/*
    * Copyright 2018 the original author or authors.
    *
    *  Licensed 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.
   */
  
  package org.openehealth.ipf.commons.audit.protocol;
  
  import org.openehealth.ipf.commons.audit.AuditContext;
  import org.openehealth.ipf.commons.audit.utils.AuditUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.net.DatagramPacket;
  import java.net.DatagramSocket;
  import java.nio.charset.StandardCharsets;
  
  /**
   * Simple UDP sender that opens a new DatagramSocket for every batch of AuditMessages
   * being sent.
   * <p>
   * Note that this implementation disobeys the ATNA specification saying,
   * that the Secure Application, Secure Node, or Audit Record Forwarder is unable to send the
   * message to the Audit Record Repository, then the actor shall store the audit record
   * locally and send it when it is able.
   * </p>
   *
   * @author Christian Ohr
   * @since 3.5
   */
  public class UDPSyslogSenderImpl extends RFC5424Protocol implements AuditTransmissionProtocol {
  
      private static final Logger LOG = LoggerFactory.getLogger(UDPSyslogSenderImpl.class);
      private static final int MAX_DATAGRAM_PACKET_SIZE = 65479;
  
      public UDPSyslogSenderImpl() {
          this(AuditUtils.getLocalHostName(), AuditUtils.getProcessId());
      }
  
      public UDPSyslogSenderImpl(String sendingHost, String sendingProcess) {
          super(sendingHost, sendingProcess);
      }
  
      @Override
      public String getTransportName() {
          return "UDP";
      }
  
      @Override
      public void send(AuditContext auditContext, String... auditMessages) throws Exception {
          if (auditMessages != null) {
              try (DatagramSocket socket = new DatagramSocket()) {
                  for (String auditMessage : auditMessages) {
                      byte[] msgBytes = getTransportPayload(auditContext.getSendingApplication(), auditMessage);
                      LOG.debug("Auditing to {}:{}",
                              auditContext.getAuditRepositoryAddress().getHostAddress(),
                              auditContext.getAuditRepositoryPort());
                      LOG.trace("{}", new String(msgBytes, StandardCharsets.UTF_8));
                      DatagramPacket packet = new DatagramPacket(
                              msgBytes,
                              Math.min(MAX_DATAGRAM_PACKET_SIZE, msgBytes.length),
                              auditContext.getAuditRepositoryAddress(),
                              auditContext.getAuditRepositoryPort());
                      socket.send(packet);
                  }
              }
          }
      }
  
      @Override
      public void shutdown() {
  
      }
  }