envoy/src/main/java/envoy/client/ui/list/ComponentList.java

package envoy.client.ui.list;

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.HashSet;
import java.util.Set;

import javax.swing.*;

/**
 * Provides a vertical list layout of components provided in a
 * {@link Model}. Similar to {@link javax.swing.JList} but capable
 * of rendering {@link JPanel}s.<br>
 * <br>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>ComponentList.java</strong><br>
 * Created: <strong>25.01.2020</strong><br>
 *
 * @param <E> the type of object displayed in this list
 * @author Kai S. K. Engelbart
 * @since Envoy Client v0.3-alpha
 */
public class ComponentList<E> extends JPanel {

	private Model<E>			model;
	private Renderer<E>			renderer;
	private SelectionHandler<E>	selectionHandler;
	private SelectionMode		selectionMode	= SelectionMode.NONE;
	private Set<Integer>		selection		= new HashSet<>();

	private static final long serialVersionUID = 0L;

	/**
	 * Defines the possible modes of selection that can be performed by the user
	 *
	 * @since Envoy Client v0.1-beta
	 */
	public static enum SelectionMode {
		/**
		 * Selection is completely ignored.
		 */
		NONE,

		/**
		 * Only a single element can be selected.
		 */
		SINGLE,

		/**
		 * Multiple elements can be selected regardless of their position.
		 */
		MULTIPLE
	}

	/**
	 * Creates an instance of {@link ComponentList}.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public ComponentList() { setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); }

	/**
	 * Removes all child components and then adds all components representing the
	 * elements of the {@link Model}.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public void synchronizeModel() {
		if (model != null) {
			removeAll();
			model.forEach(this::addElement);
			revalidate();
		}
	}

	/**
	 * Selects a list element by index. If the element is already selected, it is
	 * removed from the selection.
	 *
	 * @param index the index of the selected component
	 * @since Envoy Client v0.1-beta
	 */
	public void selectElement(int index) {
		final JComponent element = getComponent(index);
		if (selection.contains(index)) {

			// Deselect if clicked again
			if (selectionHandler != null) selectionHandler.selectionChanged(model.get(index), element, true);
			selection.remove(index);

		} else {

			// Remove old selection if single selection is enabled
			if (selectionMode == SelectionMode.SINGLE) clearSelection();

			// Select item
			if (selectionMode != SelectionMode.NONE) {

				// Assign new selection
				selection.add(index);

				// Update element
				if (selectionHandler != null) selectionHandler.selectionChanged(model.get(index), element, true);
			}
		}

		revalidate();
		repaint();
	}

	/**
	 * Removes the current selection.
	 *
	 * @since Envoy Client v0.1-alpha
	 */
	public void clearSelection() {
		if (selectionHandler != null) selection.forEach(i -> selectionHandler.selectionChanged(model.get(i), getComponent(i), false));
		selection.clear();
	}

	/**
	 * Adds an object to the list by rendering it with the current
	 * {@link Renderer}.
	 *
	 * @param elem the element to add
	 * @since Envoy Client v0.3-alpha
	 */
	void addElement(E elem) {
		if (renderer != null) {
			final JComponent component = renderer.getListCellComponent(this, elem);
			component.addMouseListener(getSelectionListener(getComponentCount()));
			add(component, getComponentCount());
		}
	}

	/**
	 * @param componentIndex the index of the list component to which the mouse
	 *                       listener will be added
	 * @return a mouse listener calling the
	 *         {@link ComponentList#selectElement(int)} method with the
	 *         component's index when a left click is performed by the user
	 * @since Envoy Client v0.1-beta
	 */
	private MouseListener getSelectionListener(int componentIndex) {
		return new MouseAdapter() {

			@Override
			public void mouseClicked(MouseEvent e) { if (SwingUtilities.isLeftMouseButton(e)) selectElement(componentIndex); }
		};
	}

	@Override
	public JComponent getComponent(int n) { return (JComponent) super.getComponent(n); }

	/**
	 * @return a set of all selected indices
	 * @since Envoy Client v0.1-beta
	 */
	public Set<Integer> getSelection() { return selection; }

	/**
	 * @return a set of all selected elements
	 * @since Envoy Client v0.1-beta
	 */
	public Set<E> getSelectedElements() {
		var selectedElements = new HashSet<E>();
		selection.forEach(i -> selectedElements.add(model.get(i)));
		return selectedElements;
	}

	/**
	 * @return the index of an arbitrary selected element
	 * @throws java.util.NoSuchElementException if no selection is present
	 * @since Envoy Client v0.1-beta
	 */
	public int getSingleSelection() { return selection.stream().findAny().get(); }

	/**
	 * @return an arbitrary selected element
	 * @throws java.util.NoSuchElementException if no selection is present
	 * @since Envoy Client v0.1-beta
	 */
	public E getSingleSelectedElement() { return model.get(getSingleSelection()); }

	/**
	 * @return the model
	 * @since Envoy Client v0.1-beta
	 */
	public Model<E> getModel() { return model; }

	/**
	 * Sets the list model providing the list elements to render. The rendered
	 * components will be synchronized with the contents of the new model or removed
	 * if the new model is {@code null}.
	 *
	 * @param model the list model to set
	 * @return this component list
	 * @since Envoy Client v0.3-alpha
	 */
	public ComponentList<E> setModel(Model<E> model) {

		// Remove old model
		if (this.model != null) this.model.setComponentList(null);

		// Synchronize with new model
		this.model = model;
		if (model != null) model.setComponentList(this);
		synchronizeModel();

		return this;
	}

	/**
	 * @return the renderer
	 * @since Envoy Client v0.1-beta
	 */
	public Renderer<E> getRenderer() { return renderer; }

	/**
	 * @param renderer the renderer to set
	 * @return this component list
	 * @since Envoy Client v0.1-beta
	 */
	public ComponentList<E> setRenderer(Renderer<E> renderer) {
		this.renderer = renderer;
		return this;
	}

	/**
	 * @return the selection mode
	 * @since Envoy Client v0.1-beta
	 */
	public SelectionMode getSelectionMode() { return selectionMode; }

	/**
	 * Sets a new selection mode. The current selection will be cleared during this
	 * action.
	 *
	 * @param selectionMode the selection mode to set
	 * @return this component list
	 * @since Envoy Client v0.1-beta
	 */
	public ComponentList<E> setSelectionMode(SelectionMode selectionMode) {
		this.selectionMode = selectionMode;
		clearSelection();
		return this;
	}

	/**
	 * @return the selection handler
	 * @since Envoy Client v0.1-beta
	 */
	public SelectionHandler<E> getSelectionHandler() { return selectionHandler; }

	/**
	 * @param selectionHandler the selection handler to set
	 * @since Envoy Client v0.1-beta
	 */
	public void setSelectionHandler(SelectionHandler<E> selectionHandler) { this.selectionHandler = selectionHandler; }
}