EDIT

/**

 * Copyright (C) 2007 EDIT

 * European Distributed Institute of Taxonomy 

 * http://www.e-taxonomy.eu

 * 

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.cdm.persistence.dao.hibernate;

import java.io.IOException;

import java.io.StringReader;

import java.util.Iterator;

import java.util.Vector;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.lucene.analysis.Analyzer;

import org.apache.lucene.analysis.Token;

import org.apache.lucene.analysis.TokenStream;

import org.apache.lucene.analysis.standard.StandardAnalyzer;

import org.apache.lucene.index.CorruptIndexException;

import org.apache.lucene.index.IndexReader;

import org.apache.lucene.index.Term;

import org.apache.lucene.queryParser.ParseException;

import org.apache.lucene.queryParser.QueryParser;

import org.apache.lucene.search.PhraseQuery;

import org.apache.lucene.search.Query;

import org.apache.lucene.search.TermQuery;

import org.apache.lucene.search.spell.Dictionary;

import org.apache.lucene.search.spell.LuceneDictionary;

import org.apache.lucene.search.spell.SpellChecker;

import org.apache.lucene.store.Directory;

import org.hibernate.SessionFactory;

import org.hibernate.search.FullTextSession;

import org.hibernate.search.Search;

import org.hibernate.search.SearchFactory;

import org.hibernate.search.reader.ReaderProvider;

import org.hibernate.search.store.DirectoryProvider;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import org.springmodules.lucene.index.factory.IndexFactory;

import org.springmodules.lucene.index.factory.LuceneIndexWriter;

import eu.etaxonomy.cdm.model.common.CdmBase;

import eu.etaxonomy.cdm.persistence.dao.IAlternativeSpellingSuggestionParser;

public abstract class AlternativeSpellingSuggestionParser<T extends CdmBase> extends HibernateDaoSupport  implements

		IAlternativeSpellingSuggestionParser {

	private static Log log = LogFactory.getLog(AlternativeSpellingSuggestionParser.class);

	private String defaultField;

	protected IndexFactory indexFactory;

	protected Directory directory;

	private Class<T> type;

	public AlternativeSpellingSuggestionParser(Class<T> type) {

		this.type = type;

	}

	public abstract void setDirectory(Directory directory);

	public abstract void setIndexFactory(IndexFactory indexFactory);

	@Autowired

	public void setHibernateSessionFactory(SessionFactory sessionFactory) {

		super.setSessionFactory(sessionFactory);

	}

	public void setDefaultField(String defaultField) {

		this.defaultField = defaultField;

	}

	public Query parse(String queryString) throws ParseException {

		QueryParser queryParser = new QueryParser(defaultField, new StandardAnalyzer());		

		return queryParser.parse(queryString);

	}

	public Query suggest(String queryString) throws ParseException {

		QuerySuggester querySuggester = new QuerySuggester(defaultField, new StandardAnalyzer());

		Query query = querySuggester.parse(queryString);

		return querySuggester.hasSuggestedQuery() ? query : null;

	}

	private class QuerySuggester extends QueryParser {

		private boolean suggestedQuery = false;

		public QuerySuggester(String field, Analyzer analyzer) {

			super(field, analyzer);

		}

		protected Query getFieldQuery(String field, String queryText) throws ParseException {

			// Copied from org.apache.lucene.queryParser.QueryParser

			// replacing construction of TermQuery with call to getTermQuery()

			// which finds close matches.

		    TokenStream source = getAnalyzer().tokenStream(field, new StringReader(queryText));

			Vector v = new Vector();

			Token t;

			while (true) {

				try {

					t = source.next();

				} catch (IOException e) {

					t = null;

				}

				if (t == null)

					break;

				v.addElement(t.termText());

			}

			try {

				source.close();

			} catch (IOException e) {

				// ignore

			}

			if (v.size() == 0)

				return null;

			else if (v.size() == 1)

				return new TermQuery(getTerm(field, (String) v.elementAt(0)));

			else {

				PhraseQuery q = new PhraseQuery();

				q.setSlop(getPhraseSlop());

				for (int i = 0; i < v.size(); i++) {

					q.add(getTerm(field, (String) v.elementAt(i)));

				}

				return q;

			}

		}

		private Term getTerm(String field, String queryText) throws ParseException {

			try {

				SpellChecker spellChecker = new SpellChecker(directory);

				if (spellChecker.exist(queryText)) {

					return new Term(field, queryText);

				}

				String[] similarWords = spellChecker.suggestSimilar(queryText, 1);

				if (similarWords.length == 0) {

					return new Term(field, queryText);

				}			

				suggestedQuery = true;

				return new Term(field, similarWords[0]);

			} catch (IOException e) {

				throw new ParseException(e.getMessage());

			}

		}		

		public boolean hasSuggestedQuery() {

			return suggestedQuery;

		}	

	}

	public void refresh() {

		FullTextSession fullTextSession = Search.createFullTextSession(getSession());

		SearchFactory searchFactory = fullTextSession.getSearchFactory();

        DirectoryProvider directoryProvider = searchFactory.getDirectoryProviders(type)[0];

        ReaderProvider readerProvider = searchFactory.getReaderProvider();

		IndexReader indexReader = null;

		LuceneIndexWriter indexWriter = null;

		try {

			try {

				indexWriter = indexFactory.getIndexWriter();

				indexReader = readerProvider.openReader(directoryProvider);

				log.debug("Creating new dictionary for words in " + defaultField + " docs " + indexReader.numDocs());

				Dictionary dictionary = new LuceneDictionary(indexReader, defaultField);

				if(log.isDebugEnabled()) {

				    Iterator iterator = dictionary.getWordsIterator();

				    while(iterator.hasNext()) {

					    log.debug("Indexing word " + iterator.next());

				    }

				}

	            SpellChecker spellChecker = new SpellChecker(directory);

	            spellChecker.indexDictionary(dictionary);

			} catch (CorruptIndexException cie) {

				log.error("Spellings index is corrupted", cie);

			} finally {

				if (indexReader != null) {

					readerProvider.closeReader(indexReader);

				}

				if(indexWriter != null) {

                    indexWriter.close();

                }

			} 

		} catch (IOException ioe) {

			log.error(ioe);

		}

	}

}