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This project is an log4j specific module, contains utility specific to log4j.
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/**
 * Copyright 2013-2019 Butor Inc.
 *
 * 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.butor.log4j;

import static com.google.common.collect.Iterables.skip;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Sets.newLinkedHashSet;

import java.io.File;
import java.io.IOException;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Set;

import org.apache.log4j.rolling.RolloverDescription;
import org.apache.log4j.rolling.RolloverDescriptionImpl;
import org.apache.log4j.rolling.helper.Action;
import org.apache.log4j.rolling.helper.ActionBase;

import com.google.common.primitives.Longs;

/**
 * Same as org.apache.log4j.rolling.TimeBasedRollingPolicy, but we added the ability to delete old backup files.
 * 
 * @author jdemers
 * 
 */
public class TimeBasedRollingPolicy extends TimeBasedRollingPolicyFromApacheLog4jExtras {

	private Long timeDeltaForFilenameChange;

	private int maxBackupIndex = 0;

	private int numberOfBackupFilenamesToCheckForRegularCleanup = 24;

	private int numberOfExtraBackupFilenamesToCheckForFirstCleanup = 365;

	private boolean firstCleanupRan = false;

	public void setMaxBackupIndex(int maxBackupIndex) {
		this.maxBackupIndex = maxBackupIndex;
	}

	public void setNumberOfBackupFilenamesToCheckForRegularCleanup(int numberOfBackupFilenamesToCheckForRegularCleanup) {
		this.numberOfBackupFilenamesToCheckForRegularCleanup = numberOfBackupFilenamesToCheckForRegularCleanup;
	}

	public void setNumberOfExtraBackupFilenamesToCheckForFirstCleanup(int numberOfExtraBackupFilenamesToCheckForFirstCleanup) {
		this.numberOfExtraBackupFilenamesToCheckForFirstCleanup = numberOfExtraBackupFilenamesToCheckForFirstCleanup;
	}

	@Override
	public RolloverDescription rollover(String currentActiveFile) {

		RolloverDescription rolloverDescription = super.rollover(currentActiveFile);

		if (rolloverDescription == null) {
			// We'll wait until next rollover before deleting anything
			return null;
		}

		if (maxBackupIndex <= 0) {
			// This means cleanup is deactivated
			return rolloverDescription;
		}

		String activeFileName = rolloverDescription.getActiveFileName();
		boolean append = rolloverDescription.getAppend();
		Action synchronous = rolloverDescription.getSynchronous();
		final Action asynchronous = rolloverDescription.getAsynchronous();

		Action newAsynchronous = new ActionBase() {

			@Override
			public boolean execute() throws IOException {
				boolean success = true;
				if (asynchronous != null) {
					success &= asynchronous.execute();
				}

				int searchFileCount = maxBackupIndex + numberOfBackupFilenamesToCheckForRegularCleanup;
				if (!firstCleanupRan) {
					searchFileCount += numberOfExtraBackupFilenamesToCheckForFirstCleanup;
				}

				for (String backupFileToDelete : skip(getBackupFiles(searchFileCount), maxBackupIndex)) {

					// This is not very nice, but it was also not very nice in org.apache.log4j.rolling.TimeBasedRollingPolicy
					success &= deleteFileWithoutSuffix(backupFileToDelete, "");
					success &= deleteFileWithoutSuffix(backupFileToDelete, ".gz");
					success &= deleteFileWithoutSuffix(backupFileToDelete, ".zip");
				}

				firstCleanupRan = true;

				return success;
			}

			private boolean deleteFileWithoutSuffix(String filename, String suffix) {
				if (filename.endsWith(suffix)) {
					File file = new File(filename.substring(0, filename.length() - suffix.length()));
					if (file.exists()) {
						return file.delete();
					}
				}
				return true;
			}
		};

		return new RolloverDescriptionImpl(activeFileName, append, synchronous, newAsynchronous);

	}

	private Iterable getBackupFiles(int searchFileCount) {

		// The time delta could vary according to the current time.
		// For instance, if we have a formatting with month precision ('yyyy-MM'), some months are longer than other.
		// We would not want to miss a shorther month (February), because the delta was calculated on the month of January.
		// So dividing the delta by 2 should be more than enough to prevent that
		long timeIncrement = -getTimeDeltaForFilenameChange() / 2;

		if (timeIncrement == 0) {
			return Collections.emptyList();
		}

		List backupFiles = newArrayList();
		for (String filename : getNextFilenames(searchFileCount, System.currentTimeMillis(), timeIncrement)) {
			backupFiles.add(filename);
		}

		return backupFiles;
	}

	private Iterable getNextFilenames(int filenameCount, long fromTime, long timeIncrement) {
		Set nextFilenames = newLinkedHashSet();
		for (long time = fromTime; nextFilenames.size() < filenameCount; time += timeIncrement) {
			nextFilenames.add(getFilename(time));
		}
		return nextFilenames;
	}

	private long getTimeDeltaForFilenameChange() {
		if (timeDeltaForFilenameChange == null) {
			long nextTimeThatFilenameChange = findNextTimeThatFilenameChange(System.currentTimeMillis());
			long nextTimeThatFilenameChangeAgain = findNextTimeThatFilenameChange(nextTimeThatFilenameChange);
			long timeDelta = nextTimeThatFilenameChangeAgain - nextTimeThatFilenameChange;
			timeDeltaForFilenameChange = Long.valueOf(timeDelta);
		}
		return timeDeltaForFilenameChange.longValue();
	}

	private long findNextTimeThatFilenameChange(long baseTime) {
		String baseFilename = getFilename(baseTime);
		long lowerBound = baseTime;
		long delta = 1;
		long upperBound = baseTime + delta;
		while (delta < Longs.MAX_POWER_OF_TWO && getFilename(upperBound).equals(baseFilename)) {
			lowerBound = upperBound;
			delta <<= 1;
			upperBound = baseTime + delta;
		}

		if (!(delta < Longs.MAX_POWER_OF_TWO)) {
			// The filename never changes!!
			return baseTime;
		}

		while (upperBound - lowerBound > 1) {
			long newBound = (lowerBound + upperBound) / 2;
			if (getFilename(newBound).equals(baseFilename)) {
				lowerBound = newBound;
			} else {
				upperBound = newBound;
			}
		}
		return upperBound;
	}

	private String getFilename(long n) {
		StringBuffer buf = new StringBuffer();
		formatFileName(new Date(n), buf);
		return buf.toString();
	}

}