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

package envoy.client.ui;

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

import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import envoy.client.data.Settings;
import envoy.client.event.ThemeChangeEvent;
import envoy.event.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 {

	public static enum SceneInfo {

		CHAT_SCENE("/fxml/ChatScene.fxml"), SETTINGS_SCENE("/fxml/SettingsScene.fxml"), CONTACT_SEARCH_SCENE("/fxml/ContactSearchScene.fxml");

		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 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().register(ThemeChangeEvent.class, theme -> applyCSS());
	}

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

		final var	rootNode	= (Parent) loader.load(getClass().getResourceAsStream(sceneInfo.path));
		final var	scene		= new Scene(rootNode);

		sceneStack.push(scene);
		stage.setScene(scene);
		applyCSS();
		stage.show();
	}

	/**
	 * Removes the current scene and displays the previous one.
	 * 
	 * @since Envoy Client v0.1-beta
	 */
	public void pop() {
		sceneStack.pop();
		if (!sceneStack.isEmpty()) {
			stage.setScene(sceneStack.peek());
			applyCSS();
		}
		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());
		}
	}

	/**
	 * @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 loader.getController(); }
}