/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.
   */
  // (BSD License: http://www.opensource.org/licenses/bsd-license)
  //
  // Copyright (c) 2011, Joe Walnes and contributors
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or
  // without modification, are permitted provided that the
  // following conditions are met:
  //
  // * Redistributions of source code must retain the above
  // copyright notice, this list of conditions and the
  // following disclaimer.
  //
  // * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the
  // following disclaimer in the documentation and/or other
  // materials provided with the distribution.
  //
  // * Neither the name of the Webbit nor the names of
  // its contributors may be used to endorse or promote products
  // derived from this software without specific prior written
  // permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  // CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  // INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  // GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  // BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  // OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  // POSSIBILITY OF SUCH DAMAGE.
  
  package org.jboss.netty.handler.codec.http.websocketx;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.handler.codec.frame.CorruptedFrameException;
  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
  import org.jboss.netty.handler.codec.replay.ReplayingDecoder;
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  
  /**
   * Decodes a web socket frame from wire protocol version 8 format. This code was forked from <a
   * href="https://github.com/joewalnes/webbit">webbit</a> and modified.
   */
  public class WebSocket08FrameDecoder extends ReplayingDecoder<WebSocket08FrameDecoder.State> {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(WebSocket08FrameDecoder.class);
  
      private static final byte OPCODE_CONT = 0x0;
      private static final byte OPCODE_TEXT = 0x1;
      private static final byte OPCODE_BINARY = 0x2;
      private static final byte OPCODE_CLOSE = 0x8;
      private static final byte OPCODE_PING = 0x9;
      private static final byte OPCODE_PONG = 0xA;
  
      private Utf8Validator utf8Validator;
      private int fragmentedFramesCount;
  
      private final long maxFramePayloadLength;
      private boolean frameFinalFlag;
      private int frameRsv;
      private int frameOpcode;
      private long framePayloadLength;
      private ChannelBuffer framePayload;
      private int framePayloadBytesRead;
      private ChannelBuffer maskingKey;
  
      private final boolean allowExtensions;
      private final boolean maskedPayload;
      private boolean receivedClosingHandshake;
  
      public enum State {
          FRAME_START, MASKING_KEY, PAYLOAD, CORRUPT
     }
 
     /**
      * Constructor with default values
      *
      * @param maskedPayload
      *            Web socket servers must set this to true processed incoming masked payload. Client implementations
      *            must set this to false.
      * @param allowExtensions
      *            Flag to allow reserved extension bits to be used or not
      */
     public WebSocket08FrameDecoder(boolean maskedPayload, boolean allowExtensions) {
         this(maskedPayload, allowExtensions, Long.MAX_VALUE);
     }
 
     /**
      * Constructor
      *
      * @param maskedPayload
      *            Web socket servers must set this to true processed incoming masked payload. Client implementations
      *            must set this to false.
      * @param allowExtensions
      *            Flag to allow reserved extension bits to be used or not
      * @param maxFramePayloadLength
      *            Maximum length of a frame's payload. Setting this to an appropriate value for you application
      *            helps check for denial of services attacks.
      */
     public WebSocket08FrameDecoder(boolean maskedPayload, boolean allowExtensions, long maxFramePayloadLength) {
         super(State.FRAME_START);
         this.maskedPayload = maskedPayload;
         this.allowExtensions = allowExtensions;
         this.maxFramePayloadLength = maxFramePayloadLength;
     }
 
     @Override
     protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer, State state)
             throws Exception {
 
         // Discard all data received if closing handshake was received before.
         if (receivedClosingHandshake) {
             buffer.skipBytes(actualReadableBytes());
             return null;
         }
 
         switch (state) {
         case FRAME_START:
             framePayloadBytesRead = 0;
             framePayloadLength = -1;
             framePayload = null;
 
             // FIN, RSV, OPCODE
             byte b = buffer.readByte();
             frameFinalFlag = (b & 0x80) != 0;
             frameRsv = (b & 0x70) >> 4;
             frameOpcode = b & 0x0F;
 
             if (logger.isDebugEnabled()) {
                 logger.debug("Decoding WebSocket Frame opCode=" + frameOpcode);
             }
 
             // MASK, PAYLOAD LEN 1
             b = buffer.readByte();
             boolean frameMasked = (b & 0x80) != 0;
             int framePayloadLen1 = b & 0x7F;
 
             if (frameRsv != 0 && !allowExtensions) {
                 protocolViolation(channel, "RSV != 0 and no extension negotiated, RSV:" + frameRsv);
                 return null;
             }
 
             if (maskedPayload && !frameMasked) {
                 protocolViolation(channel, "unmasked client to server frame");
                 return null;
             }
             if (frameOpcode > 7) { // control frame (have MSB in opcode set)
 
                 // control frames MUST NOT be fragmented
                 if (!frameFinalFlag) {
                     protocolViolation(channel, "fragmented control frame");
                     return null;
                 }
 
