Enhance TerminalUI eventing

- New methods in an eventloop and message builder
- Generic polish to use these methods
- Relates #761

Author: jvalkeal

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

@@ -33,8 +33,6 @@
 import org.slf4j.LoggerFactory;
 
 import org.springframework.lang.Nullable;
-import org.springframework.messaging.Message;
-import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.shell.component.view.control.View;
 import org.springframework.shell.component.view.control.ViewService;
 import org.springframework.shell.component.view.event.DefaultEventLoop;
@@ -48,10 +46,8 @@
 import org.springframework.shell.component.view.event.MouseHandler.MouseHandlerResult;
 import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.message.ShellMessageBuilder;
-import org.springframework.shell.component.view.message.ShellMessageHeaderAccessor;
 import org.springframework.shell.component.view.screen.DefaultScreen;
 import org.springframework.util.Assert;
-import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -236,40 +232,24 @@ private void display() {
 	}
 
 	private void dispatchWinch() {
-		Message<String> message = MessageBuilder.withPayload("WINCH")
-			.setHeader(ShellMessageHeaderAccessor.EVENT_TYPE, EventLoop.Type.SIGNAL)
-			.build();
-		eventLoop.dispatch(message);
+		eventLoop.dispatch(ShellMessageBuilder.ofSignal("WINCH"));
 	}
 
 	private void registerEventHandling() {
-		// XXX: think this again
-		eventLoop.onDestroy(eventLoop.events()
-			.filter(m -> {
-				return ObjectUtils.nullSafeEquals(m.getHeaders().get(ShellMessageHeaderAccessor.EVENT_TYPE), EventLoop.Type.SIGNAL);
-			})
-			.doOnNext(m -> {
+		eventLoop.onDestroy(eventLoop.signalEvents()
+			.subscribe(event -> {
 				display();
-			})
-			.subscribe());
+			}));
 
-		// XXX: think this again
-		eventLoop.onDestroy(eventLoop.events()
-			.filter(m -> {
-				return ObjectUtils.nullSafeEquals(m.getHeaders().get(ShellMessageHeaderAccessor.EVENT_TYPE), EventLoop.Type.SYSTEM);
-			})
-			.doOnNext(m -> {
-				Object payload = m.getPayload();
-				if (payload instanceof String s) {
-					if ("redraw".equals(s)) {
-						display();
-					}
-					else if ("int".equals(s)) {
-						this.terminal.raise(Signal.INT);
-					}
+		eventLoop.onDestroy(eventLoop.systemEvents()
+			.subscribe(event -> {
+				if ("redraw".equals(event)) {
+					display();
 				}
-			})
-			.subscribe());
+				else if ("int".equals(event)) {
+					this.terminal.raise(Signal.INT);
+				}
+			}));
 
 		eventLoop.onDestroy(eventLoop.keyEvents()
 			.doOnNext(m -> {
@@ -417,11 +397,8 @@ else if (operation == KeyEvent.Key.Mouse) {
 	}
 
 	private void dispatchKeyEvent(KeyEvent event) {
-		Message<KeyEvent> message = MessageBuilder
-			.withPayload(event)
-			.setHeader(ShellMessageHeaderAccessor.EVENT_TYPE, EventLoop.Type.KEY)
-			.build();
-		eventLoop.dispatch(message);
+		log.debug("Dispatch key event: {}", event);
+		eventLoop.dispatch(ShellMessageBuilder.ofKeyEvent(event));
 	}
 
 	private void dispatchMouse(MouseEvent event) {

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

@@ -150,6 +150,22 @@ public Flux<MouseEvent> mouseEvents() {
 			.ofType(MouseEvent.class);
 	}
 
+	@Override
+	public Flux<String> systemEvents() {
+		return events()
+			.filter(m -> EventLoop.Type.SYSTEM.equals(StaticShellMessageHeaderAccessor.getEventType(m)))
+			.map(m -> m.getPayload())
+			.ofType(String.class);
+	}
+
+	@Override
+	public Flux<String> signalEvents() {
+		return events()
+			.filter(m -> EventLoop.Type.SIGNAL.equals(StaticShellMessageHeaderAccessor.getEventType(m)))
+			.map(m -> m.getPayload())
+			.ofType(String.class);
+	}
+
 	@Override
 	public <T extends ViewEvent> Flux<T> viewEvents(Class<T> clazz) {
 		return events(EventLoop.Type.VIEW, clazz);

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

@@ -61,6 +61,22 @@ public interface EventLoop {
 	 */
 	Flux<MouseEvent> mouseEvents();
 
