ChaiScript/include/chaiscript/utility/json.hpp

// From github.com/nbsdx/SimpleJSON. 
// Released under the DWTFYW PL
//



#ifndef SIMPLEJSON_HPP
#define SIMPLEJSON_HPP


#include <cstdint>
#include <cmath>
#include <cctype>
#include <string>
#include <vector>
#include <map>
#include <type_traits>
#include <initializer_list>
#include <ostream>
#include <iostream>
#include <variant>
#include "../chaiscript_defines.hpp"
#include "quick_flat_map.hpp"

namespace json {

using std::enable_if;
using std::initializer_list;
using std::is_same;
using std::is_convertible;
using std::is_integral;
using std::is_floating_point;




class JSON
{
  public:
    enum class Class {
      Null = 0,
      Object,
      Array,
      String,
      Floating,
      Integral,
      Boolean
    };

  private:


    using Data = std::variant<std::nullptr_t, chaiscript::utility::QuickFlatMap<std::string, JSON>, std::vector<JSON>, std::string, double, std::int64_t, bool>;

    struct Internal
    {
      Internal(std::nullptr_t) : d(nullptr) { }
      Internal() : d(nullptr) { }
      Internal(Class c) : d(make_type(c)) { }
      template<typename T> Internal(T t) : d(std::move(t)) { }

      static Data make_type(Class c) {
        switch (c) {
          case Class::Null:     return nullptr;
          case Class::Object:   return chaiscript::utility::QuickFlatMap<std::string, JSON>{};
          case Class::Array:    return std::vector<JSON>{};
          case Class::String:   return std::string{};
          case Class::Floating: return double{};
          case Class::Integral: return std::int64_t{};
          case Class::Boolean:  return bool{};
        }
        throw std::runtime_error("unknown type");
      }

      void set_type(Class c) {
        if (type() != c) {
          d = make_type(c);
        }
      }

      Class type() const noexcept {
        return Class(d.index());
      }


      template<auto ClassValue, typename Visitor, typename Or>
      decltype(auto) visit_or(Visitor &&visitor, Or &&other) const
      {
        if (type() == Class(ClassValue)) {
          return visitor(std::get<static_cast<std::size_t>(ClassValue)>(d));
        } else {
          return other();
        }
      }

      template<auto ClassValue>
      auto &get_set_type() {
        set_type(ClassValue);
        return (std::get<static_cast<std::size_t>(ClassValue)>(d));
      }

      auto &Map() {
        return get_set_type<Class::Object>();
      }
      auto &Vector() {
        return get_set_type<Class::Array>();
      }
      auto &String() {
        return get_set_type<Class::String>();
      }
      auto &Int() {
        return get_set_type<Class::Integral>();
      }
      auto &Float() {
        return get_set_type<Class::Floating>();
      }
      auto &Bool() {
        return get_set_type<Class::Boolean>();
      }

      auto Map() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::Object)>(&d);
      }
      auto Vector() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::Array)>(&d);
      }
      auto String() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::String)>(&d);
      }
      auto Int() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::Integral)>(&d);
      }
      auto Float() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::Floating)>(&d);
      }
      auto Bool() const noexcept {
        return std::get_if<static_cast<std::size_t>(Class::Boolean)>(&d);
      }

      Data d;
    };


    Internal internal;

  public:

    template <typename Container>
      class JSONWrapper {
        Container *object = nullptr;

        public:
        JSONWrapper( Container *val ) : object( val ) {}
        JSONWrapper( std::nullptr_t ) {}

        typename Container::iterator begin() { return object ? object->begin() : typename Container::iterator(); }
        typename Container::iterator end() { return object ? object->end() : typename Container::iterator(); }
        typename Container::const_iterator begin() const { return object ? object->begin() : typename Container::iterator(); }
        typename Container::const_iterator end() const { return object ? object->end() : typename Container::iterator(); }
      };

    template <typename Container>
      class JSONConstWrapper {
        const Container *object = nullptr;

        public:
        JSONConstWrapper( const Container *val ) : object( val ) {}
        JSONConstWrapper( std::nullptr_t ) {}

        typename Container::const_iterator begin() const noexcept { return object ? object->begin() : typename Container::const_iterator(); }
        typename Container::const_iterator end() const noexcept { return object ? object->end() : typename Container::const_iterator(); }
      };

