//===----------------------------------------------------------------------===//
//
// 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
// UNSUPPORTED: msvc-19.16

// ranges::advance(it, n)

#include <iterator>

#include <cassert>

#include "test_iterators.h"
#include "test_macros.h"

template <bool Count, typename It>
constexpr void check(int* first, std::iter_difference_t<It> n, int* expected) {
  using Difference = std::iter_difference_t<It>;
  Difference const M = (expected - first); // expected travel distance (which may be negative)
  auto abs = [](auto x) { return x < 0 ? -x : x; };

  {
    It it(first);
    std::ranges::advance(it, n);
    assert(base(it) == expected);
    ASSERT_SAME_TYPE(decltype(std::ranges::advance(it, n)), void);
  }

  // Count operations
  if constexpr (Count) {
    auto it = stride_counting_iterator(It(first));
    std::ranges::advance(it, n);
    if constexpr (std::random_access_iterator<It>) {
      assert(it.stride_count() <= 1);
    } else {
      assert(it.stride_count() == abs(M));
    }
  }
}

constexpr bool test() {
  int range[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

  // Check advancing forward
  for (int n = 0; n != 10; ++n) {
    check<false, cpp17_input_iterator<int*>>(  range, n, range+n);
    check<false, cpp20_input_iterator<int*>>(  range, n, range+n);
    check<true,  forward_iterator<int*>>(      range, n, range+n);
    check<true,  bidirectional_iterator<int*>>(range, n, range+n);
    check<true,  random_access_iterator<int*>>(range, n, range+n);
    check<true,  contiguous_iterator<int*>>(   range, n, range+n);
    check<true,  int*>(                        range, n, range+n);
    check<true,  cpp17_output_iterator<int*> >(range, n, range+n);
  }

  // Check advancing backward
  for (int n = 0; n != 10; ++n) {
    check<true,  bidirectional_iterator<int*>>(range+9, -n, range+9 - n);
    check<true,  random_access_iterator<int*>>(range+9, -n, range+9 - n);
    check<true,  contiguous_iterator<int*>>(   range+9, -n, range+9 - n);
    check<true,  int*>(                        range+9, -n, range+9 - n);
  }

  return true;
}

int main(int, char**) {
  assert(test());
  static_assert(test());
  return 0;
}
