Implementation of Return Injection

event-loop/src/main/java/mc/core/events/async/AsyncEventLoop.java

@@ -22,15 +22,19 @@ public class AsyncEventLoop extends BaseEventLoop {
         Class<? extends Event> eventType = event.getClass();
         if (handlers.containsKey(eventType)) {
             for (ExecutorLink link : handlers.get(eventType)) {
+                Object preprocessResult = null;
                 if (link.getPreprocessMethod() != null) {
                     try {
-                        link.getPreprocessMethod().invoke(link.object, event);
+                        preprocessResult = link.getPreprocessMethod().invoke(link.object, event);
                     } catch (IllegalAccessException | InvocationTargetException e) {
                         log.error("Exception caught while attempting to run event preprocessing for {}.", eventType.getSimpleName(), e);
                     }
                 }
 
                 try {
+                    if (link.getResultInjection() != null)
+                        link.getMethod().invoke(link.object, event, preprocessResult);
+                    else
                         link.getMethod().invoke(link.object, event);
                 } catch (IllegalAccessException | InvocationTargetException e) {
                     log.error("Exception caught while attempting to dispatch {}.", eventType.getSimpleName(), e);
@@ -65,23 +69,55 @@ public class AsyncEventLoop extends BaseEventLoop {
                 continue;
             }
 
-            if (preprocessors.containsKey(annotation.eventName()))
-                log.warn("Attempted to register multiple EventPreprocessors for the event {}. Please note, that only the last one will be registered.", annotation.eventName());
-            preprocessors.put(annotation.eventName(), method);
+            if (preprocessors.containsKey(annotation.methodName()))
+                log.warn("Attempted to register multiple EventPreprocessors for the event {}. Please note, that only the last one will be registered.", annotation.methodName());
+            preprocessors.put(annotation.methodName() + ":" + firstParamType.getSimpleName(), method);
         }
 
 
         for (Method method : object.getClass().getDeclaredMethods()) {
             EventHandler annotation = method.getAnnotation(EventHandler.class);
 
-            if (notValidEventHandler(annotation, method))
+            if (annotation == null)
                 continue;
 
+            if (!Modifier.isPublic(method.getModifiers())) {
+                log.error("Unable to register {} as an EventHandler. Method must have a 'private' access modifier.", method.toString());
+                continue;
+
+            }
+
+            if (method.getParameterCount() == 0) {
+                log.error("Unable to register {} as an EventHandler. Method must at least one argument.", method.toString());
+                continue;
+            }
+
+            Class<?> firstParamType = method.getParameterTypes()[0];
+            if (!Event.class.isAssignableFrom(firstParamType)) {
+                log.error("Unable to register {} as an EventHandler. First parameter type must implement 'Event' interface.", method.toString());
+                continue;
+            }
             @SuppressWarnings("unchecked") Class<? extends Event> eventType = (Class<? extends Event>) method.getParameterTypes()[0];
 
+            Method preprocessMethod = preprocessors.get(method.getName() + ":" + eventType.getSimpleName());
+            Class resultInjection = null;
+            if (preprocessMethod.getReturnType() != void.class && method.getParameterCount() == 2 && preprocessMethod.getReturnType().equals(method.getParameterTypes()[1]))
+                resultInjection = preprocessMethod.getReturnType();
+
+            if (resultInjection == null && method.getParameterCount() > 1) {
+                log.error("Unable to register {} as an EventHandler. Method has {} arguments, but no EventPreprocessors found to provide DI for type {}", method.toString(), method.getParameterCount(), method.getParameterTypes()[1].toString());
+                continue;
+            }
+
+            if (resultInjection == null && preprocessMethod.getReturnType() != void.class) {
+                log.warn("DI registration for EventHandler {} failed. Injection target not found", method.toString());
+            }
+
             List<ExecutorLink> eventHandlers = handlers.computeIfAbsent(eventType, s -> new ArrayList<>());
-            eventHandlers.add(new ExecutorLink(annotation.priority().getValue(), annotation.ignoreCancelled(), method, object, preprocessors.remove(method.getName())));
+            eventHandlers.add(new ExecutorLink(annotation.priority().getValue(), annotation.ignoreCancelled(), method, object, preprocessMethod, resultInjection));
             eventHandlers.sort(Comparator.comparingInt(o -> o.priority));
+
+            preprocessors.remove(method.getName() + ":" + eventType.getSimpleName());
         }
 
         for (Map.Entry<String, Method> preprocessor : preprocessors.entrySet())
@@ -100,6 +136,7 @@ public class AsyncEventLoop extends BaseEventLoop {
         private final Method method;
         private final Object object;
         private final Method preprocessMethod;
+        private final Class resultInjection;
     }
 }
 

event-loop/src/main/java/mc/core/events/async/EventPreprocessor.java

@@ -8,5 +8,5 @@ import java.lang.annotation.*;
 @Inherited
 @Retention(RetentionPolicy.RUNTIME)
 public @interface EventPreprocessor {
-    String eventName();
+    String methodName();
 }

event-loop/src/test/java/ru/core/events/AsyncEventLoopTest.java

@@ -17,6 +17,6 @@ public class AsyncEventLoopTest {
 
         asyncEventLoop.callEvent(testEvent);
 
-        Assert.assertEquals("Event handler was not called", "Hello from Async Event Handler!", testEvent.getDenyReason());
+        Assert.assertEquals("Event handler was not called", "Hello! This is a message from Sync portion of the event", testEvent.getDenyReason());
     }
 }

event-loop/src/test/java/ru/core/events/handlers/AsyncEventHandler.java

@@ -1,18 +1,24 @@
 package ru.core.events.handlers;
 
+import lombok.extern.slf4j.Slf4j;
 import mc.core.events.EventHandler;
 import mc.core.events.LoginEvent;
 import mc.core.events.async.EventPreprocessor;
 
+@Slf4j
 public class AsyncEventHandler {
 
-    @EventHandler
-    public void onLogin(LoginEvent event) {
-        event.setDenyReason("Hello from Async Event Handler!");
-    }
-
-    @EventPreprocessor(eventName = "onLogin")
+    @EventPreprocessor(methodName = "onLogin")
     public void onLoginPreprocess(LoginEvent event) {
+        event.setDenyReason("Hello! This is a message from Async event preprocessor.");
 
+        // Представим, что здесь мы выполнили запрос к БД
+        // и это значение - кол-во денег у игрока
+        /*return 20D;*/
+    }
+
+    @EventHandler
+    public void onLogin(LoginEvent event) { // money здесь будет равно тому, что вернул onLoginPreprocess
+        event.setDenyReason("Hello! This is a message from Sync portion of the event");
     }
 }