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package org.scijava.ui.dnd;

import java.util.List;

import org.scijava.display.Display;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.Plugin;

/**
 * Drag-and-drop handler for lists of objects.
 * 
 * @author Curtis Rueden
 * @author Barry DeZonia
 */
@Plugin(type = DragAndDropHandler.class)
public class ListDragAndDropHandler extends AbstractDragAndDropHandler<List<?>>
{

	@Parameter(required = false)
	private DragAndDropService dragAndDropService;

	// -- DragAndDropHandler methods --

	@Override
	public boolean supports(final List<?> list, final Display<?> display) {
		if (dragAndDropService == null) return false;
		if (!super.supports(list, display)) return false;

		// empty lists are trivially compatible
		if (list.size() == 0) return true;

		// the list is deemed compatible if at least one item is compatible
		for (final Object item : list) {
			if (dragAndDropService.supports(item, display)) return true;
		}
		return false;
	}

	@Override
	public boolean drop(final List<?> list, final Display<?> display) {
		if (dragAndDropService == null) return false;
		check(list, display);
		if (list == null) return true; // trivial case

		// dropping an empty list trivially succeeds
		if (list.size() == 0) return true;

		// use the drag-and-drop service to handle each item separately
		boolean success = false;
		for (final Object item : list) {
			if (dragAndDropService.supports(item, display)) {
				final boolean result = dragAndDropService.drop(item, display);
				if (result) success = true;
			}
		}
		return success;
	}

	// -- Typed methods --

	@Override
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public Class<List<?>> getType() {
		return (Class) List.class;
	}

}
