cpp-lazy-stream/include/stream/iterator/common_iterator.h

//
//  common_iterator.h
//  stream
//
//  Created by Sam Jaffe on 4/2/23.
//

#pragma once

#include <iterator/proxy.h>

#include <stream/forward.h>

#include <stream/detail/macro.h>

namespace stream::ranges {
template <typename It, typename S>
class common_iterator : public proxy<It, common_iterator<It, S>> {
public:
  static_assert(!std::is_same_v<It, S>, "cannot operator on common types");
  using super_t = proxy<It, common_iterator<It, S>>;
  using sentinel_type = common_iterator;

public:
  using super_t::super_t;
  common_iterator(S) : super_t() {}

  SFINAE(super_t::category_enum == iterator::category::random_access)
  auto distance_to(common_iterator const & other) const {
    if (at_end()) {
      return other.at_end() ? 0 : -(S() - other);
    } else if (other.at_end()) {
      return S() - *this;
    } else {
      return super_t::distance_to(other);
    }
  }

  bool equal_to(common_iterator const & other) const {
    return (at_end() && other.at_end()) || super_t::impl() == other.impl();
  }
  bool at_end() const { return super_t::impl() == S(); }
};
}

MAKE_ITERATOR_FACADE_TYPEDEFS_T(stream::ranges::common_iterator);

#include <stream/detail/undef.h>