/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF 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.
   */
  package org.apache.logging.log4j.core.layout;
  
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  import java.nio.charset.Charset;
  import java.text.SimpleDateFormat;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Locale;
  import java.util.Map;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
  import org.apache.logging.log4j.core.helpers.Charsets;
  import org.apache.logging.log4j.core.net.Facility;
  import org.apache.logging.log4j.core.net.Priority;
  
  
  /**
   * Formats a log event as a BSD Log record.
   */
  @Plugin(name = "SyslogLayout", category = "Core", elementType = "layout", printObject = true)
  public class SyslogLayout extends AbstractStringLayout {
      /**
       * Match newlines in a platform-independent manner.
       */
      public static final Pattern NEWLINE_PATTERN = Pattern.compile("\\r?\\n");
  
      private final Facility facility;
      private final boolean includeNewLine;
      private final String escapeNewLine;
  
      /**
       * Date format used if header = true.
       */
      private final SimpleDateFormat dateFormat = new SimpleDateFormat("MMM dd HH:mm:ss ", Locale.ENGLISH);
      /**
       * Host name used to identify messages from this appender.
       */
      private final String localHostname = getLocalHostname();
  
  
  
      protected SyslogLayout(final Facility facility, final boolean includeNL, final String escapeNL, final Charset charset) {
          super(charset);
          this.facility = facility;
          this.includeNewLine = includeNL;
          this.escapeNewLine = escapeNL == null ? null : Matcher.quoteReplacement(escapeNL);
      }
  
      /**
       * Formats a {@link org.apache.logging.log4j.core.LogEvent} in conformance with the BSD Log record format.
       *
       * @param event The LogEvent
       * @return the event formatted as a String.
       */
      @Override
      public String toSerializable(final LogEvent event) {
          final StringBuilder buf = new StringBuilder();
  
          buf.append("<");
          buf.append(Priority.getPriority(facility, event.getLevel()));
          buf.append(">");
          addDate(event.getMillis(), buf);
          buf.append(" ");
          buf.append(localHostname);
          buf.append(" ");
  
          String message = event.getMessage().getFormattedMessage();
          if (null != escapeNewLine) {
              message = NEWLINE_PATTERN.matcher(message).replaceAll(escapeNewLine);
          }
          buf.append(message);
  
          if (includeNewLine) {
              buf.append("\n");
          }
          return buf.toString();
      }
 
     /**
      * This method gets the network name of the machine we are running on.
      * Returns "UNKNOWN_LOCALHOST" in the unlikely case where the host name
      * cannot be found.
      *
      * @return String the name of the local host
      */
     private String getLocalHostname() {
         try {
             final InetAddress addr = InetAddress.getLocalHost();
             return addr.getHostName();
         } catch (final UnknownHostException uhe) {
             LOGGER.error("Could not determine local host name", uhe);
             return "UNKNOWN_LOCALHOST";
         }
     }
 
     private synchronized void addDate(final long timestamp, final StringBuilder buf) {
         final int index = buf.length() + 4;
         buf.append(dateFormat.format(new Date(timestamp)));
         //  RFC 3164 says leading space, not leading zero on days 1-9
         if (buf.charAt(index) == '0') {
             buf.setCharAt(index, ' ');
         }
     }
 
     /**
      * SyslogLayout's content format is specified by:<p/>
      * Key: "structured" Value: "false"<p/>
      * Key: "dateFormat" Value: "MMM dd HH:mm:ss "<p/>
      * Key: "format" Value: "<LEVEL>TIMESTAMP PROP(HOSTNAME) MESSAGE"<p/>
      * Key: "formatType" Value: "logfilepatternreceiver" (format uses the keywords supported by LogFilePatternReceiver)
      * @return Map of content format keys supporting SyslogLayout
      */
     @Override
     public Map<String, String> getContentFormat()
     {
         final Map<String, String> result = new HashMap<String, String>();
         result.put("structured", "false");
         result.put("formatType", "logfilepatternreceiver");
         result.put("dateFormat", dateFormat.toPattern());
         result.put("format", "<LEVEL>TIMESTAMP PROP(HOSTNAME) MESSAGE");
         return result;
     }
 
     /**
      * Create a SyslogLayout.
      * @param facility The Facility is used to try to classify the message.
      * @param includeNL If true a newline will be appended to the result.
      * @param escapeNL Pattern to use for replacing newlines.
      * @param charsetName The character set.
      * @return A SyslogLayout.
      */
     @PluginFactory
     public static SyslogLayout createLayout(
             @PluginAttribute("facility") final String facility,
             @PluginAttribute("newLine") final String includeNL,
             @PluginAttribute("newLineEscape") final String escapeNL,
             @PluginAttribute("charset") final String charsetName) {
         final Charset charset = Charsets.getSupportedCharset(charsetName);
         final boolean includeNewLine = Boolean.parseBoolean(includeNL);
         final Facility f = Facility.toFacility(facility, Facility.LOCAL0);
         return new SyslogLayout(f, includeNewLine, escapeNL, charset);
     }
 }