daw_json_value_state.h

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// 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
 
#include "impl/version.h"
 
#include "impl/daw_json_arrow_proxy.h"
#include "impl/daw_json_parse_class.h"
#include "impl/daw_json_parse_name.h"
#include "impl/daw_json_value.h"
#include "impl/daw_murmur3.h"
 
#include <daw/daw_move.h>
#include <daw/daw_string_view.h>
#include <daw/daw_uint_buffer.h>
 
#include <cstddef>
#include <string_view>
#include <utility>
#include <vector>
 
namespace daw::json {
  inline namespace DAW_JSON_VER {
    namespace json_details {
      template<json_options_t PolicyFlags = default_policy_flag,
               typename Allocator = NoAllocator>
      class basic_stateful_json_value_state {
        using ParseState =
          TryDefaultParsePolicy<BasicParsePolicy<PolicyFlags, Allocator>>;
 
      public:
        daw::string_view name;
        daw::UInt32 hash_value;
        basic_json_value_iterator<PolicyFlags, Allocator> location;
 
        explicit constexpr basic_stateful_json_value_state(
          daw::string_view Name,
          basic_json_value_iterator<PolicyFlags, Allocator> val )
          : name( Name )
          , hash_value(
              daw::name_hash<ParseState::expect_long_strings>( Name ) )
          , location( std::move( val ) ) {}
 
        [[nodiscard]] constexpr bool is_match( daw::string_view Name ) const {
          return name == Name;
        }
 
        [[nodiscard]] constexpr bool is_match( daw::string_view Name,
                                               daw::UInt32 hash ) const {
          if( hash != hash_value ) {
            return false;
          }
          return name == Name;
        }
      };
    } // namespace json_details
 
    struct json_member_name {
      daw::string_view name;
      daw::UInt32 hash_value;
 
      constexpr json_member_name( std::string_view Name )
        : name( std::data( Name ), std::size( Name ) )
        , hash_value( daw::name_hash<false>( name ) ) {}
    };
 
    template<json_options_t PolicyFlags = json_details::default_policy_flag,
             typename Allocator = json_details::NoAllocator>
    class basic_stateful_json_value {
      using ParseState =
        TryDefaultParsePolicy<BasicParsePolicy<PolicyFlags, Allocator>>;
 
      basic_json_value<PolicyFlags, Allocator> m_value;
      std::vector<
        json_details::basic_stateful_json_value_state<PolicyFlags, Allocator>>
        m_locs{ };
 
      /***
       * Move parser until member name matches key if needed
       * @param member to move_to
       * @return position of member or size
       */
      [[nodiscard]] constexpr std::size_t move_to( json_member_name member ) {
        std::size_t pos = 0;
        std::size_t const Sz = std::size( m_locs );
        for( ; pos < Sz; ++pos ) {
          if( m_locs[pos].is_match( member.name, member.hash_value ) ) {
            return pos;
          }
        }
 
        auto it = [&] {
          if( m_locs.empty( ) ) {
            return m_value.begin( );
          }
          auto res = m_locs.back( ).location;
          ++res;
          return res;
        }( );
        auto const last = m_value.end( );
        while( it != last ) {
          auto name = it.name( );
          daw_json_assert_weak( name, ErrorReason::MissingMemberName );
          auto const &new_loc = m_locs.emplace_back(
            daw::string_view( std::data( *name ), std::size( *name ) ), it );
          if( new_loc.is_match( member.name ) ) {
            return pos;
          }
          ++pos;
          ++it;
        }
        return std::size( m_locs );
      }
 
