Autoconfigure TerminalUI

- Add TerminalUIBuilder which can be used to build TerminalUI
- Add TerminalUICustomizer which can customize TerminalUI
- What is autoconfigured is TerminalUIBuilder.
- In TerminalUI add configure for views which now allows
  easier way to set needed stuff in views.
- Various changes in a catalog app
- Fixes #900

spring-shell-core/src/main/java/org/springframework/shell/component/view/TerminalUI.java

@@ -47,6 +47,7 @@ import org.springframework.shell.component.view.event.MouseHandler;
 import org.springframework.shell.component.view.event.MouseHandler.MouseHandlerResult;
 import org.springframework.shell.component.view.screen.DefaultScreen;
 import org.springframework.shell.geom.Rectangle;
+import org.springframework.shell.style.ThemeResolver;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -73,6 +74,8 @@ public class TerminalUI implements ViewService {
 	private final KeyBinder keyBinder;
 	private DefaultEventLoop eventLoop = new DefaultEventLoop();
 	private View focus = null;
+	private ThemeResolver themeResolver;
+	private String themeName = "default";
 
 	/**
 	 * Constructs a handler with a given terminal.
@@ -135,6 +138,64 @@ public class TerminalUI implements ViewService {
 		getEventLoop().dispatch(ShellMessageBuilder.ofRedraw());
 	}
 
+	/**
+	 * Sets a {@link ThemeResolver}.
+	 *
+	 * @param themeResolver the theme resolver
+	 */
+	public void setThemeResolver(ThemeResolver themeResolver) {
+		this.themeResolver = themeResolver;
+	}
+
+	/**
+	 * Sets a {@link ThemeResolver}.
+	 *
+	 * @return a theme resolver
+	 */
+	public ThemeResolver getThemeResolver() {
+		return themeResolver;
+	}
+
+	/**
+	 * Sets a {@code theme name}.
+	 *
+	 * @param themeName the theme name
+	 */
+	public void setThemeName(String themeName) {
+		this.themeName = themeName;
+	}
+
+	/**
+	 * Gets a {@code theme name}.
+	 *
+	 * @return a theme name
+	 */
+	public String getThemeName() {
+		return themeName;
+	}
+
+	/**
+	 * Gets a {@link ViewService}.
+	 *
+	 * @return a view service
+	 */
+	public ViewService getViewService() {
+		return this;
+	}
+
+	/**
+	 * Configure view for {@link EventLoop}, {@link ThemeResolver},
+	 * {@code theme name} and {@link ViewService}.
+	 *
+	 * @param view the view to configure
+	 */
+	public void configure(View view) {
+		view.setEventLoop(eventLoop);
+		view.setThemeResolver(themeResolver);
+		view.setThemeName(themeName);
+		view.setViewService(getViewService());
+	}
+
 	public void setFocus(@Nullable View view) {
 		if (focus != null) {
 			focus.focus(focus, false);

