/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.opennlp.corpus_server.impl;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
import org.apache.opennlp.corpus_server.search.SearchService;
import org.apache.opennlp.corpus_server.store.CorporaStore;
import org.apache.opennlp.corpus_server.store.CorpusStore;
import org.apache.uima.UIMAFramework;
import org.apache.uima.analysis_engine.AnalysisEngine;
import org.apache.uima.analysis_engine.AnalysisEngineDescription;
import org.apache.uima.analysis_engine.AnalysisEngineProcessException;
import org.apache.uima.cas.CAS;
import org.apache.uima.cas.Feature;
import org.apache.uima.cas.FeatureStructure;
import org.apache.uima.cas.Type;
import org.apache.uima.lucas.indexer.IndexWriterProviderImpl;
import org.apache.uima.resource.FileResourceSpecifier;
import org.apache.uima.resource.ResourceInitializationException;
import org.apache.uima.resource.impl.FileResourceSpecifier_impl;
import org.apache.uima.resource.metadata.MetaDataObject;
import org.apache.uima.resource.metadata.TypeSystemDescription;
import org.apache.uima.util.CasCreationUtils;
import org.apache.uima.util.InvalidXMLException;
import org.apache.uima.util.XMLInputSource;

public class LuceneSearchService implements SearchService {

  final static String LUCENE_ID_FIELD = "id";
  
  private final static Logger LOGGER = Logger.getLogger(
      LuceneSearchService.class .getName());

  private CorporaStore store;
  
  /**
   * Maps the corpus id to the Lucas Indexer Analysis Engine.
   */
  private Map<String, AnalysisEngine> corpusIndexerMap = new HashMap<String, AnalysisEngine>();
  
  /**
   * Maps the corpus id to the Index Server instance, if one exists, otherwise
   * it will be created on first access.
   */
  private Map<String, IndexSearcher> corpusSearcherMap = new HashMap<String, IndexSearcher>();
  
  private static File getIndexDirectory(String corpusId) {
    return new File("index" + File.separator + corpusId);
  }
  
  private void createIndexWriter(String corpusId, boolean createIndex) throws IOException {
    
    // Set the index mapping file for this corpus in the analysis engine descriptor
    CorpusStore corpusStore = store.getCorpus(corpusId);
    
    XMLInputSource in = new XMLInputSource(LuceneSearchService.class.getResourceAsStream(
        "/org/apache/opennlp/corpus_server/impl/LuceneIndexer.xml"), new File(""));
    
    try {
      AnalysisEngineDescription specifier;
      specifier = (AnalysisEngineDescription) UIMAFramework.getXMLParser().parseResourceSpecifier(in);
      
      // TODO: How to store mapping file? Should be transmitted during corpus creation ...

      File mappingTmpFile = File.createTempFile("lucas-mapping", corpusId + ".xml");
      mappingTmpFile.deleteOnExit();

      InputStream mappingFileIn = new ByteArrayInputStream(corpusStore.getIndexMapping());
      OutputStream mappingTmpOut = null;
      
      try {
        mappingTmpOut = new FileOutputStream(mappingTmpFile);
        
        byte buffer[] = new byte[1024];
        int len = 0;
        while ((len = mappingFileIn.read(buffer)) > 0) {
          mappingTmpOut.write(buffer, 0, len);
        }
      }
      catch (IOException e) {
        // TODO: Or just ignore it ?! and do not create the indexer for this corpus?!
        throw e;
      }
      finally {
        if (mappingFileIn != null) {
          try {
            mappingFileIn.close();
          }
          catch (IOException e) {}
        }
        
        if (mappingTmpOut != null) {
          try {
            mappingTmpOut.close();
          }
          catch (IOException e) {}
        }
      }
      
      specifier.getAnalysisEngineMetaData().
      getConfigurationParameterSettings().setParameterValue("mappingFile",
          mappingTmpFile.getAbsolutePath());
      
      // Set the index writer properties file in the analysis engine
      // and replace the index path with the index location for this corpus
      
      Properties indexWriterProperties = new Properties();
      