      /***
       * Move parser until member index matches, if needed
       * @param index position of member to move to
       * @return position in members or size
       */
      [[nodiscard]] constexpr std::size_t move_to( std::size_t index ) {
        if( index < std::size( m_locs ) ) {
          return index;
        }
        auto it = [&] {
          if( m_locs.empty( ) ) {
            return m_value.begin( );
          }
          auto res = m_locs.back( ).location;
          ++res;
          return res;
        }( );
        auto last = m_value.end( );
        std::size_t pos = std::size( m_locs );
        while( it != last ) {
          auto name = it.name( );
          if( name ) {
            m_locs.emplace_back(
              daw::string_view( std::data( *name ), std::size( *name ) ), it );
          } else {
            m_locs.emplace_back( daw::string_view( ), it );
          }
          if( pos == index ) {
            return pos;
          }
          ++pos;
          ++it;
        }
        return std::size( m_locs );
      }
 
    public:
      constexpr basic_stateful_json_value(
        basic_json_value<PolicyFlags, Allocator> val )
        : m_value( std::move( val ) ) {
 
        daw_json_assert_weak( ( [&] {
                                auto t = m_value.type( );
                                return ( t == JsonBaseParseTypes::Class ) |
                                       ( t == JsonBaseParseTypes::Array );
                              }( ) ),
                              ErrorReason::ExpectedArrayOrClassStart,
                              val.get_raw_state( ) );
      }
 
      constexpr basic_stateful_json_value( )
        : basic_stateful_json_value(
            basic_json_value<PolicyFlags, Allocator>( "{}" ) ) {}
 
      constexpr basic_stateful_json_value( daw::string_view json_data )
        : basic_stateful_json_value(
            basic_json_value<PolicyFlags, Allocator>( json_data ) ) {}
      constexpr void reset( basic_json_value<PolicyFlags, Allocator> val ) {
        m_value = std::move( val );
        m_locs.clear( );
      }
 
      [[nodiscard]] constexpr basic_json_value<PolicyFlags, Allocator>
      operator[]( std::string_view key ) {
        std::size_t pos = move_to( json_member_name( key ) );
        daw_json_assert_weak( pos < std::size( m_locs ),
                              ErrorReason::UnknownMember );
        return m_locs[pos].location->value;
      }
 
      [[nodiscard]] constexpr basic_json_value<PolicyFlags, Allocator>
      operator[]( json_member_name member ) {
        std::size_t pos = move_to( member );
        daw_json_assert_weak( pos < std::size( m_locs ),
                              ErrorReason::UnknownMember );
        return m_locs[pos].location->value;
      }
 
      [[nodiscard]] constexpr basic_json_value<PolicyFlags, Allocator>
      at( std::string_view key ) {
        auto const k = std::string_view( std::data( key ), std::size( key ) );
        std::size_t pos = move_to( k );
        if( pos < std::size( m_locs ) ) {
          return m_locs[pos].location->value;
        }
        return { };
      }
 
      [[nodiscard]] std::size_t size( ) {
        JsonBaseParseTypes const current_type = m_value.type( );
        switch( current_type ) {
        case JsonBaseParseTypes::Array:
        case JsonBaseParseTypes::Class:
          return move_to( ( daw::numeric_limits<std::size_t>::max )( ) );
        case JsonBaseParseTypes::Number:
        case JsonBaseParseTypes::Bool:
        case JsonBaseParseTypes::String:
        case JsonBaseParseTypes::Null:
        case JsonBaseParseTypes::None:
        default:
          return 0;
        }
      }
 
      [[nodiscard]] std::size_t index_of( std::string_view key ) {
        auto const k = json_member_name( key );
        return move_to( k );
      }
 
      [[nodiscard]] constexpr bool contains( std::string_view key ) {
        auto const k = std::string_view( std::data( key ), std::size( key ) );
        return move_to( k ) < std::size( m_locs );
      }
 
      /***
       * Is the indexed member/element present
       * This method is O(N) worst case and O(1) if the locations have already
       * @param index position of member/element
       * @return true if the member/element is present
       */
      [[nodiscard]] constexpr bool contains( std::size_t index ) {
        return move_to( index ) < size( m_locs );
      }
 
