cpp-json/include/json/binder/json_direct_get_binder.hpp

//
//  json_direct_tuple_binder.hpp
//  json
//
//  Created by Sam Jaffe on 2/26/17.
//

#pragma once

#include "json_binder.hpp"
#include "json_direct_binder.hpp"
#include "json_tuple_binder.hpp"

#include <array>
#include <tuple>

namespace json { namespace binder {
  template <typename T, std::size_t I>
  class get_binder : public binder_impl<T> {
    // Maybe a reference type
    using ith_type = decltype(std::get<I>(std::declval<T>()));

  public:
    using value_type = typename std::remove_reference<ith_type>::type;

    get_binder() : impl(value_binder<value_type>()) {}

    get_binder(binder<value_type> val_binder) : impl(std::move(val_binder)) {}

    get_binder(binder_impl<value_type> const & val_binder) : impl(val_binder) {}

    virtual binder_impl<T> * clone() const override {
      return new get_binder(*this);
    }

    virtual void parse(T & object, char const *& data,
                       parser::options opts) const override {
      impl.parse(std::get<I>(object), data, opts);
    }

    virtual void write(T const & val, std::ostream & data) const override {
      impl.write(std::get<I>(val), data);
    }

  private:
    binder<value_type> impl;
  };

#if __cpluscplus >= 201402L
  namespace detail {
    template <typename TupleOut, typename TupleIn, std::size_t... Indexes>
    tuple_binder<TupleOut> make_tuple_binder(TupleIn && binds,
                                             std::index_sequence<Indexes...>) {
      tuple_binder<TupleOut> binder;
      using swallow = int[];
      (void)swallow{0, (void(binder(get_binder<TupleOut, Indexes>(
                            std::get<Indexes>(binds)))),
                        0)...};
      return binder;
    }

    template <typename TupleOut, typename T, std::size_t... Indexes>
    tuple_binder<TupleOut> make_array_binder(binder<T> && binds,
                                             std::index_sequence<Indexes...>) {
      tuple_binder<TupleOut> binder;
      using swallow = int[];
      (void)swallow{0,
                    (void(binder(get_binder<TupleOut, Indexes>(binds))), 0)...};
      return binder;
    }
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>> make_tuple_binder(binder<Ts> &&... binds) {
    return detail::make_tuple_binder<std::tuple<Ts...>>(
        std::make_tuple(binds...), std::make_index_sequence<sizeof...(Ts)>());
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>>
  make_tuple_binder(binder_impl<Ts> &&... binds) {
    return detail::make_tuple_binder<std::tuple<Ts...>>(
        std::make_tuple(binder<Ts>(binds)...),
        std::make_index_sequence<sizeof...(Ts)>());
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>> make_default_tuple_binder() {
    return detail::make_tuple_binder<std::tuple<Ts...>>(
        std::make_tuple(binder<Ts>(value_binder<Ts>())...),
        std::make_index_sequence<sizeof...(Ts)>());
  }

  template <typename T, std::size_t N>
  tuple_binder<std::array<T, N>> make_array_binder(binder<T> && binds) {
    return detail::make_array_binder<std::array<T, N>>(
        binds, std::make_index_sequence<N>());
  }

  template <typename T, std::size_t N>
  tuple_binder<std::array<T, N>>
  make_array_binder(binder_impl<T> const & binds = value_binder<T>()) {
    return detail::make_array_binder<std::array<T, N>>(
        binder<T>(binds), std::make_index_sequence<N>());
  }
#else
  namespace detail {
    template <std::size_t> struct tuple_binder_helper;

    template <> struct tuple_binder_helper<0> {
      template <typename BindOut>
      tuple_binder<BindOut> & operator()(tuple_binder<BindOut> & bind) const {
        return bind;
      }
    };

    template <std::size_t N> struct tuple_binder_helper {
      template <typename BindOut, typename BindIn, typename... Ts>
      tuple_binder<BindOut> & operator()(tuple_binder<BindOut> & bind,
                                         BindIn && ith,
                                         Ts &&... binders) const {
        constexpr auto get_index = std::tuple_size<BindOut>::value - N;
        using get_binder_t = get_binder<BindOut, get_index>;
        return tuple_binder_helper<N - 1>()(
            bind(get_binder_t(std::forward<BindIn>(ith))),
            std::forward<Ts>(binders)...);
      }
    };

    template <std::size_t> struct array_binder_helper;

    template <> struct array_binder_helper<1> {
      template <typename BindOut, typename BindIn>
      tuple_binder<BindOut> & operator()(tuple_binder<BindOut> & bind,
                                         BindIn &&) const {
        return bind;
      }
    };

    template <std::size_t N> struct array_binder_helper {
      template <typename BindOut, typename BindIn>
      tuple_binder<BindOut> & operator()(tuple_binder<BindOut> & bind,
                                         BindIn && ith) const {
        return array_binder_helper<N - 1>()(
            bind(get_binder<BindOut, N - 1>(ith)), std::forward<BindIn>(ith));
      }
    };
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>> make_tuple_binder(binder<Ts> &&... binds) {
    tuple_binder<std::tuple<Ts...>> binder;
    return detail::tuple_binder_helper<sizeof...(Ts)>()(
        binder, std::forward<Ts>(binds)...);
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>>
  make_tuple_binder(binder_impl<Ts> &&... binds) {
    tuple_binder<std::tuple<Ts...>> binder;
    return detail::tuple_binder_helper<sizeof...(Ts)>()(
        binder, json::binder::binder<Ts>(binds)...);
  }

  template <typename... Ts>
  tuple_binder<std::tuple<Ts...>> make_default_tuple_binder() {
    tuple_binder<std::tuple<Ts...>> binder;
    return detail::tuple_binder_helper<sizeof...(Ts)>()(
        binder, json::binder::binder<Ts>(value_binder<Ts>())...);
  }

  template <typename T, std::size_t N>
  tuple_binder<std::array<T, N>> make_array_binder(binder<T> && binds) {
    tuple_binder<std::array<T, N>> binder;
    return detail::array_binder_helper<N>(binder, binds);
  }

  template <typename T, std::size_t N>
  tuple_binder<std::array<T, N>>
  make_array_binder(binder_impl<T> const & binds = value_binder<T>()) {
    tuple_binder<std::array<T, N>> binder;
    return detail::array_binder_helper<N>(binder,
                                          json::binder::binder<T>(binds));
  }
#endif
}}