package org.apache.maven.index.updater;
   
   /*
    * 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.
   */
  
  import java.io.BufferedInputStream;
  import java.io.DataInput;
  import java.io.DataInputStream;
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UTFDataFormatException;
  import java.util.Date;
  import java.util.zip.GZIPInputStream;
  
  import org.apache.lucene.document.Document;
  import org.apache.lucene.document.Field;
  import org.apache.lucene.document.Field.Index;
  import org.apache.lucene.document.Field.Store;
  import org.apache.lucene.index.IndexWriter;
  import org.apache.maven.index.context.IndexUtils;
  import org.apache.maven.index.context.IndexingContext;
  
  /**
   * An index data reader used to parse transfer index format.
   * 
   * @author Eugene Kuleshov
   */
  public class IndexDataReader
  {
      private final DataInputStream dis;
  
      public IndexDataReader( InputStream is )
          throws IOException
      {
          BufferedInputStream bis = new BufferedInputStream( is, 1024 * 8 );
  
          // MINDEXER-13
          // LightweightHttpWagon may have performed automatic decompression
          // Handle it transparently
          bis.mark( 2 );
          InputStream data;
          if ( bis.read() == 0x1f && bis.read() == 0x8b ) // GZIPInputStream.GZIP_MAGIC
          {
              bis.reset();
              data = new GZIPInputStream( bis, 2 * 1024 );
          }
          else
          {
              bis.reset();
              data = bis;
          }
  
          this.dis = new DataInputStream( data );
      }
  
      public IndexDataReadResult readIndex( IndexWriter w, IndexingContext context )
          throws IOException
      {
          long timestamp = readHeader();
  
          Date date = null;
  
          if ( timestamp != -1 )
          {
              date = new Date( timestamp );
  
              IndexUtils.updateTimestamp( w.getDirectory(), date );
          }
  
          int n = 0;
  
          Document doc;
          while ( ( doc = readDocument() ) != null )
          {
              w.addDocument( IndexUtils.updateDocument( doc, context, false ) );
  
              n++;
          }
  
          w.commit();
          w.optimize();
  
         IndexDataReadResult result = new IndexDataReadResult();
         result.setDocumentCount( n );
         result.setTimestamp( date );
         return result;
     }
 
     public long readHeader()
         throws IOException
     {
         final byte HDRBYTE = (byte) ( ( IndexDataWriter.VERSION << 24 ) >> 24 );
 
         if ( HDRBYTE != dis.readByte() )
         {
             // data format version mismatch
             throw new IOException( "Provided input contains unexpected data (0x01 expected as 1st byte)!" );
         }
 
         return dis.readLong();
     }
 
     public Document readDocument()
         throws IOException
     {
         int fieldCount;
         try
         {
             fieldCount = dis.readInt();
         }
         catch ( EOFException ex )
         {
             return null; // no more documents
         }
 
         Document doc = new Document();
 
         for ( int i = 0; i < fieldCount; i++ )
         {
             doc.add( readField() );
         }
 
         return doc;
     }
 
     private Field readField()
         throws IOException
     {
         int flags = dis.read();
 
         Index index = Index.NO;
         if ( ( flags & IndexDataWriter.F_INDEXED ) > 0 )
         {
             boolean isTokenized = ( flags & IndexDataWriter.F_TOKENIZED ) > 0;
             index = isTokenized ? Index.ANALYZED : Index.NOT_ANALYZED;
         }
 
         Store store = Store.NO;
         if ( ( flags & IndexDataWriter.F_STORED ) > 0 )
         {
             store = Store.YES;
         }
 
