// Copyright (c) 2018-2021 Dr. Colin Hirsch and Daniel Frey
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)

#ifndef TAO_PEGTL_CONTRIB_IF_THEN_HPP
#define TAO_PEGTL_CONTRIB_IF_THEN_HPP

#include <type_traits>

#include "../config.hpp"

#include "../internal/enable_control.hpp"
#include "../internal/failure.hpp"
#include "../internal/if_then_else.hpp"
#include "../internal/seq.hpp"
#include "../internal/success.hpp"

namespace TAO_PEGTL_NAMESPACE
{
   namespace internal
   {
      template< typename Cond, typename Then >
      struct if_pair
      {};

      template< typename... Pairs >
      struct if_then;

      template< typename Cond, typename Then, typename... Pairs >
      struct if_then< if_pair< Cond, Then >, Pairs... >
         : if_then_else< Cond, Then, if_then< Pairs... > >
      {
         template< typename ElseCond, typename... Thens >
         using else_if_then = if_then< if_pair< Cond, Then >, Pairs..., if_pair< ElseCond, seq< Thens... > > >;

         template< typename... Thens >
         using else_then = if_then_else< Cond, Then, if_then< Pairs..., if_pair< success, seq< Thens... > > > >;
      };

      template<>
      struct if_then<>
         : failure
      {};

      template< typename... Pairs >
      inline constexpr bool enable_control< if_then< Pairs... > > = false;

   }  // namespace internal

   template< typename Cond, typename... Thens >
   struct if_then
      : internal::if_then< internal::if_pair< Cond, internal::seq< Thens... > > >
   {};

}  // namespace TAO_PEGTL_NAMESPACE

#endif
