package nabble.model;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Date;


public final class Batch {

	// use this logger from Runnable
	public static final Logger logger = LoggerFactory.getLogger(Batch.class);

	private static final Object lock = new Object();
	private static Batch currentBatch = null;

	public static Batch currentBatch() {
		synchronized(lock) {
			return currentBatch;
		}
	}

	public static final class AlreadyRunningException extends Exception {
		private AlreadyRunningException() {
			super( "already running batch " + currentBatch.name );
		}
	}

	private static final class StoppedException extends RuntimeException {}

	public final String name;
	private final Runnable task;
	private long startTime;
	private volatile boolean isStopped = false;

	private Batch( final String name, final Runnable task ) {
		this.name = name;
		this.task = new Runnable(){public void run(){
			try {
				logger.error( "batch " + name + " started" );
				startTime = System.currentTimeMillis();
				task.run();
				long after = System.currentTimeMillis();
				logger.error( "batch " + name + " done in " + (after - startTime) + " ms" );
			} catch(StoppedException e) {
				logger.error( "batch " + name + " was stopped" );
			} catch(RuntimeException e) {
				logger.error( "batch " + name + " failed", e );
			} finally {
				synchronized(lock) {
					currentBatch = null;
				}
			}
		}};
	}

	public static void run( final String name, final Runnable task )
		throws AlreadyRunningException
	{
		synchronized(lock) {
			if( currentBatch != null )
				throw new AlreadyRunningException();
			currentBatch = new Batch(name,task);
			Executors.executeNow(currentBatch.task);
		}
	}

	public static void checkStopped() {
		synchronized(lock) {
			if( currentBatch!=null && currentBatch.isStopped )
				throw new StoppedException();
		}
	}

	public void stop() {
		isStopped = true;
	}
	
	static void shutdown() {
		synchronized(lock) {
			if (currentBatch!=null) 
				currentBatch.stop();
		}
	}

	public String toString() {
		return "Batch - " + name + " started at " + new Date(startTime) + ", " +
				(System.currentTimeMillis() - startTime) + " ms ago";
	}
}