/*
    * 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.maven.index;
  
  import java.io.IOException;
  import java.io.StringReader;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.analysis.CachingTokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.document.Document;
  import org.apache.lucene.search.Explanation;
  import org.apache.lucene.search.IndexSearcher;
  import org.apache.lucene.search.Query;
  import org.apache.lucene.search.TopDocs;
  import org.apache.lucene.search.highlight.Formatter;
  import org.apache.lucene.search.highlight.Highlighter;
  import org.apache.lucene.search.highlight.InvalidTokenOffsetsException;
  import org.apache.lucene.search.highlight.QueryScorer;
  import org.apache.lucene.search.highlight.SimpleHTMLFormatter;
  import org.apache.lucene.search.highlight.TextFragment;
  import org.apache.maven.index.context.IndexUtils;
  import org.apache.maven.index.context.IndexingContext;
  import org.apache.maven.index.context.NexusIndexMultiSearcher;
  import org.apache.maven.index.creator.JarFileContentsIndexCreator;
  
  /**
   * Default implementation of IteratorResultSet. TODO: there is too much of logic, refactor this!
   *
   * @author cstamas
   */
  public class DefaultIteratorResultSet implements IteratorResultSet {
      private final IteratorSearchRequest searchRequest;
  
      private final NexusIndexMultiSearcher indexSearcher;
  
      private final List<IndexingContext> contexts;
  
      private final int[] starts;
  
      private final ArtifactInfoFilter filter;
  
      private final ArtifactInfoPostprocessor postprocessor;
  
      private final List<MatchHighlightRequest> matchHighlightRequests;
  
      private final TopDocs hits;
  
      private final int from;
  
      private final int count;
  
      private final int maxRecPointer;
  
      private int pointer;
  
      private int processedArtifactInfoCount;
  
      private ArtifactInfo ai;
  
      protected DefaultIteratorResultSet(
              final IteratorSearchRequest request,
              final NexusIndexMultiSearcher indexSearcher,
              final List<IndexingContext> contexts,
              final TopDocs hits)
              throws IOException {
          this.searchRequest = request;
  
          this.indexSearcher = indexSearcher;
  
          this.contexts = contexts;
  
          {
              int maxDoc = 0;
              this.starts = new int[contexts.size() + 1]; // build starts array
              // this is good to do as we have NexusIndexMultiSearcher passed in contructor, so it is already open, hence
              // #acquire() already invoked on underlying NexusIndexMultiReader
              final List<IndexSearcher> acquiredSearchers =
                      indexSearcher.getNexusIndexMultiReader().getAcquiredSearchers();
              for (int i = 0; i < contexts.size(); i++) {
                 starts[i] = maxDoc;
                 maxDoc += acquiredSearchers.get(i).getIndexReader().maxDoc(); // compute maxDocs
             }
             starts[contexts.size()] = maxDoc;
         }
 
         this.filter = request.getArtifactInfoFilter();
 
         this.postprocessor = request.getArtifactInfoPostprocessor();
 
         this.matchHighlightRequests = request.getMatchHighlightRequests();
 
         List<MatchHighlightRequest> matchHighlightRequests = new ArrayList<>();
         for (MatchHighlightRequest hr : request.getMatchHighlightRequests()) {
             Query rewrittenQuery = hr.getQuery().rewrite(indexSearcher.getIndexReader());
             matchHighlightRequests.add(new MatchHighlightRequest(hr.getField(), rewrittenQuery, hr.getHighlightMode()));
         }
 
         this.hits = hits;
 
         this.from = request.getStart();
 
         this.count = (request.getCount() == AbstractSearchRequest.UNDEFINED
                 ? hits.scoreDocs.length
                 : Math.min(request.getCount(), hits.scoreDocs.length));
 
         this.pointer = from;
 
         this.processedArtifactInfoCount = 0;
 
         this.maxRecPointer = from + count;
 