      InputStream indexWriterPropertiesIn = null;
      try {
        // TODO: Retrieve file form somewhere for this corpus
        indexWriterPropertiesIn = LuceneSearchService.class.getResourceAsStream(
            "/org/apache/opennlp/corpus_server/impl/IndexWriter.properties");
      
        indexWriterProperties.load(indexWriterPropertiesIn);
      }
      finally {
        if (indexWriterPropertiesIn != null) {
          try {
            indexWriterPropertiesIn.close();
          }
          catch (IOException e) {}
        }
      }
      
      indexWriterProperties.setProperty(IndexWriterProviderImpl.INDEX_PATH_PROPERTY,
          getIndexDirectory(corpusId).getAbsolutePath());
      
      indexWriterProperties.setProperty(IndexWriterProviderImpl.CREATE_INDEX_PROPERTY,
          Boolean.toString(createIndex));
      
      File indexWriterTmpFile = File.createTempFile("index-writer", corpusId + ".properties");
      indexWriterTmpFile.deleteOnExit();
      
      OutputStream indexPropertiesOut = null; 
      try {
        indexPropertiesOut = new FileOutputStream(indexWriterTmpFile);
        // write properties into a tmp file
        indexWriterProperties.store(indexPropertiesOut, null);
      }
      finally {
        if (indexPropertiesOut != null) {
          try {
            indexPropertiesOut.close();
          }
          catch (IOException e) {}
        }
      }
      
      FileResourceSpecifier indexWriterFileSpecifier = new FileResourceSpecifier_impl();
      indexWriterFileSpecifier.setFileUrl(indexWriterTmpFile.toURL().toString());
      // TODO: This will fail ...
      specifier.getResourceManagerConfiguration().getExternalResources()[0].setResourceSpecifier(indexWriterFileSpecifier);
      
      AnalysisEngine indexer = UIMAFramework.produceAnalysisEngine(specifier);
      corpusIndexerMap.put(corpusId, indexer);
    } catch (InvalidXMLException e) {
      throw new IOException(e);
    } catch (ResourceInitializationException e) {
      throw new IOException(e);
    }
  }
  
  @Override
  public synchronized void initialize(CorporaStore store) throws IOException {
    
    this.store = store;
    
    for (String corpusId : store.getCorpusIds()) {
      try {
        createIndexWriter(corpusId, false);
        LOGGER.info("Created Index Writer for " + corpusId + "corpus.");
      }
      catch (IOException e) {
        LOGGER.warning("Failed to open Index Writer for " + corpusId + "corpus.");
      }
    }
  }
  
  @Override
  public synchronized void createIndex(CorpusStore store) throws IOException {
    createIndexWriter(store.getCorpusId(), true);
    LOGGER.info("Created Index Writer for " + store.getCorpusId() + " corpus.");
  }
  
  public synchronized void dropIndex(CorpusStore store) throws IOException {
    
  }
  
  @Override
  public synchronized void index(CorpusStore store, String casId) throws IOException {
    
    // TODO: Need to take care for thread safety ..
    
    String corpusId = store.getCorpusId();
    
    AnalysisEngine indexer = corpusIndexerMap.get(corpusId);
    
    InputStream indexTsIn = LuceneSearchService.class.getResourceAsStream(
        "/org/apache/opennlp/corpus_server/impl/TypeSystem.xml");
    
    TypeSystemDescription indexTypeDesc;
    try {
      indexTypeDesc = UimaUtil.createTypeSystemDescription(indexTsIn);
    }
    finally {
      indexTsIn.close();
    }
    
    List<MetaDataObject> specs = new ArrayList<MetaDataObject>();
    specs.add(indexTypeDesc);
    TypeSystemDescription tsDescription = UimaUtil.createTypeSystemDescription(
          new ByteArrayInputStream(store.getTypeSystem()));
    specs.add(tsDescription);
    
