daw_json_writer.h

Go to the documentation of this file.

// Copyright (c) Darrell Wright
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/beached/daw_json_link
//
 
#pragma once
 
// Allow writing to a Writer incrementally
 
#include "daw/json/impl/version.h"
 
#include "daw/json/concepts/daw_writable_output.h"
#include "daw/json/daw_json_link.h"
 
#if defined( DAW_JSON_HAS_REFLECTION )
#include <daw/daw_concepts.h>
#endif
 
#include <daw/daw_move.h>
#include <daw/traits/daw_traits_remove_cvref.h>
 
#include <type_traits>
#include <vector>
 
namespace daw::json {
  inline namespace DAW_JSON_VER {
    namespace json_writer_details {
      template<typename JsonClass, typename Value>
      using json_write_value_class_t = typename daw::conditional_t<
        std::is_same_v<use_default, JsonClass>,
        json_details::ident_trait<json_details::json_deduced_type, Value>,
        json_details::ident_trait<json_details::json_deduced_type,
                                  JsonClass>>::type;
 
      enum class json_writer_states : std::uint8_t {
        json_writer_nothing,
        json_writer_object,
        json_writer_array
      };
    } // namespace json_writer_details
 
    template<typename WritableType, typename StackType, auto... PolicyFlags>
    class json_writer_t {
      using iterator_t =
        decltype( json_details::make_output_iterator<PolicyFlags...>(
          std::declval<WritableType>( ) ) );
 
      StackType m_stack{ };
      json_writer_details::json_writer_states m_current_state =
        json_writer_details::json_writer_states::json_writer_nothing;
      bool m_is_first = true;
      bool m_is_key_written = false;
      iterator_t m_writer;
 
      constexpr void
      push_state( json_writer_details::json_writer_states new_state ) {
        m_stack.push_back( m_current_state );
        m_current_state = new_state;
      }
 
      constexpr void pop_state( ) {
        daw_json_ensure( not m_stack.empty( ), ErrorReason::OutputError );
        m_current_state = m_stack.back( );
        m_stack.pop_back( );
      }
 
      constexpr void write_item_prefix( ) {
        daw_json_ensure( not m_is_key_written, ErrorReason::OutputError );
        if( not m_is_first ) {
          m_writer.put( ',' );
        } else {
          m_is_first = false;
        }
        m_writer.next_member( );
      }
 
      constexpr void prepare_value( ) {
        if( m_current_state ==
            json_writer_details::json_writer_states::json_writer_nothing ) {
          daw_json_ensure( m_is_first, ErrorReason::OutputError );
          return;
        }
        if( m_current_state ==
            json_writer_details::json_writer_states::json_writer_object ) {
          daw_json_ensure( m_is_key_written, ErrorReason::OutputError );
          m_is_key_written = false;
          return;
        }
        if( m_current_state !=
            json_writer_details::json_writer_states::json_writer_nothing ) {
          write_item_prefix( );
        }
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void do_write_value( T const &value ) {
        prepare_value( );
        to_json<JsonClass>( value, m_writer.get( ) );
        m_is_first = false;
      }
 
    public:
      template<typename W>
      explicit constexpr json_writer_t( W &&writer )
        : m_writer( json_details::make_output_iterator<PolicyFlags...>(
            DAW_FWD( writer ) ) ) {}
      json_writer_t( json_writer_t const & ) = delete;
      json_writer_t &operator=( json_writer_t const & ) = delete;
      json_writer_t( json_writer_t &&other ) = delete;
      json_writer_t &operator=( json_writer_t && ) = delete;
 
      constexpr void finalize( ) {
        if( m_is_key_written ) {
          write_value( nullptr );
        }
        while( m_current_state !=
               json_writer_details::json_writer_states::json_writer_nothing ) {
          switch( m_current_state ) {
          case json_writer_details::json_writer_states::json_writer_object:
            close_object( );
            break;
          case json_writer_details::json_writer_states::json_writer_array:
            close_array( );
            break;
          case json_writer_details::json_writer_states::json_writer_nothing:
          default:
            break;
          }
        }
      }
 
      constexpr void reset( ) {
        finalize( );
        m_current_state =
          json_writer_details::json_writer_states::json_writer_nothing;
        m_is_first = true;
        m_is_key_written = false;
      }
 
