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package prerna.cluster.util;

import java.io.File;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import prerna.util.Constants;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;

public class LocalFileWatcher implements Runnable
{
	WatchService ws = null;
	DBSynchronizer dbs = null;
	String db = null;
	String fileExtensions = "py;python;r;js;css;mosfet;json;"; // thse are the only file extensions to track
	private static final Logger classLogger = LogManager.getLogger(LocalFileWatcher.class);

	
	public LocalFileWatcher(DBSynchronizer dbs, String db)
	{
		this.dbs = dbs;
		this.db = db;
		makeWatcherService();
	}

	// main class for watching local file changes
	// an updating the zookeeper
	public void watchPath(String path)
	{
		try {
			System.out.println("Watching path " + path);
			Path thisPath = Paths.get(path);
			thisPath.register(ws, StandardWatchEventKinds.ENTRY_CREATE,
			        StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			classLogger.error(Constants.STACKTRACE, e);
		}
	}
	
	// main class for watching local file changes
	// an updating the zookeeper
	public void watchFilePath(String path)
	{
		try {
			System.out.println("Watching path " + path);
			Path thisPath = Paths.get(path);
			thisPath.register(ws, 
			        StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			classLogger.error(Constants.STACKTRACE, e);
		}
	}

	
	private void makeWatcherService()
	{
		if(ws == null)
		{
			try
			{
				ws = FileSystems.getDefault().newWatchService();
			}catch(Exception ex)
			{
				System.err.println("Unable to create a watcher service " + ex);
			}
		}
	}
	
	public void run()
	{
		// loop and watch
		try {
			WatchKey key;
			while ((key = ws.take()) != null) {
			    for (WatchEvent event : key.pollEvents()) {
			        System.out.println(
			          "Event kind:" + event.kind() 
			            + ". File affected: " + event.context() + ".");

			        Path parent = (Path)key.watchable();

			        // control here for specific file types
					// .mosfet
					// .py
					// .r etc. 
			        String fileName = event.context() + "";
			        String extn = fileName.substring(fileName.lastIndexOf(".") + 1);
			        
			        
			        if(event.kind() == StandardWatchEventKinds.ENTRY_MODIFY && fileExtensions.indexOf(extn) >= 0) // do it only if it is a valid file extension
			        	dbs.modifyNode(db, parent + "/" + event.context());
			        
			        else if(event.kind() == StandardWatchEventKinds.ENTRY_CREATE)
			        {
				        // need to see if the create is a new folder and then register
			        	File file = new File(parent + "/" + event.context());
			        	if(file.isDirectory())
			        		watchFilePath(parent + "/" + event.context());
			        	else if(fileExtensions.indexOf(extn) >= 0)
			        		dbs.createNode(db, parent + "/" + event.context());
			        }
			        else if(event.kind() == StandardWatchEventKinds.ENTRY_DELETE && fileExtensions.indexOf(extn) >= 0)
			        	dbs.deleteNode(db, parent + "/" + event.context());
			        
			    }
			    key.reset();
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			classLogger.error(Constants.STACKTRACE, e);
		}
	}
	
}