      /***
       * Get the position of the named member
       * @tparam Integer An integer type
       * @param index position of member.  If negative it returns the position
       * from one past last, e.g. -1 is last item
       * @return The name of the member or an empty optional
       */
      template<typename Integer>
      [[nodiscard]] std::optional<std::string_view> name_of( Integer index ) {
        static_assert( std::is_integral_v<Integer>,
                       "Only integer indices are allowed" );
        if constexpr( std::is_signed_v<Integer> ) {
          if( index < 0 ) {
            index = -index;
            auto sz = size( );
            if( static_cast<std::size_t>( index ) >= sz ) {
              return { };
            }
            sz -= static_cast<std::size_t>( index );
            return std::string_view( std::data( m_locs[sz].name( ) ),
                                     std::size( m_locs[sz].name( ) ) );
          }
        }
        std::size_t pos = move_to( static_cast<std::size_t>( index ) );
        if( pos < std::size( m_locs ) ) {
          return std::string_view( std::data( m_locs[pos].name( ) ),
                                   std::size( m_locs[pos].name( ) ) );
        }
        return { };
      }
 
      /***
       * basic_json_value for the indexed member
       * @tparam Integer An integer type
       * @param index position of member.  If negative it returns the position
       * from one past last, e.g. -1 is last item
       * @pre index must exist
       * @return A new basic_json_value for the indexed member
       */
      template<
        typename Integer DAW_JSON_ENABLEIF( std::is_integral_v<Integer> )>
      DAW_JSON_REQUIRES( std::is_integral_v<Integer> )
      [[nodiscard]] constexpr basic_json_value<PolicyFlags, Allocator>
      operator[]( Integer index ) {
        if constexpr( std::is_signed_v<Integer> ) {
          if( index < 0 ) {
            index = -index;
            auto sz = size( );
            daw_json_assert_weak( ( static_cast<std::size_t>( index ) < sz ),
                                  ErrorReason::UnknownMember );
            sz -= static_cast<std::size_t>( index );
            return m_locs[sz].location->value;
          }
        }
        std::size_t pos = move_to( static_cast<std::size_t>( index ) );
        daw_json_assert_weak( pos < std::size( m_locs ),
                              ErrorReason::UnknownMember );
        return m_locs[pos].location->value;
      }
 
      /***
       * basic_json_value for the indexed member
       * @tparam Integer An integer type
       * @param index position of member.  If negative it returns the position
       * from one past last, e.g. -1 is last item
       * @return A new basic_json_value for the indexed member
       */
      template<
        typename Integer DAW_JSON_ENABLEIF( std::is_integral_v<Integer> )>
      DAW_JSON_REQUIRES( std::is_integral_v<Integer> )
      [[nodiscard]] constexpr std::optional<
        basic_json_value<PolicyFlags, Allocator>> at( Integer index ) {
        if constexpr( std::is_signed_v<Integer> ) {
          if( index < 0 ) {
            index = -index;
            auto sz = size( );
            if( static_cast<std::size_t>( index ) >= sz ) {
              return { };
            }
            sz -= static_cast<std::size_t>( index );
            return m_locs[sz].location->value( );
          }
        }
        std::size_t pos = move_to( static_cast<std::size_t>( index ) );
        if( pos < std::size( m_locs ) ) {
          return m_locs[pos].location->value( );
        }
        return { };
      }
 
      /***
       * @return A copy of the underlying basic_json_value
       */
      [[nodiscard]] constexpr basic_json_value<PolicyFlags, Allocator>
      get_json_value( ) const {
        return m_value;
      }
    };
 
    basic_stateful_json_value( ) -> basic_stateful_json_value<>;
 
    template<json_options_t PolicyFlags, typename Allocator>
    basic_stateful_json_value( basic_json_value<PolicyFlags, Allocator> )
      -> basic_stateful_json_value<PolicyFlags, Allocator>;
 
    basic_stateful_json_value( daw::string_view )
      -> basic_stateful_json_value<>;
 
    using json_value_state = basic_stateful_json_value<>;
  } // namespace DAW_JSON_VER
} // namespace daw::json