daw_json_parse_name.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 "version.h"
 
#include "daw_json_assert.h"
#include "daw_json_find_result.h"
#include "daw_json_parse_std_string.h"
#include "daw_not_const_ex_functions.h"
 
#include <daw/daw_string_view.h>
 
#include <cstddef>
#include <daw/stdinc/data_access.h>
#include <daw/stdinc/range_access.h>
#include <limits>
 
namespace daw::json {
  inline namespace DAW_JSON_VER {
    namespace json_details {
      namespace name::name_parser {
        /*
         * end of string " -> name value separating : -> any white space
         * the string can be escaped too
         */
        template<typename ParseState>
        static constexpr void trim_end_of_name( ParseState &parse_state ) {
          parse_state.trim_left( );
          // TODO: should we check for end
          daw_json_assert_weak( parse_state.front_checked( ) == ':',
                                ErrorReason::InvalidMemberName, parse_state );
          parse_state.remove_prefix( );
          parse_state.trim_left( );
        }
 
        template<typename ParseState>
        [[nodiscard]] DAW_ATTRIB_INLINE static constexpr daw::string_view
        parse_nq( ParseState &parse_state ) {
          if constexpr( ParseState::allow_escaped_names ) {
            auto r = skip_string_nq( parse_state );
            trim_end_of_name( parse_state );
            return daw::string_view( std::data( r ), std::size( r ) );
          } else {
            char const *const ptr = parse_state.first;
            if constexpr( ParseState::is_unchecked_input ) {
              parse_state.template move_to_next_of_unchecked<'"'>( );
            } else {
              parse_state.template move_to_next_of_checked<'"'>( );
            }
            daw_json_assert_weak( parse_state.is_quotes_checked( ) and
                                    *std::prev( parse_state.first ) != '\\',
                                  ErrorReason::InvalidString, parse_state );
            auto result = daw::string_view( ptr, parse_state.first );
            parse_state.remove_prefix( );
            trim_end_of_name( parse_state );
            return result;
          }
        }
      } // namespace name::name_parser
 
      struct pop_json_path_result {
        daw::string_view current{ };
        char found_char = 0;
      };
      // Paths are specified with dot separators, if the name has a dot in it,
      // it must be escaped
      // memberA.memberB.member\.C has 3 parts['memberA', 'memberB', 'member.C']
      [[nodiscard]] static constexpr pop_json_path_result
      pop_json_path( daw::string_view &path ) {
        auto result = pop_json_path_result{ };
        if( path.empty( ) ) {
          return result;
        }
        if( path.front( ) == '.' ) {
          path.remove_prefix( );
        }
        result.current =
          path.pop_front_until( [&, in_escape = false]( char c ) mutable {
            if( in_escape ) {
              in_escape = false;
              return false;
            }
            switch( c ) {
            case '\\':
              in_escape = true;
              return false;
            case '.':
            case '[':
            case ']':
              result.found_char = c;
              return true;
            default:
              return false;
            }
          } );
        return result;
      }
 
      [[nodiscard]] static constexpr bool
      json_path_compare( daw::string_view json_path_item,
                         daw::string_view member_name ) {
        if( json_path_item.front( ) == '\\' ) {
          json_path_item.remove_prefix( );
        }
        while( not json_path_item.empty( ) and not member_name.empty( ) ) {
          if( json_path_item.front( ) != member_name.front( ) ) {
            return false;
          }
          json_path_item.remove_prefix( );
          if( not json_path_item.empty( ) and
              json_path_item.front( ) == '\\' ) {
            json_path_item.remove_prefix( );
          }
          member_name.remove_prefix( );
        }
        return std::size( json_path_item ) == std::size( member_name );
      }
 
      template<typename Result, typename ForwardIterator>
      constexpr Result parse_unsigned_int( ForwardIterator first,
                                           ForwardIterator last ) {
        std::size_t count = std::numeric_limits<Result>::digits;
 
        daw_json_ensure( '-' != *first, ErrorReason::InvalidNumber );
 
