/*
    * Copyright 2014 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:
    *
    *   https://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.
   */
  package io.netty.handler.codec.http.websocketx;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  
  /**
   *
   */
  public class Utf8FrameValidator extends ChannelInboundHandlerAdapter {
  
      private final boolean closeOnProtocolViolation;
  
      private int fragmentedFramesCount;
      private Utf8Validator utf8Validator;
  
      public Utf8FrameValidator() {
          this(true);
      }
  
      public Utf8FrameValidator(boolean closeOnProtocolViolation) {
          this.closeOnProtocolViolation = closeOnProtocolViolation;
      }
  
      // See https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.
      private static boolean isControlFrame(WebSocketFrame frame) {
          return frame instanceof CloseWebSocketFrame ||
                  frame instanceof PingWebSocketFrame ||
                  frame instanceof PongWebSocketFrame;
      }
  
      @Override
      public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
          if (msg instanceof WebSocketFrame) {
              WebSocketFrame frame = (WebSocketFrame) msg;
  
              try {
                  // Processing for possible fragmented messages for text and binary
                  // frames
                  if (frame.isFinalFragment()) {
                      // Control frames are allowed between fragments
                      // See https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.
                      if (!isControlFrame(frame)) {
  
                          // Final frame of the sequence.
                          fragmentedFramesCount = 0;
  
                          // Check text for UTF8 correctness
                          if (frame instanceof TextWebSocketFrame ||
                                  (utf8Validator != null && utf8Validator.isChecking())) {
                              // Check UTF-8 correctness for this payload
                              checkUTF8String(frame.content());
  
                              // 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 (frame instanceof TextWebSocketFrame) {
                              checkUTF8String(frame.content());
                          }
                      } else {
                          // Subsequent frames - only check if init frame is text
                          if (utf8Validator != null && utf8Validator.isChecking()) {
                              checkUTF8String(frame.content());
                          }
                      }
  
                      // Increment counter
                      fragmentedFramesCount++;
                  }
              } catch (CorruptedWebSocketFrameException e) {
                  protocolViolation(ctx, frame, e);
              }
          }
  
          super.channelRead(ctx, msg);
      }
 
     private void checkUTF8String(ByteBuf buffer) {
         if (utf8Validator == null) {
             utf8Validator = new Utf8Validator();
         }
         utf8Validator.check(buffer);
     }
 
     private void protocolViolation(ChannelHandlerContext ctx, WebSocketFrame frame,
                                    CorruptedWebSocketFrameException ex) {
         frame.release();
         if (closeOnProtocolViolation && ctx.channel().isOpen()) {
             WebSocketCloseStatus closeStatus = ex.closeStatus();
             String reasonText = ex.getMessage();
             if (reasonText == null) {
                 reasonText = closeStatus.reasonText();
             }
 
             CloseWebSocketFrame closeFrame = new CloseWebSocketFrame(closeStatus.code(), reasonText);
             ctx.writeAndFlush(closeFrame).addListener(ChannelFutureListener.CLOSE);
         }
 
         throw ex;
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         super.exceptionCaught(ctx, cause);
     }
 }