/*
* 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.
*
* Changes are Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
*/
#ifndef _lucene_index_IndexModifier_
#define _lucene_index_IndexModifier_

#if defined(_LUCENE_PRAGMA_ONCE)
#   pragma once
#endif

#include <QtCore/QString>

#include "CLucene/store/Directory.h"
#include "CLucene/document/Document.h"
#include "CLucene/analysis/AnalysisHeader.h"

CL_NS_DEF(index)

class IndexReader;
class IndexWriter;
class Term;
class TermDocs;
class TermEnum;

/** 
* A class to modify an index, i.e. to delete and add documents. This
* class hides {@link IndexReader} and {@link IndexWriter} so that you
* do not need to care about implementation details such as that adding
* documents is done via IndexWriter and deletion is done via IndexReader.
* 
* <p>Note that you cannot create more than one <code>IndexModifier</code> object
* on the same directory at the same time.
* 
* <p>Example usage:
* 
* <div align="left" class="java">
* <table border="0" cellpadding="3" cellspacing="0" bgcolor="#ffffff">
* <tr>
* <td nowrap="nowrap" valign="top" align="left">
* <code>
*     //note this code will leak memory :)
*     Analyzer* analyzer = <b>new</b> StandardAnalyzer();<br/>
*     // create an index in /tmp/index, overwriting an existing one:<br/>
*     IndexModifier* indexModifier = <b>new</b> IndexModifier("/tmp/index", analyzer, <b>true</b>);<br/>
*     Document* doc = <b>new </b>Document*();<br/>
*     doc->add(*<b>new </b>Field("id", "1", Field::STORE_YES| Field::INDEX_UNTOKENIZED));<br/>
*     doc->add(*<b>new </b>Field("body", "a simple test", Field::STORE_YES, Field::INDEX_TOKENIZED));<br/>
*     indexModifier->addDocument(doc);<br/>
*     <b>int32_t </b>deleted = indexModifier->deleteDocuments(<b>new </b>Term("id", "1"));<br/>
*     printf("Deleted %d document", deleted);<br/>
*     indexModifier->flush();<br/>
*     printf( "$d docs in index", indexModifier->docCount() );<br/>
*     indexModifier->close();
* </code></td>
* </tr>
* </table>
* </div>
*
* <p>Not all methods of IndexReader and IndexWriter are offered by this 
* class. If you need access to additional methods, either use those classes 
* directly or implement your own class that extends <code>IndexModifier</code>.
* 
* <p>Although an instance of this class can be used from more than one
* thread, you will not get the best performance. You might want to use 
* IndexReader and IndexWriter directly for that (but you will need to 
* care about synchronization yourself then).
* 
* <p>While you can freely mix calls to add() and delete() using this class,
* you should batch you calls for best performance. For example, if you
* want to update 20 documents, you should first delete all those documents,
* then add all the new documents.
* 
*/
class IndexModifier : LUCENE_BASE
{
protected:
    IndexWriter* indexWriter;
    IndexReader* indexReader;

    CL_NS(store)::Directory* directory;
    CL_NS(analysis)::Analyzer* analyzer;
    bool open;

    // Lucene defaults:
    bool useCompoundFile;
    int32_t maxBufferedDocs;
    int32_t maxFieldLength;
    int32_t mergeFactor;

public:

    /**
    * Open an index with write access.
    *
    * @param directory the index directory
    * @param analyzer the analyzer to use for adding new documents
    * @param create <code>true</code> to create the index or overwrite
    * the existing one; <code>false</code> to append to the existing index
    */
    IndexModifier(CL_NS(store)::Directory* directory,
        CL_NS(analysis)::Analyzer* analyzer, bool create);

    ~IndexModifier();

    /**
    * Open an index with write access.
    *
    * @param dirName the index directory
    * @param analyzer the analyzer to use for adding new documents
    * @param create <code>true</code> to create the index or overwrite
    * the existing one; <code>false</code> to append to the existing index
    */
    IndexModifier(const QString& dirName, CL_NS(analysis)::Analyzer* analyzer,
        bool create);

protected:

    // Initialize an IndexWriter. @throws IOException
    void init(CL_NS(store)::Directory* directory,
        CL_NS(analysis)::Analyzer* analyzer, bool create);

    // Throw an IllegalStateException if the index is closed.
    // @throws IllegalStateException
    void assureOpen() const;

    // Close the IndexReader and open an IndexWriter. @throws IOException
    void createIndexWriter();

    // Close the IndexWriter and open an IndexReader. @throws IOException
    void createIndexReader();

public:
    // Make sure all changes are written to disk. @throws IOException
    void flush();

    // Adds a document to this index, using the provided analyzer instead of
    // the one specific in the constructor.  If the document contains more than
    // {@link #setMaxFieldLength(int32_t)} terms for a given field, the
    // remainder are discarded.
    // @see IndexWriter#addDocument(Document*, Analyzer*)
    // @throws IllegalStateException if the index is closed
    void addDocument(CL_NS(document)::Document* doc, CL_NS(analysis)::Analyzer*
        docAnalyzer = NULL);


    /**
    * Deletes all documents containing <code>term</code>.
    * This is useful if one uses a document field to hold a unique ID string for
    * the document.  Then to delete such a document, one merely constructs a
    * term with the appropriate field and the unique ID string as its text and
    * passes it to this method.  Returns the number of documents deleted.
    * @return the number of documents deleted
    * @see IndexReader#deleteDocuments(Term*)
    * @throws IllegalStateException if the index is closed
    */
    int32_t deleteDocuments(Term* term);