      DAW_CPP20_CX_DTOR ~json_writer_t( ) noexcept(
        noexcept( m_writer.put( ' ' ) ) ) {
        finalize( );
      }
 
      constexpr void open_object( ) {
        prepare_value( );
        push_state(
          json_writer_details::json_writer_states::json_writer_object );
        m_writer.put( '{' );
        m_writer.add_indent( );
        m_is_first = true;
      }
 
      constexpr void close_object( ) {
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_object,
          ErrorReason::OutputError );
        if( m_is_key_written ) {
          write_value( nullptr );
        }
        m_writer.del_indent( );
        if( not m_is_first ) {
          m_writer.next_member( );
        }
        m_writer.put( '}' );
        pop_state( );
        m_is_first = false;
      }
 
      constexpr void open_array( ) {
        prepare_value( );
        push_state(
          json_writer_details::json_writer_states::json_writer_array );
        m_is_first = true;
        m_writer.add_indent( );
        m_writer.put( '[' );
      }
 
      constexpr void close_array( ) {
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_array,
          ErrorReason::OutputError );
        m_writer.del_indent( );
        if( not m_is_first ) {
          m_writer.next_member( );
        }
        m_writer.put( ']' );
        pop_state( );
        m_is_first = false;
      }
 
      constexpr void write_value( std::nullptr_t ) {
        write_null( );
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_value( T const &value ) {
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_object or
            m_is_key_written,
          ErrorReason::OutputError );
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_nothing or
            m_is_first,
          ErrorReason::OutputError );
        do_write_value<JsonClass>( value );
      }
 
      template<typename T, typename T2, typename... Ts>
      constexpr void write_value( T const &value, T2 const &value2,
                                  Ts const &...values ) {
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_object or
            m_is_key_written,
          ErrorReason::OutputError );
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_nothing or
            m_is_first,
          ErrorReason::OutputError );
        open_array( );
        write_array_values( value, value2, values... );
        close_array( );
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_value( std::initializer_list<T> const &values ) {
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_object or
            m_is_key_written,
          ErrorReason::OutputError );
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_nothing or
            m_is_first,
          ErrorReason::OutputError );
        open_array( );
        write_array_values<JsonClass>( values );
        close_array( );
      }
 
      template<typename JsonClass = use_default, std::size_t N>
      constexpr void write_value( char const ( &str )[N] ) {
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_object or
            m_is_key_written,
          ErrorReason::OutputError );
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_nothing or
            m_is_first,
          ErrorReason::OutputError );
        do_write_value<JsonClass>( daw::string_view( str, N - 1 ) );
      }
 
      constexpr void add_key( daw::string_view name ) {
        if( m_is_key_written ) {
          write_value( nullptr );
        }
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_object,
          ErrorReason::OutputError );
 
        write_item_prefix( );
        m_writer.write( "\"", name, "\":", m_writer.space );
        m_is_key_written = true;
      }
 
      constexpr void write_key_value( daw::string_view name, std::nullptr_t ) {
        add_key( name );
        write_null( );
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_key_value( daw::string_view name,
                                      std::initializer_list<T> const &values ) {
        add_key( name );
        open_array( );
        write_array_values<JsonClass>( values );
        close_array( );
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_key_value( daw::string_view name, T const &value ) {
        add_key( name );
        write_value<JsonClass>( value );
      }
 
      template<typename T, typename T2, typename... Ts>
      constexpr void write_key_value( daw::string_view name, T const &value,
                                      T2 const &value2, Ts const &...values ) {
        add_key( name );
        open_array( );
        write_array_values( value, value2, values... );
        close_array( );
      }
 
      template<typename JsonClass = use_default, std::size_t N>
      constexpr void write_key_value( daw::string_view name,
                                      char const ( &str )[N] ) {
        add_key( name );
        write_value<JsonClass>( daw::string_view( str, N - 1 ) );
      }
 
