/*------------------------------------------------------------------------------
* Copyright (C) 2003-2006 Ben van Klinken and the CLucene Team
* 
* Distributable under the terms of either the Apache License (Version 2.0) or 
* the GNU Lesser General Public License, as specified in the COPYING file.
------------------------------------------------------------------------------*/
#ifndef _lucene_index_SegmentMerger_
#define _lucene_index_SegmentMerger_

#if defined(_LUCENE_PRAGMA_ONCE)
# pragma once
#endif

#include "CLucene/store/Directory.h"
#include "CLucene/store/RAMDirectory.h"
#include "CLucene/util/VoidList.h"
#include "SegmentMergeInfo.h"
#include "SegmentMergeQueue.h"
#include "FieldInfos.h"
#include "FieldsWriter.h"
#include "TermInfosWriter.h"

CL_NS_DEF(index)

   /**
   * The SegmentMerger class combines two or more Segments, represented by an IndexReader ({@link #add},
   * into a single Segment.  After adding the appropriate readers, call the merge method to combine the 
   * segments.
   *<P> 
   * If the compoundFile flag is set, then the segments will be merged into a compound file.
   *   
   * 
   * @see #merge
   * @see #add
   */
	class SegmentMerger:LUCENE_BASE {
	private:
      bool useCompoundFile;

      CL_NS(store)::RAMIndexOutput* skipBuffer;
      int32_t lastSkipDoc;
      int64_t lastSkipFreqPointer;
      int64_t lastSkipProxPointer;

      void resetSkip();
      void bufferSkip(int32_t doc);
      int64_t writeSkip();

		//Directory of the segment
		CL_NS(store)::Directory* directory;     
		//name of the new segment
		const char* segment;
		//Set of SegmentReaders
		CL_NS(util)::CLVector<SegmentReader*,CL_NS(util)::Deletor::Object<SegmentReader> > readers;
		//Field Infos for t	he FieldInfo instances of all fields
		FieldInfos* fieldInfos;

		//The queue that holds SegmentMergeInfo instances
		SegmentMergeQueue* queue;
		//IndexOutput to the new Frequency File
		CL_NS(store)::IndexOutput* freqOutput;
      	//IndexOutput to the new Prox File
		CL_NS(store)::IndexOutput* proxOutput;
		//Writes Terminfos that have been merged
		TermInfosWriter* termInfosWriter;
		TermInfo termInfo; //(new) minimize consing

      int32_t skipInterval;
	public:		
   /**
   * 
   * @param dir The Directory to merge the other segments into
   * @param name The name of the new segment
   * @param compoundFile true if the new segment should use a compoundFile
   */
		SegmentMerger(CL_NS(store)::Directory* dir, const char* name, const bool compoundFile);

		//Destructor
		~SegmentMerger();

  /**
   * Add an IndexReader to the collection of readers that are to be merged
   * @param reader
   */
		void add(SegmentReader* reader);

  /**
   * 
   * @param i The index of the reader to return
   * @return The ith reader to be merged
   */
		IndexReader* segmentReader(const int32_t i);

  /**
   * Merges the readers specified by the {@link #add} method into the directory passed to the constructor
   * @return The number of documents that were merged
   * @throws IOException
   */
		int32_t merge();
   /**
   * close all IndexReaders that have been added.
   * Should not be called before merge().
   * @throws IOException
   */
      void closeReaders();
	private:
      void createCompoundFile();

   /**
   * Merge the fields of all segments 
   * @return The number of documents in all of the readers
   * @throws IOException
   */
		int32_t mergeFields();

  /**
   * Merge the TermVectors from each of the segments into the new one.
   * @throws IOException
   */
      void mergeVectors();

		//Merge the terms of all segments
		void mergeTerms();

		//Merges all TermInfos into a single segment
		void mergeTermInfos();

  /** Merge one term found in one or more segments. The array <code>smis</code>
   *  contains segments that are positioned at the same term. <code>N</code>
   *  is the number of cells in the array actually occupied.
   *
   * @param smis array of segments
   * @param n number of cells in the array actually occupied
   */
		void mergeTermInfo( SegmentMergeInfo** smis);
		    
  /** Process postings from multiple segments all positioned on the
   *  same term. Writes out merged entries into freqOutput and
   *  the proxOutput streams.
   *
   * @param smis array of segments
   * @param n number of cells in the array actually occupied
   * @return number of documents across all segments where this term was found
   */
		int32_t appendPostings(SegmentMergeInfo** smis);

		//Merges the norms for all fields 
		void mergeNorms();
	};
CL_NS_END
#endif