/////////////////////////////////////////////////////////////////
// VariadicClassTemplates.cpp - demonstrates variadic mixins   //
//                                                             //
// Jim Fawcett, CSE687 - Object Oriented Design, Spring 2018   //
/////////////////////////////////////////////////////////////////

#include <iostream>

class A {
public:
  A() { std::cout << "\n  an A here";  }
  A(const A& a) { std::cout << "\n  copy A here"; }
  virtual ~A() {}
};

class B {
public:
  B() { std::cout << "\n  a B here"; }
  B(const B& b) { std::cout << "\n  copy B here"; }
  virtual ~B() {}
};

class C {
public:
  C() { std::cout << "\n  a C here"; }
  C(const C& c) { std::cout << "\n  copy C here"; }
  virtual ~C() {}
  void do_C_op() { std::cout << "\n  doing C's operation"; }
};

template<typename... Mixins>
class D : public Mixins...
{
private:
  bool hasMixins = false;
public:
  // D() fails to compile because same as D(const Mixins& ... mixins)
  // when there are no mixins
  // D() { std::cout << "\n  a D here"; }
  D(const Mixins& ... mixins) : Mixins(mixins)... { 
    if (sizeof...(mixins) == 0)
      std::cout << "\n  a D here";
    else
    {
      hasMixins = true;
      std::cout << "\n  copy D here";
    }
  }
  virtual ~D() {}
  void say()
  {
    if (!hasMixins)
      std::cout << "\n  class D with no mixins here";
    else
    //std::cout << "\n  class D with mixins here";
    //std::cout << "\n  " << typeid(this).name();
    std::cout << "\n  " << typeid(this).raw_name();
    C* pC = dynamic_cast<C*>(this);
    if (pC)
      pC->do_C_op();
    std::cout << "\n";
  }
};

int main()
{
  std::cout << "\n  Demonstrating variadic template classes";
  std::cout << "\n =========================================\n";

  A a;
  B b;
  C c;
  D<> d;
  d.say();

  D<A> dA(a);
  dA.say();

  D<B, C> dBC(b, c);
  dBC.say();

  // Will fail to compile : incomplete argument list
  // D<B, C> dBC(b);

  std::cout << "\n\n";
  return 0;
}