cpp-json/json.h

//
//  json.hpp
//  json
//
//  Created by Sam Jaffe on 1/30/16.
//  Copyright © 2016 Sam Jaffe. All rights reserved.
//

#ifndef json_hpp
#define json_hpp

#include <map>
#include <vector>
#include <string>
#include <utility>

#include "../variant/variant.hpp"

#define JSON_TYPE_LIST \
  X(object) \
  X(array) \
  X(string) \
  X(double) \
  X(int) \
  X(bool)

namespace json {
  class value;
  namespace parser {
    template <typename T> void parse(T& json, char const* data);
    template <typename T> void parse(T& json, std::string const& str);
    template <typename T> void parse(T& json, std::istream & in);
  }

  class malformed_json_exception : public std::domain_error {
    using std::domain_error::domain_error;
  };
    
  class value {
  public:
    using object_jt = std::map<std::string, value>;
    using array_jt = std::vector<value>;
    using string_jt = std::string;
    using double_jt = double;
    using int_jt = int32_t;
    using bool_jt = bool;
  private:
    static const value null_value;
    
    using data_t = variant<object_jt, array_jt, string_jt, double_jt, int_jt, bool_jt>;
    data_t data;
  public:
#define X(type) bool is_##type() const { return data.is<type##_jt>(); }
    JSON_TYPE_LIST
#undef X
    bool is_null() const { return !data.valid(); }
    
    value() = default;
    value(value const&) = default;
    value(value &&) = default;
    value& operator=(value const&) = default;
    value& operator=(value &&) = default;
#define X(type) value(type##_jt val) { data.set<type##_jt>(std::move(val)); }
    JSON_TYPE_LIST
#undef X
#define X(type) value(type##_jt && val) { data.set<type##_jt>(std::forward<type##_jt>(val)); }
    JSON_TYPE_LIST
#undef X
#define X(type) value& operator=(type##_jt val) { data.set<type##_jt>(std::move(val)); return *this; }
    JSON_TYPE_LIST
#undef X
    
    void parse(char const* data);
    void parse(std::string const& str);
    void parse(std::istream & in);
    
    void clear() { data = data_t(); }
    
    value& operator[](const size_t idx);
    value const& operator[](const size_t idx) const;
    value& operator[](std::string const& key);
    value const& operator[](std::string const& key) const;
    
    string_jt const& as_string() const;
    double_jt as_double() const;
    int_jt as_int() const;
    bool_jt as_bool() const;
    
    operator string_jt const&() const { return as_string(); }
    operator double_jt() const { return as_double(); }
    operator int_jt() const { return as_int(); }
    operator bool_jt() const { return as_bool(); }
    
  };
#undef JSON_TYPE_LIST
}

namespace json {
  namespace helper {
    const char get_next_element(char const*& data) {
      while (isspace(*data)) ++data;
      return *data;
    }
    
    template <char const E>
    void advance_to_boundary(char const*& data) {
      switch (get_next_element(data)) {
        case ',': // This is there 'more data remains' token for the compound value
          ++data;
          break;
        case E: // This is the end-token for the compound value
          break;
        default: // Error, malformed JSON
          throw json::malformed_json_exception(std::string("Expected to recieve container delimiter ',' or '") + E + "', got '" + *data + "' instead");
          break;
      }
    }
    
    template <typename T>
    void parse_string(T& json, char const*& data) {
      char const* start = data;
      while (*++data) {
        if (*data == '"' && *(data-1) != '\\') {
          json = std::string(start+1, data);
          ++data;
          return;
        }
      }
      throw json::malformed_json_exception("Could not locate end of string");
    }
    
    template <typename T>
    void parse_numeric(T& json, char const*& data) {
      char const* start = data;
      while (*++data) {
        if (*data == '.') {
          while (isnumber(*++data));
          json = atof(start);
          break;
        } else if (!isnumber(*data)) {
          json = atoi(start);
          break;
        }
      }
    }

  }
}

#endif /* json_hpp */