/*
 * @(#)FileHandler.java	1.36 06/04/07
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util.logging;

import java.io.*;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.security.*;

/**
 * Simple file logging <tt>Handler</tt>.
 * <p>
 * The <tt>FileHandler</tt> can either write to a specified file,
 * or it can write to a rotating set of files.  
 * <p>
 * For a rotating set of files, as each file reaches a given size
 * limit, it is closed, rotated out, and a new file opened.
 * Successively older files are named by adding "0", "1", "2", 
 * etc into the base filename.
 * <p>
 * By default buffering is enabled in the IO libraries but each log
 * record is flushed out when it is complete. 
 * <p>
 * By default the <tt>XMLFormatter</tt> class is used for formatting.
 * <p>
 * <b>Configuration:</b>
 * By default each <tt>FileHandler</tt> is initialized using the following
 * <tt>LogManager</tt> configuration properties.  If properties are not defined
 * (or have invalid values) then the specified default values are used.
 * <ul>
 * <li>   java.util.logging.FileHandler.level 
 *	  specifies the default level for the <tt>Handler</tt>
 *	  (defaults to <tt>Level.ALL</tt>).
 * <li>   java.util.logging.FileHandler.filter 
 * 	  specifies the name of a <tt>Filter</tt> class to use
 *	  (defaults to no <tt>Filter</tt>).
 * <li>   java.util.logging.FileHandler.formatter 
 *	  specifies the name of a <tt>Formatter</tt> class to use
 *        (defaults to <tt>java.util.logging.XMLFormatter</tt>)
 * <li>   java.util.logging.FileHandler.encoding 
 *	  the name of the character set encoding to use (defaults to
 *	  the default platform encoding).
 * <li>   java.util.logging.FileHandler.limit 
 *	  specifies an approximate maximum amount to write (in bytes)
 * 	  to any one file.  If this is zero, then there is no limit.
 *	  (Defaults to no limit).
 * <li>   java.util.logging.FileHandler.count 
 *	  specifies how many output files to cycle through (defaults to 1).
 * <li>   java.util.logging.FileHandler.pattern 
 *	  specifies a pattern for generating the output file name.  See
 *        below for details. (Defaults to "%h/java%u.log").
 * <li>   java.util.logging.FileHandler.append
 *	  specifies whether the FileHandler should append onto
 *        any existing files (defaults to false).
 * </ul>
 * <p>
 * <p>
 * A pattern consists of a string that includes the following special
 * components that will be replaced at runtime:
 * <ul>
 * <li>    "/"    the local pathname separator 
 * <li>     "%t"   the system temporary directory
 * <li>     "%h"   the value of the "user.home" system property
 * <li>     "%g"   the generation number to distinguish rotated logs
 * <li>     "%u"   a unique number to resolve conflicts
 * <li>     "%%"   translates to a single percent sign "%"
 * </ul>
 * If no "%g" field has been specified and the file count is greater
 * than one, then the generation number will be added to the end of
 * the generated filename, after a dot.
 * <p> 
 * Thus for example a pattern of "%t/java%g.log" with a count of 2
 * would typically cause log files to be written on Solaris to 
 * /var/tmp/java0.log and /var/tmp/java1.log whereas on Windows 95 they
 * would be typically written to C:\TEMP\java0.log and C:\TEMP\java1.log
 * <p> 
 * Generation numbers follow the sequence 0, 1, 2, etc.
 * <p>
 * Normally the "%u" unique field is set to 0.  However, if the <tt>FileHandler</tt>
 * tries to open the filename and finds the file is currently in use by
 * another process it will increment the unique number field and try
 * again.  This will be repeated until <tt>FileHandler</tt> finds a file name that
 * is  not currently in use. If there is a conflict and no "%u" field has
 * been specified, it will be added at the end of the filename after a dot.
 * (This will be after any automatically added generation number.)
 * <p>
 * Thus if three processes were all trying to log to fred%u.%g.txt then 
 * they  might end up using fred0.0.txt, fred1.0.txt, fred2.0.txt as
 * the first file in their rotating sequences.
 * <p>
 * Note that the use of unique ids to avoid conflicts is only guaranteed
 * to work reliably when using a local disk file system.
 *
 * @version 1.36, 04/07/06
 * @since 1.4
 */

public class FileHandler extends StreamHandler {
    private MeteredStream meter;
    private boolean append;
    private int limit;       // zero => no limit.
    private int count;
    private String pattern;
    private String lockFileName;
    private FileOutputStream lockStream;
    private File files[];
    private static final int MAX_LOCKS = 100;
    private static java.util.HashMap locks = new java.util.HashMap();

