//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  
  package org.eclipse.jetty.http;
  
  import java.nio.ByteBuffer;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.ServiceLoader;
  
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  
  /* ------------------------------------------------------------ */
  /** Pre encoded HttpField.
   * <p>A HttpField that will be cached and used many times can be created as 
   * a {@link PreEncodedHttpField}, which will use the {@link HttpFieldPreEncoder}
   * instances discovered by the {@link ServiceLoader} to pre-encode the header 
   * for each version of HTTP in use.  This will save garbage 
   * and CPU each time the field is encoded into a response.
   * </p>
   */
  public class PreEncodedHttpField extends HttpField
  {
      private final static Logger LOG = Log.getLogger(PreEncodedHttpField.class);
      private final static HttpFieldPreEncoder[] __encoders;
      
      static
      { 
          List<HttpFieldPreEncoder> encoders = new ArrayList<>();
          Iterator<HttpFieldPreEncoder> iter = ServiceLoader.load(HttpFieldPreEncoder.class,PreEncodedHttpField.class.getClassLoader()).iterator();
          while (iter.hasNext())
          {
              try
              {
                  encoders.add(iter.next());
              }
              catch(Error|RuntimeException e)
              {
                  LOG.debug(e);
              }
          }
          // TODO avoid needing this catch all
          if (encoders.size()==0)
              encoders.add(new Http1FieldPreEncoder());
          LOG.debug("HttpField encoders loaded: {}",encoders);
          __encoders = encoders.toArray(new HttpFieldPreEncoder[encoders.size()]);
      }
      
      private final byte[][] _encodedField=new byte[2][];
  
      public PreEncodedHttpField(HttpHeader header,String name,String value)
      {
          super(header,name, value);
          
          for (HttpFieldPreEncoder e:__encoders)
          {
              _encodedField[e.getHttpVersion()==HttpVersion.HTTP_2?1:0]=e.getEncodedField(header,header.asString(),value);
          }
      }
      
      public PreEncodedHttpField(HttpHeader header,String value)
      {
          this(header,header.asString(),value);
      }
      
      public PreEncodedHttpField(String name,String value)
      {
          this(null,name,value);
      }
      
      public void putTo(ByteBuffer bufferInFillMode, HttpVersion version)
      {
          bufferInFillMode.put(_encodedField[version==HttpVersion.HTTP_2?1:0]);
      }
  }