package window;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import javax.swing.JOptionPane;

public class SingleInstanceLock {
    private static final String LOCK_FILE = System.getProperty("user.home") + 
                                           File.separator + ".myapp.lock";
    private static FileLock lock;
    private static FileChannel channel;
    
    /**
     * ³¢ÊÔ»ñÈ¡Ó¦ÓóÌÐòËø
     * @return true-³É¹¦»ñÈ¡Ëø£¨µÚÒ»´ÎÔËÐУ©, false-»ñȡʧ°Ü£¨ÒÑÓÐʵÀýÔËÐУ©
     */
    @SuppressWarnings("resource")
	public static boolean lock() {
        try {
            // ´´½¨Îļþ¶ÔÏó
            File file = new File(LOCK_FILE);
            
            // Èç¹ûÎļþ´æÔÚµ«ÎÞ·¨É¾³ý£¬¿ÉÄÜÊÇÆäËûʵÀýÕýÔÚÔËÐÐ
            if (file.exists() && !file.delete()) {
                return false;
            }
            
            // ´´½¨Îļþ²¢»ñȡͨµÀ
            RandomAccessFile raf = new RandomAccessFile(file, "rw");
            channel = raf.getChannel();
            
            // ³¢ÊÔ»ñÈ¡¶ÀÕ¼Ëø
            lock = channel.tryLock();
            
            // Èç¹û»ñÈ¡µ½Ëø£¬·µ»Øtrue
            return lock != null;
        } catch (IOException e) {
            // ·¢ÉúÒ쳣˵Ã÷¿ÉÄÜÒÑÓÐʵÀýÔËÐÐ
            return false;
        }
    }
    
    /**
     * ÊÍ·ÅÓ¦ÓóÌÐòËø
     */
    public static void release() {
        try {
            // ÊÍ·ÅËø
            if (lock != null && lock.isValid()) {
                lock.release();
            }
            // ¹Ø±ÕͨµÀ
            if (channel != null && channel.isOpen()) {
                channel.close();
            }
            // ɾ³ýËøÎļþ
            File file = new File(LOCK_FILE);
            if (file.exists()) {
                file.delete();
            }
        } catch (IOException e) {
            // ÊÍ·ÅËøʱºöÂÔÒì³£
        }
    }
    
    /**
     * ¼ì²é³ÌÐòÊÇ·ñÒÑÔÚÔËÐв¢ÏÔʾ¾¯¸æ
     */
    public static void showAlreadyRunningWarning() {
        JOptionPane.showMessageDialog(null,
            "³ÌÐòÒѾ­´ò¿ª£¬ÇëÎðÖظ´´ò¿ª",
            "¾¯¸æ",
            JOptionPane.WARNING_MESSAGE);
    }
}