    // A metered stream is a subclass of OutputStream that
    //   (a) forwards all its output to a target stream
    //   (b) keeps track of how many bytes have been written
    private class MeteredStream extends OutputStream {
  	OutputStream out;
	int written;

	MeteredStream(OutputStream out, int written) {
	    this.out = out;
	    this.written = written;
	}

	public void write(int b) throws IOException {
	    out.write(b);
	    written++;
	}

	public void write(byte buff[]) throws IOException {
	    out.write(buff);
	    written += buff.length;
	}
	
	public void write(byte buff[], int off, int len) throws IOException {
	    out.write(buff,off,len);
	    written += len;
	}
	
	public void flush() throws IOException {
	    out.flush();
	}

	public void close() throws IOException {
	    out.close();
	}
    }

    private void open(File fname, boolean append) throws IOException {
	int len = 0;
	if (append) {
	    len = (int)fname.length();
	}
	FileOutputStream fout = new FileOutputStream(fname.toString(), append);
	BufferedOutputStream bout = new BufferedOutputStream(fout);
	meter = new MeteredStream(bout, len);
	setOutputStream(meter);
    }

    // Private method to configure a FileHandler from LogManager
    // properties and/or default values as specified in the class
    // javadoc.
    private void configure() {
        LogManager manager = LogManager.getLogManager();

	String cname = getClass().getName();

	pattern = manager.getStringProperty(cname + ".pattern", "%h/java%u.log");
	limit = manager.getIntProperty(cname + ".limit", 0);
	if (limit < 0) {
	    limit = 0;
	}
        count = manager.getIntProperty(cname + ".count", 1);
	if (count <= 0) {
	    count = 1;
	}
        append = manager.getBooleanProperty(cname + ".append", false);
	setLevel(manager.getLevelProperty(cname + ".level", Level.ALL));
	setFilter(manager.getFilterProperty(cname + ".filter", null));
	setFormatter(manager.getFormatterProperty(cname + ".formatter",	new XMLFormatter()));
	try {
	    setEncoding(manager.getStringProperty(cname +".encoding", null));
	} catch (Exception ex) {
	    try {
	        setEncoding(null);
	    } catch (Exception ex2) {
		// doing a setEncoding with null should always work.
		// assert false;
	    }
	}
    }


    /**
     * Construct a default <tt>FileHandler</tt>.  This will be configured
     * entirely from <tt>LogManager</tt> properties (or their default values).
     * <p>
     * @exception  IOException if there are IO problems opening the files.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control"))</tt>.
     * @exception  NullPointerException if pattern property is an empty String.
     */
    public FileHandler() throws IOException, SecurityException {
	checkAccess();
	configure();
	openFiles();
    }

    /**
     * Initialize a <tt>FileHandler</tt> to write to the given filename.
     * <p>
     * The <tt>FileHandler</tt> is configured based on <tt>LogManager</tt>
     * properties (or their default values) except that the given pattern 
     * argument is used as the filename pattern, the file limit is
     * set to no limit, and the file count is set to one.
     * <p>
     * There is no limit on the amount of data that may be written,
     * so use this with care.
     *
     * @param pattern  the name of the output file
     * @exception  IOException if there are IO problems opening the files.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     * @exception  IllegalArgumentException if pattern is an empty string
     */
    public FileHandler(String pattern) throws IOException, SecurityException {
	if (pattern.length() < 1 ) {
	    throw new IllegalArgumentException();   
	}
	checkAccess();
	configure();
	this.pattern = pattern;
	this.limit = 0;
	this.count = 1;
	openFiles();
    }

    /**
     * Initialize a <tt>FileHandler</tt> to write to the given filename,
     * with optional append.
     * <p>
     * The <tt>FileHandler</tt> is configured based on <tt>LogManager</tt>
     * properties (or their default values) except that the given pattern 
     * argument is used as the filename pattern, the file limit is
     * set to no limit, the file count is set to one, and the append
     * mode is set to the given <tt>append</tt> argument.
     * <p>
     * There is no limit on the amount of data that may be written,
     * so use this with care.
     *
     * @param pattern  the name of the output file
     * @param append  specifies append mode
     * @exception  IOException if there are IO problems opening the files.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     * @exception  IllegalArgumentException if pattern is an empty string
     */
    public FileHandler(String pattern, boolean append) throws IOException, SecurityException {
	if (pattern.length() < 1 ) {
	    throw new IllegalArgumentException();   
	}
	checkAccess();
	configure();
	this.pattern = pattern;
	this.limit = 0;
	this.count = 1;
	this.append = append;
	openFiles();
    }

