From 4ab31de2097d42d249d1c09450240672765355dc Mon Sep 17 00:00:00 2001
From: Curle <curle@gemwire.uk>
Date: Sun, 12 Mar 2023 13:16:48 +0000
Subject: [PATCH] Entity System API draft.

---
 .../shadow-entity/inc/system/EntitySystem.h   | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 projs/shadow/shadow-engine/shadow-entity/inc/system/EntitySystem.h

diff --git a/projs/shadow/shadow-engine/shadow-entity/inc/system/EntitySystem.h b/projs/shadow/shadow-engine/shadow-entity/inc/system/EntitySystem.h
new file mode 100644
index 0000000..5c574f5
--- /dev/null
+++ b/projs/shadow/shadow-engine/shadow-entity/inc/system/EntitySystem.h
@@ -0,0 +1,45 @@
+#pragma once
+#include <string>
+
+namespace SE {
+
+    // Forward declaration.
+    class EntityComponent;
+
+    /**
+     * A System is a routine that operates over the Components in an Entity.
+     * A System may be local to a given Entity, or it may be glboal to the Scene.
+     *
+     * Components must be registered to the System that works over them.
+     *
+     * TODO: Think of better names for these functions
+     */
+    class EntitySystem {
+    public:
+
+        virtual ~EntitySystem();
+        virtual std::string& GetName() const = 0;
+
+        // Pre-Component Register
+        virtual void Initialize() {}
+
+        // Post-Component Register
+        virtual void Initialized() {}
+
+        // Pre-Component Unregister
+        virtual void Uninitialize() {}
+
+        // Post-Component Unregister
+        virtual void Uninitialized() {}
+
+    protected:
+
+        // Register a Component with this System
+        virtual void RegisterComponent(EntityComponent* component) = 0;
+        // Unregister a Component from this system
+        virtual void UnregisterComponent(EntityComponent* component) = 0;
+
+        // Update over all Components. TODO: Context?
+        virtual void Update() = 0;
+    };
+}
\ No newline at end of file