//===----------------------------------------------------------------------===//
//
// 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       iterator  begin() const noexcept;
// constexpr const_iterator cbegin() const noexcept;

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

#include "test_macros.h"

template <class Span>
constexpr bool testConstexprSpan(Span s) {
  bool ret                  = true;
  typename Span::iterator b = s.begin();

  if (s.empty()) {
    ret = ret && (b == s.end());
  } else {
    ret = ret && (*b == s[0]);
    ret = ret && (&*b == &s[0]);
  }
  return ret;
}

template <class Span>
void testRuntimeSpan(Span s) {
  typename Span::iterator b = s.begin();

  if (s.empty()) {
    assert(b == s.end());
  } else {
    assert(*b == s[0]);
    assert(&*b == &s[0]);
  }
}

struct A {};
bool operator==(A, A) { return true; }

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<int>()), "");
  static_assert(testConstexprSpan(std::span<long>()), "");
  static_assert(testConstexprSpan(std::span<double>()), "");
  static_assert(testConstexprSpan(std::span<A>()), "");
  static_assert(testConstexprSpan(std::span<std::string>()), "");

  static_assert(testConstexprSpan(std::span<int, 0>()), "");
  static_assert(testConstexprSpan(std::span<long, 0>()), "");
  static_assert(testConstexprSpan(std::span<double, 0>()), "");
  static_assert(testConstexprSpan(std::span<A, 0>()), "");
  static_assert(testConstexprSpan(std::span<std::string, 0>()), "");

  static_assert(testConstexprSpan(std::span<const int>(iArr1, 1)), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 2)), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 3)), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 4)), "");
  static_assert(testConstexprSpan(std::span<const int>(iArr1, 5)), "");

  testRuntimeSpan(std::span<int>());
  testRuntimeSpan(std::span<long>());
  testRuntimeSpan(std::span<double>());
  testRuntimeSpan(std::span<A>());
  testRuntimeSpan(std::span<std::string>());

  testRuntimeSpan(std::span<int, 0>());
  testRuntimeSpan(std::span<long, 0>());
  testRuntimeSpan(std::span<double, 0>());
  testRuntimeSpan(std::span<A, 0>());
  testRuntimeSpan(std::span<std::string, 0>());

  testRuntimeSpan(std::span<int>(iArr2, 1));
  testRuntimeSpan(std::span<int>(iArr2, 2));
  testRuntimeSpan(std::span<int>(iArr2, 3));
  testRuntimeSpan(std::span<int>(iArr2, 4));
  testRuntimeSpan(std::span<int>(iArr2, 5));

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

  return 0;
}