cpp-json/json/json_object_binder.hpp

//
//  json_object_binder.hpp
//  json
//
//  Created by Sam Jaffe on 4/23/16.
//

#pragma once

#include "json_binder_discard.hpp"

namespace json { namespace binder {
  template <typename T>
  class object_binder : public binder_impl<T> {
  public:
    object_binder() {}
    virtual binder_impl<T>* clone() const override { return new object_binder(*this); }
    
    template <typename V>
    object_binder& operator()(std::string const&k, V T::*ptr, binder_impl<V> const&v) {
      return (*this)(k, binder<T>(new direct_binder<T, V>(ptr, binder<V>(v) )));
    }

    object_binder& operator()(std::string const&k, binder<T> const&v) {
      mapping.emplace(k, v);
      return *this;
    }
    
    virtual void parse(T& object, char const*& data, parser::options opts) const override {
      const char ch = json::helper::get_next_element(data);
      if (ch == '{') {
        parse_object(object, ++data, opts);
      } else {
        throw json::malformed_json_exception(std::string("Expected an object type for binding to ") + typeid(T).name());
      }
    }
    
    virtual void write(T const& val, std::ostream & data) const override {
      data << '{';
      typename std::map<std::string, binder<T>>::const_iterator it = mapping.begin(),
      end = mapping.end();
      if (it != end) {
        data << '"' << it->first << '"' << ':';
        it->second.write(val, data);
        for (++it; it != end; ++it) {
          data << ',';
          data << '"' << it->first << '"' << ':';
          it->second.write(val, data);
        }
      }
      data << '}';
    }
    
    void parse_object(T& object, char const*& data, parser::options opts) const {
      std::string key;
      std::set<std::string> unparsed_keys;
      for ( auto & p : mapping ) { unparsed_keys.insert(p.first); }
      while (*data && *data != '}') {
        if (json::helper::get_next_element(data) != '"') {
          throw json::malformed_json_exception(std::string("Expected object key starting with '\"', got '") + *data + "' instead");
        }
        json::helper::parse_string(key, data);
        if (json::helper::get_next_element(data) != ':') {
          throw json::malformed_json_exception(std::string("Expected key:value pair delimited by ':', got '") + *data + "' instead");
        }
        auto it = mapping.find(key);
        if (it != mapping.end()) {
          unparsed_keys.erase(key);
          it->second.parse(object, ++data, opts);
        } else if (opts & parser::disable_unknown_keys) {
          throw json::malformed_json_exception("Unexpected key " + key);
        } else {
          parse_discard_token(++data);
        }
        json::helper::advance_to_boundary('}', data);
      }
      if (*data) ++data;
      else throw json::unterminated_json_exception("Reached end of parse string without finding object end");
      if ( !unparsed_keys.empty() && opts & parser::disable_missing_keys ) {
        throw json::malformed_json_exception("missing certain keys from object construction TODO");
      }
    }
    
    template <typename E>
    object_binder& operator()(std::string const& s, E T::*p) {
      return operator()(s, binder<T>(new direct_binder<T, E>(p)));
    }
  private:
    std::map<std::string, binder<T>> mapping;
  };
} }