                 // control frames MUST have payload 125 octets or less
                 if (framePayloadLen1 > 125) {
                     protocolViolation(channel, "control frame with payload length > 125 octets");
                     return null;
                 }
 
                 // check for reserved control frame opcodes
                 if (!(frameOpcode == OPCODE_CLOSE || frameOpcode == OPCODE_PING || frameOpcode == OPCODE_PONG)) {
                     protocolViolation(channel, "control frame using reserved opcode " + frameOpcode);
                     return null;
                 }
 
                 // close frame : if there is a body, the first two bytes of the
                 // body MUST be a 2-byte unsigned integer (in network byte
                 // order) representing a status code
                 if (frameOpcode == 8 && framePayloadLen1 == 1) {
                     protocolViolation(channel, "received close control frame with payload len 1");
                     return null;
                 }
             } else { // data frame
                 // check for reserved data frame opcodes
                 if (!(frameOpcode == OPCODE_CONT || frameOpcode == OPCODE_TEXT || frameOpcode == OPCODE_BINARY)) {
                     protocolViolation(channel, "data frame using reserved opcode " + frameOpcode);
                     return null;
                 }
 
                 // check opcode vs message fragmentation state 1/2
                 if (fragmentedFramesCount == 0 && frameOpcode == OPCODE_CONT) {
                     protocolViolation(channel, "received continuation data frame outside fragmented message");
                     return null;
                 }
 
                 // check opcode vs message fragmentation state 2/2
                 if (fragmentedFramesCount != 0 && frameOpcode != OPCODE_CONT && frameOpcode != OPCODE_PING) {
                     protocolViolation(channel, "received non-continuation data frame while inside fragmented message");
                     return null;
                 }
             }
 
             // Read frame payload length
             if (framePayloadLen1 == 126) {
                 framePayloadLength = buffer.readUnsignedShort();
                 if (framePayloadLength < 126) {
                     protocolViolation(channel, "invalid data frame length (not using minimal length encoding)");
                     return null;
                 }
             } else if (framePayloadLen1 == 127) {
                 framePayloadLength = buffer.readLong();
                 // TODO: check if it's bigger than 0x7FFFFFFFFFFFFFFF, Maybe
                 // just check if it's negative?
 
                 if (framePayloadLength < 65536) {
                     protocolViolation(channel, "invalid data frame length (not using minimal length encoding)");
                     return null;
                 }
             } else {
                 framePayloadLength = framePayloadLen1;
             }
 
             if (framePayloadLength > maxFramePayloadLength) {
                 protocolViolation(channel, "Max frame length of " + maxFramePayloadLength + " has been exceeded.");
                 return null;
             }
             if (logger.isDebugEnabled()) {
                 logger.debug("Decoding WebSocket Frame length=" + framePayloadLength);
             }
 
             checkpoint(State.MASKING_KEY);
         case MASKING_KEY:
             if (maskedPayload) {
                 maskingKey = buffer.readBytes(4);
             }
             checkpoint(State.PAYLOAD);
         case PAYLOAD:
             // Sometimes, the payload may not be delivered in 1 nice packet
             // We need to accumulate the data until we have it all
             int rbytes = actualReadableBytes();
             ChannelBuffer payloadBuffer = null;
 
             long  willHaveReadByteCount = framePayloadBytesRead + rbytes;
             // logger.debug("Frame rbytes=" + rbytes + " willHaveReadByteCount="
             // + willHaveReadByteCount + " framePayloadLength=" +
             // framePayloadLength);
             if (willHaveReadByteCount == framePayloadLength) {
                 // We have all our content so proceed to process
                 payloadBuffer = buffer.readBytes(rbytes);
             } else if (willHaveReadByteCount < framePayloadLength) {
                 // We don't have all our content so accumulate payload.
                 // Returning null means we will get called back
                 payloadBuffer = buffer.readBytes(rbytes);
                 if (framePayload == null) {
                     framePayload = channel.getConfig().getBufferFactory().getBuffer(toFrameLength(framePayloadLength));
                 }
                 framePayload.writeBytes(payloadBuffer);
                 framePayloadBytesRead += rbytes;
 
                 // Return null to wait for more bytes to arrive
                 return null;
             } else if (willHaveReadByteCount > framePayloadLength) {
                 // We have more than what we need so read up to the end of frame
                 // Leave the remainder in the buffer for next frame
                 payloadBuffer = buffer.readBytes(toFrameLength(framePayloadLength - framePayloadBytesRead));
             }
 
             // Now we have all the data, the next checkpoint must be the next
             // frame
             checkpoint(State.FRAME_START);
 
             // Take the data that we have in this packet
             if (framePayload == null) {
                 framePayload = payloadBuffer;
             } else {
                 framePayload.writeBytes(payloadBuffer);
             }
 
             // Unmask data if needed
             if (maskedPayload) {
                 unmask(framePayload);
             }
 
