#include <torch/csrc/autograd/python_legacy_variable.h>

#include <ATen/ATen.h>

#include <torch/csrc/Exceptions.h>
#include <torch/csrc/autograd/python_function.h>
#include <torch/csrc/autograd/python_variable.h>
#include <torch/csrc/jit/frontend/tracer.h>
#include <torch/csrc/tensor/python_tensor.h>

using namespace at;

namespace torch {
namespace autograd {

static PyObject* THPVariable_pynew(
    PyTypeObject* type,
    PyObject* args,
    PyObject* kwds) {
  HANDLE_TH_ERRORS
  THPObjectPtr _data;
  PyObject* data = nullptr;
  PyObject* grad_fn = nullptr;
  char is_volatile = 0;
  char requires_grad = 0;
  const char* name = nullptr;

  // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,modernize-avoid-c-arrays)
  constexpr const char* accepted_args[] = {
      "data", "requires_grad", "volatile", "_grad_fn", "name", nullptr};
  if (!PyArg_ParseTupleAndKeywords(
          args,
          kwds,
          "|ObbOz",
          const_cast<char**>(accepted_args),
          &data,
          &requires_grad,
          &is_volatile,
          &grad_fn,
          &name))
    return nullptr;

  if (grad_fn == Py_None)
    grad_fn = nullptr;

  if (is_volatile) {
    auto r = PyErr_WarnEx(
        PyExc_UserWarning,
        "volatile was removed and now has no effect. Use `with torch.no_grad():` "
        "instead.",
        1);
    if (r != 0)
      throw python_error();
  }

  if (is_volatile && requires_grad) {
    throw ValueError(
        "Variable can't be volatile and require_grad at the same time!");
  }
  if (grad_fn && !THPFunction_Check(grad_fn)) {
    throw TypeError(
        "_grad_fn has to be a Function object or None, but got %s",
        Py_TYPE(grad_fn)->tp_name);
  }
  Variable var;
  if (!data || data == Py_None) {
    // For legacy serialization code, create an empty tensor. This is also used
    // by nn.Parameter() with no arguments.
    auto dispatch_key = torch::tensors::get_default_dispatch_key();
    auto scalar_type = torch::tensors::get_default_scalar_type();
    auto options = TensorOptions(scalar_type)
                       .device(dispatchKeyToDeviceType(dispatch_key))
                       .layout(dispatchKeyToLayout(dispatch_key));
    var = at::empty({0}, options);
  } else if (THPVariable_Check(data)) {
    var = THPVariable_Unpack(data).detach();
  } else {
    throw torch::TypeError(
        "Variable data has to be a tensor, but got %s", Py_TYPE(data)->tp_name);
  }
  // We set `tensor`'s `allow_tensor_metadata_change` to true here, because we
  // want to allow the following use case for backward compatibility:
  //
  // ```python
  // var = Variable(torch.randn(2, 3))
  // var.resize_(4, 5)
  // ```
  var.unsafeGetTensorImpl()->set_allow_tensor_metadata_change(true);

  TORCH_CHECK(
      !grad_fn,
      "_grad_fn argument to legacy Variable constructor is no longer supported.  "
      "Instead, please invoke your _grad_fn to produce a variable with it as the "
      "_grad_fn.");
  var.set_requires_grad(requires_grad);

  if (name) {
    impl::set_name(var, name);
  }

  if (jit::tracer::isTracing() && data && data != Py_None &&
      THPVariable_Check(data)) {
    if (auto* v = jit::tracer::getValueTrace(THPVariable_Unpack(data))) {
      jit::tracer::setValueTrace(var, v);
    }
  }

  return THPVariable_Wrap(std::move(var));
  END_HANDLE_TH_ERRORS
}

PyTypeObject THPLegacyVariableType = {
    PyVarObject_HEAD_INIT(
        nullptr,
        0) "torch._C._LegacyVariableBase", /* tp_name */
    0, /* tp_basicsize */
    0, /* tp_itemsize */
    nullptr, /* tp_dealloc */
    0, /* tp_vectorcall_offset */
    nullptr, /* tp_getattr */
    nullptr, /* tp_setattr */
    nullptr, /* tp_reserved */
    nullptr, /* tp_repr */
    nullptr, /* tp_as_number */
    nullptr, /* tp_as_sequence */
    nullptr, /* tp_as_mapping */
    nullptr, /* tp_hash  */
    nullptr, /* tp_call */
    nullptr, /* tp_str */
    nullptr, /* tp_getattro */
    nullptr, /* tp_setattro */
    nullptr, /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
    nullptr, /* tp_doc */
    nullptr, /* tp_traverse */
    nullptr, /* tp_clear */
    nullptr, /* tp_richcompare */
    0, /* tp_weaklistoffset */
    nullptr, /* tp_iter */
    nullptr, /* tp_iternext */
    nullptr, /* tp_methods */
    nullptr, /* tp_members */
    nullptr, /* tp_getset */
    nullptr, /* tp_base */
    nullptr, /* tp_dict */
    nullptr, /* tp_descr_get */
    nullptr, /* tp_descr_set */
    0, /* tp_dictoffset */
    nullptr, /* tp_init */
    nullptr, /* tp_alloc */
    THPVariable_pynew /* tp_new */
};

void init_legacy_variable(PyObject* module) {
  if (PyType_Ready(&THPLegacyVariableType) < 0) {
    throw python_error();
  }
  auto obj = (PyObject*)&THPLegacyVariableType;
  Py_INCREF(obj);
  if (PyModule_AddObject(module, "_LegacyVariableBase", obj) < 0) {
    throw python_error();
  }
}

} // namespace autograd
} // namespace torch
