/*
    * 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.appender.rolling;
  
  import java.io.File;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.zip.Deflater;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.appender.rolling.action.Action;
  import org.apache.logging.log4j.core.appender.rolling.action.FileRenameAction;
  import org.apache.logging.log4j.core.appender.rolling.action.GzCompressAction;
  import org.apache.logging.log4j.core.appender.rolling.action.ZipCompressAction;
  import org.apache.logging.log4j.core.config.Configuration;
  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.PluginConfiguration;
  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
  import org.apache.logging.log4j.core.lookup.StrSubstitutor;
  import org.apache.logging.log4j.core.util.Integers;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * When rolling over, <code>DefaultRolloverStrategy</code> renames files
   * according to an algorithm as described below.
   *
   * <p>
   * The DefaultRolloverStrategy is a combination of a time-based policy and a fixed-window policy. When
   * the file name pattern contains a date format then the rollover time interval will be used to calculate the
   * time to use in the file pattern. When the file pattern contains an integer replacement token one of the
   * counting techniques will be used.
   * </p>
   * <p>
   * When the ascending attribute is set to true (the default) then the counter will be incremented and the
   * current log file will be renamed to include the counter value. If the counter hits the maximum value then
   * the oldest file, which will have the smallest counter, will be deleted, all other files will be renamed to
   * have their counter decremented and then the current file will be renamed to have the maximum counter value.
   * Note that with this counting strategy specifying a large maximum value may entirely avoid renaming files.
   * </p>
   * <p>
   * When the ascending attribute is false, then the "normal" fixed-window strategy will be used.
   * </p>
   * <p>
   * Let <em>max</em> and <em>min</em> represent the values of respectively
   * the <b>MaxIndex</b> and <b>MinIndex</b> options. Let "foo.log" be the value
   * of the <b>ActiveFile</b> option and "foo.%i.log" the value of
   * <b>FileNamePattern</b>. Then, when rolling over, the file
   * <code>foo.<em>max</em>.log</code> will be deleted, the file
   * <code>foo.<em>max-1</em>.log</code> will be renamed as
   * <code>foo.<em>max</em>.log</code>, the file <code>foo.<em>max-2</em>.log</code>
   * renamed as <code>foo.<em>max-1</em>.log</code>, and so on,
   * the file <code>foo.<em>min+1</em>.log</code> renamed as
   * <code>foo.<em>min+2</em>.log</code>. Lastly, the active file <code>foo.log</code>
   * will be renamed as <code>foo.<em>min</em>.log</code> and a new active file name
   * <code>foo.log</code> will be created.
   * </p>
   * <p>
   * Given that this rollover algorithm requires as many file renaming
   * operations as the window size, large window sizes are discouraged.
   * </p>
   */
  @Plugin(name = "DefaultRolloverStrategy", category = "Core", printObject = true)
  public class DefaultRolloverStrategy implements RolloverStrategy {
  
      private static final String EXT_ZIP = ".zip";
      private static final String EXT_GZIP = ".gz";
  
      /**
       * Allow subclasses access to the status logger without creating another instance.
       */
      protected static final Logger LOGGER = StatusLogger.getLogger();
  
      private static final int MIN_WINDOW_SIZE = 1;
      private static final int DEFAULT_WINDOW_SIZE = 7;
  
      /**
       * Create the DefaultRolloverStrategy.
       * @param max The maximum number of files to keep.
       * @param min The minimum number of files to keep.
       * @param fileIndex If set to "max" (the default), files with a higher index will be newer than files with a
       * smaller index. If set to "min", file renaming and the counter will follow the Fixed Window strategy.
       * @param compressionLevelStr The compression level, 0 (less) through 9 (more); applies only to ZIP files.
       * @param config The Configuration.
       * @return A DefaultRolloverStrategy.
      */
     @PluginFactory
     public static DefaultRolloverStrategy createStrategy(
             @PluginAttribute("max") final String max,
             @PluginAttribute("min") final String min,
             @PluginAttribute("fileIndex") final String fileIndex,
             @PluginAttribute("compressionLevel") final String compressionLevelStr,
             @PluginConfiguration final Configuration config) {
         final boolean useMax = fileIndex == null ? true : fileIndex.equalsIgnoreCase("max");
         int minIndex = MIN_WINDOW_SIZE;
         if (min != null) {
             minIndex = Integer.parseInt(min);
             if (minIndex < 1) {
                 LOGGER.error("Minimum window size too small. Limited to " + MIN_WINDOW_SIZE);
                 minIndex = MIN_WINDOW_SIZE;
             }
         }
         int maxIndex = DEFAULT_WINDOW_SIZE;
         if (max != null) {
             maxIndex = Integer.parseInt(max);
             if (maxIndex < minIndex) {
                 maxIndex = minIndex < DEFAULT_WINDOW_SIZE ? DEFAULT_WINDOW_SIZE : minIndex;
                 LOGGER.error("Maximum window size must be greater than the minimum windows size. Set to " + maxIndex);
             }
         }
         final int compressionLevel = Integers.parseInt(compressionLevelStr, Deflater.DEFAULT_COMPRESSION);
         return new DefaultRolloverStrategy(minIndex, maxIndex, useMax, compressionLevel, config.getStrSubstitutor());
     }
 
