#include <iostream>
#include <string>
#include <vector>

enum Size {
  small,
  medium,
  large
};

enum Color {
  red,
  green,
  blue
};

struct Item {
  std::string name;
  Size size;
  Color color;
  Item(const std::string& name, Size size, Color color):
  name(name)
  ,size(size)
  ,color(color) {}
};

struct ItemContainer {
  std::vector<Item> items;

  void addItem(const Item& item) {
    items.push_back(item);
  }

  std::vector<Item>& getItems() {
    return items;
  }
};

template <typename T>
struct Specification {
  virtual bool is_satisfied(const T&) const = 0;
};

template <typename T>
struct Filter {
  virtual std::vector<T*> filter(ItemContainer& container, const Specification<T>& spec) {
    auto &vec = container.getItems();

    std::vector<T*> res;

     for (auto& i: vec) {
       if (spec.is_satisfied(i)) {
         res.push_back(&i);
       }
     }

     return res;
  };
};

struct SizeSpecification: Specification<Item> {
  Size size;
  SizeSpecification(Size size): size(size) {}

   bool is_satisfied(const Item& item) const {
     return item.size == size;
   }
};


int main()
{
  auto container = ItemContainer();
  container.addItem(Item("Medium Green", Size::medium, Color::green));
  container.addItem(Item("Large Red", Size::large, Color::red));
  container.addItem(Item("Small Blue", Size::small, Color::blue));
  container.addItem(Item("Small Red", Size::small, Color::red));

  Filter<Item> sizeFilter;
  SizeSpecification sizeSpec(Size::small);

  auto filteredItems = sizeFilter.filter(container, sizeSpec);
  for (const auto &item: filteredItems) {
    std::cout << "Filtered: " << item->name << std::endl;
  }

}