package ranab.io;

import java.io.File;
import java.io.Writer;
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.io.RandomAccessFile;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Date;
import java.util.Random;
import java.text.DateFormat;
import java.text.SimpleDateFormat;


/**
 * Log class to write log data. It uses <code>RandomAccessFile</code>.
 * If the log file size exceeds the limit, a new log file will be created.
 *
 * @author <a href="mailto:rana_b@yahoo.com">Rana Bhattacharyya</a>
 */
public
class LogFile {
    
    /**
     * Line separator
     */
    private final static String LINE_SEP = System.getProperty("line.separator", "\n");
    
    
    /**
     * Date format to backup old files. 
     */
    private DateFormat LOG_FILE_DATE = new SimpleDateFormat("yyyy-MM-dd-hh-mm-ss");
    
    /**
     * Debug log level - lowest priority.
     */
    public static final int DEBUG  = 0;
    
    /**
     * Normal log level - print messages.
     */
    public static final int INFO   = 1;
    
    /**
     * Warning message
     */
    public static final int WARN   = 2;    
    
    /**
     * Eror log level - print errors.
     */
    public static final int ERROR  = 3;
    
    private static final String mstLogHeader[] = { 
        "DEB",
        "INF",
        "WAR",
        "ERR"
    };

    private DateFormat mDateFmt = null;
    private Writer mOfs         = null;
    private File mLogFile       = null;
    private int miLogLevel      = INFO;
    private long mlMaxSize      = -1;    // no size limit
    private long mlSize         = 0;     // current size
    private boolean mbAutoFlush = false; 

    /**
     * Constructor. 
     */
    public LogFile(File logFile) {

        if (logFile == null) {
            throw new NullPointerException("Log file is null.");
        }

        mDateFmt = new SimpleDateFormat("MM/dd HH:mm:ss");
        mLogFile = logFile;
        open();
    }

    /**
     * Set log date format
     */
    public void setDateFormat(DateFormat fmt)  {
        mDateFmt = fmt;
    }
    
    /**
     * Get the log date format.
     */
    public DateFormat getDateFormat() {
        return mDateFmt;
    }
    
    /**
     * Get auto flush
     */
    public boolean getAutoFlush() {
        return mbAutoFlush;
    }
    
    /**
     * Set auto flush
     */
    public void setAutoFlush(boolean flush) {
        mbAutoFlush = flush;
    }
    
    /**
     * Get log file.
     */
    public File getFile() {
        return mLogFile;
    }
     
    /**
     * Get max size.
     */
    public long getMaxSize() {
        return mlMaxSize;
    }
    
    /**
     * Set max file size.
     * Set <code>max</code> less than or equal
     * to zero to disable max size limitation.
     */
    public synchronized void setMaxSize(long max) {
        mlMaxSize = max;
    }

    /**
     * Get the current file size.
     */
    public long getCurrentSize() {
        return mlSize;
    }
    
    /**
     * Get current log level.
     */
    public int getLogLevel() {
        return miLogLevel;
    }
    
    /**
     * Set log level. If <code>level</code> is beypnd the
     * range, it uses <code>LOG_NORMAL</code> to wtite log data.
     */
    public synchronized void setLogLevel(int level) {
        miLogLevel = calculateLogLevel(level);
    }
    
    /**
     * Open log file.
     */
    private synchronized void open() {
        try {
            if (mLogFile != null) {
                mlSize = mLogFile.length();
                RandomAccessFile raf = new RandomAccessFile(mLogFile, "rw");
                raf.seek(raf.length());
                FileWriter fw = new FileWriter(raf.getFD()); 
                mOfs = new BufferedWriter(fw);
            }
        } catch (Exception ex) {
            ex.printStackTrace();
            mOfs = null;
        }
    }

    

    /**
     * Print log data.
     *
     * @param str - log message
     * @param level - log level of this message.
     */
    public synchronized void write(int level, String str) {

        level = calculateLogLevel(level);

        // write the string
        if (level >= miLogLevel) {
            String logStr = "[" + mDateFmt.format(new Date()) + " (" + mstLogHeader[level] +")] " + str + LINE_SEP;
            long strLen = logStr.length();
            
            if (mOfs != null) {

                // save file if needed
                if ( (mlMaxSize > 0) && ((mlSize + strLen) > mlMaxSize) ) {
                    save();
                }
                
                // now write it
                try {
                    mOfs.write(logStr);
                    if (mbAutoFlush) {
                        mOfs.flush();
                    }
                    mlSize += strLen;
                } catch (Exception ex) {
                    mOfs = null;
                    ex.printStackTrace();
                }
            } 
            else {
                System.out.print(logStr);
            }
        }
    }
    
    
    /**
     * Print debug log.
     * Here the log level is <code>DEBUG</code>.
     */
    public void debug(String str) {
        write(DEBUG ,str);
    }
    
    /**
     * Print info log.
     */
    public void info(String str) {
        write(INFO ,str);
    }
    
    /**
     * Print warning log.
     */
    public void warn(String str) {
        write(WARN ,str);
    }
    
    /**
     * Print info log.
     */
    public void error(String str) {
        write(ERROR ,str);
    }
    
    /**
     * Print debug log.
     * Here the log level is <code>DEBUG</code>.
     */
    public void debug(Throwable th) {
        write(DEBUG ,IoUtils.getStackTrace(th));
    }
    
    /**
     * Print info log.
     */
    public void info(Throwable th) {
        write(INFO ,IoUtils.getStackTrace(th));
    }
    
    /**
     * Print warning log.
     */
    public void warn(Throwable th) {
        write(WARN ,IoUtils.getStackTrace(th));
    }
    
    /**
     * Print info log.
     */
    public void error(Throwable th) {
        write(ERROR ,IoUtils.getStackTrace(th));
    }
    
    /**
     * Log exception
     */
    public synchronized void write(int level, Throwable th) {
        write(level, IoUtils.getStackTrace(th));
    }
    

    /**
     * Set the log file and open a new log file.
     * Returns the name of the saved log file.
     */
    private synchronized void save() {
        if (mLogFile == null) {
            return;
        }

        try {
            dispose();
            File sf = new File(mLogFile.getAbsolutePath() + '.' + LOG_FILE_DATE.format(new Date()));
            sf = IoUtils.getUniqueFile(sf);
            mLogFile.renameTo(sf);
            open();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }  
    

    /**
     * Calculate the log level
     */
    private static int calculateLogLevel(int level) {
        int logLevel = level;

        if (level > ERROR) {
            logLevel = ERROR;
        }    
        else if (level < DEBUG) {
            logLevel = DEBUG;
        } 
        return logLevel;
    }
    
    /**
     * Close the log file.
     */
    public synchronized void dispose() {
        if (mOfs != null){
            IoUtils.close(mOfs);
            mOfs = null;
        }
    }
    
}