// DatasetMergerCreator.h

#ifndef dset__DatasetMergerCreator_H
#define dset__DatasetMergerCreator_H

// Base class for factory to create dataset mergers.
//
// This is an abtract base.

#include <string>
#include <iosfwd>
#include "dataset_base/Dataset.h"

class XmlElement;

namespace dset {

  class DatasetMerger;

class DatasetMergerCreator {

public:  // Typedefs.

  // Pointer to a function to create a merger creator from an XML element.
  typedef const DatasetMergerCreator* (*Creator) (const XmlElement&);

  // Creator name.
  typedef std::string CreatorName;

  // List of Creator Names.
  typedef std::vector<CreatorName> CreatorList;

public:  // Static methods.

  // Create a merger creator from an XML description.
  // Caller is responsible for managing the creator.
  // The creator is selected using ele.name().
  static const DatasetMergerCreator* create(const XmlElement& ele);

  // Register a creator.
  // Returns 0 for success.
  // Fails if name is already used for a different creator.
  static int register_creator(std::string name, Creator pfun);

  // Return list of registered creators.
  static const CreatorList& creators();

  // Return if a creator is registered.
  static bool has_creator(CreatorName name);

public:  // Virtual methods

  // Destructor.
  virtual ~DatasetMergerCreator();
  
  // Validity.
  virtual bool is_valid() const =0;

  // Return a new merger instance.
  // Caller is responsible for management.
  // Argument is the working directory for the creator.
  virtual DatasetMerger* create(std::string dir) const =0;

  // Write to XML.
  virtual const XmlElement* xml() const =0;

  // Output stream.
  virtual std::ostream& ostr(std::ostream& str) const =0;

};

}  // end namespace dset

// Free functions.
std::ostream&
operator<<(std::ostream& lhs, const dset::DatasetMergerCreator& rhs);

#endif