/*
 * 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 java.util.logging;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Hashtable;

/**
 * A {@code FileHandler} writes logging records into a specified file or a
 * rotating set of files.
 * <p>
 * When a set of files is used and a given amount of data has been written to
 * one file, then this file is closed and another file is opened. The name of
 * these files are generated by given name pattern, see below for details.
 * When the files have all been filled the Handler returns to the first and goes
 * through the set again.
 * <p>
 * By default, the I/O buffering mechanism is enabled, but when each log record
 * is complete, it is flushed out.
 * <p>
 * {@code XMLFormatter} is the default formatter for {@code FileHandler}.
 * <p>
 * {@code FileHandler} reads the following {@code LogManager} properties for
 * initialization; if a property is not defined or has an invalid value, a
 * default value is used.
 * <ul>
 * <li>java.util.logging.FileHandler.append specifies whether this
 * {@code FileHandler} should append onto existing files, defaults to
 * {@code false}.</li>
 * <li>java.util.logging.FileHandler.count specifies how many output files to
 * rotate, defaults to 1.</li>
 * <li>java.util.logging.FileHandler.filter specifies the {@code Filter} class
 * name, defaults to no {@code Filter}.</li>
 * <li>java.util.logging.FileHandler.formatter specifies the {@code Formatter}
 * class, defaults to {@code java.util.logging.XMLFormatter}.</li>
 * <li>java.util.logging.FileHandler.encoding specifies the character set
 * encoding name, defaults to the default platform encoding.</li>
 * <li>java.util.logging.FileHandler.level specifies the level for this
 * {@code Handler}, defaults to {@code Level.ALL}.</li>
 * <li>java.util.logging.FileHandler.limit specifies the maximum number of
 * bytes to write to any one file, defaults to zero, which means no limit.</li>
 * <li>java.util.logging.FileHandler.pattern specifies name pattern for the
 * output files. See below for details. Defaults to "%h/java%u.log".</li>
 * </ul>
 * <p>
 * Name pattern is a string that may include some special substrings, which will
 * be replaced to generate output files:
 * <ul>
 * <li>"/" represents the local pathname separator</li>
 * <li>"%g" represents the generation number to distinguish rotated logs</li>
 * <li>"%h" represents the home directory of the current user, which is
 * specified by "user.home" system property</li>
 * <li>"%t" represents the system's temporary directory</li>
 * <li>"%u" represents a unique number to resolve conflicts</li>
 * <li>"%%" represents the percent sign character '%'</li>
 * </ul>
 * <p>
 * Normally, the generation numbers are not larger than the given file count and
 * follow the sequence 0, 1, 2.... If the file count is larger than one, but the
 * generation field("%g") has not been specified in the pattern, then the
 * generation number after a dot will be added to the end of the file name.
 * <p>
 * The "%u" unique field is used to avoid conflicts and is set to 0 at first. If
 * one {@code FileHandler} tries to open the filename which is currently in use
 * by another process, it will repeatedly increment the unique number field and
 * try again. If the "%u" component has not been included in the file name
 * pattern and some contention on a file does occur, then a unique numerical
 * value will be added to the end of the filename in question immediately to the
 * right of a dot. The generation of unique IDs for avoiding conflicts is only
 * guaranteed to work reliably when using a local disk file system.
 */
public class FileHandler extends StreamHandler {

    private static final String LCK_EXT = ".lck";

    private static final int DEFAULT_COUNT = 1;

    private static final int DEFAULT_LIMIT = 0;

    private static final boolean DEFAULT_APPEND = false;

    private static final String DEFAULT_PATTERN = "%h/java%u.log";

    // maintain all file locks hold by this process
    private static final Hashtable<String, FileLock> allLocks = new Hashtable<String, FileLock>();

    // the count of files which the output cycle through
    private int count;

    // the size limitation in byte of log file
    private int limit;

    // whether the FileHandler should open a existing file for output in append
    // mode
    private boolean append;

    // the pattern for output file name
    private String pattern;

    // maintain a LogManager instance for convenience
    private LogManager manager;

    // output stream, which can measure the output file length
    private MeasureOutputStream output;

    // used output file
    private File[] files;

    // output file lock
    FileLock lock = null;

    // current output file name
    String fileName = null;

    // current unique ID
    int uniqueID = -1;

