assert isinstance(environment, SexpEnvironment)
        error_occured = _rinterface.ffi.new('int *', 0)

        with memorymanagement.rmemory() as rmemory:
            call_r = rmemory.protect(
                _rinterface.build_rcall(self.__sexp__._cdata, [],
                                        keyvals))
            res = rmemory.protect(
                openrlib.rlib.R_tryEval(call_r,
                                        environment.__sexp__._cdata,
                                        error_occured))
            if error_occured[0]:
                raise embedded.RRuntimeError(_rinterface._geterrmessage())
        return res

    @property  # type: ignore
    @_cdata_res_to_rinterface
    def closureenv(self) -> SexpEnvironment:
        """Closure of the R function."""
        return openrlib.rlib.CLOENV(self.__sexp__._cdata)


class SexpS4(Sexp):
    """R "S4" object.

    S4 objects as one of the available forms of Object-Oriented Programming
    in R."""
    pass


# TODO: clean up
def make_extptr(obj, tag, protected):
    if protected is None:
        cdata_protected = openrlib.rlib.R_NilValue
    else:
        try:
            cdata_protected = protected.__sexp__._cdata
        except AttributeError:
            raise TypeError('Argument protected must inherit from %s' %
                            type(Sexp))

    ptr = _rinterface.ffi.new_handle(obj)
    with memorymanagement.rmemory() as rmemory:
        cdata = rmemory.protect(
            openrlib.rlib.R_MakeExternalPtr(
                ptr,
                tag,
                cdata_protected))
        openrlib.rlib.R_RegisterCFinalizer(
            cdata,
            (_rinterface._capsule_finalizer_c
             if _rinterface._capsule_finalizer_c
             else _rinterface._capsule_finalizer))
        res = _rinterface.SexpCapsuleWithPassenger(cdata, obj, ptr)
    return res


class SexpExtPtr(Sexp):
    """R "External Pointer" object."""
    TYPE_TAG = 'Python'

    @classmethod
    def from_pyobject(cls, func, tag: str = TYPE_TAG,
                      protected=None):
        if not isinstance(tag, str):
            raise TypeError('The tag must be a string.')
        scaps = make_extptr(func,
                            conversion._str_to_charsxp(cls.TYPE_TAG),
                            protected)
        res = cls(scaps)
        if tag != cls.TYPE_TAG:
            res.TYPE_TAG = tag
        return res


# TODO: Only use rinterface-level ?
conversion._R_RPY2_MAP.update({
    openrlib.rlib.NILSXP: NULLType,
    openrlib.rlib.EXPRSXP: ExprSexpVector,
    openrlib.rlib.LANGSXP: LangSexpVector,
    openrlib.rlib.ENVSXP: SexpEnvironment,
    openrlib.rlib.RAWSXP: ByteSexpVector,
    openrlib.rlib.LGLSXP: BoolSexpVector,
    openrlib.rlib.INTSXP: IntSexpVector,
    openrlib.rlib.REALSXP: FloatSexpVector,
    openrlib.rlib.CPLXSXP: ComplexSexpVector,
    openrlib.rlib.STRSXP: StrSexpVector,
    openrlib.rlib.VECSXP: ListSexpVector,
    openrlib.rlib.LISTSXP: PairlistSexpVector,
    openrlib.rlib.CLOSXP: SexpClosure,
    openrlib.rlib.BUILTINSXP: SexpClosure,
    openrlib.rlib.SPECIALSXP: SexpClosure,
    openrlib.rlib.EXTPTRSXP: SexpExtPtr,
    openrlib.rlib.SYMSXP: SexpSymbol,
    openrlib.rlib.S4SXP: SexpS4
    })
conversion._R_RPY2_DEFAULT_MAP = Sexp

conversion._PY_RPY2_MAP.update({
    int: conversion._int_to_sexp,
    float: conversion._float_to_sexp,
    complex: conversion._complex_to_sexp
    })

conversion._PY_R_MAP.update({
    _rinterface.ffi.CData: False,
    # integer
    int: conversion._int_to_sexp,
    sexp.NAIntegerType: conversion._int_to_sexp,
    # float
    float: conversion._float_to_sexp,
    sexp.NARealType: conversion._float_to_sexp,
    # boolean
    bool: conversion._bool_to_sexp,
    sexp.NALogicalType: conversion._bool_to_sexp,
    # string
    str: conversion._str_to_sexp,
    sexp.CharSexp: None,
    sexp.NACharacterType: None,
    # complex
    complex: conversion._complex_to_sexp,
    sexp.NAComplexType: conversion._complex_to_sexp,
    # None
    type(None): lambda x: openrlib.rlib.R_NilValue})


def vector(iterable, rtype: RTYPES) -> SexpVector:
    """Create an R vector.

