///////////////////////////////////////////////////
// MT4Q2.cpp - Non-virtual Base class clone()    //
//                                               //
// Jim Fawcett, CSE687 - Midterm, Spring 2010    //
///////////////////////////////////////////////////

#include <string>
#include <iostream>

class IBase { public: virtual std::string id()=0; };

template <typename D>
class Base : public IBase
{
public:
  IBase* clone() 
  { 
    // this cast is necessary since compiler doesn't
    // know now that D derives from Base (see below).

    D* pD = dynamic_cast<D*>(this);
    if(pD == 0)
      throw std::exception("D must derive from Base");
    return new D(*pD); 
  }
  virtual std::string id() 
  { 
    return std::string("\n  my id is: ") + typeid(Base<D>).name(); 
  }
  virtual ~Base() {}
};

class Derived1 : public Base<Derived1>
{
public:
  Derived1(const std::string& msg) : msg_(msg) {}
  // will use inherited clone()
  virtual std::string id() 
  { 
    std::string temp = "\n  my id is: ";
    temp += typeid(*this).name();
    temp += std::string("\n  my message is: ") + msg_;
    temp += std::string("\n  my base class says: ") + Base<Derived1>::id();
    return temp;
  } 
private:
  std::string msg_;
};

class Derived2 : public Base<Derived2>
{
public:
  Derived2(const std::string& msg) : msg_(msg) {}
  // will use inherited clone
  virtual std::string id() 
  { 
    std::string temp = "\n  my id is: ";
    temp += typeid(*this).name();
    temp += std::string("\n  my message is: ") + msg_;
    temp += std::string("\n  my base class says: ") + Base<Derived2>::id();
    return temp;
  } 
private:
  std::string msg_;
};

void main()
{
  std::cout << "\n  MT4Q2 - Non-Virtual Base Clone()";
  std::cout << "\n ==================================\n";

  Base<Derived1> b;
  std::cout << b.id().c_str() << std::endl;;

  Derived1 d1("Hello CSE687");
  IBase* pB = d1.clone();
  // note that message state is copied by clone()
  // to copy on heap
  std::cout << pB->id().c_str() << std::endl;;

  Derived2 d2("Hello Object Oriented Design");
  pB = d2.clone();
  // yup, still copied!
  std::cout << pB->id().c_str();
  std::cout << "\n\n";
}