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package org.scijava.ui.dnd;

import org.scijava.app.StatusService;
import org.scijava.event.EventHandler;
import org.scijava.plugin.AbstractHandlerService;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.Plugin;
import org.scijava.service.Service;
import org.scijava.ui.dnd.event.DragEnterEvent;
import org.scijava.ui.dnd.event.DragExitEvent;
import org.scijava.ui.dnd.event.DragOverEvent;
import org.scijava.ui.dnd.event.DropEvent;

/**
 * Default service for handling drag and drop events.
 * 
 * @author Curtis Rueden
 */
@Plugin(type = Service.class)
public class DefaultDragAndDropService extends
	AbstractHandlerService<Object, DragAndDropHandler<Object>> implements
	DragAndDropService
{

	private static final String SUPPORTED = "Drag and Drop";
	private static final String UNSUPPORTED = "Unsupported Object";

	@Parameter
	private StatusService statusService;

	// -- Event handlers --

	@EventHandler
	protected void onEvent(final DragEnterEvent e) {
		// determine whether the given drop operation is supported
		final boolean compatible = supports(e.getData(), e.getDisplay());

		// update the status accordingly
		final String message = compatible ? SUPPORTED : UNSUPPORTED;
		statusService.showStatus("< <" + message + "> >");

		// accept the drag if the operation is supported
		if (compatible) e.setAccepted(true);
	}

	@EventHandler
	protected void onEvent(@SuppressWarnings("unused") final DragExitEvent e) {
		statusService.clearStatus();
	}

	@EventHandler
	protected void onEvent(@SuppressWarnings("unused") final DragOverEvent e) {
		// NB: No action needed.
	}

	@EventHandler
	protected void onEvent(final DropEvent e) {
		if (!supports(e.getData(), e.getDisplay())) return;

		// perform the drop
		final boolean success = drop(e.getData(), e.getDisplay());
		e.setSuccessful(success);
	}

}