    While the different types of R vectors all have their own class,
    the creation of array in Python is often available through factory
    function that accept the type of the array as a parameters. This
    function is providing a similar functionality for R vectors."""
    error = False
    try:
        cls = conversion._R_RPY2_MAP[rtype]
    except KeyError:
        error = True
    if not error and not issubclass(cls, SexpVector):
        error = True
    if error:
        raise ValueError(
            'Unable to build a vector from type "%s"' % RTYPES(rtype))
    return cls.from_iterable(iterable)


class RRuntimeWarning(RuntimeWarning):
    pass


MissingArg = _MissingArgType()
NA_Character = None
NA_Integer = None
NA_Logical = None
NA = None
NA_Real = None
NA_Complex = None


def initr_simple() -> typing.Optional[int]:
    """Initialize R's embedded C library."""
    with openrlib.rlock:
        status = embedded._initr()
        atexit.register(endr, 0)
        _rinterface._register_external_symbols()
        _post_initr_setup()
        return status


def initr_checkenv(
        interactive: typing.Optional[bool] = None,
        _want_setcallbacks: bool = True,
        _c_stack_limit: typing.Optional[int] = None
) -> typing.Optional[int]:
    """Initialize the embedded R.

    :param interactive: Should R run in interactive or non-interactive mode?
    if `None` the value in `_DEFAULT_R_INTERACTIVE` will be used.
    :param _want_setcallbacks: Should custom rpy2 callbacks for R frontends
    be set?.
    :param _c_stack_limit: Limit for the C Stack.
    if `None` the value in `_DEFAULT_C_STACK_LIMIT` will be used.
    """

    # Force the internal initialization flag if there is an environment
    # variable that indicates that R was already initialized in the current
    # process.

    status = None
    with openrlib.rlock:
        if embedded.is_r_externally_initialized():
            embedded._setinitialized()
        else:
            status = embedded._initr(interactive=interactive,
                                     _want_setcallbacks=_want_setcallbacks,
                                     _c_stack_limit=_c_stack_limit)
            embedded.set_python_process_info()
        _rinterface._register_external_symbols()
        _post_initr_setup()
    return status


initr = initr_checkenv


def _update_R_ENC_PY():
    conversion._R_ENC_PY[openrlib.rlib.CE_UTF8] = 'utf-8'

    l10n_info = tuple(baseenv['l10n_info']())
    if platform.system() == 'Windows':
        val_latin1 = 'cp{:d}'.format(l10n_info[3][0])
    else:
        val_latin1 = 'latin1'
    conversion._R_ENC_PY[openrlib.rlib.CE_LATIN1] = val_latin1

    if l10n_info[1]:
        val_native = conversion._R_ENC_PY[openrlib.rlib.CE_UTF8]
    else:
        val_native = val_latin1
    conversion._R_ENC_PY[openrlib.rlib.CE_NATIVE] = val_native

    conversion._R_ENC_PY[openrlib.rlib.CE_ANY] = 'utf-8'


def _post_initr_setup() -> None:

    emptyenv.__sexp__ = _rinterface.SexpCapsule(openrlib.rlib.R_EmptyEnv)
    baseenv.__sexp__ = _rinterface.SexpCapsule(openrlib.rlib.R_BaseEnv)
    globalenv.__sexp__ = _rinterface.SexpCapsule(openrlib.rlib.R_GlobalEnv)
    NULL._sexpobject = _rinterface.UnmanagedSexpCapsule(
        openrlib.rlib.R_NilValue
    )

    MissingArg._sexpobject = _rinterface.UnmanagedSexpCapsule(
        openrlib.rlib.R_MissingArg
    )

    global NA_Character
    na_values.NA_Character = sexp.NACharacterType()
    NA_Character = na_values.NA_Character

    global NA_Integer
    na_values.NA_Integer = sexp.NAIntegerType(openrlib.rlib.R_NaInt)
    NA_Integer = na_values.NA_Integer

    global NA_Logical, NA
    na_values.NA_Logical = sexp.NALogicalType(openrlib.rlib.R_NaInt)
    NA_Logical = na_values.NA_Logical
    NA = NA_Logical

    global NA_Real
    na_values.NA_Real = sexp.NARealType(openrlib.rlib.R_NaReal)
    NA_Real = na_values.NA_Real

    global NA_Complex
    na_values.NA_Complex = sexp.NAComplexType(
        _rinterface.ffi.new(
            'Rcomplex *',
            [openrlib.rlib.R_NaReal, openrlib.rlib.R_NaReal])
    )
    NA_Complex = na_values.NA_Complex

    warn_about_thread = False
    if threading.current_thread() is threading.main_thread():
        try:
            signal.signal(signal.SIGINT, _sigint_handler)
        except ValueError as ve:
            if str(ve) == 'signal only works in main thread':
                warn_about_thread = True
            else:
                raise ve
    else:
        warn_about_thread = True
    if warn_about_thread:
        warnings.warn(
            textwrap.dedent(
                """R is not initialized by the main thread.
                Its taking over SIGINT cannot be reversed here, and as a
                consequence the embedded R cannot be interrupted with Ctrl-C.
                Consider (re)setting the signal handler of your choice from
                the main thread."""
            )
        )

    _update_R_ENC_PY()


def _find_first(nodes, of_type):
    for node in nodes:
        if isinstance(node, of_type):
            return node
    raise ValueError(
        f'No node of type {of_type}'
    )


def rternalize(
        function: typing.Optional[typing.Callable] = None, *,
        signature: bool = False
) -> typing.Union[SexpClosure, functools.partial]:
    """ Make a Python function callable from R.