         String name = dis.readUTF();
         String value = readUTF( dis );
 
         return new Field( name, value, store, index );
     }
 
     private static String readUTF( DataInput in )
         throws IOException
     {
         int utflen = in.readInt();
 
         byte[] bytearr;
         char[] chararr;
 
         try
         {
             bytearr = new byte[utflen];
             chararr = new char[utflen];
         }
         catch ( OutOfMemoryError e )
         {
             final IOException ex =
                 new IOException(
                     "Index data content is inappropriate (is junk?), leads to OutOfMemoryError! See MINDEXER-28 for more information!" );
             ex.initCause( e );
             throw ex;
         }
 
         int c, char2, char3;
         int count = 0;
         int chararr_count = 0;
 
         in.readFully( bytearr, 0, utflen );
 
         while ( count < utflen )
         {
             c = bytearr[count] & 0xff;
             if ( c > 127 )
             {
                 break;
             }
             count++;
             chararr[chararr_count++] = (char) c;
         }
 
         while ( count < utflen )
         {
             c = bytearr[count] & 0xff;
             switch ( c >> 4 )
             {
                 case 0:
                 case 1:
                 case 2:
                 case 3:
                 case 4:
                 case 5:
                 case 6:
                 case 7:
                     /* 0xxxxxxx */
                     count++;
                     chararr[chararr_count++] = (char) c;
                     break;
 
                 case 12:
                 case 13:
                     /* 110x xxxx 10xx xxxx */
                     count += 2;
                     if ( count > utflen )
                     {
                         throw new UTFDataFormatException( "malformed input: partial character at end" );
                     }
                     char2 = bytearr[count - 1];
                     if ( ( char2 & 0xC0 ) != 0x80 )
                     {
                         throw new UTFDataFormatException( "malformed input around byte " + count );
                     }
                     chararr[chararr_count++] = (char) ( ( ( c & 0x1F ) << 6 ) | ( char2 & 0x3F ) );
                     break;
 
                 case 14:
                     /* 1110 xxxx 10xx xxxx 10xx xxxx */
                     count += 3;
                     if ( count > utflen )
                     {
                         throw new UTFDataFormatException( "malformed input: partial character at end" );
                     }
                     char2 = bytearr[count - 2];
                     char3 = bytearr[count - 1];
                     if ( ( ( char2 & 0xC0 ) != 0x80 ) || ( ( char3 & 0xC0 ) != 0x80 ) )
                     {
                         throw new UTFDataFormatException( "malformed input around byte " + ( count - 1 ) );
                     }
                     chararr[chararr_count++] =
                         (char) ( ( ( c & 0x0F ) << 12 ) | ( ( char2 & 0x3F ) << 6 ) | ( ( char3 & 0x3F ) << 0 ) );
                     break;
 
                 default:
                     /* 10xx xxxx, 1111 xxxx */
                     throw new UTFDataFormatException( "malformed input around byte " + count );
             }
         }
 
         // The number of chars produced may be less than utflen
         return new String( chararr, 0, chararr_count );
     }
 
     /**
      * An index data read result holder
      */
     public static class IndexDataReadResult
     {
         private Date timestamp;
 
         private int documentCount;
 
         public void setDocumentCount( int documentCount )
         {
             this.documentCount = documentCount;
         }
 
         public int getDocumentCount()
         {
             return documentCount;
         }
 
         public void setTimestamp( Date timestamp )
         {
             this.timestamp = timestamp;
         }
 
         public Date getTimestamp()
         {
             return timestamp;
         }
 
     }
 
     /**
      * Reads index content by using a visitor. <br>
      * The visitor is called for each read documents after it has been populated with Lucene fields.
      * 
      * @param visitor an index data visitor
      * @param context indexing context
      * @return statistics about read data
      * @throws IOException in case of an IO exception during index file access
      */
     public IndexDataReadResult readIndex( final IndexDataReadVisitor visitor, final IndexingContext context )
         throws IOException
     {
         dis.readByte(); // data format version
 
         long timestamp = dis.readLong();
 
         Date date = null;
 
         if ( timestamp != -1 )
         {
             date = new Date( timestamp );
         }
 
         int n = 0;
 
         Document doc;
         while ( ( doc = readDocument() ) != null )
         {
             visitor.visitDocument( IndexUtils.updateDocument( doc, context, false ) );
 
             n++;
         }
 
         IndexDataReadResult result = new IndexDataReadResult();
         result.setDocumentCount( n );
         result.setTimestamp( date );
         return result;
     }
 
     /**
      * Visitor of indexed Lucene documents.
      */
     public static interface IndexDataReadVisitor
     {
 
         /**
          * Called on each read document. The document is already populated with fields.
          * 
          * @param document read document
          */
         void visitDocument( Document document );
 
     }
 
 }