     /**
      * Index for oldest retained log file.
      */
     private final int maxIndex;
 
     /**
      * Index for most recent log file.
      */
     private final int minIndex;
     private final boolean useMax;
     private final StrSubstitutor subst;
     private final int compressionLevel;
 
     /**
      * Constructs a new instance.
      * @param minIndex The minimum index.
      * @param maxIndex The maximum index.
      */
     protected DefaultRolloverStrategy(final int minIndex, final int maxIndex, final boolean useMax, final int compressionLevel, final StrSubstitutor subst) {
         this.minIndex = minIndex;
         this.maxIndex = maxIndex;
         this.useMax = useMax;
         this.compressionLevel = compressionLevel;
         this.subst = subst;
     }
 
     public int getCompressionLevel() {
         return this.compressionLevel;
     }
 
     public int getMaxIndex() {
         return this.maxIndex;
     }
 
     public int getMinIndex() {
         return this.minIndex;
     }
 
     private int purge(final int lowIndex, final int highIndex, final RollingFileManager manager) {
         return useMax ? purgeAscending(lowIndex, highIndex, manager) :
             purgeDescending(lowIndex, highIndex, manager);
     }
 
     /**
      * Purge and rename old log files in preparation for rollover. The oldest file will have the smallest index,
      * the newest the highest.
      *
      * @param lowIndex  low index
      * @param highIndex high index.  Log file associated with high index will be deleted if needed.
      * @param manager The RollingFileManager
      * @return true if purge was successful and rollover should be attempted.
      */
     private int purgeAscending(final int lowIndex, final int highIndex, final RollingFileManager manager) {
         int suffixLength = 0;
 
         final List<FileRenameAction> renames = new ArrayList<FileRenameAction>();
         final StringBuilder buf = new StringBuilder();
 
         // LOG4J2-531: directory scan & rollover must use same format
         manager.getPatternProcessor().formatFileName(subst, buf, highIndex);
 
         String highFilename = subst.replace(buf);
 
         if (highFilename.endsWith(EXT_GZIP)) {
             suffixLength = EXT_GZIP.length();
         } else if (highFilename.endsWith(EXT_ZIP)) {
             suffixLength = EXT_ZIP.length();
         }
 
         int maxIndex = 0;
 
         for (int i = highIndex; i >= lowIndex; i--) {
             File toRename = new File(highFilename);
             if (i == highIndex && toRename.exists()) {
                 maxIndex = highIndex;
             } else if (maxIndex == 0 && toRename.exists()) {
                 maxIndex = i + 1;
                 break;
             }
 
             boolean isBase = false;
 
             if (suffixLength > 0) {
                 final File toRenameBase =
                     new File(highFilename.substring(0, highFilename.length() - suffixLength));
 
                 if (toRename.exists()) {
                     if (toRenameBase.exists()) {
                         LOGGER.debug("DefaultRolloverStrategy.purgeAscending deleting {} base of {}.", //
                                 toRenameBase, toRename);
                         toRenameBase.delete();
                     }
                 } else {
                     toRename = toRenameBase;
                     isBase = true;
                 }
             }
 
             if (toRename.exists()) {
                 //
                 //    if at lower index and then all slots full
                 //        attempt to delete last file
                 //        if that fails then abandon purge
                 if (i == lowIndex) {
                     LOGGER.debug("DefaultRolloverStrategy.purgeAscending deleting {} at low index {}: all slots full.", //
                             toRename, i);
                     if (!toRename.delete()) {
                         return -1;
                     }
 
                     break;
                 }
 
                 //
                 //   if intermediate index
                 //     add a rename action to the list
                 buf.setLength(0);
                 // LOG4J2-531: directory scan & rollover must use same format
                 manager.getPatternProcessor().formatFileName(subst, buf, i - 1);
 
                 final String lowFilename = subst.replace(buf);
                 String renameTo = lowFilename;
 
                 if (isBase) {
                     renameTo = lowFilename.substring(0, lowFilename.length() - suffixLength);
                 }
 
                 renames.add(new FileRenameAction(toRename, new File(renameTo), true));
                 highFilename = lowFilename;
             } else {
                 buf.setLength(0);
                 // LOG4J2-531: directory scan & rollover must use same format
                 manager.getPatternProcessor().formatFileName(subst, buf, i - 1);
 
                 highFilename = subst.replace(buf);
             }
         }
         if (maxIndex == 0) {
             maxIndex = lowIndex;
         }
 
         //
         //   work renames backwards
         //
         for (int i = renames.size() - 1; i >= 0; i--) {
             final Action action = renames.get(i);
             try {
                 LOGGER.debug("DefaultRolloverStrategy.purgeAscending executing {} of {}: {}", //
                         i, renames.size(), action);
                 if (!action.execute()) {
                     return -1;
                 }
             } catch (final Exception ex) {
                 LOGGER.warn("Exception during purge in RollingFileAppender", ex);
                 return -1;
             }
         }
         return maxIndex;
     }
 
