/*
 * ObjectFileHandler.java
 *
 * Created on 12 March 2003, 16:10
 */

package org.bodington.logging;

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

public class ObjectFileHandler extends Handler
{
    
    private MeteredStream meter;
    
    private ObjectOutputStream oos;
    
    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);
        oos = new ObjectOutputStream( meter );
    }
    
    // Private method to configure a FileHandler from LogManager
    // properties and/or default values as specified in the class
    // javadoc.
    private void configure()
    {
        pattern = "%h/java%u.log";
        limit = 0;
        if (limit < 0)
        {
            limit = 0;
        }
        count =1;
        if (count <= 0)
        {
            count = 1;
        }
        append = false;
        setLevel( Level.ALL);
        setFilter(null);
        try
        {
            setEncoding( 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>.
     */
    public ObjectFileHandler() 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>.
     */
    public ObjectFileHandler(String pattern) throws IOException, SecurityException
    {
        _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>.
     */
    public ObjectFileHandler(String pattern, boolean append) throws IOException, SecurityException
    {
        _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.
     */
    public ObjectFileHandler(String pattern, int limit, int count)
    throws IOException, SecurityException
    {
        if (limit < 0 || count < 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.
     *
     */
    public ObjectFileHandler(String pattern, int limit, int count, boolean append)
    throws IOException, SecurityException
    {
        if (limit < 0 || count < 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
    {
        _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 if (ex instanceof NullPointerException)
            {
                throw (NullPointerException)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);
        
        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
     */
    public synchronized void publish(LogRecord record)
    {
        if (!isLoggable(record))
        {
            return;
        }
        
        try
        {
            oos.writeObject( record );
            oos.flush();
            //logrecords don't reference each other - there's no need for
            //a huge collection of records.  reset() makes oos forget
            //previous objects in the stream and resets tables etc.
            oos.reset();
        }
        catch ( Exception e )
        {
            reportError(null, e, ErrorManager.WRITE_FAILURE);
        }
        
        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
    {
        try
        {
            if ( oos != null )
                oos.close();
        } catch (Exception ex)
        {
            // We don't want to throw an exception here, but we
            // report the exception to any registered ErrorManager.
            reportError(null, ex, ErrorManager.CLOSE_FAILURE);
        }
        
        // 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);
        }
        lockFileName = null;
        lockStream = null;
    }
    
    
    void _checkAccess() throws SecurityException
    {
        if ( false )
            throw new SecurityException( "?" );
    }
    
    /** Flush any buffered output.
     */
    public void flush()
    {
        try
        {
            oos.flush();
        }
        catch (Exception ex)
        {
            // We don't want to throw an exception here, but we
            // report the exception to any registered ErrorManager.
            reportError(null, ex, ErrorManager.FLUSH_FAILURE);
        }
    }
    
    
    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();
    
}