#ifndef AGDDBUILDABLEHH
#define AGDDBUILDABLEHH

#include <iostream>
#include <strstream>
#include "agddHasTag.hh"

namespace agdd {

  class Buildable : public HasTag {
  private:
    bool _haveBeenBuiltAlready;
  public:
    Buildable(const string & tag) : 
      HasTag(tag), 
      _haveBeenBuiltAlready(false) {
    };
    virtual ~Buildable() {};
  private:	
    virtual void howToBuildMe() = 0;
  public:
    void buildMe() {
      if (_haveBeenBuiltAlready) {
        cerr << "ERROR: An attempt has been made to build a Buildable element "
	     << "which has already been made. "
	     << "Build elements once and once only." << endl;
      };
      assert (!_haveBeenBuiltAlready);
      howToBuildMe();
      _haveBeenBuiltAlready=true;
    };
    void sendMeTo(ostream & os) {
       if (!_haveBeenBuiltAlready) {
         cerr << "ERROR: You are trying to send an AGDD element to "
	      << "an output stream without having first built it." << endl;
       };
       assert(_haveBeenBuiltAlready);
       ostrstream preamble;
       preamble << "<!DOCTYPE AGDD SYSTEM \"AGDD.dtd\">" << endl << ends;
       theElement()->print(os<<preamble.str(), "");
    };
  };
}; // end of agdd namespace

#endif