    /**
     * Initialize a <tt>FileHandler</tt> to write to a set of files.  When
     * (approximately) the given limit has been written to one file,
     * another file will be opened.  The output will cycle through a set
     * of count files.
     * <p>
     * The <tt>FileHandler</tt> is configured based on <tt>LogManager</tt>
     * properties (or their default values) except that the given pattern 
     * argument is used as the filename pattern, the file limit is
     * set to the limit argument, and the file count is set to the
     * given count argument.
     * <p>
     * The count must be at least 1.
     *
     * @param pattern  the pattern for naming the output file
     * @param limit  the maximum number of bytes to write to any one file
     * @param count  the number of files to use
     * @exception  IOException if there are IO problems opening the files.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     * @exception IllegalArgumentException if limit < 0, or count < 1.
     * @exception  IllegalArgumentException if pattern is an empty string
     */
    public FileHandler(String pattern, int limit, int count)
					throws IOException, SecurityException {
	if (limit < 0 || count < 1 || pattern.length() < 1) {
	    throw new IllegalArgumentException();
	}
	checkAccess();
	configure();
	this.pattern = pattern;
	this.limit = limit;
	this.count = count;
	openFiles();
    }

    /**
     * Initialize a <tt>FileHandler</tt> to write to a set of files
     * with optional append.  When (approximately) the given limit has
     * been written to one file, another file will be opened.  The
     * output will cycle through a set of count files.
     * <p>
     * The <tt>FileHandler</tt> is configured based on <tt>LogManager</tt>
     * properties (or their default values) except that the given pattern 
     * argument is used as the filename pattern, the file limit is
     * set to the limit argument, and the file count is set to the
     * given count argument, and the append mode is set to the given
     * <tt>append</tt> argument.
     * <p>
     * The count must be at least 1.
     *
     * @param pattern  the pattern for naming the output file
     * @param limit  the maximum number of bytes to write to any one file
     * @param count  the number of files to use
     * @param append  specifies append mode
     * @exception  IOException if there are IO problems opening the files.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     * @exception IllegalArgumentException if limit < 0, or count < 1.
     * @exception  IllegalArgumentException if pattern is an empty string
     *
     */
    public FileHandler(String pattern, int limit, int count, boolean append)
					throws IOException, SecurityException {
	if (limit < 0 || count < 1 || pattern.length() < 1) {
	    throw new IllegalArgumentException();
	}
	checkAccess();
	configure();
	this.pattern = pattern;
	this.limit = limit;
	this.count = count;
	this.append = append;
	openFiles();
    }

    // Private method to open the set of output files, based on the
    // configured instance variables.
    private void openFiles() throws IOException {
        LogManager manager = LogManager.getLogManager();
	manager.checkAccess();
	if (count < 1) {
	   throw new IllegalArgumentException("file count = " + count);
	}
	if (limit < 0) {
	    limit = 0;
	}

	// We register our own ErrorManager during initialization
	// so we can record exceptions.
	InitializationErrorManager em = new InitializationErrorManager();
	setErrorManager(em);

	// Create a lock file.  This grants us exclusive access
	// to our set of output files, as long as we are alive.
	int unique = -1;
	for (;;) {
	    unique++;
	    if (unique > MAX_LOCKS) {
		throw new IOException("Couldn't get lock for " + pattern);
	    }
	    // Generate a lock file name from the "unique" int.
	    lockFileName = generate(pattern, 0, unique).toString() + ".lck";
	    // Now try to lock that filename.
	    // Because some systems (e.g. Solaris) can only do file locks
	    // between processes (and not within a process), we first check
	    // if we ourself already have the file locked.
	    synchronized(locks) {
		if (locks.get(lockFileName) != null) {
		    // We already own this lock, for a different FileHandler
		    // object.  Try again.
		    continue;
	        }
		FileChannel fc;
		try {
		    lockStream = new FileOutputStream(lockFileName);
		    fc = lockStream.getChannel();
		} catch (IOException ix) {
		    // We got an IOException while trying to open the file.
		    // Try the next file.
		    continue;
		}
		try {
		    FileLock fl = fc.tryLock();
		    if (fl == null) {
		        // We failed to get the lock.  Try next file.
			continue;
		    }
		    // We got the lock OK.
		} catch (IOException ix) {
		    // We got an IOException while trying to get the lock.
		    // This normally indicates that locking is not supported
		    // on the target directory.  We have to proceed without
		    // getting a lock.   Drop through.
		}
		// We got the lock.  Remember it.
		locks.put(lockFileName, lockFileName);
		break;
	    }
	}

	files = new File[count];
	for (int i = 0; i < count; i++) {
	    files[i] = generate(pattern, i, unique);
	}

	// Create the initial log file.
	if (append) {
	    open(files[0], true);
	} else {
            rotate();
	}

