//
   //  ========================================================================
   //  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.websocket.common.io.http;
  
  import java.nio.ByteBuffer;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.eclipse.jetty.util.BufferUtil;
  import org.eclipse.jetty.util.StringUtil;
  import org.eclipse.jetty.util.Utf8LineParser;
  
  /**
   * Responsible for reading UTF8 Response Header lines and parsing them into a provided UpgradeResponse object.
   */
  public class HttpResponseHeaderParser
  {
      @SuppressWarnings("serial")
      public static class ParseException extends RuntimeException
      {
          public ParseException(String message)
          {
              super(message);
          }
  
          public ParseException(String message, Throwable cause)
          {
              super(message,cause);
          }
      }
  
      private enum State
      {
          STATUS_LINE,
          HEADER,
          END
      }
  
      private static final Pattern PAT_HEADER = Pattern.compile("([^:]+):\\s*(.*)");
      private static final Pattern PAT_STATUS_LINE = Pattern.compile("^HTTP/1.[01]\\s+(\\d+)\\s+(.*)",Pattern.CASE_INSENSITIVE);
  
      private final HttpResponseHeaderParseListener listener;
      private final Utf8LineParser lineParser;
      private State state;
  
      public HttpResponseHeaderParser(HttpResponseHeaderParseListener listener)
      {
          this.listener = listener;
          this.lineParser = new Utf8LineParser();
          this.state = State.STATUS_LINE;
      }
  
      public boolean isDone()
      {
          return (state == State.END);
      }
  
      public HttpResponseHeaderParseListener parse(ByteBuffer buf) throws ParseException
      {
          while (!isDone() && (buf.remaining() > 0))
          {
              String line = lineParser.parse(buf);
              if (line != null)
              {
                  if (parseHeader(line))
                  {
                      // Now finished with parsing the entire response header
                      // Save the remaining bytes for WebSocket to process.
                      
                      ByteBuffer copy = ByteBuffer.allocate(buf.remaining());
                      BufferUtil.put(buf,copy);
                      BufferUtil.flipToFlush(copy,0);
                      this.listener.setRemainingBuffer(copy);
                      return listener;
                  }
              }
          }
          return null;
      }
  
      private boolean parseHeader(String line) throws ParseException
      {
          switch (state)
         {
             case STATUS_LINE:
             {
                 Matcher mat = PAT_STATUS_LINE.matcher(line);
                 if (!mat.matches())
                 {
                     throw new ParseException("Unexpected HTTP response status line [" + line + "]");
                 }
 
                 try
                 {
                     listener.setStatusCode(Integer.parseInt(mat.group(1)));
                 }
                 catch (NumberFormatException e)
                 {
                     throw new ParseException("Unexpected HTTP response status code",e);
                 }
                 listener.setStatusReason(mat.group(2));
                 state = State.HEADER;
                 break;
             }
             case HEADER:
             {
                 if (StringUtil.isBlank(line))
                 {
                     state = State.END;
                     return parseHeader(line);
                 }
 
                 Matcher header = PAT_HEADER.matcher(line);
                 if (header.matches())
                 {
                     String headerName = header.group(1);
                     String headerValue = header.group(2);
                     // do need to split header/value if comma delimited?
                     listener.addHeader(headerName,headerValue);
                 }
                 break;
             }
             case END:
                 state = State.STATUS_LINE;
                 return true;
         }
         return false;
     }
 }