Add event support

base/build.gradle

@@ -15,6 +15,9 @@ dependencies {
     // ANSI support
     implementation 'org.fusesource.jansi:jansi:' + project.dependencyJansi
 
+    // Reflections
+    implementation 'org.reflections:reflections:' + project.dependencyReflections
+
     // -> Testing <-
     // Jetbrains Annotations
     testCompileOnly 'org.jetbrains:annotations:' + project.dependencyJetbrainsAnnotations

base/src/main/java/de/staropensource/sosengine/base/Engine.java

@@ -91,6 +91,9 @@ public class Engine {
         // Initialize classes
         initializeClasses();
 
+        // Initialize events
+        initializeEvents();
+
         // Populate crash content
         populateCrashContent();
 
@@ -116,6 +119,14 @@ public class Engine {
         new ShortcodeConverter();
     }
 
+    /**
+     * Initializes all events.
+     *
+     * @since 1-alpha0
+     */
+    protected void initializeEvents() {
+    }
+
     /**
      * This method populates the Crash Handler's content with the default set of content.
      *

base/src/main/java/de/staropensource/sosengine/base/annotations/EventListener.java

@@ -0,0 +1,15 @@
+package de.staropensource.sosengine.base.annotations;
+
+import de.staropensource.sosengine.base.classes.Event;
+
+import java.lang.annotation.*;
+
+/**
+ * Annotation for registering events on methods.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+@Documented
+public @interface EventListener {
+    Class<? extends Event> event();
+}

base/src/main/java/de/staropensource/sosengine/base/annotations/package-info.java

@@ -0,0 +1,6 @@
+/**
+ * Contains annotations.
+ *
+ * @since 1-alpha0
+ */
+package de.staropensource.sosengine.base.annotations;

base/src/main/java/de/staropensource/sosengine/base/classes/Event.java

@@ -0,0 +1,113 @@
+package de.staropensource.sosengine.base.classes;
+
+import de.staropensource.sosengine.base.annotations.EventListener;
+import de.staropensource.sosengine.base.logging.Logger;
+import de.staropensource.sosengine.base.types.CodePart;
+import de.staropensource.sosengine.base.types.LogIssuer;
+import lombok.AccessLevel;
+import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
+import org.reflections.Reflections;
+import org.reflections.scanners.Scanners;
+import org.reflections.util.ClasspathHelper;
+import org.reflections.util.ConfigurationBuilder;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Represents an event.
+ *
+ * @since 1-alpha0
+ */
+@Getter
+@SuppressWarnings({ "unused", "JavadocDeclaration", "JavadocBlankLines" })
+public abstract class Event {
+    /**
+     * Instance.
+     *
+     * @since 1-alpha0
+     *
+     * -- GETTER --
+     * Returns the extending {@link Event} instance.
+     *
+     * @return extending {@link Event} instance
+     * @since 1-alpha0
+     */
+    @Getter()
+    protected static Event instance;
+
+    /**
+     * The name of the event.
+     *
+     * @since 1-alpha0
+     *
+     * -- GETTER --
+     * Returns the name of the event.
+     *
+     * @return the event name
+     * @since 1-alpha0
+     */
+    @NotNull
+    private final String eventName;
+
+    /**
+     * Constructor.
+     *
+     * @since 1-alpha0
+     */
+    public Event() {
+        this.eventName = this.getClass().getName().replace(this.getClass().getPackage() + ".", "");
+
+        // Only allow one instance
+        if (instance == null)
+            instance = this;
+        else
+            Logger.crash(new LogIssuer(getClass(), CodePart.ENGINE), "Tried reinitializing " + getClass().getName() + " twice");
+    }
+
+    /**
+     * Returns all annotated methods.
+     *
+     * @return list of annotated methods
+     * @since 1-alpha0
+     */
+    @NotNull
+    protected List<Method> getAnnotatedMethods() {
+        List<Method> methods = new ArrayList<>();
+
+        Reflections reflections = new Reflections(
+                new ConfigurationBuilder()
+                .setUrls(ClasspathHelper.forJavaClassPath())
+                .setScanners(Scanners.MethodsAnnotated)
+        );
+        Set<Method> annotatedMethods = reflections.getMethodsAnnotatedWith(EventListener.class);
+
+        for (Method method : annotatedMethods)
+            if (method.getAnnotation(EventListener.class).event() == this.getClass())
+                methods.add(method);
+
+        return methods;
+    }
+
+    /**
+     * Invokes all annotated methods without any arguments.
+     */
+    protected void invokeAnnotatedMethods() {
+        for (Method method : getAnnotatedMethods()) {
+            try {
+                method.invoke(null);
+            } catch (IllegalAccessException | InvocationTargetException ignored) {}
+        }
+    }
+
+    /**
+     * Calls the event and notifies all annotated methods about it.
+     *
+     * @since 1-alpha0
+     */
+    public abstract void callEvent();
+}

gradle.properties

@@ -14,6 +14,7 @@ dependencyJoor=0.9.14
 
 # Subsystem dependencies
 dependencyJansi=2.4.1
+dependencyReflections=0.10.2
 
 # Plugins
 pluginShadow=8.1.1