// Copyright (c) 2018-2019 Dr. Colin Hirsch and Daniel Frey
// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/

#ifndef TAO_PEGTL_CONTRIB_INTEGER_HPP
#define TAO_PEGTL_CONTRIB_INTEGER_HPP

#include <limits>
#include <type_traits>

#include "../ascii.hpp"
#include "../parse_error.hpp"
#include "../rules.hpp"

namespace tao
{
   namespace TAO_PEGTL_NAMESPACE
   {
      namespace integer
      {
         namespace internal
         {
            template< typename I, I Limit, typename Input >
            I actual_convert( const Input& in, std::size_t index )
            {
               static constexpr I cutoff = Limit / 10;
               static constexpr I cutlim = Limit % 10;

               I out = in.peek_char( index ) - '0';
               while( ++index < in.size() ) {
                  const I c = in.peek_char( index ) - '0';
                  if( ( out > cutoff ) || ( ( out == cutoff ) && ( c > cutlim ) ) ) {
                     throw parse_error( "integer out of range", in );
                  }
                  out *= 10;
                  out += c;
               }
               return out;
            }

            template< typename I, typename Input >
            I convert_positive( const Input& in, std::size_t index )
            {
               static constexpr I limit = ( std::numeric_limits< I >::max )();
               return actual_convert< I, limit >( in, index );
            }

            template< typename I, typename Input >
            I convert_negative( const Input& in, std::size_t index )
            {
               using U = typename std::make_unsigned< I >::type;
               static constexpr U limit = static_cast< U >( ( std::numeric_limits< I >::max )() ) + 1;
               return static_cast< I >( ~actual_convert< U, limit >( in, index ) ) + 1;
            }

         }  // namespace internal

         struct unsigned_rule
            : plus< digit >
         {
         };

         struct unsigned_action
         {
            // Assumes that 'in' contains a non-empty sequence of ASCII digits.

            template< typename Input, typename State, typename... States >
            static void apply( const Input& in, State& st, States&&... /*unused*/ )
            {
               using T = typename std::decay< decltype( st.converted ) >::type;
               static_assert( std::is_integral< T >::value, "need integral type" );
               static_assert( std::is_unsigned< T >::value, "need unsigned type" );
               st.converted = internal::convert_positive< T >( in, 0 );
            }
         };

         struct signed_rule
            : seq< opt< one< '+', '-' > >, plus< digit > >
         {
         };

         struct signed_action
         {
            // Assumes that 'in' contains a non-empty sequence of ASCII digits,
            // with optional leading sign; with sign, in.size() must be >= 2.

            template< typename Input, typename State, typename... States >
            static void apply( const Input& in, State& st, States&&... /*unused*/ )
            {
               using T = typename std::decay< decltype( st.converted ) >::type;
               static_assert( std::is_integral< T >::value, "need integral type" );
               static_assert( std::is_signed< T >::value, "need signed type" );
               const auto c = in.peek_char();
               if( c == '-' ) {
                  st.converted = internal::convert_negative< T >( in, 1 );
               }
               else {
                  st.converted = internal::convert_positive< T >( in, std::size_t( c == '+' ) );
               }
            }
         };

      }  // namespace integer

   }  // namespace TAO_PEGTL_NAMESPACE

}  // namespace tao

#endif
