lift.h

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*
* This file contains private API, this might break at any time between releases.
* You have been warned!
*
*/
#ifndef ZYPPNG_MONADIC_LIFT_H_INCLUDED
#define ZYPPNG_MONADIC_LIFT_H_INCLUDED
 
#include <utility>
#include <memory>
#include <iostream>
 
#include <zypp-core/zyppng/meta/Functional>
#include <zypp-core/zyppng/pipelines/AsyncResult>
 
namespace zyppng {
 
  namespace detail {
  template <typename LiftedFun, typename extra = void >
  struct lifter {
 
    lifter( LiftedFun &&fun ) : _fun(std::move(fun)) {}
    lifter( lifter && ) = default;
    ~lifter(){}
 
    template< typename T1
      , typename T2
      , typename Ret = std::pair<std::result_of_t<LiftedFun(T1)>, T2>
      >
    Ret operator()( std::pair<T1, T2> &&data ) {
      return std::make_pair( std::invoke( _fun, std::move(data.first) ), std::move(data.second) );
    }
  private:
    LiftedFun _fun;
  };
 
  template < typename AsyncOp >
  struct lifter< std::shared_ptr<AsyncOp>, std::void_t< std::enable_if_t< zyppng::detail::is_async_op<AsyncOp>::value > > > {
 
    using LiftedFun = std::shared_ptr<AsyncOp>;
 
    lifter( LiftedFun &&fun ) : _fun(std::move(fun)) {}
    lifter( lifter && ) = default;
    ~lifter(){}
 
    template< typename T1
      , typename T2
      >
    auto operator()( std::pair<T1, T2> &&data ) {
 
      using namespace zyppng;
      using namespace zyppng::operators;
 
      return std::move(data.first)
             | ( std::move(_fun) )
             | [ other = std::move(data.second)]( auto && res ) mutable {
                 return std::make_pair( std::forward<decltype (res)>(res), std::move(other) );
               };
    }
  private:
    LiftedFun _fun;
  };
  }
 
  template< typename Fun >
  auto lift ( Fun && func ) {
    return detail::lifter<Fun>( std::forward<Fun>(func) );
  }
 
}
 
#endif