      // Must be in array state
      template<
        typename JsonClass = use_default,
        typename Range DAW_ENABLEIF( daw::traits::is_container_like_v<Range> )>
      DAW_REQUIRES( daw::traits::is_container_like_v<Range> )
      constexpr void write_array_values( Range const &values ) {
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_array,
          ErrorReason::OutputError );
        for( auto const &value : values ) {
          do_write_value<JsonClass>( value );
        }
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void
      write_array_values( std::initializer_list<T> const &values ) {
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_array,
          ErrorReason::OutputError );
        for( auto const &value : values ) {
          write_value<JsonClass>( value );
        }
      }
 
      template<typename T, typename... Ts>
      constexpr void write_array_values( T const &value, Ts const &...values ) {
        daw_json_ensure(
          m_current_state ==
            json_writer_details::json_writer_states::json_writer_array,
          ErrorReason::OutputError );
        write_value( value );
        (void)( ( write_value( values ), true ) and ... );
      }
 
      constexpr void write_boolean( bool b ) {
        write_value( b );
      }
 
      constexpr void write_null( ) {
        daw_json_ensure(
          m_current_state !=
              json_writer_details::json_writer_states::json_writer_nothing or
            m_is_first,
          ErrorReason::OutputError );
        prepare_value( );
        m_writer.write( "null" );
        m_is_first = false;
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_number( T const &value ) {
        using JsonMember =
          json_writer_details::json_write_value_class_t<JsonClass, T>;
        constexpr JsonBaseParseTypes json_base_type =
          JsonMember::underlying_json_type;
        static_assert(
          json_base_type == JsonBaseParseTypes::Number or
            json_base_type == JsonBaseParseTypes::Bool,
          "The underlying mapping must be a number or boolean type" );
        if constexpr( json_base_type == JsonBaseParseTypes::Bool ) {
          write_value<JsonClass>( static_cast<bool>( value ) ? 1 : 0 );
          return;
        } else {
          write_value<JsonClass>( value );
        }
      }
 
      template<typename JsonClass = use_default, typename T>
      constexpr void write_string( T const &value ) {
        using JsonMember =
          json_writer_details::json_write_value_class_t<JsonClass, T>;
        constexpr JsonBaseParseTypes json_base_type =
          JsonMember::underlying_json_type;
        if constexpr( json_base_type == JsonBaseParseTypes::String ) {
          write_value<JsonClass>( value );
        } else if constexpr( json_base_type == JsonBaseParseTypes::Bool or
                             json_base_type == JsonBaseParseTypes::Number ) {
          prepare_value( );
          m_writer.put( '"' );
          to_json<JsonClass>( value, m_writer.get( ) );
          m_writer.put( '"' );
          m_is_first = false;
        } else {
          auto const tmp = to_json( value );
          do_write_value<json_string_no_name<>>( tmp );
        }
      }
 
      template<typename JsonClass = use_default, std::size_t N>
      constexpr void write_string( char const ( &str )[N] ) {
        write_value<JsonClass>( daw::string_view( str, N - 1 ) );
      }
 
#if defined( DAW_JSON_HAS_REFLECTION )
      constexpr void write_enum_string( daw::EnumType auto e ) {
        write_string( refl_details::enum_to_string( e ) );
      }
#endif
    };
 
    template<auto... PolicyFlags, typename WriterType>
    constexpr auto json_writer( WriterType &&writer ) {
      return json_writer_t<daw::remove_cvref_t<WriterType>,
                           std::vector<json_writer_details::json_writer_states>,
                           PolicyFlags...>( writer );
    }
  } // namespace DAW_JSON_VER
} // namespace daw::json