    JSON() = default;
    JSON( std::nullptr_t ) {} 

    explicit JSON(Class type)
      : internal(type)
    {
    }

    JSON( initializer_list<JSON> list ) 
      : internal(Class::Object)
    {
      for( auto i = list.begin(), e = list.end(); i != e; ++i, ++i ) {
        operator[]( i->to_string() ) = *std::next( i );
      }
    }

    template <typename T>
      explicit JSON( T b, typename enable_if<is_same<T,bool>::value>::type* = nullptr ) noexcept : internal( static_cast<bool>(b) ) {}

    template <typename T>
      explicit JSON( T i, typename enable_if<is_integral<T>::value && !is_same<T,bool>::value>::type* = nullptr ) noexcept : internal( static_cast<std::int64_t>(i) ) {}

    template <typename T>
      explicit JSON( T f, typename enable_if<is_floating_point<T>::value>::type* = nullptr ) noexcept : internal( static_cast<double>(f) ) {}

    template <typename T>
      explicit JSON( T s, typename enable_if<is_convertible<T,std::string>::value>::type* = nullptr ) : internal( static_cast<std::string>(s) ) {}



    static JSON Load( const std::string & );

    JSON& operator[]( const std::string &key ) {
      return internal.Map().operator[]( key );
    }

    JSON& operator[]( const size_t index ) {
      auto &vec = internal.Vector();
      if( index >= vec.size() ) {
        vec.resize( index + 1 );
      }

      return vec.operator[]( index );
    }


    JSON &at( const std::string &key ) {
      return operator[]( key );
    }

    const JSON &at( const std::string &key ) const {
      return internal.visit_or<Class::Object>(
          [&](const auto &m)->const JSON &{ return m.at(key); },
          []()->const JSON &{ throw std::range_error("Not an object, no keys"); }
        );
    }

    JSON &at( size_t index ) {
      return operator[]( index );
    }

    const JSON &at( size_t index ) const {
      return internal.visit_or<Class::Array>(
          [&](const auto &m)->const JSON&{ return m.at(index); },
          []()->const JSON &{ throw std::range_error("Not an array, no indexes"); }
        );
    }

    auto length() const noexcept {
      return internal.visit_or<Class::Array>(
          [&](const auto &m){ return static_cast<int>(m.size()); },
          [](){ return -1; }
        );
    }

    bool has_key( const std::string &key ) const noexcept {
      return internal.visit_or<Class::Object>(
          [&](const auto &m){ return m.count(key) != 0; },
          [](){ return false; }
        );
    }

    int size() const noexcept {
      if (auto m = internal.Map(); m != nullptr) {
        return static_cast<int>(m->size());
      } if (auto v = internal.Vector(); v != nullptr) {
        return static_cast<int>(v->size());
      } else {
        return -1;
      }
    }

    Class JSONType() const noexcept { return internal.type(); }

    /// Functions for getting primitives from the JSON object.
    bool is_null() const noexcept { return internal.type() == Class::Null; }

    std::string to_string() const noexcept { 
      return internal.visit_or<Class::String>(
          [](const auto &o){ return o; },
          [](){ return std::string{}; }
        );
    }
    double to_float() const noexcept { 
      return internal.visit_or<Class::Floating>(
          [](const auto &o){ return o; },
          [](){ return double{}; }
        );
    }
    std::int64_t to_int() const noexcept { 
      return internal.visit_or<Class::Integral>(
          [](const auto &o){ return o; },
          [](){ return std::int64_t{}; }
        );
    }
    bool to_bool() const noexcept { 
      return internal.visit_or<Class::Boolean>(
          [](const auto &o){ return o; },
          [](){ return false; }
        );
    }

    JSONWrapper<chaiscript::utility::QuickFlatMap<std::string, JSON>> object_range() {
      return std::get_if<static_cast<std::size_t>(Class::Object)>(&internal.d);
    }

    JSONWrapper<std::vector<JSON>> array_range() {
      return std::get_if<static_cast<std::size_t>(Class::Array)>(&internal.d);
    }

    JSONConstWrapper<chaiscript::utility::QuickFlatMap<std::string, JSON>> object_range() const {
      return std::get_if<static_cast<std::size_t>(Class::Object)>(&internal.d);
    }

    JSONConstWrapper<std::vector<JSON>> array_range() const { 
      return std::get_if<static_cast<std::size_t>(Class::Array)>(&internal.d);
    }

    std::string dump( long depth = 1, std::string tab = "  ") const {
      switch( internal.type() ) {
        case Class::Null:
          return "null";
        case Class::Object: {
                              std::string pad = "";
                              for( long i = 0; i < depth; ++i, pad += tab ) { }