        Result result = 0;
        for( ; first != last and count > 0; ++first, --count ) {
          result *= static_cast<Result>( 10 );
          Result val =
            static_cast<Result>( *first ) - static_cast<Result>( '0' );
          result += val;
        }
        daw_json_ensure( first == last, ErrorReason::InvalidNumber );
        return result;
      }
 
      // Get the next member name
      // Assumes that the current item in stream is a double quote
      // Ensures that the stream is left at the position of the associated
      // value(e.g after the colon(:) and trimmed)
      template<typename ParseState>
      [[nodiscard]] DAW_ATTRIB_FLATTEN static inline constexpr daw::string_view
      parse_name( ParseState &parse_state ) {
        daw_json_assert_weak( parse_state.is_quotes_checked( ),
                              ErrorReason::InvalidMemberName, parse_state );
        parse_state.remove_prefix( );
        return name::name_parser::parse_nq( parse_state );
      }
 
      template<typename ParseState>
      static constexpr bool find_range2( ParseState &parse_state,
                                         daw::string_view path ) {
 
        auto pop_result = pop_json_path( path );
        while( not pop_result.current.empty( ) ) {
          if( pop_result.found_char == ']' ) {
            // Array Index
            daw_json_assert_weak( parse_state.is_opening_bracket_checked( ),
                                  ErrorReason::InvalidJSONPath, parse_state );
            parse_state.remove_prefix( );
            parse_state.trim_left_unchecked( );
            auto idx = parse_unsigned_int<std::size_t>(
              pop_result.current.data( ), pop_result.current.data_end( ) );
 
            while( idx > 0 ) {
              --idx;
              (void)skip_value( parse_state );
              parse_state.trim_left_checked( );
              if( ( idx > 0 ) & ( parse_state.has_more( ) and
                                  ( parse_state.front( ) != ',' ) ) ) {
                return false;
              }
              parse_state.move_next_member_or_end( );
            }
          } else {
            daw_json_assert_weak( parse_state.is_opening_brace_checked( ),
                                  ErrorReason::InvalidJSONPath, parse_state );
            parse_state.remove_prefix( );
            parse_state.trim_left_unchecked( );
            auto name = parse_name( parse_state );
            while( not json_path_compare( pop_result.current, name ) ) {
              (void)skip_value( parse_state );
              parse_state.move_next_member_or_end( );
              if( parse_state.empty( ) or parse_state.front( ) != '"' ) {
                return false;
              }
              name = parse_name( parse_state );
            }
          }
          pop_result = pop_json_path( path );
        }
        return true;
      }
 
      template<typename ParsePolicy>
      [[nodiscard]] static constexpr find_result<ParsePolicy>
      find_range( daw::string_view str, daw::string_view start_path ) {
        auto parse_state =
          ParsePolicy( std::data( str ), daw::data_end( str ) );
        parse_state.trim_left_checked( );
        bool found = true;
        if( parse_state.has_more( ) and not start_path.empty( ) ) {
          found = find_range2( parse_state, start_path );
        }
        return find_result<ParsePolicy>{ parse_state, found };
      }
 
      template<typename ParsePolicy, typename Allocator>
      [[nodiscard]] static constexpr find_result<ParsePolicy>
      find_range( daw::string_view str, daw::string_view start_path,
                  Allocator &alloc ) {
        static_assert(
          std::is_same_v<char const *, typename ParsePolicy::iterator>,
          "Only char const * ranges are currently supported" );
        auto parse_state = ParsePolicy::with_allocator(
          std::data( str ), daw::data_end( str ), alloc );
        parse_state.trim_left_checked( );
        if( parse_state.has_more( ) and not start_path.empty( ) ) {
          if( not find_range2( parse_state, start_path ) ) {
            return find_result<ParsePolicy>{ parse_state, false };
          }
        }
        return find_result<ParsePolicy>{ parse_state, true };
      }
    } // namespace json_details
  } // namespace DAW_JSON_VER
} // namespace daw::json