	// Did we detect any exceptions during initialization?
	Exception ex = em.lastException;
	if (ex != null) {
	    if (ex instanceof IOException) {
		throw (IOException) ex;
	    } else if (ex instanceof SecurityException) {
		throw (SecurityException) ex;
	    } else {
		throw new IOException("Exception: " + ex);
	    }
	}

	// Install the normal default ErrorManager.
	setErrorManager(new ErrorManager());
    }

    // Generate a filename from a pattern.
    private File generate(String pattern, int generation, int unique) throws IOException {
	File file = null;
	String word = "";
	int ix = 0;
  	boolean sawg = false;
  	boolean sawu = false;
	while (ix < pattern.length()) {
	    char ch = pattern.charAt(ix);
	    ix++;
	    char ch2 = 0;
	    if (ix < pattern.length()) {
		ch2 = Character.toLowerCase(pattern.charAt(ix));
	    }
	    if (ch == '/') {
		if (file == null) {
		    file = new File(word);
		} else {
		    file = new File(file, word);
		}
		word = "";
		continue;
	    } else  if (ch == '%') {
		if (ch2 == 't') {
	    	    String tmpDir = System.getProperty("java.io.tmpdir");
		    if (tmpDir == null) {
			tmpDir = System.getProperty("user.home");
		    }
		    file = new File(tmpDir);
		    ix++;
		    word = "";
		    continue;
	        } else if (ch2 == 'h') {
		    file = new File(System.getProperty("user.home"));
		    if (isSetUID()) {
			// Ok, we are in a set UID program.  For safety's sake
			// we disallow attempts to open files relative to %h.
			throw new IOException("can't use %h in set UID program");
		    }
		    ix++;
		    word = "";
		    continue;
	        } else if (ch2 == 'g') {
		    word = word + generation;
		    sawg = true;
		    ix++;
		    continue;
	        } else if (ch2 == 'u') {
		    word = word + unique;
		    sawu = true;
		    ix++;
		    continue;
	        } else if (ch2 == '%') {
		    word = word + "%";
		    ix++;
		    continue;
		}
	    }
	    word = word + ch;
	}
	if (count > 1 && !sawg) {
	    word = word + "." + generation;
	}
	if (unique > 0 && !sawu) {
	    word = word + "." + unique;
	}
	if (word.length() > 0) {
	    if (file == null) {
		file = new File(word);
	    } else {
		file = new File(file, word);
	    }
	}
	return file;
    }

    // Rotate the set of output files
    private synchronized void rotate() {
	Level oldLevel = getLevel();
	setLevel(Level.OFF);

	super.close();
	for (int i = count-2; i >= 0; i--) {
	    File f1 = files[i];
	    File f2 = files[i+1];
	    if (f1.exists()) {
		if (f2.exists()) {
		    f2.delete();
		}
		f1.renameTo(f2);
	    }
	}
	try {
	    open(files[0], false);
        } catch (IOException ix) {
	    // We don't want to throw an exception here, but we
	    // report the exception to any registered ErrorManager.
	    reportError(null, ix, ErrorManager.OPEN_FAILURE);

	}
	setLevel(oldLevel);
    }

    /**
     * Format and publish a <tt>LogRecord</tt>.
     *
     * @param  record  description of the log event. A null record is
     *                 silently ignored and is not published
     */
    public synchronized void publish(LogRecord record) {
	if (!isLoggable(record)) {
	    return;
	}
	super.publish(record);
	flush();
	if (limit > 0 && meter.written >= limit) {
            // We performed access checks in the "init" method to make sure
            // we are only initialized from trusted code.  So we assume
	    // it is OK to write the target files, even if we are
	    // currently being called from untrusted code.
            // So it is safe to raise privilege here.
	    AccessController.doPrivileged(new PrivilegedAction() {
		public Object run() {
		    rotate();
		    return null;
		}
	    });
	}
    }

    /**
     * Close all the files.
     *
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     */
    public synchronized void close() throws SecurityException {
	super.close();
	// Unlock any lock file.
	if (lockFileName == null) {
	    return;
	}
	try {
	    // Closing the lock file's FileOutputStream will close
	    // the underlying channel and free any locks.
	    lockStream.close();
	} catch (Exception ex) {
	    // Problems closing the stream.  Punt.
	}
	synchronized(locks) {
	    locks.remove(lockFileName);
	}
        new File(lockFileName).delete();
	lockFileName = null;
	lockStream = null;
    }

    private static class InitializationErrorManager extends ErrorManager {
	Exception lastException;
	public void error(String msg, Exception ex, int code) {
	    lastException = ex;
	}
    }

    // Private native method to check if we are in a set UID program.
    private static native boolean isSetUID();
}