+	/**
+	 * Specialisation of {@link #events()} which returns type safe
+	 * {code system} events.
+	 *
+	 * @return the system events from an event loop
+	 */
+	Flux<String> systemEvents();
+
+	/**
+	 * Specialisation of {@link #events()} which returns type safe
+	 * {code signal} events.
+	 *
+	 * @return the signal events from an event loop
+	 */
+	Flux<String> signalEvents();
+
 	/**
 	 * Specialisation of {@link #events()} which returns type safe {@link ViewEvent}s.
 	 *

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

@@ -20,6 +20,7 @@
 import org.springframework.messaging.support.GenericMessage;
 import org.springframework.shell.component.view.control.View;
 import org.springframework.shell.component.view.event.EventLoop;
+import org.springframework.shell.component.view.event.KeyEvent;
 import org.springframework.shell.component.view.event.MouseEvent;
 import org.springframework.util.Assert;
 
@@ -83,6 +84,30 @@ public static Message<String> ofInterrupt() {
 			.build();
 	}
 
+	/**
+	 * Create a {@code signal} message.
+	 *
+	 * @return a signal message
+	 */
+	public static Message<String> ofSignal(String signal) {
+		return new ShellMessageBuilder<>(signal, null)
+			.setEventType(EventLoop.Type.SIGNAL)
+			.setPriority(0)
+			.build();
+	}
+
+	/**
+	 * Create a message of a {@link KeyEvent}.
+	 *
+	 * @param event the event type
+	 * @return a message with {@link KeyEvent} as a payload
+	 */
+	public static Message<KeyEvent> ofKeyEvent(KeyEvent event) {
+		return new ShellMessageBuilder<>(event, null)
+			.setEventType(EventLoop.Type.KEY)
+			.build();
+	}
+
 	/**
 	 * Create a message of a {@link MouseEvent}.
 	 *

spring-shell-core/src/test/java/org/springframework/shell/component/view/event/DefaultEventLoopTests.java

@@ -17,6 +17,7 @@
 
 import java.time.Duration;
 import java.util.Arrays;
+import java.util.EnumSet;
 
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
@@ -190,4 +191,70 @@ public void run() {
 		}
 	}
 
+	@Test
+	void keyEvents() {
+		initDefault();
+
+		KeyEvent event = KeyEvent.of(KeyEvent.Key.a);
+		Message<KeyEvent> message = ShellMessageBuilder.ofKeyEvent(event);
+
+		StepVerifier verifier1 = StepVerifier.create(loop.keyEvents())
+			.expectNextCount(1)
+			.thenCancel()
+			.verifyLater();
+
+		loop.dispatch(message);
+		verifier1.verify(Duration.ofSeconds(1));
+	}
+
+	@Test
+	void mouseEvents() {
+		initDefault();
+
+		org.jline.terminal.MouseEvent jlineMouseEvent = new org.jline.terminal.MouseEvent(
+				org.jline.terminal.MouseEvent.Type.Released,
+				org.jline.terminal.MouseEvent.Button.Button1,
+				EnumSet.noneOf(org.jline.terminal.MouseEvent.Modifier.class), 0, 0);
+		MouseEvent event = MouseEvent.of(jlineMouseEvent);
+		Message<MouseEvent> message = ShellMessageBuilder.ofMouseEvent(event);
+
+		StepVerifier verifier1 = StepVerifier.create(loop.mouseEvents())
+			.expectNextCount(1)
+			.thenCancel()
+			.verifyLater();
+
+		loop.dispatch(message);
+		verifier1.verify(Duration.ofSeconds(1));
+	}
+
+	@Test
+	void systemEvents() {
+		initDefault();
+
+		Message<String> message = ShellMessageBuilder.ofRedraw();
+
+		StepVerifier verifier1 = StepVerifier.create(loop.systemEvents())
+			.expectNextCount(1)
+			.thenCancel()
+			.verifyLater();
+
+		loop.dispatch(message);
+		verifier1.verify(Duration.ofSeconds(1));
+	}
+
+	@Test
+	void signalEvents() {
+		initDefault();
+
+		Message<String> message = ShellMessageBuilder.ofSignal("WINCH");
+
+		StepVerifier verifier1 = StepVerifier.create(loop.signalEvents())
+			.expectNextCount(1)
+			.thenCancel()
+			.verifyLater();
+
+		loop.dispatch(message);
+		verifier1.verify(Duration.ofSeconds(1));
+	}
+
 }