/*
 * Copyright (c) 2014, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.http.server.accesslog;

import static java.util.logging.Level.WARNING;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.logging.Logger;

import org.glassfish.grizzly.Grizzly;
import org.glassfish.grizzly.http.server.HttpServer;

An appender writing log entries to Files, and rotating/archiving them when necessary. 
Author:
Pier Fumagalli, USRZ.com/**
 * An {@link AccessLogAppender appender} writing log entries to {@link File}s, and rotating/archiving them when
 * necessary.
 *
 * @author <a href="mailto:pier@usrz.com">Pier Fumagalli</a>
 * @author <a href="http://www.usrz.com/">USRZ.com</a>
 */
public class RotatingFileAppender implements AccessLogAppender {

    private static final Logger LOGGER = Grizzly.logger(HttpServer.class);

    /* The SDF that will format the "current" file name */
    private final SimpleDateFormatThreadLocal fileFormat;
    /* The SDF that will format the "archive" file name */
    private final SimpleDateFormatThreadLocal archiveFormat;

    /* Our current file appender */
    private FileAppender appender;
    /* The directory where to keep files */
    private final File directory;
    /* The name of the current archive file name */
    private File currentArchive;
    /* The name of the file we're actualy writing to */
    private File currentFile;
    /* Flag, closed, byebye */
    private boolean closed;

    
Create a RotatingFileAppender writing access log files in the specified directory and using the specified SimpleDateFormat pattern to generate file names. 

For example when the specified pattern is 'access-'yyyyMMDDhh'.log' (note the quotes), access log files
will be rotated on a hourly basis, and the output will be written to files like access-2013120422.log,
access-2013120423.log, ... and so on.
Params:
directory – The directory where access log files will be written to.
filePattern – A properly escaped SimpleDateFormat pattern for the access log files.
Throws:
IOException – If an I/O error occurred accessing the filesystem./**
     * Create a {@link RotatingFileAppender} writing access log files in the specified directory and using the specified
     * {@link SimpleDateFormat} pattern to generate file names.
     *
     * <p>
     * For example when the specified pattern is <code>'access-'yyyyMMDDhh'.log'</code> (note the quotes), access log files
     * will be rotated on a hourly basis, and the output will be written to files like <code>access-2013120422.log</code>,
     * <code>access-2013120423.log</code>, ... and so on.
     *
     * @param directory The directory where access log files will be written to.
     * @param filePattern A properly escaped {@link SimpleDateFormat} pattern for the access log files.
     * @throws IOException If an I/O error occurred accessing the filesystem.
     */
    public RotatingFileAppender(File directory, String filePattern) throws IOException {
        this(filePattern, filePattern, directory);
        LOGGER.fine("Creating rotating log appender in \"" + directory + "\" with file pattern \"" + filePattern + "\"");
    }

    
Create a RotatingFileAppender writing access log files in the specified directory. 

When using this constructor the current log file (the one being written to) will always be the one
identified by the fileName parameter, and then archival of files will be delegated to the archive
pattern.


