//
   //  ========================================================================
   //  Copyright (c) 1995-2014 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.util;
  
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.util.Utf8Appendable.NotUtf8Exception;
  
  /**
   * Stateful parser for lines of UTF8 formatted text, looking for <code>"\n"</code> as a line termination character.
   * <p>
   * For use with new IO framework that is based on ByteBuffer parsing.
   */
  public class Utf8LineParser
  {
      private enum State
      {
          START,
          PARSE,
          END;
      }
  
      private State state;
      private Utf8StringBuilder utf;
  
      public Utf8LineParser()
      {
          this.state = State.START;
      }
  
      /**
       * Parse a ByteBuffer (could be a partial buffer), and return once a complete line of UTF8 parsed text has been reached.
       *
       * @param buf
       *            the buffer to parse (could be an incomplete buffer)
       * @return the line of UTF8 parsed text, or null if no line end termination has been reached within the {@link ByteBuffer#remaining() remaining} bytes of
       *         the provided ByteBuffer. (In the case of a null, a subsequent ByteBuffer with a line end termination should be provided)
       * @throws NotUtf8Exception
       *             if the input buffer has bytes that do not conform to UTF8 validation (validation performed by {@link Utf8StringBuilder}
       */
      public String parse(ByteBuffer buf)
      {
          byte b;
          while (buf.remaining() > 0)
          {
              b = buf.get();
              if (parseByte(b))
              {
                  state = State.START;
                  return utf.toString();
              }
          }
          // have not reached end of line (yet)
          return null;
      }
  
      private boolean parseByte(byte b)
      {
          switch (state)
          {
              case START:
                  utf = new Utf8StringBuilder();
                  state = State.PARSE;
                  return parseByte(b);
              case PARSE:
                  // not waiting on more UTF sequence parts.
                  if (utf.isUtf8SequenceComplete() && ((b == '\r') || (b == '\n')))
                  {
                      state = State.END;
                      return parseByte(b);
                  }
                  utf.append(b);
                  break;
              case END:
                  if (b == '\n')
                  {
                      // we've reached the end
                      state = State.START;
                      return true;
                  }
                  break;
          }
          return false;
     }
 }