/*
    * Copyright 2025 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.socksx.v5;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.DecoderException;
  import io.netty.handler.codec.DecoderResult;
  import io.netty.handler.codec.ByteToMessageDecoder;
  import io.netty.util.internal.EmptyArrays;
  
  import java.util.List;
  
  /**
   * Decodes a single {@link Socks5PrivateAuthRequest} from the inbound {@link ByteBuf}s.
   * On successful decode, this decoder will forward the received data to the next handler, so that
   * other handler can remove or replace this decoder later.
   */
  public final class Socks5PrivateAuthRequestDecoder extends ByteToMessageDecoder {
  
      private boolean decoded;
  
      @Override
      protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
          try {
              if (decoded) {
                  int readableBytes = in.readableBytes();
                  if (readableBytes > 0) {
                      out.add(in.readRetainedSlice(readableBytes));
                  }
                  return;
              }
  
              // Check if we have enough data to decode the message
              if (in.readableBytes() < 2) {
                  return;
              }
  
              final int startOffset = in.readerIndex();
              final byte version = in.getByte(startOffset);
              if (version != 1) {
                  throw new DecoderException("unsupported subnegotiation version: " + version + " (expected: 1)");
              }
  
              final int tokenLength = in.getUnsignedByte(startOffset + 1);
  
              // Check if the full message is available
              if (in.readableBytes() < 2 + tokenLength) {
                  return;
              }
  
              // Read the version and token length
              in.skipBytes(2);
  
              // Read the token
              byte[] token = new byte[tokenLength];
              in.readBytes(token);
  
              // Add the decoded token to the output list
              out.add(new DefaultSocks5PrivateAuthRequest(token));
  
              // Mark as decoded to handle remaining bytes in future calls
              decoded = true;
          } catch (Exception e) {
              fail(out, e);
          }
      }
  
      private void fail(List<Object> out, Exception cause) {
          if (!(cause instanceof DecoderException)) {
              cause = new DecoderException(cause);
          }
  
          decoded = true;
  
          Socks5Message m = new
              DefaultSocks5PrivateAuthRequest(EmptyArrays.EMPTY_BYTES);
          m.setDecoderResult(DecoderResult.failure(cause));
          out.add(m);
      }
  }