    /**
     * Construct a {@code FileHandler} using {@code LogManager} properties or
     * their default value.
     *
     * @throws IOException
     *             if any I/O error occurs.
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     */
    public FileHandler() throws IOException {
        init(null, null, null, null);
    }

    // init properties
    private void init(String p, Boolean a, Integer l, Integer c)
            throws IOException {
        // check access
        manager = LogManager.getLogManager();
        manager.checkAccess();
        initProperties(p, a, l, c);
        initOutputFiles();
    }

    private void initOutputFiles() throws FileNotFoundException, IOException {
        while (true) {
            // try to find a unique file which is not locked by other process
            uniqueID++;
            // FIXME: improve performance here
            for (int generation = 0; generation < count; generation++) {
                // cache all file names for rotation use
                files[generation] = new File(parseFileName(generation));
            }
            fileName = files[0].getAbsolutePath();
            synchronized (allLocks) {
                /*
                 * if current process has held lock for this fileName continue
                 * to find next file
                 */
                if (null != allLocks.get(fileName)) {
                    continue;
                }
                if (files[0].exists()
                        && (!append || files[0].length() >= limit)) {
                    for (int i = count - 1; i > 0; i--) {
                        if (files[i].exists()) {
                            files[i].delete();
                        }
                        files[i - 1].renameTo(files[i]);
                    }
                }
                FileOutputStream fileStream = new FileOutputStream(fileName
                        + LCK_EXT);
                FileChannel channel = fileStream.getChannel();
                /*
                 * if lock is unsupported and IOException thrown, just let the
                 * IOException throws out and exit otherwise it will go into an
                 * undead cycle
                 */
                lock = channel.tryLock();
                if (null == lock) {
                    try {
                        fileStream.close();
                    } catch (Exception e) {
                        // ignore
                    }
                    continue;
                }
                allLocks.put(fileName, lock);
                break;
            }
        }
        output = new MeasureOutputStream(new BufferedOutputStream(
                new FileOutputStream(fileName, append)), files[0].length());
        setOutputStream(output);
    }

    @SuppressWarnings("nls")
    private void initProperties(String p, Boolean a, Integer l, Integer c) {
        super.initProperties("ALL", null, "java.util.logging.XMLFormatter",
                null);
        String className = this.getClass().getName();
        pattern = (null == p) ? getStringProperty(className + ".pattern",
                DEFAULT_PATTERN) : p;
        if (pattern == null || pattern.isEmpty()) {
            throw new NullPointerException("Pattern cannot be empty or null");
        }
        append = (null == a) ? getBooleanProperty(className + ".append",
                DEFAULT_APPEND) : a.booleanValue();
        count = (null == c) ? getIntProperty(className + ".count",
                DEFAULT_COUNT) : c.intValue();
        limit = (null == l) ? getIntProperty(className + ".limit",
                DEFAULT_LIMIT) : l.intValue();
        count = count < 1 ? DEFAULT_COUNT : count;
        limit = limit < 0 ? DEFAULT_LIMIT : limit;
        files = new File[count];
    }

    void findNextGeneration() {
        super.close();
        for (int i = count - 1; i > 0; i--) {
            if (files[i].exists()) {
                files[i].delete();
            }
            files[i - 1].renameTo(files[i]);
        }
        try {
            output = new MeasureOutputStream(new BufferedOutputStream(
                    new FileOutputStream(files[0])));
        } catch (FileNotFoundException e1) {
            this.getErrorManager().error("Error opening log file", e1, ErrorManager.OPEN_FAILURE);
        }
        setOutputStream(output);
    }

    /**
     * Transform the pattern to the valid file name, replacing any patterns, and
     * applying generation and uniqueID if present.
     *
     * @param gen
     *            generation of this file
     * @return transformed filename ready for use.
     */
    private String parseFileName(int gen) {
        int cur = 0;
        int next = 0;
        boolean hasUniqueID = false;
        boolean hasGeneration = false;

        // TODO privilege code?