             // Processing ping/pong/close frames because they cannot be
             // fragmented
             if (frameOpcode == OPCODE_PING) {
                 return new PingWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             }
             if (frameOpcode == OPCODE_PONG) {
                 return new PongWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             }
             if (frameOpcode == OPCODE_CLOSE) {
                 checkCloseFrameBody(channel, framePayload);
                 receivedClosingHandshake = true;
                 return new CloseWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             }
 
             // Processing for possible fragmented messages for text and binary
             // frames
             if (frameFinalFlag) {
                 // Final frame of the sequence. Apparently ping frames are
                 // allowed in the middle of a fragmented message
                 if (frameOpcode != OPCODE_PING) {
                     fragmentedFramesCount = 0;
 
                     // Check text for UTF8 correctness
                     if (frameOpcode == OPCODE_TEXT || (utf8Validator != null && utf8Validator.isChecking())) {
                         // Check UTF-8 correctness for this payload
                         checkUTF8String(channel, framePayload.array());
 
                         // This does a second check to make sure UTF-8
                         // correctness for entire text message
                         utf8Validator.finish();
                     }
                 }
             } else {
                 // Not final frame so we can expect more frames in the
                 // fragmented sequence
                 if (fragmentedFramesCount == 0) {
                     // First text or binary frame for a fragmented set
                     if (frameOpcode == OPCODE_TEXT) {
                         checkUTF8String(channel, framePayload.array());
                     }
                 } else {
                     // Subsequent frames - only check if init frame is text
                     if (utf8Validator != null && utf8Validator.isChecking()) {
                         checkUTF8String(channel, framePayload.array());
                     }
                 }
 
                 // Increment counter
                 fragmentedFramesCount++;
             }
 
             // Return the frame
             if (frameOpcode == OPCODE_TEXT) {
                 return new TextWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             } else if (frameOpcode == OPCODE_BINARY) {
                 return new BinaryWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             } else if (frameOpcode == OPCODE_CONT) {
                 return new ContinuationWebSocketFrame(frameFinalFlag, frameRsv, framePayload);
             } else {
                 throw new UnsupportedOperationException("Cannot decode web socket frame with opcode: " + frameOpcode);
             }
         case CORRUPT:
             // If we don't keep reading Netty will throw an exception saying
             // we can't return null if no bytes read and state not changed.
             buffer.readByte();
             return null;
         default:
             throw new Error("Shouldn't reach here.");
         }
     }
 
     private void unmask(ChannelBuffer frame) {
         byte[] bytes = frame.array();
         for (int i = 0; i < bytes.length; i++) {
             frame.setByte(i, frame.getByte(i) ^ maskingKey.getByte(i % 4));
         }
     }
 
     private void protocolViolation(Channel channel, String reason) throws CorruptedFrameException {
         protocolViolation(channel, new CorruptedFrameException(reason));
     }
 
     private void protocolViolation(Channel channel, CorruptedFrameException ex) throws CorruptedFrameException {
         checkpoint(State.CORRUPT);
         if (channel.isConnected()) {
             channel.write(ChannelBuffers.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
         }
         throw ex;
     }
 
     private static int toFrameLength(long l) throws TooLongFrameException {
         if (l > Integer.MAX_VALUE) {
             throw new TooLongFrameException("Length:" + l);
         } else {
             return (int) l;
         }
     }
 
     private void checkUTF8String(Channel channel, byte[] bytes) throws CorruptedFrameException {
         try {
             if (utf8Validator == null) {
                 utf8Validator = new Utf8Validator();
             }
             utf8Validator.check(bytes);
         } catch (CorruptedFrameException ex) {
             protocolViolation(channel, ex);
         }
     }
 
     protected void checkCloseFrameBody(Channel channel, ChannelBuffer buffer) throws CorruptedFrameException {
         if (buffer == null || buffer.capacity() == 0) {
             return;
         }
         if (buffer.capacity() == 1) {
             protocolViolation(channel, "Invalid close frame body");
         }
 
         // Save reader index
         int idx = buffer.readerIndex();
         buffer.readerIndex(0);
 
         // Must have 2 byte integer within the valid range
         int statusCode = buffer.readShort();
         if (statusCode >= 0 && statusCode <= 999 || statusCode >= 1004 && statusCode <= 1006
                 || statusCode >= 1012 && statusCode <= 2999) {
             protocolViolation(channel, "Invalid close frame status code: " + statusCode);
         }
 
         // May have UTF-8 message
         if (buffer.readableBytes() > 0) {
             byte[] b = new byte[buffer.readableBytes()];
             buffer.readBytes(b);
             try {
                 Utf8Validator validator = new Utf8Validator();
                 validator.check(b);
             } catch (CorruptedFrameException ex) {
                 protocolViolation(channel, ex);
             }
         }
 
         // Restore reader index
         buffer.readerIndex(idx);
     }
 }