#pragma once

#include <torch/csrc/python_headers.h>

#include <ATen/ATen.h>
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>

#include <torch/csrc/DynamicTypes.h>
#include <torch/csrc/autograd/python_variable.h>
#include <torch/csrc/utils/python_tuples.h>
#include <torch/csrc/utils/python_numbers.h>

#include <stdexcept>
#include <utility>

namespace py = pybind11;

namespace pybind11 { namespace detail {

// torch.autograd.Variable <-> at::Tensor conversions (without unwrapping)
template <>
struct type_caster<at::Tensor> {
 public:
  PYBIND11_TYPE_CASTER(at::Tensor, _("at::Tensor"));

  bool load(handle src, bool) {
    PyObject* obj = src.ptr();
    if (THPVariable_Check(obj)) {
      value = reinterpret_cast<THPVariable*>(obj)->cdata;
      return true;
    }
    return false;
  }

  static handle
  cast(const at::Tensor& src, return_value_policy /* policy */, handle /* parent */) {
    if (!src.is_variable()) {
      throw std::runtime_error(
          "Expected tensor's dynamic type to be Variable, not Tensor");
    }
    return handle(THPVariable_Wrap(torch::autograd::Variable(src)));
  }
};

template<> struct type_caster<torch::autograd::Variable> {
public:
  PYBIND11_TYPE_CASTER(torch::autograd::Variable, _("torch::autograd::Variable"));
  bool load(handle src, bool) {
    PyObject *source = src.ptr();
    if (THPVariable_Check(source)) {
      value = ((THPVariable*)source)->cdata;
      return true;
    } else {
      return false;
    }
  }
  static handle cast(torch::autograd::Variable src, return_value_policy /* policy */, handle /* parent */) {
    return handle(THPVariable_Wrap(std::move(src)));
  }
};

template<> struct type_caster<at::IntArrayRef> {
public:
  PYBIND11_TYPE_CASTER(at::IntArrayRef, _("at::IntArrayRef"));

  bool load(handle src, bool) {
    PyObject *source = src.ptr();
    auto tuple = PyTuple_Check(source);
    if (tuple || PyList_Check(source)) {
      auto size = tuple ? PyTuple_GET_SIZE(source) : PyList_GET_SIZE(source);
      v_value.resize(size);
      for (int idx = 0; idx < size; idx++) {
        PyObject* obj = tuple ? PyTuple_GET_ITEM(source, idx) : PyList_GET_ITEM(source, idx);
        if (THPVariable_Check(obj)) {
          v_value[idx] = THPVariable_Unpack(obj).item<int64_t>();
        } else if (PyLong_Check(obj)) {
          // use THPUtils_unpackLong after it is safe to include python_numbers.h
          v_value[idx] = THPUtils_unpackLong(obj);
        } else {
          return false;
        }
      }
      value = v_value;
      return true;
    }
    return false;
  }
  static handle cast(at::IntArrayRef src, return_value_policy /* policy */, handle /* parent */) {
    return handle(THPUtils_packInt64Array(src.size(), src.data()));
  }
private:
  std::vector<int64_t> v_value;
};

// Pybind11 bindings for our optional type.
// http://pybind11.readthedocs.io/en/stable/advanced/cast/stl.html#c-17-library-containers
template <typename T>
struct type_caster<c10::optional<T>> : optional_caster<c10::optional<T>> {};
}} // namespace pybind11::detail