                              std::string s = "{\n";
                              bool skip = true;
                              for( auto &p : *internal.Map() ) {
                                if( !skip ) { s += ",\n"; }
                                s += ( pad + "\"" + json_escape(p.first) + "\" : " + p.second.dump( depth + 1, tab ) );
                                skip = false;
                              }
                              s += ( "\n" + pad.erase( 0, 2 ) + "}" ) ;
                              return s;
                            }
        case Class::Array: {
                             std::string s = "[";
                             bool skip = true;
                             for( auto &p : *internal.Vector() ) {
                               if( !skip ) { s += ", "; }
                               s += p.dump( depth + 1, tab );
                               skip = false;
                             }
                             s += "]";
                             return s;
                           }
        case Class::String:
                           return "\"" + json_escape( *internal.String() ) + "\"";
        case Class::Floating:
                           return std::to_string( *internal.Float() );
        case Class::Integral:
                           return std::to_string( *internal.Int() );
        case Class::Boolean:
                           return *internal.Bool() ? "true" : "false";
      }

      throw std::runtime_error("Unhandled JSON type");
    }


  private:
    static std::string json_escape( const std::string &str ) {
      std::string output;
      for(char i : str) {
        switch( i ) {
          case '\"': output += "\\\""; break;
          case '\\': output += "\\\\"; break;
          case '\b': output += "\\b";  break;
          case '\f': output += "\\f";  break;
          case '\n': output += "\\n";  break;
          case '\r': output += "\\r";  break;
          case '\t': output += "\\t";  break;
          default  : output += i; break;
        }
}
      return output;
    }


  private:
};


struct JSONParser {
  static bool isspace(const char c) noexcept
  {
#ifdef CHAISCRIPT_MSVC
    // MSVC warns on these line in some circumstances
#pragma warning(push)
#pragma warning(disable : 6330)
#endif
    return ::isspace(c) != 0;
#ifdef CHAISCRIPT_MSVC
#pragma warning(pop)
#endif


  }

  static void consume_ws( const std::string &str, size_t &offset ) {
    while( isspace( str.at(offset) ) && offset <= str.size() ) { ++offset; }
  }

  static JSON parse_object( const std::string &str, size_t &offset ) {
    JSON Object( JSON::Class::Object );

    ++offset;
    consume_ws( str, offset );
    if( str.at(offset) == '}' ) {
      ++offset; return Object;
    }

    for (;offset<str.size();) {
      JSON Key = parse_next( str, offset );
      consume_ws( str, offset );
      if( str.at(offset) != ':' ) {
        throw std::runtime_error(std::string("JSON ERROR: Object: Expected colon, found '") + str.at(offset) + "'\n");
      }
      consume_ws( str, ++offset );
      JSON Value = parse_next( str, offset );
      Object[Key.to_string()] = Value;

      consume_ws( str, offset );
      if( str.at(offset) == ',' ) {
        ++offset; continue;
      }
      else if( str.at(offset) == '}' ) {
        ++offset; break;
      }
      else {
        throw std::runtime_error(std::string("JSON ERROR: Object: Expected comma, found '") + str.at(offset) + "'\n");
      }
    }

    return Object;
  }

  static JSON parse_array( const std::string &str, size_t &offset ) {
    JSON Array( JSON::Class::Array );
    size_t index = 0;

    ++offset;
    consume_ws( str, offset );
    if( str.at(offset) == ']' ) {
      ++offset; return Array;
    }

    for (;offset < str.size();) {
      Array[index++] = parse_next( str, offset );
      consume_ws( str, offset );

      if( str.at(offset) == ',' ) {
        ++offset; continue;
      }
      else if( str.at(offset) == ']' ) {
        ++offset; break;
      }
      else {
        throw std::runtime_error(std::string("JSON ERROR: Array: Expected ',' or ']', found '") + str.at(offset) + "'\n");
      }
    }

