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

//
//  capture_iterator.h
//  iterator
//
//  Created by Sam Jaffe on 4/1/23.
//  Copyright © 2023 Sam Jaffe. All rights reserved.
//

#pragma once

#include <iterator/forwards.h>
#include <iterator/proxy.h>

#include <iterator/detail/macro.h>

namespace iterator {

template <typename It>
class capture_iterator : public proxy<It, capture_iterator<It>> {
public:
  using super_t = proxy<It, capture_iterator<It>>;
  using value_type = typename std::iterator_traits<It>::value_type;
  using difference_type = typename std::iterator_traits<It>::difference_type;

private:
  value_type cache_;

public:
  capture_iterator() = default;
  capture_iterator(It it) : super_t(it) { cache_ = super_t::dereference(); }

  value_type const & dereference() const { return cache_; }

  SFINAE(super_t::category_enum >= category::forward) void increment() {
    super_t::increment();
    cache_ = super_t::dereference();
  }

  SFINAE(super_t::category_enum >= category::bidirectional)
  void decrement() {
    super_t::decrement();
    cache_ = super_t::dereference();
  }

  SFINAE(super_t::category_enum >= category::random_access)
  void advance(difference_type off) {
    super_t::advance(off);
    cache_ = super_t::dereference();
  }
};

template <typename It> capture_iterator(It) -> capture_iterator<It>;

}

#include <iterator/detail/undef.h>