cpp-useful-iterators/include/iterator/end_aware_iterator.hpp

//
//  end_aware_iterator.hpp
//  iterator
//
//  Created by Sam Jaffe on 2/7/17.
//

#pragma once

#include "iterator_fwd.hpp"

#include "facade.h"

namespace iterator {
  /**
   * @class end_aware_iterator
   * @brief An iterator that keeps track of the relative end of the range.
   *
   * @tparam It The underlying iterator type
   */
  template <typename It>
  class end_aware_iterator : public facade<end_aware_iterator<It>> {
  public:
    using value_type = typename It::value_type;
    struct sentinel_type {};
    static constexpr sentinel_type sentinel;

  public:
    end_aware_iterator() = default;
    end_aware_iterator(It it, It end) : curr_(it), end_(end) {}
    end_aware_iterator(It end) : curr_(end), end_(end) {}

    template <typename I>
    end_aware_iterator(end_aware_iterator<I> const & other)
        : curr_(other.curr_), end_(other.end_) {}

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

  private:
    template <typename O> friend class end_aware_iterator;
    It curr_, end_;
  };

  template <typename It> end_aware_iterator(It) -> end_aware_iterator<It>;
  template <typename It> end_aware_iterator(It, It) -> end_aware_iterator<It>;
}

MAKE_ITERATOR_FACADE_TYPEDEFS_T(::iterator::end_aware_iterator);

template <typename Iter>
iterator::end_aware_iterator<Iter> make_end_aware_iterator(Iter a, Iter b) {
  return iterator::end_aware_iterator<Iter>(a, b);
}

template <typename C> auto make_end_aware_iterator(C & collect) {
  return make_end_aware_iterator(std::begin(collect), std::end(collect));
}

template <typename C> auto make_end_aware_iterator(C const & collect) {
  return make_end_aware_iterator(std::begin(collect), std::end(collect));
}