For example when fileName is current.log and archivePattern is
'archive-'yyyyMMDD'.log' (note the quotes), access logs will be written to the current.log
file and this file will be rotated on a daily basis to files like archive-20131204.log,
archive-20131205.log, ... and so on.
Params:
directory – The directory where access log files will be written to.
fileName – A file name where log entries will be written to.
archivePattern – A properly escaped SimpleDateFormat pattern for the access log archive files.
Throws:
IOException – If an I/O error occurred accessing the filesystem./**
     * Create a {@link RotatingFileAppender} writing access log files in the specified directory.
     *
     * <p>
     * When using this constructor the <em>current</em> log file (the one being written to) will <em>always</em> be the one
     * identified by the <code>fileName</code> parameter, and then archival of files will be delegated to the archive
     * pattern.
     * </p>
     *
     * <p>
     * For example when <code>fileName</code> is <code>current.log</code> and <code>archivePattern</code> is
     * <code>'archive-'yyyyMMDD'.log'</code> (note the quotes), access logs will be written to the <code>current.log</code>
     * file and this file will be rotated on a daily basis to files like <code>archive-20131204.log</code>,
     * <code>archive-20131205.log</code>, ... and so on.
     *
     * @param directory The directory where access log files will be written to.
     * @param fileName A file name where log entries will be written to.
     * @param archivePattern A properly escaped {@link SimpleDateFormat} pattern for the access log archive files.
     * @throws IOException If an I/O error occurred accessing the filesystem.
     */
    public RotatingFileAppender(File directory, String fileName, String archivePattern) throws IOException {
        this(escape(fileName), archivePattern, directory);
        LOGGER.fine("Creating rotating log appender in \"" + directory + "\" writing to \"" + fileName + "\" and archive pattern \"" + archivePattern + "\"");
    }

    /* ====================================================================== */

    private static String escape(String fileName) {
        if (fileName == null) {
            throw new NullPointerException("Null file name");
        }
        return "'" + fileName.replace("'", "''") + "'";
    }

    /* ====================================================================== */

    private RotatingFileAppender(String filePattern, String archivePattern, File directory) throws IOException {

        this.directory = directory.getCanonicalFile();
        archiveFormat = new SimpleDateFormatThreadLocal(archivePattern);
        fileFormat = new SimpleDateFormatThreadLocal(filePattern);

        final Date now = new Date();
        currentArchive = new File(directory, archiveFormat.get().format(now)).getCanonicalFile();
        currentFile = new File(directory, fileFormat.get().format(now)).getCanonicalFile();

        /* Validate the arguments */
        if (!this.directory.equals(currentArchive.getParentFile())) {
            throw new IllegalArgumentException("Archive file \"" + currentArchive + "\" is not a child of the configured directory \"" + this.directory + "\"");
        }
        if (!this.directory.equals(currentFile.getParentFile())) {
            throw new IllegalArgumentException("Access log file \"" + currentFile + "\" is not a child of the configured directory \"" + this.directory + "\"");
        }
        if (currentArchive.equals(currentFile)) {
            throw new IllegalArgumentException("Access log file and archive file point to the same file \"" + currentFile + "\"");
        }

        /* Validated, we can open files */
        appender = new FileAppender(currentFile, true);
    }

    /* ====================================================================== */
    /* DO SOME ACTUAL WORK */
    /* ====================================================================== */

    @Override
    public void append(String accessLogEntry) throws IOException {
        if (closed) {
            return;
        }

        /* It's all about date and time */
        final Date date = new Date();
        synchronized (this) {
            /* Calculate the name of the current archive */
            final SimpleDateFormat archiveFormat = this.archiveFormat.get();
            final File archive = new File(directory, archiveFormat.format(date));

            /* If this archive is *NOT* the one we wrote to last, rotate */
            if (!archive.equals(currentArchive)) {
                try {

                    /* Close our current appender */
                    appender.close();

                    /* If we have different file names, move the file to archive */
                    if (!currentFile.equals(currentArchive)) {
                        LOGGER.info("Archiving \"" + currentFile + "\" to \"" + currentArchive + "\"");
                        if (!currentFile.renameTo(currentArchive)) {
                            throw new IOException("Unable to rename \"" + currentFile + "\" to \"" + currentArchive + "\"");
                        }
                    }

                    /* Save our new state */
                    currentArchive = archive;
                    currentFile = new File(directory, fileFormat.get().format(date));

                    /* Create our new appender */
                    appender = new FileAppender(currentFile, true);

                } catch (IOException exception) {
                    LOGGER.log(WARNING, "I/O error rotating access log file", exception);
                }
            }

            appender.append(accessLogEntry);
        }

    }

    @Override
    public void close() throws IOException {
        closed = true;
        appender.close();
    }

}