//===----------------------------------------------------------------------===//
//
// 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

// constexpr split_view(View base, Pattern pattern);

#include <algorithm>
#include <cassert>
#include <ranges>
#include <string_view>
#include <utility>

struct ViewWithCounting : std::ranges::view_base {
  int* times_copied = nullptr;
  int* times_moved  = nullptr;

  constexpr ViewWithCounting(int& copies_ctr, int& moves_ctr) : times_copied(&copies_ctr), times_moved(&moves_ctr) {}

  constexpr ViewWithCounting(const ViewWithCounting& rhs)
      : times_copied(rhs.times_copied), times_moved(rhs.times_moved) {
    ++(*times_copied);
  }
  constexpr ViewWithCounting(ViewWithCounting&& rhs) : times_copied(rhs.times_copied), times_moved(rhs.times_moved) {
    ++(*times_moved);
  }

  constexpr const char* begin() const { return nullptr; }
  constexpr const char* end() const { return nullptr; }

  constexpr ViewWithCounting& operator=(const ViewWithCounting&) = default;
  constexpr ViewWithCounting& operator=(ViewWithCounting&&)      = default;
  constexpr bool operator==(const ViewWithCounting&) const { return true; }
};

constexpr bool test() {
  {
    std::string_view input = "abc def";
    std::ranges::lazy_split_view<std::string_view, std::string_view> v(input, " ");
    assert(v.base() == input);
    assert(std::ranges::equal(*v.begin(), std::string_view{"abc"}));
  }

  // Make sure the arguments are moved, not copied.
  {
    using View    = ViewWithCounting;
    using Pattern = ViewWithCounting;

    // Arguments are lvalues.
    {
      int view_copied = 0, view_moved = 0, pattern_copied = 0, pattern_moved = 0;
      View view(view_copied, view_moved);
      Pattern pattern(pattern_copied, pattern_moved);

      std::ranges::split_view<View, Pattern> v(view, pattern);
      assert(view_copied == 1); // The local variable is copied into the argument.
      assert(view_moved == 1);
      assert(pattern_copied == 1);
      assert(pattern_moved == 1);
    }

    // Arguments are rvalues.
    {
      int view_copied = 0, view_moved = 0, pattern_copied = 0, pattern_moved = 0;
      std::ranges::split_view<View, Pattern> v(View(view_copied, view_moved), Pattern(pattern_copied, pattern_moved));
      assert(view_copied == 0);
      assert(view_moved == 1);
      assert(pattern_copied == 0);
      assert(pattern_moved == 1);
    }
  }

  return true;
}

int main(int, char**) {
  test();
  static_assert(test());

  return 0;
}