cpp-lazy-stream/include/stream/view/transform.h

#pragma once

#include <functional>

#include <stream/forward.h>

#include <stream/detail/traits.h>
#include <stream/iterator/sentinel.h>
#include <stream/iterator/transform_iterator.h>
#include <stream/view/interface.h>

#include <stream/detail/macro.h>

namespace stream::ranges {
template <typename S, typename Proj>
class transform_view : public proxy_view_interface<transform_view<S, Proj>, S,
                                                   transform_iterator, Proj> {
public:
  using iterator = transform_iterator<detail::begin_t<S>, Proj>;

private:
  S stream_;
  Proj projection_;

public:
  transform_view(S && stream, Proj projection)
      : stream_(FWD(stream)), projection_(projection) {}

  auto begin() const { return iterator(stream_.begin(), projection_); }
  auto end() const { return sentinel_end(this, stream_, projection_); }
};

template <typename S, typename Proj>
transform_view(S &&, Proj) -> transform_view<S, Proj>;
}

namespace stream::ranges::views {
template <typename Proj> class transform {
public:
  transform(Proj const & projection) : projection_(projection) {}

  template <typename Stream>
  friend auto operator|(Stream && stream, transform map) {
    // TODO: if constexpr transform_view
    return transform_view(FWD(stream), std::move(map.projection_));
  }

private:
  Proj projection_;
};
}

#include <stream/detail/undef.h>