spring-shell-core/src/main/java/org/springframework/shell/component/view/TerminalUIBuilder.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.component.view;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import org.jline.terminal.Terminal;
+
+import org.springframework.shell.style.ThemeResolver;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * Builder that can be used to configure and create a {@link TerminalUI}.
+ *
+ * @author Janne Valkealahti
+ */
+public class TerminalUIBuilder {
+
+	private final Terminal terminal;
+	private final Set<TerminalUICustomizer> customizers;
+	private final ThemeResolver themeResolver;
+	private final String themeName;
+
+	/**
+	 * Create a new {@link TerminalUIBuilder} instance.
+	 *
+	 * @param terminal the terminal
+	 * @param customizers any {@link TerminalUICustomizer TerminalUICustomizers}
+	 *                    that should be applied when the {@link TerminalUI} is
+	 *                    built
+	 */
+	public TerminalUIBuilder(Terminal terminal, TerminalUICustomizer... customizers) {
+		this.terminal = terminal;
+		this.customizers = copiedSetOf(customizers);
+		this.themeResolver = null;
+		this.themeName = null;
+	}
+
+	/**
+	 * Create a new {@link TerminalUIBuilder} instance.
+	 *
+	 * @param terminal the terminal
+	 * @param customizers any {@link TerminalUICustomizer TerminalUICustomizers}
+	 *                    that should be applied when the {@link TerminalUI} is
+	 *                    built
+	 * @param themeResolver the theme resolver
+	 * @param themeName the theme name
+	 */
+	public TerminalUIBuilder(Terminal terminal, Set<TerminalUICustomizer> customizers, ThemeResolver themeResolver,
+			String themeName) {
+		this.terminal = terminal;
+		this.customizers = customizers;
+		this.themeResolver = themeResolver;
+		this.themeName = themeName;
+	}
+
+	/**
+	 * Sets a {@link ThemeResolver} for {@link TerminalUI} to build.
+	 *
+	 * @param themeResolver the theme resolver
+	 * @return a new builder instance
+	 */
+	public TerminalUIBuilder themeResolver(ThemeResolver themeResolver) {
+		return new TerminalUIBuilder(terminal, customizers, themeResolver, themeName);
+	}
+
+	/**
+	 * Sets a {@code theme name} for {@link TerminalUI} to build.
+	 *
+	 * @param themeName the theme name
+	 * @return a new builder instance
+	 */
+	public TerminalUIBuilder themeName(String themeName) {
+		return new TerminalUIBuilder(terminal, customizers, themeResolver, themeName);
+	}
+
+	/**
+	 * Set the {@link TerminalUICustomizer TerminalUICustomizer} that should be
+	 * applied to the {@link TerminalUI}. Customizers are applied in the order that they
+	 * were added after builder configuration has been applied. Setting this value will
+	 * replace any previously configured customizers.
+	 *
+	 * @param customizers the customizers to set
+	 * @return a new builder instance
+	 */
+	public TerminalUIBuilder customizers(Collection<? extends TerminalUICustomizer> customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
+		return new TerminalUIBuilder(terminal, copiedSetOf(customizers), themeResolver, themeName);
+	}
+
+	/**
+	 * Build a new {@link TerminalUI} instance and configure it using this builder.
+	 *
+	 * @return a configured {@link TerminalUI} instance.
+	 */
+	public TerminalUI build() {
+		return configure(new TerminalUI(terminal));
+	}
+
+	/**
+	 * Configure the provided {@link TerminalUI} instance using this builder.
+	 *
+	 * @param <T> the type of terminal ui
+	 * @param terminalUI the {@link TerminalUI} to configure
+	 * @return the terminal ui instance
+	 */
+	public <T extends TerminalUI> T configure(T terminalUI) {
+		if (themeResolver != null) {
+			terminalUI.setThemeResolver(themeResolver);
+		}
+		if (StringUtils.hasText(themeName)) {
+			terminalUI.setThemeName(themeName);
+		}
+		if (!CollectionUtils.isEmpty(customizers)) {
+			for (TerminalUICustomizer customizer : customizers) {
+				customizer.customize(terminalUI);
+			}
+		}
+		return terminalUI;
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T> Set<T> copiedSetOf(T... items) {
+		return copiedSetOf(Arrays.asList(items));
+	}
+
+	private <T> Set<T> copiedSetOf(Collection<? extends T> collection) {
+		return Collections.unmodifiableSet(new LinkedHashSet<>(collection));
+	}
+
+}

spring-shell-core/src/main/java/org/springframework/shell/component/view/TerminalUICustomizer.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.component.view;
+
+/**
+ * Callback interface that can be used to customize a {@link TerminalUI}.
+ *
+ * @author Janne Valkealahti
+ * @see TerminalUIBuilder
+ */
+@FunctionalInterface
+public interface TerminalUICustomizer {
+
+	/**
+	 * Callback to customize a {@link TerminalUI} instance.
+	 *
+	 * @param terminalUI the terminal ui to customize
+	 */
+	void customize(TerminalUI terminalUI);
+
+}

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/AbstractView.java

@@ -263,6 +263,7 @@ public abstract class AbstractView extends AbstractControl implements View {
 	 *
 	 * @param viewService the view service
 	 */
+	@Override
 	public void setViewService(ViewService viewService) {
 		this.viewService = viewService;
 	}

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/View.java

@@ -89,6 +89,13 @@ public interface View extends Control {
 	 */
 	void setEventLoop(@Nullable EventLoop eventLoop);
 
+	/**
+	 * Sets a {@link ViewService}.
+	 *
+	 * @param viewService the view service
+	 */
+	void setViewService(ViewService viewService);
+
 	/**
 	 * Get supported commands.
 	 *