cpp-json/json_binder.hpp

//
//  json_binder.h
//  json
//
//  Created by Sam Jaffe on 1/31/16.
//  Copyright © 2016 Sam Jaffe. All rights reserved.
//

#ifndef json_binder_h
#define json_binder_h
#pragma once

namespace json {
  namespace binder {
    template <typename T>
    class binder_impl {
    public:
      virtual binder_impl<T>* clone() const = 0;
      virtual ~binder_impl() {}
      virtual void parse(T&, char const*&) const = 0;
    };
    
    template <typename T>
    class binder {
    public:
      binder() : impl(nullptr), owned(false) {}
      binder(binder const& other) : impl(other.impl->clone()), owned(true) {}
      binder(binder_impl<T> const* p) : impl(p), owned(true) {}
      binder(binder_impl<T> const& r) : impl(&r), owned(false) {}
      ~binder() { if (impl && owned) delete impl; }
      
      void parse(T& object, char const*& data) const {
        if (!impl) return;
        impl->parse(object, data);
      }
    private:
      binder_impl<T> const* impl;
      bool owned;
    };
    
    template <typename T, typename E>
    class direct_binder : public binder_impl<T> {
    public:
      direct_binder(E T::*p, binder<E> const& i) : ptr(p), impl(i) {}
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }
      
      virtual void parse(T& val, char const*& data) const override {
        impl.parse(val.*ptr, data);
      }
    private:
      E T::*ptr;
      binder<E> impl;
    };
    
    template <typename T>
    class direct_binder<T, bool> : public binder_impl<T> {
    public:
      direct_binder(bool T::*p) : ptr(p) {}
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }
      
      virtual void parse(T& val, char const*& data) override {
        if (!strncmp(data, "true", 4)) {
          val.*ptr = true;
        } else if (!strncmp(data, "false", 5)) {
          val.*ptr = false;
        } else {
          throw json::malformed_json_exception("Expected a boolean type here");
        }
      }
      
    private:
      bool T::*ptr;
    };
    
    template <typename T>
    class direct_binder<T, int> : public binder_impl<T> {
    public:
      direct_binder(int T::*p) : ptr(p) {}
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }

      virtual void parse(T& val, char const*& data) const override {
//        if (false) {
        json::helper::parse_numeric(val.*ptr, data);
//        } else {
//          throw json::malformed_json_exception("Expected an integral type here");
//        }
      }
    private:
      int T::*ptr;
    };
    
    template <typename T>
    class direct_binder<T, double> : public binder_impl<T> {
    public:
      direct_binder(double T::*p) : ptr(p) {}
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }

      virtual void parse(T& val, char const*& data) const override {
//        if (false) {
          json::helper::parse_numeric(val.*ptr, data);
//        } else {
//          throw json::malformed_json_exception("Expected a floating point type here");
//        }
      }
    private:
      double T::*ptr;
    };
    
    template <typename T>
    class direct_binder<T, std::string> : public binder_impl<T> {
    public:
      direct_binder(std::string T::*p) : ptr(p) {}
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }

      virtual void parse(T& val, char const*& data) const override {
        json::helper::parse_string(val.*ptr, data);
      }
    private:
      std::string T::*ptr;
    };
    
    template <typename T, typename V>
    class direct_binder<T, std::vector<V> > : public binder_impl<T> {
    public:
      direct_binder(std::vector<V> T::*p, binder<V> const&i);
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }
      
      virtual void parse(T& val, char const*& data) const override {
        const char ch = json::helper::get_next_element(data);
        if (ch != '[') {
          throw json::malformed_json_exception("Expected an array type");
        }
        ++data;

        V to_make;
        std::vector<V>& vec = val.*ptr;
        while (*data && *data != ']') {
          impl.parse(to_make, data);
          vec.emplace_back(to_make);
          json::helper::advance_to_boundary<']'>(data);
        }
        if (*data) ++data;
        else throw json::malformed_json_exception("Reached end of parse string without finding array end");
      }
    private:
      std::vector<V> T::*ptr;
      binder<V> impl;
    };
    
    template <typename T, typename V>
    class direct_binder<T, std::map<std::string, V> > : public binder_impl<T> {
    public:
      direct_binder(std::vector<V> T::*p, binder<V> const&i);
      virtual binder_impl<T>* clone() const override { return new direct_binder(*this); }
      
      virtual void parse(T& val, char const*& data) const override {
        const char ch = json::helper::get_next_element(data);
        if (ch != '{') {
          throw json::malformed_json_exception("Expected an array type");
        }
        ++data;
        
        V to_make;
        std::map<std::string, V>& vec = val.*ptr;
        std::string key;
        while (*data && *data != '}') {
          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");
          }
          impl.parse(to_make, ++data);
          vec.emplace(key, to_make);
          json::helper::advance_to_boundary<'}'>(data);
        }
        if (*data) ++data;
        else throw json::malformed_json_exception("Reached end of parse string without finding object end");
      }
    private:
      std::map<std::string, V> T::*ptr;
      binder<V> impl;
    };
    
    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) const override {
        const char ch = json::helper::get_next_element(data);
        if (ch == '{') {
          parse_object(object, ++data);
        } else {
          throw json::malformed_json_exception(std::string("Expected an object type for binding to ") + typeid(T).name());
        }
      }
      
      void parse_object(T& object, char const*& data) const {
        std::string key;
        while (*data && *data != '}') {
          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()) {
            it->second.parse(object, ++data);
          } else {
            throw json::malformed_json_exception("Unexpected key " + key);
          }
          json::helper::advance_to_boundary<'}'>(data);
        }
        if (*data) ++data;
        else throw json::malformed_json_exception("Reached end of parse string without finding object end");
      }

      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;
    };
    
    template <typename T>
    class tuple_binder : public binder_impl<T> {
    public:
      virtual binder_impl<T>* clone() const override { return new tuple_binder(*this); }

      tuple_binder& operator()(binder<T> const&b) {
        members.push_back(b);
        return *this;
      }
      
      virtual void parse(T& object, char const*& data) const override {
        const char ch = json::helper::get_next_element(data);
        if (ch == '[') {
          parse_tuple(object, ++data);
        } else {
          throw json::malformed_json_exception(std::string("Expected an object type for binding to ") + typeid(T).name());
        }
      }
      
      void parse_tuple(T& object, char const*& data) const {
        auto it = members.begin();
        while (*data && *data != ']' && it != members.end()) {
          it->parse(object, data);
          json::helper::advance_to_boundary<']'>(data);
          ++it;
        }
        if (it != members.end()) {
          throw json::malformed_json_exception("Failed to parse every member of tuple");
        }
        if (*data) ++data;
        else throw json::malformed_json_exception("Reached end of parse string without finding array end");
      }

      template <typename E>
      tuple_binder& operator()(E T::*p) {
        return operator()(binder<T>(new direct_binder<T, E>(p)));
      }
    
    private:
      std::vector<binder<T>> members;
    };
    
    template <typename T>
    class visitor {
    public:
      visitor(T& o, binder_impl<T>& b) : obj(o), b(b) {}
      
      void parse(char const* data) {
        b.parse(obj, data);
      }
      
    private:
      T& obj;
      binder_impl<T>& b;
    };
    
    template <typename T>
    visitor<T> bind(T& object, binder_impl<T>& b) {
      return visitor<T>{object, b};
    }
  }
  
  namespace parser {
    template <typename T>
    void parse(binder::visitor<T>& visitor, char const* data) {
      visitor.parse(data);
    }    
  }
  
}

#endif /* json_binder_h */