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   /*
    * Copyright 2020 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.haproxy;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToByteEncoder;
  import io.netty.util.CharsetUtil;
  import io.netty.util.NetUtil;
  
  import java.util.List;
  
  import static io.netty.handler.codec.haproxy.HAProxyConstants.*;
  
  /**
   * Encodes an HAProxy proxy protocol message
   *
   * @see <a href="https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt">Proxy Protocol Specification</a>
   */
  @Sharable
  public final class HAProxyMessageEncoder extends MessageToByteEncoder<HAProxyMessage> {
  
      private static final int V2_VERSION_BITMASK = 0x02 << 4;
  
      // Length for source/destination addresses for the UNIX family must be 108 bytes each.
      static final int UNIX_ADDRESS_BYTES_LENGTH = 108;
      static final int TOTAL_UNIX_ADDRESS_BYTES_LENGTH = UNIX_ADDRESS_BYTES_LENGTH * 2;
  
      public static final HAProxyMessageEncoder INSTANCE = new HAProxyMessageEncoder();
  
      private HAProxyMessageEncoder() {
      }
  
      @Override
      protected void encode(ChannelHandlerContext ctx, HAProxyMessage msg, ByteBuf out) throws Exception {
          switch (msg.protocolVersion()) {
              case V1:
                  encodeV1(msg, out);
                  break;
              case V2:
                  encodeV2(msg, out);
                  break;
              default:
                  throw new HAProxyProtocolException("Unsupported version: " + msg.protocolVersion());
          }
      }
  
      private static void encodeV1(HAProxyMessage msg, ByteBuf out) {
          out.writeBytes(TEXT_PREFIX);
          out.writeByte((byte) ' ');
          out.writeCharSequence(msg.proxiedProtocol().name(), CharsetUtil.US_ASCII);
          out.writeByte((byte) ' ');
          out.writeCharSequence(msg.sourceAddress(), CharsetUtil.US_ASCII);
          out.writeByte((byte) ' ');
          out.writeCharSequence(msg.destinationAddress(), CharsetUtil.US_ASCII);
          out.writeByte((byte) ' ');
          out.writeCharSequence(String.valueOf(msg.sourcePort()), CharsetUtil.US_ASCII);
          out.writeByte((byte) ' ');
          out.writeCharSequence(String.valueOf(msg.destinationPort()), CharsetUtil.US_ASCII);
          out.writeByte((byte) '\r');
          out.writeByte((byte) '\n');
      }
  
      private static void encodeV2(HAProxyMessage msg, ByteBuf out) {
          out.writeBytes(BINARY_PREFIX);
          out.writeByte(V2_VERSION_BITMASK | msg.command().byteValue());
          out.writeByte(msg.proxiedProtocol().byteValue());
  
          switch (msg.proxiedProtocol().addressFamily()) {
              case AF_IPv4:
              case AF_IPv6:
                  byte[] srcAddrBytes = NetUtil.createByteArrayFromIpAddressString(msg.sourceAddress());
                  byte[] dstAddrBytes = NetUtil.createByteArrayFromIpAddressString(msg.destinationAddress());
                  // srcAddrLen + dstAddrLen + 4 (srcPort + dstPort) + numTlvBytes
                  out.writeShort(srcAddrBytes.length + dstAddrBytes.length + 4 + msg.tlvNumBytes());
                  out.writeBytes(srcAddrBytes);
                  out.writeBytes(dstAddrBytes);
                  out.writeShort(msg.sourcePort());
                  out.writeShort(msg.destinationPort());
                  encodeTlvs(msg.tlvs(), out);
                  break;
              case AF_UNIX:
                  out.writeShort(TOTAL_UNIX_ADDRESS_BYTES_LENGTH + msg.tlvNumBytes());
                  int srcAddrBytesWritten = out.writeCharSequence(msg.sourceAddress(), CharsetUtil.US_ASCII);
                  out.writeZero(UNIX_ADDRESS_BYTES_LENGTH - srcAddrBytesWritten);
                 int dstAddrBytesWritten = out.writeCharSequence(msg.destinationAddress(), CharsetUtil.US_ASCII);
                 out.writeZero(UNIX_ADDRESS_BYTES_LENGTH - dstAddrBytesWritten);
                 encodeTlvs(msg.tlvs(), out);
                 break;
             case AF_UNSPEC:
                 out.writeShort(0);
                 break;
             default:
                 throw new HAProxyProtocolException("unexpected addrFamily");
         }
     }
 
     private static void encodeTlv(HAProxyTLV haProxyTLV, ByteBuf out) {
         if (haProxyTLV instanceof HAProxySSLTLV) {
             HAProxySSLTLV ssltlv = (HAProxySSLTLV) haProxyTLV;
             out.writeByte(haProxyTLV.typeByteValue());
             out.writeShort(ssltlv.contentNumBytes());
             out.writeByte(ssltlv.client());
             out.writeInt(ssltlv.verify());
             encodeTlvs(ssltlv.encapsulatedTLVs(), out);
         } else {
             out.writeByte(haProxyTLV.typeByteValue());
             ByteBuf value = haProxyTLV.content();
             int readableBytes = value.readableBytes();
             out.writeShort(readableBytes);
             out.writeBytes(value.readSlice(readableBytes));
         }
     }
 
     private static void encodeTlvs(List<HAProxyTLV> haProxyTLVs, ByteBuf out) {
         for (int i = 0; i < haProxyTLVs.size(); i++) {
             encodeTlv(haProxyTLVs.get(i), out);
         }
     }
 }