envoy/client/src/main/java/envoy/client/ui/SceneContext.java

package envoy.client.ui;

import java.io.IOException;
import java.util.Stack;
import java.util.logging.Level;

import javafx.application.Platform;
import javafx.fxml.FXMLLoader;
import javafx.scene.*;
import javafx.scene.input.*;
import javafx.stage.Stage;

import envoy.client.data.Settings;
import envoy.client.event.*;
import envoy.util.EnvoyLog;

import dev.kske.eventbus.*;

/**
 * Manages a stack of scenes. The most recently added scene is displayed inside
 * a stage. When a scene is removed from the stack, its predecessor is
 * displayed.
 * <p>
 * When a scene is loaded, the style sheet for the current theme is applied to
 * it.
 * <p>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>SceneContext.java</strong><br>
 * Created: <strong>06.06.2020</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Client v0.1-beta
 */
public final class SceneContext implements EventListener {

	/**
	 * Contains information about different scenes and their FXML resource files.
	 *
	 * @author Kai S. K. Engelbart
	 * @since Envoy Client v0.1-beta
	 */
	public enum SceneInfo {

		/**
		 * The main scene in which the chat screen is displayed.
		 *
		 * @since Envoy Client v0.1-beta
		 */
		CHAT_SCENE("/fxml/ChatScene.fxml"),

		/**
		 * The scene in which the settings screen is displayed.
		 *
		 * @since Envoy Client v0.1-beta
		 */
		SETTINGS_SCENE("/fxml/SettingsScene.fxml"),

		/**
		 * The scene in which the login screen is displayed.
		 *
		 * @since Envoy Client v0.1-beta
		 */
		LOGIN_SCENE("/fxml/LoginScene.fxml");

		/**
		 * The path to the FXML resource.
		 */
		public final String path;

		SceneInfo(String path) { this.path = path; }
	}

	private final Stage			stage;
	private final FXMLLoader	loader			= new FXMLLoader();
	private final Stack<Scene>	sceneStack		= new Stack<>();
	private final Stack<Object>	controllerStack	= new Stack<>();

	private static final Settings settings = Settings.getInstance();

	/**
	 * Initializes the scene context.
	 *
	 * @param stage the stage in which scenes will be displayed
	 * @since Envoy Client v0.1-beta
	 */
	public SceneContext(Stage stage) {
		this.stage = stage;
		EventBus.getInstance().registerListener(this);
	}

	/**
	 * Loads a new scene specified by a scene info.
	 *
	 * @param sceneInfo specifies the scene to load
	 * @throws RuntimeException if the loading process fails
	 * @since Envoy Client v0.1-beta
	 */
	public void load(SceneInfo sceneInfo) {
		loader.setRoot(null);
		loader.setController(null);

		try {
			final var	rootNode	= (Parent) loader.load(getClass().getResourceAsStream(sceneInfo.path));
			final var	scene		= new Scene(rootNode);
			controllerStack.push(loader.getController());

			sceneStack.push(scene);
			stage.setScene(scene);

			// Adding the option to exit Linux-like with "Control" + "Q"
			scene.getAccelerators()
				.put(new KeyCodeCombination(KeyCode.Q, KeyCombination.CONTROL_DOWN),
						() -> {
							// Presumably no Settings are loaded in the login scene, hence Envoy is closed
							// directly
							if (sceneInfo != SceneInfo.LOGIN_SCENE && settings.isHideOnClose()) stage.setIconified(true);
							else {
								EventBus.getInstance().dispatch(new EnvoyCloseEvent());
								System.exit(0);
							}
						});

			// The LoginScene is the only scene not intended to be resized
			// As strange as it seems, this is needed as otherwise the LoginScene won't be
			// displayed on some OS (...Debian...)
			stage.sizeToScene();
			Platform.runLater(() -> stage.setResizable(sceneInfo != SceneInfo.LOGIN_SCENE));
			applyCSS();
			stage.show();
		} catch (final IOException e) {
			EnvoyLog.getLogger(SceneContext.class).log(Level.SEVERE, String.format("Could not load scene for %s: ", sceneInfo), e);
			throw new RuntimeException(e);
		}
	}

	/**
	 * Removes the current scene and displays the previous one.
	 *
	 * @since Envoy Client v0.1-beta
	 */
	public void pop() {

		// Pop scene and controller
		sceneStack.pop();
		controllerStack.pop();

		// Apply new scene if present
		if (!sceneStack.isEmpty()) {
			final var newScene = sceneStack.peek();
			stage.setScene(newScene);
			applyCSS();
			stage.sizeToScene();
			// If the controller implements the Restorable interface,
			// the actions to perform on restoration will be executed here
			final var controller = controllerStack.peek();
			if (controller instanceof Restorable) ((Restorable) controller).onRestore();
		}
		stage.show();
	}

	private void applyCSS() {
		if (!sceneStack.isEmpty()) {
			final var	styleSheets	= stage.getScene().getStylesheets();
			final var	themeCSS	= "/css/" + settings.getCurrentTheme() + ".css";
			styleSheets.clear();
			styleSheets.addAll(getClass().getResource("/css/base.css").toExternalForm(), getClass().getResource(themeCSS).toExternalForm());
		}
	}

	@Event(priority = 150, eventType = ThemeChangeEvent.class)
	private void onThemeChange() { applyCSS(); }

	/**
	 * @param <T> the type of the controller
	 * @return the controller used by the current scene
	 * @since Envoy Client v0.1-beta
	 */
	public <T> T getController() { return (T) controllerStack.peek(); }

	/**
	 * @return the stage in which the scenes are displayed
	 * @since Envoy Client v0.1-beta
	 */
	public Stage getStage() { return stage; }

	/**
	 * @return whether the scene stack is empty
	 * @since Envoy Client v0.2-beta
	 */
	public boolean isEmpty() { return sceneStack.isEmpty(); }
}