        String tempPath = System.getProperty("java.io.tmpdir");
        boolean tempPathHasSepEnd = (tempPath == null ? false : tempPath
                .endsWith(File.separator));

        String homePath = System.getProperty("user.home");
        boolean homePathHasSepEnd = (homePath == null ? false : homePath
                .endsWith(File.separator));

        StringBuilder sb = new StringBuilder();
        pattern = pattern.replace('/', File.separatorChar);

        char[] value = pattern.toCharArray();
        while ((next = pattern.indexOf('%', cur)) >= 0) {
            if (++next < pattern.length()) {
                switch (value[next]) {
                    case 'g':
                        sb.append(value, cur, next - cur - 1).append(gen);
                        hasGeneration = true;
                        break;
                    case 'u':
                        sb.append(value, cur, next - cur - 1).append(uniqueID);
                        hasUniqueID = true;
                        break;
                    case 't':
                        /*
                         * we should probably try to do something cute here like
                         * lookahead for adjacent '/'
                         */
                        sb.append(value, cur, next - cur - 1).append(tempPath);
                        if (!tempPathHasSepEnd) {
                            sb.append(File.separator);
                        }
                        break;
                    case 'h':
                        sb.append(value, cur, next - cur - 1).append(homePath);
                        if (!homePathHasSepEnd) {
                            sb.append(File.separator);
                        }
                        break;
                    case '%':
                        sb.append(value, cur, next - cur - 1).append('%');
                        break;
                    default:
                        sb.append(value, cur, next - cur);
                }
                cur = ++next;
            } else {
                // fail silently
            }
        }

        sb.append(value, cur, value.length - cur);

        if (!hasGeneration && count > 1) {
            sb.append(".").append(gen);
        }

        if (!hasUniqueID && uniqueID > 0) {
            sb.append(".").append(uniqueID);
        }

        return sb.toString();
    }

    // get boolean LogManager property, if invalid value got, using default
    // value
    private boolean getBooleanProperty(String key, boolean defaultValue) {
        String property = manager.getProperty(key);
        if (null == property) {
            return defaultValue;
        }
        boolean result = defaultValue;
        if ("true".equalsIgnoreCase(property)) {
            result = true;
        } else if ("false".equalsIgnoreCase(property)) {
            result = false;
        }
        return result;
    }

    // get String LogManager property, if invalid value got, using default value
    private String getStringProperty(String key, String defaultValue) {
        String property = manager.getProperty(key);
        return property == null ? defaultValue : property;
    }

    // get int LogManager property, if invalid value got, using default value
    private int getIntProperty(String key, int defaultValue) {
        String property = manager.getProperty(key);
        int result = defaultValue;
        if (null != property) {
            try {
                result = Integer.parseInt(property);
            } catch (Exception e) {
                // ignore
            }
        }
        return result;
    }

    /**
     * Constructs a new {@code FileHandler}. The given name pattern is used as
     * output filename, the file limit is set to zero (no limit), the file count
     * is set to one; the remaining configuration is done using
     * {@code LogManager} properties or their default values. This handler
     * writes to only one file with no size limit.
     *
     * @param pattern
     *            the name pattern for the output file.
     * @throws IOException
     *             if any I/O error occurs.
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     * @throws IllegalArgumentException
     *             if the pattern is empty.
     * @throws NullPointerException
     *             if the pattern is {@code null}.
     */
    public FileHandler(String pattern) throws IOException {
        if (pattern.isEmpty()) {
            throw new IllegalArgumentException("Pattern cannot be empty");
        }
        init(pattern, null, Integer.valueOf(DEFAULT_LIMIT), Integer.valueOf(DEFAULT_COUNT));
    }

    /**
     * Construct a new {@code FileHandler}. The given name pattern is used as
     * output filename, the file limit is set to zero (no limit), the file count
     * is initialized to one and the value of {@code append} becomes the new
     * instance's append mode. The remaining configuration is done using
     * {@code LogManager} properties. This handler writes to only one file
     * with no size limit.
     *
     * @param pattern
     *            the name pattern for the output file.
     * @param append
     *            the append mode.
     * @throws IOException
     *             if any I/O error occurs.
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     * @throws IllegalArgumentException
     *             if {@code pattern} is empty.
     * @throws NullPointerException
     *             if {@code pattern} is {@code null}.
     */
    public FileHandler(String pattern, boolean append) throws IOException {
        if (pattern.isEmpty()) {
            throw new IllegalArgumentException("Pattern cannot be empty");
        }
        init(pattern, Boolean.valueOf(append), Integer.valueOf(DEFAULT_LIMIT),
                Integer.valueOf(DEFAULT_COUNT));
    }

