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

// REQUIRES: std-at-least-c++23

// <ranges>

// constexpr View base() const& requires copy_constructible<View>;
// constexpr View base() &&;

#include <ranges>

#include <cassert>
#include <utility>
#include <vector>

using InnerRange = std::vector<int>;

struct Range : std::ranges::view_base {
  constexpr explicit Range(InnerRange* b, InnerRange* e) : begin_(b), end_(e) {}
  constexpr Range(const Range& other) : begin_(other.begin_), end_(other.end_), was_copy_initialized_(true) {}
  constexpr Range(Range&& other) : begin_(other.begin_), end_(other.end_), was_move_initialized_(true) {}
  Range& operator=(const Range&) = default;
  Range& operator=(Range&&)      = default;
  constexpr InnerRange* begin() const { return begin_; }
  constexpr InnerRange* end() const { return end_; }

  InnerRange* begin_;
  InnerRange* end_;
  bool was_copy_initialized_ = false;
  bool was_move_initialized_ = false;
};

static_assert(std::ranges::view<Range>);
static_assert(std::ranges::input_range<Range>);

struct Pattern : std::ranges::view_base {
  static constexpr int pat[2] = {0, 0};
  constexpr const int* begin() const { return pat; }
  constexpr const int* end() const { return pat + 2; }
};

static_assert(std::ranges::view<Pattern>);
static_assert(std::ranges::forward_range<Pattern>);

template <class Tp>
struct NonCopyableRange : std::ranges::view_base {
  NonCopyableRange(const NonCopyableRange&)            = delete;
  NonCopyableRange(NonCopyableRange&&)                 = default;
  NonCopyableRange& operator=(const NonCopyableRange&) = default;
  NonCopyableRange& operator=(NonCopyableRange&&)      = default;
  Tp* begin() const;
  Tp* end() const;
};

static_assert(!std::copy_constructible<NonCopyableRange<InnerRange>>);
static_assert(!std::copy_constructible<NonCopyableRange<int>>);

template <typename T>
concept CanCallBaseOn = requires(T&& t) { std::forward<T>(t).base(); };

constexpr bool test() {
  InnerRange buff[3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
  Pattern pattern;

  { // Check the const& overload
    Range range(buff, buff + 3);
    std::ranges::join_with_view<Range, Pattern> view(range, pattern);
    std::same_as<Range> decltype(auto) result = view.base();
    assert(result.was_copy_initialized_);
    assert(result.begin() == buff);
    assert(result.end() == buff + 3);
  }

  { // Check the const& overload on const `view`
    Range range(buff, buff + 3);
    const std::ranges::join_with_view<Range, Pattern> view(range, pattern);
    std::same_as<Range> decltype(auto) result = view.base();
    assert(result.was_copy_initialized_);
    assert(result.begin() == buff);
    assert(result.end() == buff + 3);
  }

  { // Check the && overload
    Range range(buff, buff + 3);
    std::ranges::join_with_view<Range, Pattern> view(range, pattern);
    std::same_as<Range> decltype(auto) result = std::move(view).base();
    assert(result.was_move_initialized_);
    assert(result.begin() == buff);
    assert(result.end() == buff + 3);
  }

  { // Ensure the const& overload is not considered when the base is not copy-constructible
    static_assert(!CanCallBaseOn<const std::ranges::join_with_view<NonCopyableRange<InnerRange>, Pattern>&>);
    static_assert(!CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, Pattern>&>);
    static_assert(!CanCallBaseOn<const std::ranges::join_with_view<NonCopyableRange<InnerRange>, Pattern>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, Pattern>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, Pattern>>);
  }

  { // Ensure the const& overload does not depend on Pattern's copy-constructability
    static_assert(CanCallBaseOn<const std::ranges::join_with_view<Range, NonCopyableRange<int>>&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<Range, NonCopyableRange<int>>&>);
    static_assert(CanCallBaseOn<const std::ranges::join_with_view<Range, NonCopyableRange<int>>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<Range, NonCopyableRange<int>>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<Range, NonCopyableRange<int>>>);
  }

  { // Check above two at the same time
    static_assert(
        !CanCallBaseOn<const std::ranges::join_with_view<NonCopyableRange<InnerRange>, NonCopyableRange<int>>&>);
    static_assert(!CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, NonCopyableRange<int>>&>);
    static_assert(
        !CanCallBaseOn<const std::ranges::join_with_view< NonCopyableRange<InnerRange>, NonCopyableRange<int>>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, NonCopyableRange<int>>&&>);
    static_assert(CanCallBaseOn<std::ranges::join_with_view<NonCopyableRange<InnerRange>, NonCopyableRange<int>>>);
  }

  return true;
}

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

  return 0;
}