/* ****************************************************************** 
 * 
 *   Marcos Abreu Bento
 * 
 *   marcosbento@gmail.com
 * 
 * ------------------------------------------------------------------
 * 
 * My implementation of Factory Method design pattern
 * 
 * ****************************************************************** */

#ifndef FACTORY_HPP_
#define FACTORY_HPP_

#include <map>
#include <string>

template <class P> // P is for factory Product
class Factory {
private:

  /* Generation of products is based on calling a specific function. */
  typedef P*(*Generator)(void);

  std::map<std::string, Generator> products;

public:

  void registerProduct(const std::string& key, const Generator& generator);

  P *newProduct(const std::string& key);

  /* Derived Products (DP) are created by default construction.
   * Generation depends of Base and Derived types,
   * and can be specified  outside he factory. */
  template <class DP> static P* generate();
};

template <class P>
void Factory<P>::registerProduct(const std::string& key, const Generator& generator)
{
  /* Generator is assigned at registration time */
  products[key] = generator;
}

template <class P>
P* Factory<P>::newProduct(const std::string& key)
{
  return products[key]();  
}

template <class P> template <class DP>
P* Factory<P>::generate()
{
  return new DP();
}

#endif