    /**
     * Construct a new {@code FileHandler}. The given name pattern is used as
     * output filename, the maximum file size is set to {@code limit} and the
     * file count is initialized to {@code count}. The remaining configuration
     * is done using {@code LogManager} properties. This handler is configured
     * to write to a rotating set of count files, when the limit of bytes has
     * been written to one output file, another file will be opened instead.
     *
     * @param pattern
     *            the name pattern for the output file.
     * @param limit
     *            the data amount limit in bytes of one output file, can not be
     *            negative.
     * @param count
     *            the maximum number of files to use, can not be less than one.
     * @throws IOException
     *             if any I/O error occurs.
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     * @throws IllegalArgumentException
     *             if {@code pattern} is empty, {@code limit < 0} or
     *             {@code count < 1}.
     * @throws NullPointerException
     *             if {@code pattern} is {@code null}.
     */
    public FileHandler(String pattern, int limit, int count) throws IOException {
        if (pattern.isEmpty()) {
            throw new IllegalArgumentException("Pattern cannot be empty");
        }
        if (limit < 0 || count < 1) {
            throw new IllegalArgumentException("limit < 0 || count < 1");
        }
        init(pattern, null, Integer.valueOf(limit), Integer.valueOf(count));
    }

    /**
     * Construct a new {@code FileHandler}. The given name pattern is used as
     * output filename, the maximum file size is set to {@code limit}, the file
     * count is initialized to {@code count} and the append mode is set to
     * {@code append}. The remaining configuration is done using
     * {@code LogManager} properties. This handler is configured to write to a
     * rotating set of count files, when the limit of bytes has been written to
     * one output file, another file will be opened instead.
     *
     * @param pattern
     *            the name pattern for the output file.
     * @param limit
     *            the data amount limit in bytes of one output file, can not be
     *            negative.
     * @param count
     *            the maximum number of files to use, can not be less than one.
     * @param append
     *            the append mode.
     * @throws IOException
     *             if any I/O error occurs.
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     * @throws IllegalArgumentException
     *             if {@code pattern} is empty, {@code limit < 0} or
     *             {@code count < 1}.
     * @throws NullPointerException
     *             if {@code pattern} is {@code null}.
     */
    public FileHandler(String pattern, int limit, int count, boolean append) throws IOException {
        if (pattern.isEmpty()) {
            throw new IllegalArgumentException("Pattern cannot be empty");
        }
        if (limit < 0 || count < 1) {
            throw new IllegalArgumentException("limit < 0 || count < 1");
        }
        init(pattern, Boolean.valueOf(append), Integer.valueOf(limit), Integer.valueOf(count));
    }

    /**
     * Flushes and closes all opened files.
     *
     * @throws SecurityException
     *             if a security manager exists and it determines that the
     *             caller does not have the required permissions to control this
     *             handler; required permissions include
     *             {@code LogPermission("control")},
     *             {@code FilePermission("write")} etc.
     */
    @Override
    public void close() {
        // release locks
        super.close();
        allLocks.remove(fileName);
        try {
            FileChannel channel = lock.channel();
            lock.release();
            channel.close();
            File file = new File(fileName + LCK_EXT);
            file.delete();
        } catch (IOException e) {
            // ignore
        }
    }

    /**
     * Publish a {@code LogRecord}.
     *
     * @param record
     *            the log record to publish.
     */
    @Override
    public synchronized void publish(LogRecord record) {
        super.publish(record);
        flush();
        if (limit > 0 && output.getLength() >= limit) {
            AccessController.doPrivileged(new PrivilegedAction<Object>() {
                public Object run() {
                    findNextGeneration();
                    return null;
                }
            });
        }
    }

    /**
     * This output stream uses the decorator pattern to add measurement features
     * to OutputStream which can detect the total size(in bytes) of output, the
     * initial size can be set.
     */
    static class MeasureOutputStream extends OutputStream {

        OutputStream wrapped;

        long length;

        public MeasureOutputStream(OutputStream stream, long currentLength) {
            wrapped = stream;
            length = currentLength;
        }

        public MeasureOutputStream(OutputStream stream) {
            this(stream, 0);
        }

        @Override
        public void write(int oneByte) throws IOException {
            wrapped.write(oneByte);
            length++;
        }

        @Override
        public void write(byte[] bytes) throws IOException {
            wrapped.write(bytes);
            length += bytes.length;
        }

        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            wrapped.write(b, off, len);
            length += len;
        }

        @Override
        public void close() throws IOException {
            wrapped.close();
        }

        @Override
        public void flush() throws IOException {
            wrapped.flush();
        }

        public long getLength() {
            return length;
        }

        public void setLength(long newLength) {
            length = newLength;
        }
    }
}