java-recipe-manager/src/main/lombok/org/leumasjaffe/recipe/view/AutoGrowPanel.java

package org.leumasjaffe.recipe.view;

import java.awt.Component;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;

import javax.swing.JPanel;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

import org.jdesktop.swingx.VerticalLayout;

import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import lombok.experimental.Delegate;
import lombok.experimental.FieldDefaults;
import lombok.experimental.NonFinal;

@FieldDefaults(level=AccessLevel.PRIVATE, makeFinal=true)
public class AutoGrowPanel<C extends Component & AutoGrowPanel.ChildComponent, T> extends JPanel {
	/**
	 * 
	 */
	private static final long serialVersionUID = 3815045801030954255L;

	private static interface SetGap { void setGap(int gap); }

	public static interface ChildComponent {
		void addGrowShrinkListener(DocumentListener dl);
		void removeGrowShrinkListener(DocumentListener dl);
		default void setListPosition(int zeroIndex) {}
	}
	
	@RequiredArgsConstructor
	@FieldDefaults(level=AccessLevel.PRIVATE, makeFinal=true)
	private class GrowOnData implements DocumentListener {
		Supplier<T> makeEmptyModel;
		Function<T, C> makeComponent;
		@NonFinal T model = null;
		
		@Override public void changedUpdate(DocumentEvent e) {}
		@Override public void removeUpdate(DocumentEvent e) {}

		@Override
		public void insertUpdate(DocumentEvent e) {
			if (model != null) {
				models.add(model);
				last().removeGrowShrinkListener(this);
				last().addGrowShrinkListener(new ShrinkOnEmpty(last()));
			}
			
			model = makeEmptyModel.get();
			final C comp = makeComponent.apply(model);

			members.add(comp);
			add(comp);
			comp.addGrowShrinkListener(this);
			comp.setListPosition(lastIndex());
			callback.accept(true);
		}		
	}
	
	@AllArgsConstructor
	private class ShrinkOnEmpty implements DocumentListener {
		ChildComponent component;
		
		@Override public void insertUpdate(DocumentEvent e) {}
		@Override public void changedUpdate(DocumentEvent e) {}

		@Override
		public void removeUpdate(DocumentEvent e) {
			if (e.getDocument().getLength() > 0) {
				return;
			}
			
			component.removeGrowShrinkListener(this);
			remove(members.indexOf(component));
			callback.accept(false);
		}
	}
	
	@Delegate(types={SetGap.class})
	VerticalLayout layout = new VerticalLayout();
	List<ChildComponent> members = new ArrayList<>();
	GrowOnData grow;
	
	@NonFinal List<T> models = null;
	@NonFinal Consumer<Boolean> callback = (b) -> {};
	
	/**
	 * 
	 * @param makeEmptyModel A function to produce a blank model object for display.
	 * If the model is updated in such a way as to be non-empty, it will be inserted
	 * into the list of models.
	 * @param makeComponent A function to generate a UI object given a model. The
	 * object must meet the ChildComponent interface to install the AutoGrowPanel's
	 * growing/shrinking listener objects.
	 */
	public AutoGrowPanel(final @NonNull Supplier<T> makeEmptyModel,
			final @NonNull Function<T, C> makeComponent) {
		setLayout(layout);
		this.grow = new GrowOnData(makeEmptyModel, makeComponent);
		this.grow.insertUpdate(null);
	}
	
	/**
	 * Activate this component against the target list of children
	 * @param models A mutable list object containing the "child models" to be
	 * rendered in this component
	 */
	public void setModel(final @NonNull List<T> models) {
		setModel(models, (b) -> {});
	}
	
	/**
	 * 
	 * @param models A mutable list object containing the "child models" to be
	 * rendered in this component
	 * @param callback A callback that will be invoked each time a child is
	 * added or removed. This allows us to provide some custom interactions
	 * with the parent's context in case other actions need to occur.
	 */
	public void setModel(final @NonNull List<T> models,
			final Consumer<Boolean> callback) {
		this.models = models;
		this.callback = callback;
		
		this.members.subList(0, lastIndex()).clear();
		models.forEach(model -> {
			final C comp = this.grow.makeComponent.apply(model);
			comp.addGrowShrinkListener(new ShrinkOnEmpty(comp));
			add(comp, lastIndex());
			comp.setListPosition(lastIndex());
			this.members.add(lastIndex(), comp);
		});
		
		last().setListPosition(lastIndex());
	}
	
	@Override
	public void remove(final int index) {
		super.remove(index);
		members.remove(index);
		for (int size = lastIndex(); size >= index; --size) {
			members.get(index).setListPosition(index);
		}
		models.remove(index);
	}
	
	private int lastIndex() { return members.size() - 1; }
	
	private ChildComponent last() {
		return members.get(lastIndex());
	}
}