    /**
    * Deletes the document numbered <code>docNum</code>.
    * @see IndexReader#deleteDocument(int32_t)
    * @throws IllegalStateException if the index is closed
    */
    void deleteDocument(int32_t docNum);

    /**
    * Returns the number of documents currently in this index.
    * @see IndexWriter#docCount()
    * @see IndexReader#numDocs()
    * @throws IllegalStateException if the index is closed
    */
    int32_t docCount();

    /**
    * Merges all segments together into a single segment, optimizing an index
    * for search.
    * @see IndexWriter#optimize()
    * @throws IllegalStateException if the index is closed
    */
    void optimize();

    /**
    * Setting to turn on usage of a compound file. When on, multiple files
    * for each segment are merged into a single file once the segment creation
    * is finished. This is done regardless of what directory is in use.
    * @see IndexWriter#setUseCompoundFile(bool)
    * @throws IllegalStateException if the index is closed
    */
    void setUseCompoundFile(bool useCompoundFile);

    /**
    * @throws IOException
    * @see IndexModifier#setUseCompoundFile(bool)
    */
    bool getUseCompoundFile();

    /**
    * The maximum number of terms that will be indexed for a single field in a
    * document.  This limits the amount of memory required for indexing, so that
    * collections with very large files will not crash the indexing process by
    * running out of memory.<p/>
    * Note that this effectively truncates large documents, excluding from the
    * index terms that occur further in the document.  If you know your source
    * documents are large, be sure to set this value high enough to accomodate
    * the expected size.  If you set it to Integer.MAX_VALUE, then the only limit
    * is your memory, but you should anticipate an OutOfMemoryError.<p/>
    * By default, no more than 10,000 terms will be indexed for a field.
    * @see IndexWriter#setMaxFieldLength(int32_t)
    * @throws IllegalStateException if the index is closed
    */
    void setMaxFieldLength(int32_t maxFieldLength);

    /**
    * @throws IOException
    * @see IndexModifier#setMaxFieldLength(int32_t)
    */
    int32_t getMaxFieldLength();

    /*
     * The maximum number of terms that will be indexed for a single field in a
     * document.  This limits the amount of memory required for indexing, so that
     * collections with very large files will not crash the indexing process by
     * running out of memory.<p/>
     * Note that this effectively truncates large documents, excluding from the
     * index terms that occur further in the document.  If you know your source
     * documents are large, be sure to set this value high enough to accomodate
     * the expected size.  If you set it to Integer.MAX_VALUE, then the only limit
     * is your memory, but you should anticipate an OutOfMemoryError.<p/>
     * By default, no more than 10,000 terms will be indexed for a field.
     * @see IndexWriter#setMaxBufferedDocs(int32_t)
     * @throws IllegalStateException if the index is closed
    */
    void setMaxBufferedDocs(int32_t maxBufferedDocs);

    // @see IndexModifier#setMaxBufferedDocs(int32_t) @throws IOException
    int32_t getMaxBufferedDocs();

    /*
    * Determines how often segment indices are merged by addDocument(). With
    * smaller values, less RAM is used while indexing, and searches on
    * unoptimized indices are faster, but indexing speed is slower. With larger
    * values, more RAM is used during indexing, and while searches on unoptimized
    * indices are slower, indexing is faster. Thus larger values (&gt; 10) are
    * best for batch index creation, and smaller values (&lt; 10) for indices
    * that are interactively maintained.
    * <p>This must never be less than 2.  The default value is 10.
    *
    * @see IndexWriter#setMergeFactor(int32_t)
    * @throws IllegalStateException if the index is closed
    */
    void setMergeFactor(int32_t mergeFactor);

    /**
    * @throws IOException
    * @see IndexModifier#setMergeFactor(int32_t)
    */
    int32_t getMergeFactor();

    /**
    * Close this index, writing all pending changes to disk.
    *
    * @throws IllegalStateException if the index has been closed before already
    */
    void close();

    QString toString() const;	

    /**
    * Gets the version number of the currently open index.
    */
    int64_t getCurrentVersion() const;

    /**
    * Returns an enumeration of all the documents which contain term. 
    *
    * Warning: This is not threadsafe. Make sure you lock the modifier object
    * while using the TermDocs. If the IndexReader that the modifier manages
    * is closed, the TermDocs object will fail.
    */
    TermDocs* termDocs(Term* term = NULL);

    /**
    * Returns an enumeration of all terms after a given term.
    * If no term is given, an enumeration of all the terms 
    * in the index is returned.
    * The enumeration is ordered by Term.compareTo().  Each term
    * is greater than all that precede it in the enumeration.
    *
    * Warning: This is not threadsafe. Make sure you lock the modifier object
    * while using the TermDocs. If the IndexReader that the modifier manages
    * is closed, the Document will be invalid
    */
    TermEnum* terms(Term* term = NULL);

    /**
    * Returns the stored fields of the n-th Document in this index. 
    *
    * Warning: This is not threadsafe. Make sure you lock the modifier object
    * while using the TermDocs. If the IndexReader that the modifier manages
    * is closed, the Document will be invalid
    */
    bool document(const int32_t n, CL_NS(document)::Document* doc);
    _CL_DEPRECATED(document(i, document))
        CL_NS(document)::Document* document(const int32_t n);

    // Returns the directory used by this index.
    CL_NS(store)::Directory* getDirectory();
};

CL_NS_END

#endif