         ai = createNextAi();
 
         if (ai == null) {
             cleanUp();
         }
     }
 
     public boolean hasNext() {
         return ai != null;
     }
 
     public ArtifactInfo next() {
         ArtifactInfo result = ai;
 
         try {
             ai = createNextAi();
         } catch (IOException e) {
             ai = null;
 
             throw new IllegalStateException("Cannot fetch next ArtifactInfo!", e);
         } finally {
             if (ai == null) {
                 cleanUp();
             }
         }
 
         return result;
     }
 
     public void remove() {
         throw new UnsupportedOperationException(
                 "Method not supported on " + getClass().getName());
     }
 
     public Iterator<ArtifactInfo> iterator() {
         return this;
     }
 
     public void close() {
         cleanUp();
     }
 
     public int getTotalProcessedArtifactInfoCount() {
         return processedArtifactInfoCount;
     }
 
     @Override
     public void finalize() throws Throwable {
         super.finalize();
 
         if (!cleanedUp) {
             System.err.println("#WARNING: Lock leaking from " + getClass().getName() + " for query "
                     + searchRequest.getQuery().toString());
 
             cleanUp();
         }
     }
 
     // ==
 
     protected ArtifactInfo createNextAi() throws IOException {
         ArtifactInfo result = null;
 
         // we should stop if:
         // a) we found what we want
         // b) pointer advanced over more documents that user requested
         // c) pointer advanced over more documents that hits has
         // or we found what we need
         while ((result == null) && (pointer < maxRecPointer) && (pointer < hits.scoreDocs.length)) {
             Document doc = indexSearcher.doc(hits.scoreDocs[pointer].doc);
 
             IndexingContext context = getIndexingContextForPointer(doc, hits.scoreDocs[pointer].doc);
 
             result = IndexUtils.constructArtifactInfo(doc, context);
 
             if (result != null) {
                 // WARNING: NOT FOR PRODUCTION SYSTEMS, THIS IS VERY COSTLY OPERATION
                 // For debugging only!!!
                 if (searchRequest.isLuceneExplain()) {
                     result.getAttributes()
                             .put(
                                     Explanation.class.getName(),
                                     indexSearcher
                                             .explain(searchRequest.getQuery(), hits.scoreDocs[pointer].doc)
                                             .toString());
                 }
 
                 result.setLuceneScore(hits.scoreDocs[pointer].score);
 
                 result.setRepository(context.getRepositoryId());
 
                 result.setContext(context.getId());
 
                 if (filter != null) {
                     if (!filter.accepts(context, result)) {
                         result = null;
                     }
                 }
 
                 if (result != null && postprocessor != null) {
                     postprocessor.postprocess(context, result);
                 }
 
                 if (result != null && matchHighlightRequests.size() > 0) {
                     calculateHighlights(context, doc, result);
                 }
             }
 
             pointer++;
             processedArtifactInfoCount++;
         }
 
         return result;
     }
 
     private volatile boolean cleanedUp = false;
 
     protected synchronized void cleanUp() {
         if (cleanedUp) {
             return;
         }
 
         try {
             indexSearcher.release();
         } catch (IOException e) {
             throw new IllegalStateException(e);
         }
 
         this.cleanedUp = true;
     }
 
     /**
      * Creates the MatchHighlights and adds them to ArtifactInfo if found/can.
      *
      * @param context
      * @param d
      * @param ai
      */
     protected void calculateHighlights(IndexingContext context, Document d, ArtifactInfo ai) throws IOException {
         IndexerField field;
 
         String text;
 
         List<String> highlightFragment;
 
         for (MatchHighlightRequest hr : matchHighlightRequests) {
             field = selectStoredIndexerField(hr.getField());
 
             if (field != null) {
                 text = ai.getFieldValue(field.getOntology());
 
                 if (text != null) {
                     highlightFragment = highlightField(context, hr, field, text);
 
                     if (highlightFragment != null && highlightFragment.size() > 0) {
                         MatchHighlight matchHighlight = new MatchHighlight(hr.getField(), highlightFragment);
 
