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package org.scijava.menu;

/**
 * Abstract helper class for generating a menu structure.
 * <p>
 * The class differentiates between top-level menu components (such as
 * {@link javax.swing.JMenuBar}), and hierarchical menu components (such as
 * {@link javax.swing.JMenu}).
 * </p>
 * 
 * @author Curtis Rueden
 * @param <T> Top-level menu class to populate (e.g.,
 *          {@link javax.swing.JMenuBar} or {@link javax.swing.JMenu} or
 *          {@link java.awt.MenuBar})
 * @param <M> Hierarchical menu class (e.g., {@link javax.swing.JMenu} or
 *          {@link java.awt.Menu})
 */
public abstract class AbstractMenuCreator<T, M> implements MenuCreator<T> {

	// -- MenuCreator methods --

	@Override
	public void createMenus(final ShadowMenu root, final T target) {
		double lastWeight = Double.NaN;
		for (final ShadowMenu child : root.getChildren()) {
			final double weight = child.getMenuEntry().getWeight();
			final double difference = Math.abs(weight - lastWeight);
			if (difference > 1) addSeparatorToTop(target);
			lastWeight = weight;
			if (child.isLeaf()) {
				addLeafToTop(child, target);
			}
			else {
				final M nonLeaf = addNonLeafToTop(child, target);
				populateMenu(child, nonLeaf);
			}
		}
	}

	// -- Internal methods --

	protected abstract void addLeafToMenu(ShadowMenu shadow, M target);

	protected abstract void addLeafToTop(ShadowMenu shadow, T target);

	protected abstract M addNonLeafToMenu(ShadowMenu shadow, M target);

	protected abstract M addNonLeafToTop(ShadowMenu shadow, T target);

	protected abstract void addSeparatorToMenu(M target);

	protected abstract void addSeparatorToTop(T target);

	// -- Helper methods --

	private void populateMenu(final ShadowMenu shadow, final M target) {
		double lastWeight = Double.NaN;
		for (final ShadowMenu child : shadow.getChildren()) {
			final double weight = child.getMenuEntry().getWeight();
			final double difference = Math.abs(weight - lastWeight);
			if (difference > 1) addSeparatorToMenu(target);
			lastWeight = weight;
			if (child.isLeaf()) {
				addLeafToMenu(child, target);
			}
			else {
				final M nonLeaf = addNonLeafToMenu(child, target);
				populateMenu(child, nonLeaf);
			}
		}
	}

}
