From cd01647247fa0af95a4584af4831b70c7aa3645b Mon Sep 17 00:00:00 2001
From: kske <kai@kske.dev>
Date: Fri, 2 Aug 2019 18:46:00 +0200
Subject: [PATCH] Added event package with EventBus class

---
 src/dev/kske/chess/event/EventBus.java   | 58 ++++++++++++++++++++++++
 src/dev/kske/chess/event/Invocation.java | 29 ++++++++++++
 src/dev/kske/chess/event/Subscribe.java  | 19 ++++++++
 src/dev/kske/chess/ui/MainWindow.java    | 15 +++---
 4 files changed, 112 insertions(+), 9 deletions(-)
 create mode 100644 src/dev/kske/chess/event/EventBus.java
 create mode 100644 src/dev/kske/chess/event/Invocation.java
 create mode 100644 src/dev/kske/chess/event/Subscribe.java

diff --git a/src/dev/kske/chess/event/EventBus.java b/src/dev/kske/chess/event/EventBus.java
new file mode 100644
index 0000000..f9351aa
--- /dev/null
+++ b/src/dev/kske/chess/event/EventBus.java
@@ -0,0 +1,58 @@
+package dev.kske.chess.event;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Vector;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>EventBus.java</strong><br>
+ * Created: <strong>02.08.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public final class EventBus {
+
+	private Map<Class<?>, List<Invocation>> invocations;
+
+	public EventBus() {
+		invocations = new ConcurrentHashMap<>();
+	}
+
+	public void post(Object object) {
+		Class<?> type = object.getClass();
+		if (invocations.containsKey(type)) invocations.get(type).forEach(invocation -> invocation.invoke(object));
+	}
+
+	public void register(Object object) {
+		Class<?> currentClass = object.getClass();
+		while (currentClass != null) {
+			for (Method method : findSubscriptionMethods(currentClass)) {
+				Class<?> type = method.getParameterTypes()[0];
+				if (invocations.containsKey(type)) invocations.get(type).add(new Invocation(method, object));
+				else {
+					List<Invocation> temp = new Vector<>();
+					temp.add(new Invocation(method, object));
+					invocations.put(type, temp);
+				}
+			}
+			currentClass = currentClass.getSuperclass();
+		}
+	}
+
+	private List<Method> findSubscriptionMethods(Class<?> type) {
+		List<Method> subscriberMethods = Arrays.stream(type.getDeclaredMethods())
+			.filter(method -> method.isAnnotationPresent(Subscribe.class))
+			.collect(Collectors.toList());
+		checkSubscriberMethods(subscriberMethods);
+		return subscriberMethods;
+	}
+
+	private void checkSubscriberMethods(List<Method> subscriberMethods) {
+		if (subscriberMethods.stream().anyMatch(method -> method.getParameterCount() != 1))
+			throw new IllegalArgumentException("Method annotated with @Subscribe must have exactly one parameter");
+	}
+}
diff --git a/src/dev/kske/chess/event/Invocation.java b/src/dev/kske/chess/event/Invocation.java
new file mode 100644
index 0000000..d0ce29f
--- /dev/null
+++ b/src/dev/kske/chess/event/Invocation.java
@@ -0,0 +1,29 @@
+package dev.kske.chess.event;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>Invocation.java</strong><br>
+ * Created: <strong>02.08.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public final class Invocation {
+
+	private final Method	method;
+	private final Object	object;
+
+	public Invocation(Method method, Object object) {
+		this.method	= method;
+		this.object	= object;
+	}
+
+	public void invoke(Object arg) {
+		try {
+			method.invoke(object, arg);
+		} catch (IllegalArgumentException | IllegalAccessException | InvocationTargetException ex) {
+			ex.printStackTrace();
+		}
+	}
+}
diff --git a/src/dev/kske/chess/event/Subscribe.java b/src/dev/kske/chess/event/Subscribe.java
new file mode 100644
index 0000000..6cae9a4
--- /dev/null
+++ b/src/dev/kske/chess/event/Subscribe.java
@@ -0,0 +1,19 @@
+package dev.kske.chess.event;
+
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Retention(RUNTIME)
+@Target(METHOD)
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>Subscribe.java</strong><br>
+ * Created: <strong>02.08.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public @interface Subscribe {
+
+}
diff --git a/src/dev/kske/chess/ui/MainWindow.java b/src/dev/kske/chess/ui/MainWindow.java
index c6aaae6..fef681f 100644
--- a/src/dev/kske/chess/ui/MainWindow.java
+++ b/src/dev/kske/chess/ui/MainWindow.java
@@ -32,15 +32,12 @@ public class MainWindow {
 	 * Launch the application.
 	 */
 	public static void main(String[] args) {
-		EventQueue.invokeLater(new Runnable() {
-
-			public void run() {
-				try {
-					MainWindow window = new MainWindow();
-					window.mframe.setVisible(true);
-				} catch (Exception e) {
-					e.printStackTrace();
-				}
+		EventQueue.invokeLater(() -> {
+			try {
+				MainWindow window = new MainWindow();
+				window.mframe.setVisible(true);
+			} catch (Exception e) {
+				e.printStackTrace();
 			}
 		});
 	}