                         ai.getMatchHighlights().add(matchHighlight);
                     }
                 }
             }
         }
     }
 
     /**
      * Select a STORED IndexerField assigned to passed in Field.
      *
      * @param field
      * @return
      */
     protected IndexerField selectStoredIndexerField(Field field) {
         // hack here
         if (MAVEN.CLASSNAMES.equals(field)) {
             return JarFileContentsIndexCreator.FLD_CLASSNAMES;
         } else {
             return field.getIndexerFields().isEmpty()
                     ? null
                     : field.getIndexerFields().iterator().next();
         }
     }
 
     /**
      * Returns a string that contains match fragment highlighted in style as user requested.
      *
      * @param context
      * @param hr
      * @param field
      * @param text
      * @return
      * @throws IOException
      */
     protected List<String> highlightField(
             IndexingContext context, MatchHighlightRequest hr, IndexerField field, String text) throws IOException {
         // exception with classnames
         if (MAVEN.CLASSNAMES.equals(field.getOntology())) {
             text = text.replace('/', '.').replaceAll("^\\.", "").replaceAll("\n\\.", "\n");
         }
 
         Analyzer analyzer = context.getAnalyzer();
         TokenStream baseTokenStream = analyzer.tokenStream(field.getKey(), new StringReader(text));
 
         CachingTokenFilter tokenStream = new CachingTokenFilter(baseTokenStream);
 
         Formatter formatter;
 
         if (MatchHighlightMode.HTML.equals(hr.getHighlightMode())) {
             formatter = new SimpleHTMLFormatter();
         } else {
             tokenStream.reset();
             tokenStream.end();
             tokenStream.close();
             throw new UnsupportedOperationException(
                     "Hightlight more \"" + hr.getHighlightMode().toString() + "\" is not supported!");
         }
 
         List<String> bestFragments = getBestFragments(hr.getQuery(), formatter, tokenStream, text, 3);
 
         return bestFragments;
     }
 
     protected final List<String> getBestFragments(
             Query query, Formatter formatter, TokenStream tokenStream, String text, int maxNumFragments)
             throws IOException {
         Highlighter highlighter = new Highlighter(formatter, new CleaningEncoder(), new QueryScorer(query));
 
         highlighter.setTextFragmenter(new OneLineFragmenter());
 
         maxNumFragments = Math.max(1, maxNumFragments); // sanity check
 
         TextFragment[] frag;
         // Get text
         ArrayList<String> fragTexts = new ArrayList<>(maxNumFragments);
 
         try {
             frag = highlighter.getBestTextFragments(tokenStream, text, false, maxNumFragments);
 
             for (TextFragment textFragment : frag) {
                 if ((textFragment != null) && (textFragment.getScore() > 0)) {
                     fragTexts.add(textFragment.toString());
                 }
             }
         } catch (InvalidTokenOffsetsException e) {
             // empty?
         }
 
         return fragTexts;
     }
 
     protected IndexingContext getIndexingContextForPointer(Document doc, int docPtr) {
         return contexts.get(readerIndex(docPtr, this.starts, this.contexts.size()));
     }
 
     private static int readerIndex(int n, int[] starts, int numSubReaders) { // find reader for doc n:
         int lo = 0; // search starts array
         int hi = numSubReaders - 1; // for first element less
 
         while (hi >= lo) {
             int mid = (lo + hi) >>> 1;
             int midValue = starts[mid];
             if (n < midValue) {
                 hi = mid - 1;
             } else if (n > midValue) {
                 lo = mid + 1;
             } else { // found a match
                 while (mid + 1 < numSubReaders && starts[mid + 1] == midValue) {
                     mid++; // scan to last match
                 }
                 return mid;
             }
         }
         return hi;
     }
 }