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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by both ImageJ and SCIFIO.

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/*
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 * SciJava Common shared library for SciJava software.
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 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
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 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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package org.scijava.ui.dnd;

import org.scijava.display.Display;
import org.scijava.plugin.AbstractHandlerPlugin;

/**
 * Abstract superclass for {@link DragAndDropHandler}s.
 * 
 * @author Curtis Rueden
 */
public abstract class AbstractDragAndDropHandler extends
	AbstractHandlerPlugin implements DragAndDropHandler
{

	// -- DragAndDropHandler methods --

	@Override
	public boolean supports(final D dataObject, final Display display) {
		return supportsDisplay(display) && supports(dataObject);
	}

	@Override
	public boolean supportsData(final DragAndDropData data) {
		return data.isSupported(getType()) && supports(convertDataUnchecked(data));
	}

	@Override
	public boolean supportsData(final DragAndDropData data,
		final Display display)
	{
		return supportsDisplay(display) && supportsData(data);
	}

	@Override
	public boolean supportsObject(final Object object) {
		return object != null && getType().isAssignableFrom(object.getClass()) &&
			supports(convertObjectUnchecked(object));
	}

	@Override
	public boolean supportsObject(final Object object, final Display display) {
		return supportsDisplay(display) && supportsObject(object);
	}

	@Override
	public boolean supportsDisplay(final Display display) {
		return true;
	}

	@Override
	public D convertData(final DragAndDropData data) {
		if (!supportsData(data)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		return convertDataUnchecked(data);
	}

	@Override
	public D convertObject(final Object object) {
		if (!supportsObject(object)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		return convertObjectUnchecked(object);
	}

	@Override
	public boolean dropData(final DragAndDropData data, final Display display)
	{
		return drop(convertData(data), display);
	}

	@Override
	public boolean dropObject(final Object object, final Display display) {
		return drop(convertObject(object), display);
	}

	// -- Internal methods --

	/**
	 * Throws {@link IllegalArgumentException} if (data, display) pair is
	 * incompatible.
	 */
	protected void check(final D dataObject, final Display display) {
		// NB: First check compatibility of data and display individually.
		if (!supports(dataObject)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		if (!supportsDisplay(display)) {
			throw new IllegalArgumentException("Incompatible display");
		}
		// NB: The data and display are individually compatible,
		// but are they compatible with one another?
		if (!supports(dataObject, display)) {
			throw new IllegalArgumentException(
				"Data object and display are incompatible");
		}
	}

	/**
	 * Converts the given data to this handler's native data type, without
	 * verifying compatibility first.
	 */
	protected D convertDataUnchecked(final DragAndDropData data) {
		return data.getData(getType());
	}

	/**
	 * Converts the given object to this handler's native data type, without
	 * verifying compatibility first.
	 */
	protected D convertObjectUnchecked(final Object object) {
		@SuppressWarnings("unchecked")
		final D dataObject = (D) object;
		return dataObject;
	}

}