    Takes an arbitrary Python function and wrap it in such a way that
    it can be called from the R side.

    This factory can be used as a decorator, and has an optional
    named argument "signature" that can be True or False (default is
    False). When True, the R function wrapping the Python one will
    have a matching signature or a close one, as detailed below.

    The Python ellipsis arguments`*args` and `**kwargs` are
    translated to the R ellipsis `...`.

    For example:

    .. code-block:: python
       @rternalize(signature=True)
       def foo(x, *args, y=2):
           pass

    will be visible in R with the signature:

    .. code-block:: r
       function (x, ..., y)

    The only limitation is that whenever `*args` and `**kwargs` are
    both present in the Python declaration they must be consecutive.
    For example:

    .. code-block:: python
       def foo(x, *args, y=2, **kwargs):
           pass

    is a valid Python declaration. However, it cannot be "rternalized"
    because the R ellipsis can only appear at most once in the signature
    of a given function. Trying to apply the decorator `rternalize` would
    raise an exception.

    The following Python function can be "rternalized":

    .. code-block:: python
       def foo(x, *args, **kwargs):
           pass

    It is visible to R with the signature

    .. code-block:: r
       function (x, ...)

    Python function definitions can allow the optional naming of required
    arguments. The mapping of signatures between Python and R is then
    quasi-indentical since R does it for unnamed arguments. The check
    that all arguments are present is still performed on the Python side.

    Example:

    .. code-block:: python
       @rternalize(signature=True)
       def foo(x, *, y, z):
           print(f'x: {x[0]}, y: {y[0]}, z: {z[0]}')
           return ri.NULL

    >>> _ = foo(1, 2, 3)
    x: 1, y: 2, z: 3
    ValueErro: None
    >>> _ = foo(1)
    TypeError: rternalized foo() missing 2 required keyword-only arguments: 'y' and 'z'
    >>> _ = foo(1, z=2, y=3)
    x: 1, y: 3, z: 2
    >>> _ = foo(1, z=2, y=3)
    x: 1, y: 3, z: 2

    Note that whenever the Python function has an ellipsis (either `*args`
    or `**kwargs`) earlier parameters in the signature that are
    positional-or-keyword are considered to be positional arguments in a
    function call.

    :param function: A Python callable object. This is a positional
    argument with a default value `None` to allow the decorator function
    without parentheses when optional argument is not wanted.

    :return: A wrapped R object that can be use like any other rpy2
    object.
    """
    if not embedded.isinitialized():
        raise embedded.RNotReadyError('The embedded R is not yet initialized.')

    if function is None:
        return functools.partial(rternalize, signature=signature)

    assert callable(function)
    rpy_fun = SexpExtPtr.from_pyobject(function)

    if not signature:
        template = parse("""
        function(...) { .External(".Python", foo, ...);
        }
        """)
        template[0][2][1][2] = rpy_fun
    else:
        has_ellipsis = None
        params_r_sig = []
        for p_i, (name, param) in enumerate(
                inspect.signature(function).parameters.items()
        ):
            if (
                    param.kind is inspect.Parameter.VAR_POSITIONAL or
                    param.kind is inspect.Parameter.VAR_KEYWORD
            ):
                if has_ellipsis:
                    if has_ellipsis != (p_i - 1):
                        raise ValueError(
                            'R functions can only have one ellipsis. '
                            'As consequence your Python function must have *args '
                            'and **kwargs that are consecutive in function '
                            'signature.'
                        )
                else:
                    # The ellipsis can only be added once.
                    has_ellipsis = p_i
                    params_r_sig.append('...')
            else:
                params_r_sig.append(name)

        r_func_args = ', '.join(params_r_sig)

        r_src = f"""
        function({r_func_args}) {{
            py_func <- RPY2_FUN_PLACEHOLDER
            lst_args <- base::as.list(base::match.call()[-1])
            RPY2_ARGUMENTS <- base::c(
                base::list(
                    ".Python",
                    py_func
                ),
                lst_args
            )
            res <- base::do.call(
               base::.External,
               RPY2_ARGUMENTS
            );

            res
        }}
        """
        template = parse(r_src)

        function_definition = _find_first(template, of_type=LangSexpVector)
        function_body = _find_first(function_definition, of_type=LangSexpVector)
        rpy_fun_node = function_body[1]

        assert str(rpy_fun_node[2]) == 'RPY2_FUN_PLACEHOLDER'
        rpy_fun_node[2] = rpy_fun

    # TODO: use lower-level eval ?
    res = baseenv['eval'](template)
    # TODO: hack to prevent the nested function from having its
    #   refcount down to zero when returning
    res.__nested_sexp__ = rpy_fun.__sexp__
    return res


def process_revents() -> None:
    """Process R events.

    Calling this function a regular interval can help ensure that
    R is processing input events (e.g., resizing of a window with
    graphics)."""
    openrlib.rlib.rpy2_runHandlers(openrlib.rlib.R_InputHandlers)
