package zk.support.cht;

import org.zkoss.bind.BindUtils;
import org.zkoss.bind.annotation.Command;
import org.zkoss.bind.annotation.NotifyChange;
import org.zkoss.zk.ui.event.Event;
import org.zkoss.zk.ui.event.EventListener;
import org.zkoss.zk.ui.event.EventQueue;
import org.zkoss.zk.ui.event.EventQueues;
import org.zkoss.zk.ui.util.Clients;

public class LongOperationsViewModel {

	private String progress;
	
	@Command("startLongOperation")
	@NotifyChange("progress")
	public void onStartLongOperation() {
		progress = "started";
		startLongOperationSequence();
	}

	private void startLongOperationSequence() {
		final LongOperation processOperation = new BusyLongOperation("processQueue", "processing in backend") {
			@Override
			protected void execute() {
				try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
			
			protected void onFinish() {
				super.onFinish();
				progress += " ,processing done";
				BindUtils.postNotifyChange(null, null, LongOperationsViewModel.this, "progress");
			};
		};
		
		LongOperation loadOperation = new BusyLongOperation("loadQueue", "loading from DB") {
			@Override
			protected void execute() {
				try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
			
			@Override
			protected void onFinish() {
				super.onFinish();
				progress += " ,loading done";
				BindUtils.postNotifyChange(null, null, LongOperationsViewModel.this, "progress");

				processOperation.start();
			}
		};

		
		loadOperation.start();
	}

	public String getProgress() {
		return progress;
	}
	
	
	
	public static abstract class BusyLongOperation extends LongOperation {
		private String busyMessage;

		public BusyLongOperation(String queueName, String busyMessage) {
			super(queueName);
			this.busyMessage = busyMessage;
		}
		
		@Override
		protected void onStart() {
			Clients.showBusy(busyMessage);
		}
		
		@Override
		protected void onFinish() {
			Clients.clearBusy();
		}
		
	}

	
	
	public static abstract class LongOperation {
		private String queueName;
		
		public LongOperation(String queueName) {
			super();
			this.queueName = queueName;
		}
		
		abstract protected void onStart();
		abstract protected void execute();
		abstract protected void onFinish();
		
		public void start() {
			if (EventQueues.exists(queueName)) {
				Clients.showNotification("Queue with name '" + queueName + "' is already running. Try later.");
				return;
			}
			
			final EventQueue<Event> eventQueue = EventQueues.lookup(queueName, true);
			
			final EventListener<Event> executionListener = new EventListener<Event>() {
				@Override
				public void onEvent(Event event) throws Exception {
					execute();
				}
				
			};
			
			final EventListener<Event> callbackListener = new EventListener<Event>() {
				@Override
				public void onEvent(Event event) throws Exception {
					eventQueue.unsubscribe(executionListener); //problem here
					EventQueues.remove(queueName); //or problem here
					onFinish();
				}
			};
			
			onStart();
			eventQueue.subscribe(executionListener, callbackListener);
			eventQueue.publish(new Event("launch dummy"));
		}
	}
}