/*
 * 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.exoplatform.services.jcr.impl.core.query.lucene;

import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PayloadAttribute;
import org.apache.lucene.index.Payload;
import org.exoplatform.services.jcr.impl.Constants;

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

/**
 * <code>SingletonTokenStream</code> implements a token stream that wraps a
 * single value with a given property type. The property type is stored as a
 * payload on the single returned token.
 */
public final class SingletonTokenStream extends TokenStream implements Externalizable
{
   /**
    * The string value of the token.
    */
   private String value;

   /**
    * The payload of the token.
    */
   private Payload payload;

   /**
    * The term attribute of the current token
    */
   private CharTermAttribute termAttribute;

   /**
    * The payload attribute of the current token
    */
   private PayloadAttribute payloadAttribute;

   private volatile boolean consumed = false;

   /**
    * Default constructor for serialization
    */
   public SingletonTokenStream()
   {
      termAttribute = addAttribute(CharTermAttribute.class);
      payloadAttribute = addAttribute(PayloadAttribute.class);
   }

   /**
    * Creates a new SingleTokenStream with the given value and payload.
    * 
    * @param value
    *            the string value that will be returned with the token.
    * @param payload
    *            the payload that will be attached to this token
    */
   public SingletonTokenStream(String value, Payload payload)
   {
      this.value = value;
      this.payload = payload;
      termAttribute = addAttribute(CharTermAttribute.class);
      payloadAttribute = addAttribute(PayloadAttribute.class);
   }

   /**
    * Creates a new SingleTokenStream with the given value and a property
    * <code>type</code>.
    * 
    * @param value
    *            the string value that will be returned with the token.
    * @param type
    *            the JCR property type.
    */
   public SingletonTokenStream(String value, int type)
   {
      this(value, new Payload(new PropertyMetaData(type).toByteArray()));
   }

   @Override
   public boolean incrementToken() throws IOException
   {
      if (consumed)
      {
         return false;
      }
      clearAttributes();
      termAttribute.setEmpty();
      termAttribute.append(value);
      payloadAttribute.setPayload(payload);
      consumed = true;
      return true;
   }

   /**
    * {@inheritDoc}
    */
   @Override
   public void reset() throws IOException
   {
      consumed = false;
      if (termAttribute == null)
      {
         termAttribute = addAttribute(CharTermAttribute.class);
      }
      if (payloadAttribute == null)
      {
         payloadAttribute = addAttribute(PayloadAttribute.class);
      }
   }

   /**
    * {@inheritDoc}
    */
   @Override
   public void close() throws IOException
   {
      consumed = true;
      payloadAttribute = null;
      termAttribute = null;
   }

   /**
    * {@inheritDoc}
    */
   public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
   {
      payload = (Payload)in.readObject();
      int length = in.readInt();
      byte[] binValue = new byte[length];
      in.read(binValue);
      value = new String(binValue, Constants.DEFAULT_ENCODING);
   }

   /**
    * {@inheritDoc}
    */
   public void writeExternal(ObjectOutput out) throws IOException
   {
      // skip writing hasNext field
      out.writeObject(payload);
      byte[] binValue = value.getBytes(Constants.DEFAULT_ENCODING);
      out.writeInt(binValue.length);
      out.write(binValue);
   }
}
