/*
    * 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 io.netty.handler.codec.http.websocketx;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToMessageEncoder;
  import io.netty.handler.codec.TooLongFrameException;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.util.List;
  
  /**
   * <p>
   * Encodes a web socket frame into wire protocol version 8 format. This code was forked from <a
   * href="https://github.com/joewalnes/webbit">webbit</a> and modified.
   * </p>
   */
  public class WebSocket08FrameEncoder extends MessageToMessageEncoder<WebSocketFrame> implements WebSocketFrameEncoder {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(WebSocket08FrameEncoder.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;
  
      /**
       * The size threshold for gathering writes. Non-Masked messages bigger than this size will be be sent fragmented as
       * a header and a content ByteBuf whereas messages smaller than the size will be merged into a single buffer and
       * sent at once.<br>
       * Masked messages will always be sent at once.
       */
      private static final int GATHERING_WRITE_THRESHOLD = 1024;
  
      private final boolean maskPayload;
  
      /**
       * Constructor
       *
       * @param maskPayload
       *            Web socket clients must set this to true to mask payload. Server implementations must set this to
       *            false.
      */
     public WebSocket08FrameEncoder(boolean maskPayload) {
         this.maskPayload = maskPayload;
     }
 
     @Override
     protected void encode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
         final ByteBuf data = msg.content();
         byte[] mask;
 
         byte opcode;
         if (msg instanceof TextWebSocketFrame) {
             opcode = OPCODE_TEXT;
         } else if (msg instanceof PingWebSocketFrame) {
             opcode = OPCODE_PING;
         } else if (msg instanceof PongWebSocketFrame) {
             opcode = OPCODE_PONG;
         } else if (msg instanceof CloseWebSocketFrame) {
             opcode = OPCODE_CLOSE;
         } else if (msg instanceof BinaryWebSocketFrame) {
             opcode = OPCODE_BINARY;
         } else if (msg instanceof ContinuationWebSocketFrame) {
             opcode = OPCODE_CONT;
         } else {
             throw new UnsupportedOperationException("Cannot encode frame of type: " + msg.getClass().getName());
         }
 
         int length = data.readableBytes();
 
         if (logger.isTraceEnabled()) {
             logger.trace("Encoding WebSocket Frame opCode={} length={}", opcode, length);
         }
 
         int b0 = 0;
         if (msg.isFinalFragment()) {
             b0 |= 1 << 7;
         }
         b0 |= msg.rsv() % 8 << 4;
         b0 |= opcode % 128;
 
         if (opcode == OPCODE_PING && length > 125) {
             throw new TooLongFrameException("invalid payload for PING (payload length must be <= 125, was "
                     + length);
         }
 
         boolean release = true;
         ByteBuf buf = null;
         try {
             int maskLength = maskPayload ? 4 : 0;
             if (length <= 125) {
                 int size = 2 + maskLength;
                 if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                     size += length;
                 }
                 buf = ctx.alloc().buffer(size);
                 buf.writeByte(b0);
                 byte b = (byte) (maskPayload ? 0x80 | (byte) length : (byte) length);
                 buf.writeByte(b);
             } else if (length <= 0xFFFF) {
                 int size = 4 + maskLength;
                 if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                     size += length;
                 }
                 buf = ctx.alloc().buffer(size);
                 buf.writeByte(b0);
                 buf.writeByte(maskPayload ? 0xFE : 126);
                 buf.writeByte(length >>> 8 & 0xFF);
                 buf.writeByte(length & 0xFF);
             } else {
                 int size = 10 + maskLength;
                 if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                     size += length;
                 }
                 buf = ctx.alloc().buffer(size);
                 buf.writeByte(b0);
                 buf.writeByte(maskPayload ? 0xFF : 127);
                 buf.writeLong(length);
             }
 
             // Write payload
             if (maskPayload) {
                 int random = (int) (Math.random() * Integer.MAX_VALUE);
                 mask = ByteBuffer.allocate(4).putInt(random).array();
                 buf.writeBytes(mask);
 
                 ByteOrder srcOrder = data.order();
                 ByteOrder dstOrder = buf.order();
 
                 int counter = 0;
                 int i = data.readerIndex();
                 int end = data.writerIndex();
 
                 if (srcOrder == dstOrder) {
                     // Use the optimized path only when byte orders match
                     // Remark: & 0xFF is necessary because Java will do signed expansion from
                     // byte to int which we don't want.
                     int intMask = ((mask[0] & 0xFF) << 24)
                                 | ((mask[1] & 0xFF) << 16)
                                 | ((mask[2] & 0xFF) << 8)
                                 | (mask[3] & 0xFF);
 
                     // If the byte order of our buffers it little endian we have to bring our mask
                     // into the same format, because getInt() and writeInt() will use a reversed byte order
                     if (srcOrder == ByteOrder.LITTLE_ENDIAN) {
                         intMask = Integer.reverseBytes(intMask);
                     }
 
                     for (; i + 3 < end; i += 4) {
                         int intData = data.getInt(i);
                         buf.writeInt(intData ^ intMask);
                     }
                 }
                 for (; i < end; i++) {
                     byte byteData = data.getByte(i);
                     buf.writeByte(byteData ^ mask[counter++ % 4]);
                 }
                 out.add(buf);
             } else {
                 if (buf.writableBytes() >= data.readableBytes()) {
                     // merge buffers as this is cheaper then a gathering write if the payload is small enough
                     buf.writeBytes(data);
                     out.add(buf);
                 } else {
                     out.add(buf);
                     out.add(data.retain());
                 }
             }
             release = false;
         } finally {
             if (release && buf != null) {
                 buf.release();
             }
         }
     }
 }