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package org.scijava.ui.dnd;

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

/**
 * Interface for drag-and-drop handlers. A drag-and-drop handler defines
 * behavior for drag-and-drop operations with respect to a specific sort of
 * objects.
 * <p>
 * Drag-and-drop handlers discoverable at runtime must implement this interface
 * and be annotated with @{@link Plugin} with attribute {@link Plugin#type()} =
 * {@link DragAndDropHandler}.class. While it possible to create a drag-and-drop
 * handler merely by implementing this interface, it is encouraged to instead
 * extend {@link AbstractDragAndDropHandler}, for convenience.
 * </p>
 * 
 * @author Curtis Rueden
 * @see Plugin
 * @see DragAndDropService
 */
public interface DragAndDropHandler<D> extends HandlerPlugin<D> {

	/**
	 * Gets whether this handler supports dropping the given data object onto the
	 * specified display.
	 */
	boolean supports(final D dataObject, final Display<?> display);

	/**
	 * Gets whether this handler supports dropping the given
	 * {@link DragAndDropData} onto a compatible display.
	 */
	boolean supportsData(final DragAndDropData data);

	/**
	 * Gets whether this handler supports dropping the given
	 * {@link DragAndDropData} onto the specified display.
	 */
	boolean supportsData(final DragAndDropData data, final Display<?> display);

	/**
	 * Gets whether this handler supports dropping the given object onto a
	 * compatible display.
	 */
	boolean supportsObject(final Object object);

	/**
	 * Gets whether this handler supports dropping the given object onto the
	 * specified display.
	 */
	boolean supportsObject(final Object object, final Display<?> display);

	/**
	 * Gets whether this handler supports dropping an assumed-to-be-compatible
	 * data object onto the given {@link Display}.
	 */
	boolean supportsDisplay(final Display<?> display);

	/**
	 * Converts the given {@link DragAndDropData} to the type of data object
	 * supported by this handler.
	 * 
	 * @throws IllegalArgumentException if the handler does not support the given
	 *           {@link DragAndDropData}.
	 */
	D convertData(final DragAndDropData data);

	/**
	 * Converts the given object to the type of data object supported by this
	 * handler.
	 * 
	 * @throws IllegalArgumentException if the handler does not support the given
	 *           object.
	 */
	D convertObject(final Object object);

	/**
	 * Performs a drop operation with the given data object in the specified
	 * {@link Display}.
	 * 
	 * @throws IllegalArgumentException if the handler is not compatible with the
	 *           given data/display combination.
	 */
	boolean drop(final D dataObject, final Display<?> display);

	/**
	 * Performs a drop operation with the given data in the specified
	 * {@link Display}.
	 * 
	 * @throws IllegalArgumentException if the handler is not compatible with the
	 *           given data/display combination.
	 */
	boolean dropData(final DragAndDropData data, final Display<?> display);

	/**
	 * Performs a drop operation with the given data in the specified
	 * {@link Display}.
	 * 
	 * @throws IllegalArgumentException if the handler is not compatible with the
	 *           given data/display combination.
	 */
	boolean dropObject(final Object object, final Display<?> display);

	// NB: Javadoc overrides.

	// -- Typed methods --

	/**
	 * Gets whether this handler supports dropping the given data object onto a
	 * compatible display.
	 */
	@Override
	default boolean supports(final D dataObject) {
		return true;
	}

}