    return Array;
  }

  static JSON parse_string( const std::string &str, size_t &offset ) {
    std::string val;
    for( char c = str.at(++offset); c != '\"' ; c = str.at(++offset) ) {
      if( c == '\\' ) {
        switch( str.at(++offset) ) {
          case '\"': val += '\"'; break;
          case '\\': val += '\\'; break;
          case '/' : val += '/' ; break;
          case 'b' : val += '\b'; break;
          case 'f' : val += '\f'; break;
          case 'n' : val += '\n'; break;
          case 'r' : val += '\r'; break;
          case 't' : val += '\t'; break;
          case 'u' : {
                       val += "\\u" ;
                       for( size_t i = 1; i <= 4; ++i ) {
                         c = str.at(offset+i);
                         if( (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F') ) {
                           val += c;
                         } else {
                           throw std::runtime_error(std::string("JSON ERROR: String: Expected hex character in unicode escape, found '") + c + "'");
                         }
                       }
                       offset += 4;
                     } break;
          default  : val += '\\'; break;
        }
      } else {
        val += c;
      }
    }
    ++offset;
    return JSON(val);
  }

  static JSON parse_number( const std::string &str, size_t &offset ) {
    std::string val, exp_str;
    char c = '\0';
    bool isDouble = false;
    bool isNegative = false;
    std::int64_t exp = 0;
    bool isExpNegative = false;
    if( offset < str.size() && str.at(offset) == '-' ) {
      isNegative = true;
      ++offset;
    }
    for (; offset < str.size() ;) {
      c = str.at(offset++);
      if( c >= '0' && c <= '9' ) {
        val += c;
      } else if( c == '.' && !isDouble ) {
        val += c; 
        isDouble = true;
      } else {
        break;
      }
    }
    if( offset < str.size() && (c == 'E' || c == 'e' )) {
      c = str.at(offset++);
      if( c == '-' ) { 
        isExpNegative = true;
      } else if( c == '+' ) {
        // do nothing
      } else { 
        --offset; 
      }

      for (; offset < str.size() ;) {
        c = str.at(offset++);
        if( c >= '0' && c <= '9' ) {
          exp_str += c;
        } else if( !isspace( c ) && c != ',' && c != ']' && c != '}' ) {
          throw std::runtime_error(std::string("JSON ERROR: Number: Expected a number for exponent, found '") + c + "'");
        }
        else {
          break;
        }
      }
      exp = chaiscript::parse_num<std::int64_t>( exp_str ) * (isExpNegative?-1:1);
    }
    else if( offset < str.size() && (!isspace( c ) && c != ',' && c != ']' && c != '}' )) {
      throw std::runtime_error(std::string("JSON ERROR: Number: unexpected character '") + c + "'");
    }
    --offset;

    if( isDouble ) {
      return JSON((isNegative?-1:1) * chaiscript::parse_num<double>( val ) * std::pow( 10, exp ));
    } else {
      if( !exp_str.empty() ) {
        return JSON((isNegative?-1:1) * static_cast<double>(chaiscript::parse_num<std::int64_t>( val )) * std::pow( 10, exp ));
      } else {
        return JSON((isNegative?-1:1) * chaiscript::parse_num<std::int64_t>( val ));
      }
    }
  }

  static JSON parse_bool( const std::string &str, size_t &offset ) {
    if( str.substr( offset, 4 ) == "true" ) {
      offset += 4;
      return JSON(true);
    } else if( str.substr( offset, 5 ) == "false" ) {
      offset += 5;
      return JSON(false);
    } else {
      throw std::runtime_error(std::string("JSON ERROR: Bool: Expected 'true' or 'false', found '") + str.substr( offset, 5 ) + "'");
    }
  }

  static JSON parse_null( const std::string &str, size_t &offset ) {
    if( str.substr( offset, 4 ) != "null" ) {
      throw std::runtime_error(std::string("JSON ERROR: Null: Expected 'null', found '") + str.substr( offset, 4 ) + "'");
    }
    offset += 4;
    return JSON();
  }

  static JSON parse_next( const std::string &str, size_t &offset ) {
    char value;
    consume_ws( str, offset );
    value = str.at(offset);
    switch( value ) {
      case '[' : return parse_array( str, offset );
      case '{' : return parse_object( str, offset );
      case '\"': return parse_string( str, offset );
      case 't' :
      case 'f' : return parse_bool( str, offset );
      case 'n' : return parse_null( str, offset );
      default  : if( ( value <= '9' && value >= '0' ) || value == '-' ) {
                   return parse_number( str, offset );
                 }
    }
    throw std::runtime_error(std::string("JSON ERROR: Parse: Unexpected starting character '") + value + "'");
  }

};

inline JSON JSON::Load( const std::string &str ) {
  size_t offset = 0;
  return JSONParser::parse_next( str, offset );
}

} // End Namespace json


#endif