/*
    * 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 org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.StringLayout;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.LoggerConfig;
  import org.apache.logging.log4j.core.util.Constants;
  import org.apache.logging.log4j.core.util.StringEncoder;
  import org.apache.logging.log4j.util.Strings;
  
  import java.io.UnsupportedEncodingException;
  import java.nio.charset.Charset;
  import java.nio.charset.StandardCharsets;
  
  /**
   * Abstract base class for Layouts that result in a String.
   * <p>
   * Since 2.4.1, this class has custom logic to convert ISO-8859-1 or US-ASCII Strings to byte[] arrays to improve
   * performance: all characters are simply cast to bytes.
   */
  /*
   * Implementation note: prefer String.getBytes(String) to String.getBytes(Charset) for performance reasons. See
   * https://issues.apache.org/jira/browse/LOG4J2-935 for details.
   */
  public abstract class AbstractStringLayout extends AbstractLayout<String> implements StringLayout {
  
      public interface Serializer {
          String toSerializable(final LogEvent event);
      }
  
      /**
       * Variation of {@link Serializer} that avoids allocating temporary objects.
       * @since 2.6
       */
      public interface Serializer2 {
          StringBuilder toSerializable(final LogEvent event, final StringBuilder builder);
      }
  
      /**
       * Default length for new StringBuilder instances: {@value} .
       */
      protected static final int DEFAULT_STRING_BUILDER_SIZE = 1024;
  
      private static final ThreadLocal<StringBuilder> threadLocal = new ThreadLocal<>();
  
      private Encoder<StringBuilder> textEncoder;
  
      /**
       * Returns a {@code StringBuilder} that this Layout implementation can use to write the formatted log event to.
       *
       * @return a {@code StringBuilder}
       */
      protected static StringBuilder getStringBuilder() {
          StringBuilder result = threadLocal.get();
          if (result == null) {
              result = new StringBuilder(DEFAULT_STRING_BUILDER_SIZE);
              threadLocal.set(result);
          }
          result.setLength(0);
          return result;
      }
  
      // LOG4J2-1151: If the built-in JDK 8 encoders are available we should use them.
      private static boolean isPreJava8() {
          final String version = System.getProperty("java.version");
          final String[] parts = version.split("\\.");
          try {
              final int major = Integer.parseInt(parts[1]);
              return major < 8;
          } catch (final Exception ex) {
              return true;
          }
      }
      /**
       * The charset for the formatted message.
       */
      // LOG4J2-1099: charset cannot be final due to serialization needs, so we serialize as charset name instead
      private transient Charset charset;
  
      private final String charsetName;
  
      private final Serializer footerSerializer;
  
     private final Serializer headerSerializer;
 
     private final boolean useCustomEncoding;
 
     protected AbstractStringLayout(final Charset charset) {
         this(charset, (byte[]) null, (byte[]) null);
     }
 
     /**
      * Builds a new layout.
      * @param aCharset the charset used to encode the header bytes, footer bytes and anything else that needs to be
      *      converted from strings to bytes.
      * @param header the header bytes
      * @param footer the footer bytes
      */
     protected AbstractStringLayout(final Charset aCharset, final byte[] header, final byte[] footer) {
         super(null, header, footer);
         this.headerSerializer = null;
         this.footerSerializer = null;
         this.charset = aCharset == null ? StandardCharsets.UTF_8 : aCharset;
         this.charsetName = this.charset.name();
         useCustomEncoding = isPreJava8()
                 && (StandardCharsets.ISO_8859_1.equals(aCharset) || StandardCharsets.US_ASCII.equals(aCharset));
         textEncoder = Constants.ENABLE_DIRECT_ENCODERS ? new StringBuilderEncoder(charset) : null;
     }
 
     /**
      * Builds a new layout.
      * @param config the configuration
      * @param aCharset the charset used to encode the header bytes, footer bytes and anything else that needs to be
      *      converted from strings to bytes.
      * @param headerSerializer the header bytes serializer
      * @param footerSerializer the footer bytes serializer
      */
     protected AbstractStringLayout(final Configuration config, final Charset aCharset,
             final Serializer headerSerializer, final Serializer footerSerializer) {
         super(config, null, null);
         this.headerSerializer = headerSerializer;
         this.footerSerializer = footerSerializer;
         this.charset = aCharset == null ? StandardCharsets.UTF_8 : aCharset;
         this.charsetName = this.charset.name();
         useCustomEncoding = isPreJava8()
                 && (StandardCharsets.ISO_8859_1.equals(aCharset) || StandardCharsets.US_ASCII.equals(aCharset));
         textEncoder = Constants.ENABLE_DIRECT_ENCODERS ? new StringBuilderEncoder(charset) : null;
     }
 
     /**
      * Returns a {@code Encoder<StringBuilder>} that this Layout implementation can use for encoding log events.
      *
      * @return a {@code Encoder<StringBuilder>}
      */
     protected Encoder<StringBuilder> getStringBuilderEncoder() {
         if (textEncoder == null) {
             textEncoder = new StringBuilderEncoder(getCharset());
         }
         return textEncoder;
     }
 
     protected byte[] getBytes(final String s) {
         if (useCustomEncoding) { // rely on branch prediction to eliminate this check if false
             return StringEncoder.encodeSingleByteChars(s);
         }
         try { // LOG4J2-935: String.getBytes(String) gives better performance
             return s.getBytes(charsetName);
         } catch (final UnsupportedEncodingException e) {
             return s.getBytes(charset);
         }
     }
 
     @Override
     public Charset getCharset() {
         return charset;
     }
 
     /**
      * @return The default content type for Strings.
      */
     @Override
     public String getContentType() {
         return "text/plain";
     }
 
     /**
      * Returns the footer, if one is available.
      *
      * @return A byte array containing the footer.
      */
     @Override
     public byte[] getFooter() {
         return serializeToBytes(footerSerializer, super.getFooter());
     }
 
     public Serializer getFooterSerializer() {
         return footerSerializer;
     }
 
     /**
      * Returns the header, if one is available.
      *
      * @return A byte array containing the header.
      */
     @Override
     public byte[] getHeader() {
         return serializeToBytes(headerSerializer, super.getHeader());
     }
 
     public Serializer getHeaderSerializer() {
         return headerSerializer;
     }
 
     protected byte[] serializeToBytes(final Serializer serializer, final byte[] defaultValue) {
         final String serializable = serializeToString(serializer);
         if (serializer == null) {
             return defaultValue;
         }
         return StringEncoder.toBytes(serializable, getCharset());
     }
 
     protected String serializeToString(final Serializer serializer) {
         if (serializer == null) {
             return null;
         }
         final LoggerConfig rootLogger = getConfiguration().getRootLogger();
         // Using "" for the FQCN, does it matter?
         final LogEvent logEvent = rootLogger.getLogEventFactory().createEvent(rootLogger.getName(), null, Strings.EMPTY,
                 rootLogger.getLevel(), null, null, null);
         return serializer.toSerializable(logEvent);
     }
 
     /**
      * Formats the Log Event as a byte array.
      *
      * @param event The Log Event.
      * @return The formatted event as a byte array.
      */
     @Override
     public byte[] toByteArray(final LogEvent event) {
         return getBytes(toSerializable(event));
     }
 
 }