// CompoundDatasetMerger.h

#ifndef dset__CompoundDatasetMerger_H
#define dset__CompoundDatasetMerger_H

// David Adams
// February 2005.
//
// This dataset merger takes a simple compound dataset as input,
// splits it into sub-datasets by content label, separately
// merges each sub-dataset and then combines the results back into
// a simple compound dataset.
// 
// If the input is any other kind of dataset, then it behaves like 
// a DefaultDatasetMerger.
//
// All compound datasets returned as results are stored in
// the current default dataset repository.
//
// The merger manages the datasets it returns in its result.
// A call to result deletes the dataset returned in the
// previous call if it has changed.

#include <vector>
#include "dataset_util/Text.h"
#include "dataset_split/DatasetMerger.h"
#include "dataset_split/DefaultDatasetMerger.h"

namespace dset {

class Dataset;

class CompoundDatasetMerger : public DatasetMerger {

private: // typedefs

  typedef std::vector<DefaultDatasetMerger*> MergerList;

private:  // data

  std::string m_dir;
  int m_err;
  DatasetList m_dsts;
  DefaultDatasetMerger* m_pmrg;
  Dataset* m_pdst;
  MergerList m_mrgs;
  DatasetMergeResult* m_pres;
  bool m_open;
  bool m_update_result;

private:  // No copy or assignment

  // Copy.
  CompoundDatasetMerger(const CompoundDatasetMerger& rhs);

  // Assignment.
  CompoundDatasetMerger& operator=(const CompoundDatasetMerger& rhs);

public:  // constructors and destructor.

  // Constructor.
  // Argument is the working directory.
  CompoundDatasetMerger(std::string dir);

  // Destructor.
  ~CompoundDatasetMerger();

public:  // inherited functions

  // Validity.
  bool is_valid() const;

  // Open.
  bool is_open() const;

  // Append a dataset.
  int append(const Dataset& dst);

  // Return the result.
  // This should not be blocking--if the result will require a long
  // time to calculate, then this method should quickly return a
  // (consistent) partial result.
  DatasetMergeResult result();

  // Close.
  int close();

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

public:  // local functions

  // Set error and return error code.
  int set_error(int err);

  // Return the error code.
  int error() const;

};

}  // end namespace dset

#endif