From 099d9a15c3163c86d6cb48040c07a723fb545b95 Mon Sep 17 00:00:00 2001
From: Dominic Masters <dominic@domsplace.com>
Date: Mon, 27 Feb 2023 12:46:02 -0800
Subject: [PATCH] Added state event.

---
 src/dawn/state/State.hpp                    |  1 +
 src/dawn/state/StateEvent.hpp               | 33 +++++++++++++
 src/dawn/state/StateOwner.hpp               | 55 ++++++++++++++++-----
 src/dawn/state/StateProperty.hpp            | 13 ++++-
 src/dawntictactoe/scenes/TicTacToeScene.hpp |  4 --
 5 files changed, 88 insertions(+), 18 deletions(-)
 create mode 100644 src/dawn/state/StateEvent.hpp

diff --git a/src/dawn/state/State.hpp b/src/dawn/state/State.hpp
index 91b0ed6c..41a88719 100644
--- a/src/dawn/state/State.hpp
+++ b/src/dawn/state/State.hpp
@@ -5,5 +5,6 @@
 
 #pragma once
 
+#include "StateEvent.hpp"
 #include "StateOwner.hpp"
 #include "StateProperty.hpp"
\ No newline at end of file
diff --git a/src/dawn/state/StateEvent.hpp b/src/dawn/state/StateEvent.hpp
new file mode 100644
index 00000000..6aa72dff
--- /dev/null
+++ b/src/dawn/state/StateEvent.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2023 Dominic Masters
+// 
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#pragma once
+#include "assert/assert.hpp"
+
+namespace Dawn {
+  class StateOwner;
+
+  template<typename...A>
+  class StateEvent {
+    private:
+      std::vector<std::function<void(A...)>> listeners;
+
+    public:
+      /**
+       * 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 itListeners = this->listeners.begin();
+        while(itListeners != this->listeners.end()) {
+          (*itListeners)(args...);
+          ++itListeners;
+        }
+      }
+
+      friend class StateOwner;
+  };
+}
\ No newline at end of file
diff --git a/src/dawn/state/StateOwner.hpp b/src/dawn/state/StateOwner.hpp
index f7957e80..8668e402 100644
--- a/src/dawn/state/StateOwner.hpp
+++ b/src/dawn/state/StateOwner.hpp
@@ -4,7 +4,7 @@
 // https://opensource.org/licenses/MIT
 
 #pragma once
-#include "assert/assert.hpp"
+#include "StateEvent.hpp"
 
 namespace Dawn {
   template<class V>
@@ -12,15 +12,10 @@ namespace Dawn {
 
   class StateOwner {
     private:
-      std::map<void*, std::vector<std::function<void()>>> effects;
+      std::map<void*, std::vector<std::function<void()>>> effectListeners;
+      std::vector<std::function<void()>> stateUpdateListeners;
 
     public:
-      /**
-       * Invoked event listener for the subclass that listens for all changes
-       * to any part of this state updated.
-       */
-      virtual void onStateUpdate() = 0;
-
       /**
        * Creates a new state property and listens for its change.
        * 
@@ -46,7 +41,32 @@ namespace Dawn {
        */
       template<class V>
       void useEffect(StateProperty<V> &property, const std::function<void()> &fn) {
-        this->effects[(void*)&property].push_back(fn);
+        assertFalse(property.owner == this);
+        this->effectListeners[(void*)&property].push_back(fn);
+      }
+
+      /**
+       * Listen for changes to any single state property managed by this state
+       * owner.
+       * 
+       * @param fn Function to be invoked when any state property is updated.
+       */
+      void useStateUpdated(const std::function<void()> &fn) {
+        this->stateUpdateListeners.push_back(fn);
+      }
+
+      /**
+       * Listen for when an event is invoked by a state event. This is intended
+       * to allow for cross-state-owner communication in a simple and effective
+       * way.
+       * 
+       * @tparam A The arguments from the state event that are calledback.
+       * @param event The event that is being subscribed to.
+       * @param fn The function to be inokved on event trigger.
+       */
+      template<typename...A>
+      void useEvent(StateEvent<A...> &event, const std::function<void(A...)> &fn) {
+        event.listeners.push_back(fn);
       }
 
       /**
@@ -60,14 +80,19 @@ namespace Dawn {
        */
       template<class V>
       void _statePropertyUpdated(StateProperty<V> *prop, V n, V o) {
-        this->onStateUpdate();
-
-        auto eff = &this->effects[prop];
+        auto eff = &this->effectListeners[prop];
+        
         auto itEff = eff->begin();
         while(itEff != eff->end()) {
           (*itEff)();
           ++itEff;
         }
+
+        auto itUpdate = this->stateUpdateListeners.begin();
+        while(itUpdate != this->stateUpdateListeners.end()) {
+          (*itUpdate)();
+          ++itUpdate;
+        }
       }
 
       /**
@@ -79,7 +104,11 @@ namespace Dawn {
        */
       template<class V>
       void _statePropertyDestroyed(StateProperty<V> *prop) {
-        this->effects.erase((void*)prop);
+        this->effectListeners.erase((void*)prop);
+      }
+
+      virtual ~StateOwner() {
+        
       }
   };
 }
\ No newline at end of file
diff --git a/src/dawn/state/StateProperty.hpp b/src/dawn/state/StateProperty.hpp
index 92d53c24..f41bbaf6 100644
--- a/src/dawn/state/StateProperty.hpp
+++ b/src/dawn/state/StateProperty.hpp
@@ -4,15 +4,23 @@
 // https://opensource.org/licenses/MIT
 
 #pragma once
-#include "StateOwner.hpp"
+#include "assert/assert.hpp"
 
 namespace Dawn {
+  class StateOwner;
+
   template<class V>
   class StateProperty {
     private:
       StateOwner *owner;
       V value;
       
+      /**
+       * Method that is invoked every time that the value of this state property
+       * is updated.
+       * 
+       * @param val Value that is to be used for this property.
+       */
       void setInternal(V val) {
         if(val == this->value) return;// TODO: can I omit this? kinda bad tbh.
         assertNotNull(this->owner);
@@ -44,6 +52,9 @@ namespace Dawn {
         return this->value;
       }
 
+      /**
+       * Destructor for StateProperty.
+       */
       ~StateProperty() {
         this->owner->_statePropertyDestroyed(this);
       }
diff --git a/src/dawntictactoe/scenes/TicTacToeScene.hpp b/src/dawntictactoe/scenes/TicTacToeScene.hpp
index 40dc78d5..008cc5ad 100644
--- a/src/dawntictactoe/scenes/TicTacToeScene.hpp
+++ b/src/dawntictactoe/scenes/TicTacToeScene.hpp
@@ -42,10 +42,6 @@ namespace Dawn {
           }
         }
       }
-
-      void onStateUpdate() override {
-        std::cout << "State Update Invoked" << std::endl;
-      }
       
       std::vector<Asset*> getRequiredAssets() override {
         auto assMan = &this->game->assetManager;