//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

// <span>

// constexpr reference front() const noexcept;
//   Expects: empty() is false.
//   Effects: Equivalent to: return *data();
//

#include <cuda/std/cassert>
#include <cuda/std/span>

#include "test_macros.h"

template <typename Span>
__host__ __device__ constexpr bool testConstexprSpan(Span sp)
{
  static_assert(noexcept(sp.front()));
  return &sp.front() == sp.data();
}

template <typename Span>
__host__ __device__ void testRuntimeSpan(Span sp)
{
  static_assert(noexcept(sp.front()));
  assert(&sp.front() == sp.data());
}

template <typename Span>
__host__ __device__ void testEmptySpan(Span sp)
{
  if (!sp.empty())
  {
    unused(sp.front());
  }
}

struct A
{};
constexpr int iArr1[]            = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
TEST_GLOBAL_VARIABLE int iArr2[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};

int main(int, char**)
{
  static_assert(testConstexprSpan(cuda::std::span<const int>(iArr1, 1)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int>(iArr1, 2)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int>(iArr1, 3)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int>(iArr1, 4)), "");

  static_assert(testConstexprSpan(cuda::std::span<const int, 1>(iArr1, 1)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int, 2>(iArr1, 2)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int, 3>(iArr1, 3)), "");
  static_assert(testConstexprSpan(cuda::std::span<const int, 4>(iArr1, 4)), "");

  testRuntimeSpan(cuda::std::span<int>(iArr2, 1));
  testRuntimeSpan(cuda::std::span<int>(iArr2, 2));
  testRuntimeSpan(cuda::std::span<int>(iArr2, 3));
  testRuntimeSpan(cuda::std::span<int>(iArr2, 4));

  testRuntimeSpan(cuda::std::span<int, 1>(iArr2, 1));
  testRuntimeSpan(cuda::std::span<int, 2>(iArr2, 2));
  testRuntimeSpan(cuda::std::span<int, 3>(iArr2, 3));
  testRuntimeSpan(cuda::std::span<int, 4>(iArr2, 4));

  cuda::std::span<int, 0> sp;
  testEmptySpan(sp);

  return 0;
}
