read.hpp

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//
// Copyright (C) 2014, 2015 Ableton AG, Berlin. All rights reserved.
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#pragma once

#include <atria/xform/maybe_reduced.hpp>
#include <atria/xform/skip.hpp>
#include <atria/xform/transducer_impl.hpp>
#include <atria/prelude/comp.hpp>
#include <functional>

namespace atria {
namespace xform {

namespace detail {

template <typename ValueT>
struct read_rf_gen
{
  template <typename ReducingFnT, typename InputStreamRefT>
  struct apply
  {
    ReducingFnT step;
    InputStreamRefT stream_ref;

    template <typename StateT, typename ...InputTs>
    auto operator() (StateT&& s, InputTs&& ...is)
      -> decltype(reduced(skip(step,
                               state_unwrap(std::forward<StateT>(s)),
                               std::forward<InputTs>(is)...,
                               std::declval<ValueT>())))
    {
      ValueT value{};
      auto& stream = stream_ref.get();
      if (stream) {
        stream >> value;
        if (!stream.fail())
          return not_reduced(
            call(step,
                 state_unwrap(std::forward<StateT>(s)),
                 std::forward<InputTs>(is)...,
                 std::move(value)));
      }
      return reduced(
        skip(step,
             state_unwrap(std::forward<StateT>(s)),
             std::forward<InputTs>(is)...,
             std::move(value)));
    }
  };
};

} // namespace detail

template <typename T, typename InputStreamRefT>
using read_t = transducer_impl<detail::read_rf_gen<T>, InputStreamRefT>;

template <typename T, typename InputStreamT>
auto read(InputStreamT& stream)
  -> read_t<T, std::reference_wrapper<InputStreamT> >
{
  return { std::ref(stream) };
}

template <typename T1, typename T2, typename ...Ts, typename InputStreamT>
auto read(InputStreamT& stream)
  -> ABL_DECLTYPE_RETURN(
    comp(read<T1>(stream),
         read<T2>(stream),
         read<Ts>(stream)...))

} // namespace xform
} // namespace atria