    // Note: This might be a performance problem
    CAS cas;
    try {
      cas = CasCreationUtils.createCas(specs);
    } catch (ResourceInitializationException e) {
      throw new IOException(e);
    }
    
    byte[] casBytes = store.getCAS(casId);
    
    if (casBytes != null) {
      UimaUtil.deserializeXmiCAS(cas, new ByteArrayInputStream(casBytes));
    }
    else {
      cas.setDocumentText(null);
    }
    
    // Inject id feature structure into the CAS
    Type casIdType = cas.getTypeSystem().getType(LuceneIndexer.CAS_ID_TYPE);
    Feature casIdFeature =  casIdType.getFeatureByBaseName(LuceneIndexer.CAS_ID_FEEATURE);

    FeatureStructure casIdFS = cas.createFS(casIdType);
    casIdFS.setStringValue(casIdFeature, casId);
    cas.addFsToIndexes(casIdFS);
    
    try {
      indexer.process(cas);
    } catch (AnalysisEngineProcessException e) {
      LOGGER.log(Level.SEVERE, "Failed to index CAS: " + casId, e);
    }
  }

  @Override
  public void removeFromIndex(CorpusStore store, String casId)
      throws IOException {
    index(store, casId);
  }
  
  @Override
  public synchronized List<String> search(CorpusStore store, String q)
      throws IOException {
    
    // PERFORMANCE: This method can only be executed by one thread at a time
    //              when there are concurrent search requests this will result
    //              in longer than necessary delays to answer them.
    
    IndexSearcher searcher = corpusSearcherMap.get(store.getCorpusId());
    
    // Opening or reopening an index might fail,
    // in this case every search request fails as well.
    if (searcher == null) { 
      File indexLocation = getIndexDirectory(store.getCorpusId());
      
      Directory indexDirectory = FSDirectory.open(indexLocation);
      
      IndexReader indexReader = IndexReader.open(indexDirectory, false);
      
      // Note: Reopening index for every request is slow,
      // modify code again to keep indexes open!
      
      searcher = new IndexSearcher(indexReader);
      
      corpusSearcherMap.put(store.getCorpusId(), searcher);
    }
    
    if (!searcher.getIndexReader().isCurrent()) {
      IndexReader freshIndexReader = searcher.getIndexReader().reopen();
      
      searcher.close();
      
      searcher = new IndexSearcher(freshIndexReader);
      corpusSearcherMap.put(store.getCorpusId(), searcher);
    }
    
    QueryParser parser = new QueryParser(Version.LUCENE_29, "text", new StandardAnalyzer(Version.LUCENE_29));
    
    Query query;
    try {
      query = parser.parse(q);
    } catch (ParseException e) {
      throw new IOException(e);
    }
    
    final List<String> results = new ArrayList<String>();
    
    
    final IndexSearcher finalSearcher = searcher;
    
    // query index ...
    searcher.search(query, new Collector() {
      
      int docBase = Integer.MIN_VALUE;
      
      @Override
      public void setScorer(Scorer scorer) throws IOException {
      }
      
      @Override
      public void setNextReader(IndexReader reader, int docBase) throws IOException {
        this.docBase = docBase;
      }
      
      @Override
      public void collect(int id) throws IOException {
        Document doc = finalSearcher.doc(docBase + id);
        String idString = doc.get(LUCENE_ID_FIELD);
        results.add(idString);
      }
      
      @Override
      public boolean acceptsDocsOutOfOrder() {
        return false;
      }
    });
      
    searcher.close();
    
    return results;
  }

  @Override
  public void shutdown() throws IOException {
    
    for (String corpusId : corpusIndexerMap.keySet()) {
      AnalysisEngine indexer = corpusIndexerMap.get(corpusId);
      
      if (indexer != null) {
        indexer.destroy();
      }
    }
    
    for (String corpusId : corpusSearcherMap.keySet()) {
      IndexSearcher searcher = corpusSearcherMap.get(corpusId);
      
      if (searcher != null) {
        try {
          searcher.close();
        }
        catch (IOException e) {
          LOGGER.log(Level.SEVERE, "Failed to shutdown searcher for "
              + corpusId + " corpus!", e);
        }
      }
    }
  }
}