//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17

// <span>

// constexpr reference operator[](size_type idx) const;
//

#include <span>
#include <cassert>
#include <string>

#include "test_macros.h"

template <typename Span>
constexpr bool testConstexprSpan(Span sp, std::size_t idx) {
  LIBCPP_ASSERT(noexcept(sp[idx]));

  typename Span::reference r1 = sp[idx];
  typename Span::reference r2 = *(sp.data() + idx);
  return r1 == r2;
}

template <typename Span>
void testRuntimeSpan(Span sp, std::size_t idx) {
  LIBCPP_ASSERT(noexcept(sp[idx]));

  typename Span::reference r1 = sp[idx];
  typename Span::reference r2 = *(sp.data() + idx);
  assert(r1 == r2);
}

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

int main(int, char**) {
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 1), 0), "");

  static_assert(testConstexprSpan(std::span<const int>(iArr1, 2), 0), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 2), 1), "");

  static_assert(testConstexprSpan(std::span<const int>(iArr1, 3), 0), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 3), 1), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 3), 2), "");

  static_assert(testConstexprSpan(std::span<const int>(iArr1, 4), 0), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 4), 1), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 4), 2), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 4), 3), "");

  static_assert(testConstexprSpan(std::span<const int, 1>(iArr1, 1), 0), "");

  static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2), 0), "");
  static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2), 1), "");

  static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3), 0), "");
  static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3), 1), "");
  static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3), 2), "");

  static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4), 0), "");
  static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4), 1), "");
  static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4), 2), "");
  static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4), 3), "");

  testRuntimeSpan(std::span<int>(iArr2, 1), 0);

  testRuntimeSpan(std::span<int>(iArr2, 2), 0);
  testRuntimeSpan(std::span<int>(iArr2, 2), 1);

  testRuntimeSpan(std::span<int>(iArr2, 3), 0);
  testRuntimeSpan(std::span<int>(iArr2, 3), 1);
  testRuntimeSpan(std::span<int>(iArr2, 3), 2);

  testRuntimeSpan(std::span<int>(iArr2, 4), 0);
  testRuntimeSpan(std::span<int>(iArr2, 4), 1);
  testRuntimeSpan(std::span<int>(iArr2, 4), 2);
  testRuntimeSpan(std::span<int>(iArr2, 4), 3);

  testRuntimeSpan(std::span<int, 1>(iArr2, 1), 0);

  testRuntimeSpan(std::span<int, 2>(iArr2, 2), 0);
  testRuntimeSpan(std::span<int, 2>(iArr2, 2), 1);

  testRuntimeSpan(std::span<int, 3>(iArr2, 3), 0);
  testRuntimeSpan(std::span<int, 3>(iArr2, 3), 1);
  testRuntimeSpan(std::span<int, 3>(iArr2, 3), 2);

  testRuntimeSpan(std::span<int, 4>(iArr2, 4), 0);
  testRuntimeSpan(std::span<int, 4>(iArr2, 4), 1);
  testRuntimeSpan(std::span<int, 4>(iArr2, 4), 2);
  testRuntimeSpan(std::span<int, 4>(iArr2, 4), 3);

  std::string s;
  testRuntimeSpan(std::span<std::string>(&s, 1), 0);
  testRuntimeSpan(std::span<std::string, 1>(&s, 1), 0);

  return 0;
}
