//
   //  ========================================================================
   //  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.spdy.parser;
  
  import java.nio.ByteBuffer;
  import java.nio.charset.Charset;
  import java.nio.charset.StandardCharsets;
  import java.util.Arrays;
  import java.util.zip.ZipException;
  
  import org.eclipse.jetty.spdy.CompressionDictionary;
  import org.eclipse.jetty.spdy.CompressionFactory;
  import org.eclipse.jetty.spdy.SessionException;
  import org.eclipse.jetty.spdy.StreamException;
  import org.eclipse.jetty.spdy.api.SPDY;
  import org.eclipse.jetty.spdy.api.SessionStatus;
  import org.eclipse.jetty.spdy.api.StreamStatus;
  
  public abstract class HeadersBlockParser
  {
      private final CompressionFactory.Decompressor decompressor;
      private byte[] data;
      private boolean needsDictionary = true;
  
      protected HeadersBlockParser(CompressionFactory.Decompressor decompressor)
      {
          this.decompressor = decompressor;
      }
  
      public boolean parse(int streamId, short version, int length, ByteBuffer buffer)
      {
          // Need to be sure that all the compressed data has arrived
          // Because SPDY uses SYNC_FLUSH mode, and the Java API
          // does not expose when decompression is finished with this mode
          // (but only when using NO_FLUSH), then we need to
          // accumulate the compressed bytes until we have all of them
  
          boolean accumulated = accumulate(length, buffer);
          if (!accumulated)
              return false;
  
          byte[] compressedHeaders = data;
          data = null;
          ByteBuffer decompressedHeaders = decompress(version, compressedHeaders);
  
          Charset iso1 = StandardCharsets.ISO_8859_1;
          // We know the decoded bytes contain the full headers,
          // so optimize instead of looping byte by byte
          int count = readCount(version, decompressedHeaders);
          for (int i = 0; i < count; ++i)
          {
              int nameLength = readNameLength(version, decompressedHeaders);
              if (nameLength == 0)
                  throw new StreamException(streamId, StreamStatus.PROTOCOL_ERROR, "Invalid header name length");
              byte[] nameBytes = new byte[nameLength];
              decompressedHeaders.get(nameBytes);
              String name = new String(nameBytes, iso1);
  
              int valueLength = readValueLength(version, decompressedHeaders);
              if (valueLength == 0)
                  throw new StreamException(streamId, StreamStatus.PROTOCOL_ERROR, "Invalid header value length");
              byte[] valueBytes = new byte[valueLength];
              decompressedHeaders.get(valueBytes);
              String value = new String(valueBytes, iso1);
              // Multi valued headers are separate by NUL
              String[] values = value.split("\u0000");
              // Check if there are multiple NULs (section 2.6.9)
              for (String v : values)
                  if (v.length() == 0)
                      throw new StreamException(streamId, StreamStatus.PROTOCOL_ERROR, "Invalid multi valued header");
  
              onHeader(name, values);
          }
  
          return true;
      }
  
      private boolean accumulate(int length, ByteBuffer buffer)
      {
          int remaining = buffer.remaining();
          if (data == null)
          {
              if (remaining < length)
             {
                 data = new byte[remaining];
                 buffer.get(data);
                 return false;
             }
             else
             {
                 data = new byte[length];
                 buffer.get(data);
                 return true;
             }
         }
         else
         {
             int accumulated = data.length;
             int needed = length - accumulated;
             if (remaining < needed)
             {
                 byte[] local = Arrays.copyOf(data,accumulated + remaining);
                 buffer.get(local, accumulated, remaining);
                 data = local;
                 return false;
             }
             else
             {
                 byte[] local = Arrays.copyOf(data,length);
                 buffer.get(local, accumulated, needed);
                 data = local;
                 return true;
             }
         }
     }
 
     private int readCount(int version, ByteBuffer buffer)
     {
         switch (version)
         {
             case SPDY.V2:
                 return buffer.getShort();
             case SPDY.V3:
                 return buffer.getInt();
             default:
                 throw new IllegalStateException();
         }
     }
 
     private int readNameLength(int version, ByteBuffer buffer)
     {
         return readCount(version, buffer);
     }
 
     private int readValueLength(int version, ByteBuffer buffer)
     {
         return readCount(version, buffer);
     }
 
     protected abstract void onHeader(String name, String[] values);
 
     private ByteBuffer decompress(short version, byte[] compressed)
     {
         // Differently from compression, decompression always happens
         // non-concurrently because we read and parse with a single
         // thread, and therefore there is no need for synchronization.
 
         try
         {
             byte[] decompressed = null;
             byte[] buffer = new byte[compressed.length * 2];
             decompressor.setInput(compressed);
 
             while (true)
             {
                 int count = decompressor.decompress(buffer);
                 if (count == 0)
                 {
                     if (decompressed != null)
                     {
                         return ByteBuffer.wrap(decompressed);
                     }
                     else if (needsDictionary)
                     {
                         decompressor.setDictionary(CompressionDictionary.get(version));
                         needsDictionary = false;
                     }
                     else
                     {
                         throw new IllegalStateException();
                     }
                 }
                 else
                 {
                     if (count < buffer.length)
                     {
                         if (decompressed == null)
                         {
                             // Only one pass was needed to decompress
                             return ByteBuffer.wrap(buffer, 0, count);
                         }
                         else
                         {
                             // Last pass needed to decompress, merge decompressed bytes
                             byte[] result = Arrays.copyOf(decompressed,decompressed.length+count);
                             System.arraycopy(buffer, 0, result, decompressed.length, count);
                             return ByteBuffer.wrap(result);
                         }
                     }
                     else
                     {
                         if (decompressed == null)
                         {
                             decompressed = buffer;
                             buffer = new byte[buffer.length];
                         }
                         else
                         {
                             byte[] result = Arrays.copyOf(decompressed,decompressed.length+buffer.length);
                             System.arraycopy(buffer, 0, result, decompressed.length, buffer.length);
                             decompressed = result;
                         }
                     }
                 }
             }
         }
         catch (ZipException x)
         {
             // We had a compression problem, and since the compression context
             // is per-connection, we need to tear down the connection
             throw new SessionException(SessionStatus.PROTOCOL_ERROR, x);
         }
     }
 }