From 375b25ff590c4d7394a36c61374856af9ba83e20 Mon Sep 17 00:00:00 2001
From: Dominic Masters <dominic@domsplace.com>
Date: Thu, 20 Oct 2022 09:29:02 -0700
Subject: [PATCH] Added event system

---
 src/dawn/display/RenderPipeline.hpp      |   2 +-
 src/dawn/event/Event.hpp                 | 119 +++++++++++++++++++++++
 src/dawnpokergame/game/DawnPokerGame.cpp |   1 +
 3 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 src/dawn/event/Event.hpp

diff --git a/src/dawn/display/RenderPipeline.hpp b/src/dawn/display/RenderPipeline.hpp
index 7c70530c..3ab436fd 100644
--- a/src/dawn/display/RenderPipeline.hpp
+++ b/src/dawn/display/RenderPipeline.hpp
@@ -47,7 +47,7 @@ namespace Dawn {
        * @param scene Scene to render.
        * @param camera Camera within the scene to render.
        */
-      virtual void renderSceneCamera(Scene &scene, Camera &camera) = 0;
+      virtual void renderSceneCamera(Scene &scene, Camera &camera);
 
       /**
        * Cleanup a render pipeline that has been initialized.
diff --git a/src/dawn/event/Event.hpp b/src/dawn/event/Event.hpp
new file mode 100644
index 00000000..85f22bd6
--- /dev/null
+++ b/src/dawn/event/Event.hpp
@@ -0,0 +1,119 @@
+// Copyright (c) 2022 Dominic Masters
+// 
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#pragma once
+#include "dawnlibs.hpp"
+
+namespace Dawn {
+
+  template<typename... A>
+  struct IEventListener {
+    /**
+     * Abstracted method for C++ template reasons. Invokes the listener.
+     * 
+     * @param args Arguments to pass to the listener.
+     */
+    virtual void invoke(A... args) = 0;
+  };
+
+  template <class T, typename... A>
+  struct EventListener : public IEventListener<A...> {
+    T *instance;
+    void (T::*callback)(A... args);
+
+    /**
+     * Construct a new event listener structure.
+     * 
+     * @param instance Instance that the callback belongs to.
+     * @param callback Callback method that invokes back.
+     */
+    EventListener(T *instance, void (T::*callback)(A... args)) :
+      instance(instance),
+      callback(callback)
+    {
+    }
+
+    void invoke(A... args) {
+      ((*this->instance).*(this->callback))(args...);
+    }
+  };
+
+  template<typename...A>
+  class Event {
+    private:  
+      std::vector<IEventListener<A...>*> listeners;
+
+    public:
+      /**
+       * Add a listener to this event.
+       * 
+       * @tparam T The class that will receive the event.
+       * @param instance Instance of type T that will receive the callback.
+       * @param callback Callback method attached to T to receive the event.
+       * @return The initialized event listener. You don't really need this.
+       */
+      template<class T>
+      EventListener<T, A...> * addListener(
+        T *instance,
+        void (T::*callback)(A... args)
+      ) {
+        auto listener = new EventListener<T,A...>(instance, callback);
+        this->listeners.push_back(listener);
+        return listener;
+      }
+
+      /**
+       * Removes an event listener from this event.
+       * 
+       * @tparam T The class that was once receiving the event.
+       * @param instance Instance of type T that did receive the callback.
+       * @param callback Callback method attached to T for the event.
+       */
+      template<class T>
+      void removeListener(
+        T *instance,
+        void (T::*callback)(A... args)
+      ) {
+        auto it = this->listeners.begin();
+        while(it != this->listeners.end()) {
+          auto listener = static_cast<EventListener<T,A...>*>(*it);
+
+          if(listener->instance != instance || listener->callback != callback) {
+            ++it;
+            continue;
+          }
+
+          this->listeners.erase(it);
+          delete listener;
+          break;
+        }
+      }
+
+      /**
+       * Invokes the event and emits to all of the listeners.
+       * 
+       * @param args Arguments for this event to pass to the listeners.
+       */
+      void invoke(A... args) {
+        auto it = this->listeners.begin();
+        while(it != this->listeners.end()) {
+          (*it)->invoke(args...);
+          ++it;
+        }
+      }
+
+      /**
+       * Disposes the event instance. Will also destroy all of the event 
+       * listeners.
+       */
+      ~Event() {
+        auto it = this->listeners.begin();
+        while(it != this->listeners.end()) {
+          delete *it;
+          ++it;
+        }
+      }
+  };
+}
\ No newline at end of file
diff --git a/src/dawnpokergame/game/DawnPokerGame.cpp b/src/dawnpokergame/game/DawnPokerGame.cpp
index e0f694be..6c59d1b9 100644
--- a/src/dawnpokergame/game/DawnPokerGame.cpp
+++ b/src/dawnpokergame/game/DawnPokerGame.cpp
@@ -4,6 +4,7 @@
 // https://opensource.org/licenses/MIT
 
 #include "DawnPokerGame.hpp"
+#include "event/Event.hpp"
 
 using namespace Dawn;