     /**
      * Purge and rename old log files in preparation for rollover. The newest file will have the smallest index, the
      * oldest will have the highest.
      *
      * @param lowIndex  low index
      * @param highIndex high index.  Log file associated with high index will be deleted if needed.
      * @param manager The RollingFileManager
      * @return true if purge was successful and rollover should be attempted.
      */
     private int purgeDescending(final int lowIndex, final int highIndex, final RollingFileManager manager) {
         int suffixLength = 0;
 
         final List<FileRenameAction> renames = new ArrayList<FileRenameAction>();
         final StringBuilder buf = new StringBuilder();
 
         // LOG4J2-531: directory scan & rollover must use same format
         manager.getPatternProcessor().formatFileName(subst, buf, lowIndex);
 
         String lowFilename = subst.replace(buf);
 
         if (lowFilename.endsWith(EXT_GZIP)) {
             suffixLength = EXT_GZIP.length();
         } else if (lowFilename.endsWith(EXT_ZIP)) {
             suffixLength = EXT_ZIP.length();
         }
 
         for (int i = lowIndex; i <= highIndex; i++) {
             File toRename = new File(lowFilename);
             boolean isBase = false;
 
             if (suffixLength > 0) {
                 final File toRenameBase =
                     new File(lowFilename.substring(0, lowFilename.length() - suffixLength));
 
                 if (toRename.exists()) {
                     if (toRenameBase.exists()) {
                         LOGGER.debug("DefaultRolloverStrategy.purgeDescending deleting {} base of {}.", //
                                 toRenameBase, toRename);
                         toRenameBase.delete();
                     }
                 } else {
                     toRename = toRenameBase;
                     isBase = true;
                 }
             }
 
             if (toRename.exists()) {
                 //
                 //    if at upper index then
                 //        attempt to delete last file
                 //        if that fails then abandon purge
                 if (i == highIndex) {
                     LOGGER.debug("DefaultRolloverStrategy.purgeDescending deleting {} at high index {}: all slots full.", //
                             toRename, i);
                     if (!toRename.delete()) {
                         return -1;
                     }
 
                     break;
                 }
 
                 //
                 //   if intermediate index
                 //     add a rename action to the list
                 buf.setLength(0);
                 // LOG4J2-531: directory scan & rollover must use same format
                 manager.getPatternProcessor().formatFileName(subst, buf, i + 1);
 
                 final String highFilename = subst.replace(buf);
                 String renameTo = highFilename;
 
                 if (isBase) {
                     renameTo = highFilename.substring(0, highFilename.length() - suffixLength);
                 }
 
                 renames.add(new FileRenameAction(toRename, new File(renameTo), true));
                 lowFilename = highFilename;
             } else {
                 break;
             }
         }
 
         //
         //   work renames backwards
         //
         for (int i = renames.size() - 1; i >= 0; i--) {
             final Action action = renames.get(i);
             try {
                 LOGGER.debug("DefaultRolloverStrategy.purgeDescending executing {} of {}: {}", //
                         i, renames.size(), action);
                 if (!action.execute()) {
                     return -1;
                 }
             } catch (final Exception ex) {
                 LOGGER.warn("Exception during purge in RollingFileAppender", ex);
                 return -1;
             }
         }
 
         return lowIndex;
     }
 
     /**
      * Perform the rollover.
      * @param manager The RollingFileManager name for current active log file.
      * @return A RolloverDescription.
      * @throws SecurityException if an error occurs.
      */
     @Override
     public RolloverDescription rollover(final RollingFileManager manager) throws SecurityException {
         if (maxIndex < 0) {
             return null;
         }
         final long start = System.nanoTime();
         final int fileIndex = purge(minIndex, maxIndex, manager);
         if (fileIndex < 0) {
             return null;
         }
         if (LOGGER.isTraceEnabled()) {
             final double duration = (System.nanoTime() - start) / (1000.0 * 1000.0 * 1000.0);
             LOGGER.trace("DefaultRolloverStrategy.purge() took {} seconds", duration);
         }
         final StringBuilder buf = new StringBuilder(255);
         manager.getPatternProcessor().formatFileName(subst, buf, fileIndex);
         final String currentFileName = manager.getFileName();
 
         String renameTo = buf.toString();
         final String compressedName = renameTo;
         Action compressAction = null;
 
         if (renameTo.endsWith(EXT_GZIP)) {
             renameTo = renameTo.substring(0, renameTo.length() - EXT_GZIP.length());
             compressAction = new GzCompressAction(new File(renameTo), new File(compressedName), true);
         } else if (renameTo.endsWith(EXT_ZIP)) {
             renameTo = renameTo.substring(0, renameTo.length() - EXT_ZIP.length());
             compressAction = new ZipCompressAction(new File(renameTo), new File(compressedName), true,
                     compressionLevel);
         }
 
         final FileRenameAction renameAction =
             new FileRenameAction(new File(currentFileName), new File(renameTo), false);
 
         return new RolloverDescriptionImpl(currentFileName, false, renameAction, compressAction);
     }
 
     @Override
     public String toString() {
         return "DefaultRolloverStrategy(min=" + minIndex + ", max=" + maxIndex + ')';
     }
 
 }