#include <c10/util/TypeTraits.h>
#include <gtest/gtest.h>

using namespace c10::guts;

namespace {

namespace test_is_equality_comparable {
class NotEqualityComparable {};
class EqualityComparable {};

inline bool operator==(const EqualityComparable&, const EqualityComparable&) {
  return false;
}

static_assert(!is_equality_comparable<NotEqualityComparable>::value, "");
static_assert(is_equality_comparable<EqualityComparable>::value, "");
static_assert(is_equality_comparable<int>::value, "");

// v_ just exists to silence a compiler warning about
// operator==(EqualityComparable, EqualityComparable) not being needed
const bool v_ = EqualityComparable() == EqualityComparable();
} // namespace test_is_equality_comparable

namespace test_is_hashable {
class NotHashable {};
class Hashable {};
} // namespace test_is_hashable
} // namespace
namespace std {
template <>
struct hash<test_is_hashable::Hashable> final {
  size_t operator()(const test_is_hashable::Hashable&) {
    return 0;
  }
};
} // namespace std
namespace {
namespace test_is_hashable {
static_assert(is_hashable<int>::value, "");
static_assert(is_hashable<Hashable>::value, "");
static_assert(!is_hashable<NotHashable>::value, "");
} // namespace test_is_hashable

namespace test_is_function_type {
class MyClass {};
struct Functor {
  void operator()() {}
};
auto lambda = []() {};
// func() and func__ just exists to silence a compiler warning about lambda
// being unused
bool func() {
  lambda();
  return true;
}
bool func__ = func();

static_assert(is_function_type<void()>::value, "");
static_assert(is_function_type<int()>::value, "");
static_assert(is_function_type<MyClass()>::value, "");
static_assert(is_function_type<void(MyClass)>::value, "");
static_assert(is_function_type<void(int)>::value, "");
static_assert(is_function_type<void(void*)>::value, "");
static_assert(is_function_type<int()>::value, "");
static_assert(is_function_type<int(MyClass)>::value, "");
static_assert(is_function_type<int(const MyClass&)>::value, "");
static_assert(is_function_type<int(MyClass&&)>::value, "");
static_assert(is_function_type < MyClass && () > ::value, "");
static_assert(is_function_type < MyClass && (MyClass &&) > ::value, "");
static_assert(is_function_type<const MyClass&(int, float, MyClass)>::value, "");

static_assert(!is_function_type<void>::value, "");
static_assert(!is_function_type<int>::value, "");
static_assert(!is_function_type<MyClass>::value, "");
static_assert(!is_function_type<void*>::value, "");
static_assert(!is_function_type<const MyClass&>::value, "");
static_assert(!is_function_type<MyClass&&>::value, "");

static_assert(
    !is_function_type<void (*)()>::value,
    "function pointers aren't plain functions");
static_assert(
    !is_function_type<Functor>::value,
    "Functors aren't plain functions");
static_assert(
    !is_function_type<decltype(lambda)>::value,
    "Lambdas aren't plain functions");
} // namespace test_is_function_type

namespace test_is_instantiation_of {
class MyClass {};
template <class T>
class Single {};
template <class T1, class T2>
class Double {};
template <class... T>
class Multiple {};

static_assert(is_instantiation_of<Single, Single<void>>::value, "");
static_assert(is_instantiation_of<Single, Single<MyClass>>::value, "");
static_assert(is_instantiation_of<Single, Single<int>>::value, "");
static_assert(is_instantiation_of<Single, Single<void*>>::value, "");
static_assert(is_instantiation_of<Single, Single<int*>>::value, "");
static_assert(is_instantiation_of<Single, Single<const MyClass&>>::value, "");
static_assert(is_instantiation_of<Single, Single<MyClass&&>>::value, "");
static_assert(is_instantiation_of<Double, Double<int, void>>::value, "");
static_assert(
    is_instantiation_of<Double, Double<const int&, MyClass*>>::value,
    "");
static_assert(is_instantiation_of<Multiple, Multiple<>>::value, "");
static_assert(is_instantiation_of<Multiple, Multiple<int>>::value, "");
static_assert(
    is_instantiation_of<Multiple, Multiple<MyClass&, int>>::value,
    "");
static_assert(
    is_instantiation_of<Multiple, Multiple<MyClass&, int, MyClass>>::value,
    "");
static_assert(
    is_instantiation_of<Multiple, Multiple<MyClass&, int, MyClass, void*>>::
        value,
    "");

static_assert(!is_instantiation_of<Single, Double<int, int>>::value, "");
static_assert(!is_instantiation_of<Single, Double<int, void>>::value, "");
static_assert(!is_instantiation_of<Single, Multiple<int>>::value, "");
static_assert(!is_instantiation_of<Double, Single<int>>::value, "");
static_assert(!is_instantiation_of<Double, Multiple<int, int>>::value, "");
static_assert(!is_instantiation_of<Double, Multiple<>>::value, "");
static_assert(!is_instantiation_of<Multiple, Double<int, int>>::value, "");
static_assert(!is_instantiation_of<Multiple, Single<int>>::value, "");
} // namespace test_is_instantiation_of

namespace test_is_type_condition {
template <class>
class NotATypeCondition {};
static_assert(is_type_condition<std::is_reference>::value, "");
static_assert(!is_type_condition<NotATypeCondition>::value, "");
} // namespace test_is_type_condition
} // namespace

namespace test_lambda_is_stateless {
template <class Result, class... Args>
struct MyStatelessFunctor final {
  Result operator()(Args...) {}
};

template <class Result, class... Args>
struct MyStatelessConstFunctor final {
  Result operator()(Args...) const {}
};

void func() {
  auto stateless_lambda = [](int a) { return a; };
  static_assert(is_stateless_lambda<decltype(stateless_lambda)>::value, "");

  int b = 4;
  auto stateful_lambda_1 = [&](int a) { return a + b; };
  static_assert(!is_stateless_lambda<decltype(stateful_lambda_1)>::value, "");

  auto stateful_lambda_2 = [=](int a) { return a + b; };
  static_assert(!is_stateless_lambda<decltype(stateful_lambda_2)>::value, "");

  auto stateful_lambda_3 = [b](int a) { return a + b; };
  static_assert(!is_stateless_lambda<decltype(stateful_lambda_3)>::value, "");

  static_assert(
      !is_stateless_lambda<MyStatelessFunctor<int, int>>::value,
      "even if stateless, a functor is not a lambda, so it's false");
  static_assert(
      !is_stateless_lambda<MyStatelessFunctor<void, int>>::value,
      "even if stateless, a functor is not a lambda, so it's false");
  static_assert(
      !is_stateless_lambda<MyStatelessConstFunctor<int, int>>::value,
      "even if stateless, a functor is not a lambda, so it's false");
  static_assert(
      !is_stateless_lambda<MyStatelessConstFunctor<void, int>>::value,
      "even if stateless, a functor is not a lambda, so it's false");

  class Dummy final {};
  static_assert(
      !is_stateless_lambda<Dummy>::value,
      "A non-functor type is also not a lambda");

  static_assert(!is_stateless_lambda<int>::value, "An int is not a lambda");

  using Func = int(int);
  static_assert(
      !is_stateless_lambda<Func>::value, "A function is not a lambda");
  static_assert(
      !is_stateless_lambda<Func*>::value, "A function pointer is not a lambda");
}
} // namespace test_lambda_is_stateless
