/*
    * 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.pattern;
  
  import java.util.Date;
  import java.util.Objects;
  import java.util.TimeZone;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.util.datetime.FastDateFormat;
  import org.apache.logging.log4j.core.util.datetime.FixedDateFormat;
  import org.apache.logging.log4j.core.util.datetime.FixedDateFormat.FixedFormat;
  
  /**
   * Converts and formats the event's date in a StringBuilder.
   */
  @Plugin(name = "DatePatternConverter", category = PatternConverter.CATEGORY)
  @ConverterKeys({ "d", "date" })
  public final class DatePatternConverter extends LogEventPatternConverter implements ArrayPatternConverter {
  
      private final class CachedTime {
          public long timestampMillis;
          public String formatted;
  
          public CachedTime(final long timestampMillis) {
              this.timestampMillis = timestampMillis;
              this.formatted = formatter.format(this.timestampMillis);
          }
      }
  
      private final AtomicReference<CachedTime> cachedTime;
  
      private abstract static class Formatter {
          abstract String format(long timeMillis);
  
          public String toPattern() {
              return null;
          }
      }
  
      private static final class PatternFormatter extends Formatter {
          private final FastDateFormat fastDateFormat;
  
          PatternFormatter(final FastDateFormat fastDateFormat) {
              this.fastDateFormat = fastDateFormat;
          }
  
          @Override
          String format(final long timeMillis) {
              return fastDateFormat.format(timeMillis);
          }
  
          @Override
          public String toPattern() {
              return fastDateFormat.toPattern();
          }
      }
  
      private static final class FixedFormatter extends Formatter {
          private final FixedDateFormat fixedDateFormat;
  
          FixedFormatter(final FixedDateFormat fixedDateFormat) {
              this.fixedDateFormat = fixedDateFormat;
          }
  
          @Override
          String format(final long timeMillis) {
              return fixedDateFormat.format(timeMillis);
          }
  
          @Override
          public String toPattern() {
              return fixedDateFormat.getFormat();
          }
      }
  
      private static final class UnixFormatter extends Formatter {
  
          @Override
          String format(final long timeMillis) {
              return Long.toString(timeMillis / 1000);
          }
      }
 
     private static final class UnixMillisFormatter extends Formatter {
 
         @Override
         String format(final long timeMillis) {
             return Long.toString(timeMillis);
         }
     }
 
     /**
      * UNIX formatter in seconds (standard).
      */
     private static final String UNIX_FORMAT = "UNIX";
 
     /**
      * UNIX formatter in milliseconds
      */
     private static final String UNIX_MILLIS_FORMAT = "UNIX_MILLIS";
 
     /**
      * Obtains an instance of pattern converter.
      *
      * @param options
      *            options, may be null.
      * @return instance of pattern converter.
      */
     public static DatePatternConverter newInstance(final String[] options) {
         return new DatePatternConverter(options);
     }
 
     private final Formatter formatter;
 
     /**
      * Private constructor.
      *
      * @param options
      *            options, may be null.
      */
     private DatePatternConverter(final String[] options) {
         super("Date", "date");
 
         final FixedDateFormat fixedDateFormat = FixedDateFormat.createIfSupported(options);
         if (fixedDateFormat != null) {
             formatter = createFormatter(fixedDateFormat);
         } else {
             formatter = createFormatter(options);
         }
         cachedTime = new AtomicReference<>(new CachedTime(System.currentTimeMillis()));
     }
 
     private static Formatter createFormatter(final FixedDateFormat fixedDateFormat) {
         return new FixedFormatter(fixedDateFormat);
     }
 
     private static Formatter createFormatter(final String[] options) {
         // if we get here, options is a non-null array with at least one element (first of which non-null)
         Objects.requireNonNull(options);
         if (options.length == 0) {
             throw new IllegalArgumentException("options array must have at least one element");
         }
         Objects.requireNonNull(options[0]);
         final String patternOption = options[0];
         if (UNIX_FORMAT.equals(patternOption)) {
             return new UnixFormatter();
         }
         if (UNIX_MILLIS_FORMAT.equals(patternOption)) {
             return new UnixMillisFormatter();
         }
 
         // if the option list contains a TZ option, then set it.
         TimeZone tz = null;
         if (options != null && options.length > 1) {
             tz = TimeZone.getTimeZone(options[1]);
         }
 
         try {
             final FastDateFormat tempFormat = FastDateFormat.getInstance(patternOption, tz);
             return new PatternFormatter(tempFormat);
         } catch (final IllegalArgumentException e) {
             LOGGER.warn("Could not instantiate FastDateFormat with pattern " + patternOption, e);
 
             // default to the DEFAULT format
             return createFormatter(FixedDateFormat.create(FixedFormat.DEFAULT));
         }
     }
 
     /**
      * Appends formatted date to string buffer.
      *
      * @param date
      *            date
      * @param toAppendTo
      *            buffer to which formatted date is appended.
      */
     public void format(final Date date, final StringBuilder toAppendTo) {
         format(date.getTime(), toAppendTo);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void format(final LogEvent event, final StringBuilder output) {
         format(event.getTimeMillis(), output);
     }
     
     public void format(final long timestampMillis, final StringBuilder output) {
         CachedTime cached = cachedTime.get();
         if (timestampMillis != cached.timestampMillis) {
             final CachedTime newTime = new CachedTime(timestampMillis);
             if (cachedTime.compareAndSet(cached, newTime)) {
                 cached = newTime;
             } else {
                 cached = cachedTime.get();
             }
         }
         output.append(cached.formatted);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void format(final Object obj, final StringBuilder output) {
         if (obj instanceof Date) {
             format((Date) obj, output);
         }
         super.format(obj, output);
     }
 
     @Override
     public void format(final StringBuilder toAppendTo, final Object... objects) {
         for (final Object obj : objects) {
             if (obj instanceof Date) {
                 format(obj, toAppendTo);
                 break;
             }
         }
     }
 
     /**
      * Gets the pattern string describing this date format.
      *
      * @return the pattern string describing this date format.
      */
     public String getPattern() {
         return formatter.toPattern();
     }
 
 }