#pragma once

#include <c10/util/hash.h>
#include <c10/util/irange.h>
#include <torch/csrc/autograd/variable.h>
#include <torch/csrc/jit/python/pybind.h>

#include <ATen/ATen.h>
#include <functional>
#include <tuple>
#include <vector>

namespace torch::jit::python {

struct IODescriptor {
  struct VariableMetadata {
    VariableMetadata(const autograd::Variable& var)
        : sizes(var.sizes().vec()),
          type(var.scalar_type()),
          device(var.device()),
          requires_grad(var.requires_grad()) {}

    bool operator==(const VariableMetadata& o) const {
      return std::tie(device, requires_grad, type, sizes) ==
          std::tie(o.device, o.requires_grad, o.type, o.sizes);
    }

    static size_t hash(const VariableMetadata& m) {
      return c10::get_hash(m.sizes, m.device, m.requires_grad, m.type);
    }

    std::vector<int64_t> sizes;
    at::ScalarType type;
    at::Device device;
    bool requires_grad;
  };

  bool operator==(const IODescriptor& o) const {
    return std::tie(structure, metadata, grad_enabled) ==
        std::tie(o.structure, o.metadata, o.grad_enabled);
  }

  static size_t hash(const IODescriptor& o) {
    return c10::get_hash(o.structure, o.metadata, o.grad_enabled);
  }

  void extend(const autograd::variable_list& list) {
    metadata.reserve(metadata.size() + list.size());
    for (auto& var : list)
      metadata.emplace_back(var);
  }

  // Description of argument structure. Variables are replaced with
  // different characters, depending on their flags, beginnings and
  // ends of tuples and lists are denoted by a pair of parenthesis
  // of their corresponding kind. They should always be paired.
  // Example desc: (vv[v(v)v])
  // NOTE: if extend() was ever called then metadata.size() can be
  // different than the number of 'v's in structure.
  std::string structure;
  std::vector<std::string> strings;
  std::vector<VariableMetadata> metadata;
  bool grad_enabled = false;
};

static inline std::ostream& operator<<(
    std::ostream& out,
    const IODescriptor::VariableMetadata& meta) {
  at::Device meta_device = meta.device;
  auto& t = at::getDeprecatedTypeProperties(
      meta_device.is_cpu() ? at::Backend::CPU : at::Backend::CUDA, meta.type);
  out << t << "(requires_grad=" << meta.requires_grad;
  if (meta_device.is_cuda()) {
    out << ", device=" << meta_device.index();
  }
  out << ") {";
  for (const auto i : c10::irange(meta.sizes.size())) {
    if (i > 0)
      out << ", ";
    out << meta.sizes[i];
  }
  out << '}';
  return out;
}

static inline std::ostream& operator<<(
    std::ostream& out,
    const IODescriptor& desc) {
  out << desc.structure << '\n';
  out << "  with grad_enabled=" << desc.grad_enabled << '\n';
  for (const auto i : c10::irange(desc.metadata.size())) {
    out << "  with v" << i << " having type " << desc.metadata[i] << '\n';
  }
  return out;
}

struct ParsedArgs {
  // Flat vector of Variables found in arguments
  autograd::variable_list vars;
  // Metadata describing nesting of objects received from Python and
  // metadata of vars and whether grad is enabled.
  IODescriptor desc;

  void extend(const autograd::variable_list& list) {
    if (list.empty())
      return;
    vars.reserve(vars.size() + list.size());
    for (auto& var : list)
      vars.emplace_back(var);
    desc.extend(list);
  }
};

ParsedArgs flatten(py::handle obj);
PyObject* unflatten(
    at::ArrayRef<autograd::Variable> vars,
    const IODescriptor& structure);

} // namespace torch::jit::python
