cpp-useful-iterators/include/iterator/sentinal_iterator.h

//
//  sentinal_iterator.h
//  iterator
//
//  Created by Sam Jaffe on 3/30/23.
//  Copyright © 2023 Sam Jaffe. All rights reserved.
//

#pragma once

#include <iterator/detail/traits.h>
#include <iterator/facade.h>
#include <iterator/iterator_fwd.hpp>

namespace iterator {
template <typename It>
class sentinal_iterator : public facade<sentinal_iterator<It>> {
public:
  using sentinal_type = typename It::sentinal_type;
  static constexpr sentinal_type sentinal{};

public:
  sentinal_iterator() = default;
  sentinal_iterator(It it) : curr_(it) {}

  template <typename C, typename = std::enable_if_t<detail::is_container_v<C>>>
  sentinal_iterator(C && container) : curr_(std::begin(container)) {
    static_assert(std::is_reference_v<C>,
                  "Cannot access iterator of a temporary");
  }

  decltype(auto) dereference() const { return *curr_; }
  void increment() { ++curr_; }
  bool at_end() const { return curr_.at_end() || curr_ == It(); }
  bool equal_to(sentinal_iterator const & other) const {
    // TODO: Fix this clause
    return (at_end() && other.at_end()) || curr_ == other.curr_;
  }

private:
  It curr_;
};

template <typename C> sentinal_iterator(C &&) -> sentinal_iterator<iter<C>>;
template <typename It> sentinal_iterator(It) -> sentinal_iterator<It>;
}

MAKE_ITERATOR_FACADE_TYPEDEFS_T(::iterator::sentinal_iterator);