Big update.

src/LazyCalculatedValue.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016+ AzerothCore <www.azerothcore.org>, released under GNU GPL v2 license, you may redistribute it and/or modify it under version 2 of the License, or (at your option), any later version.
+ */
+
+#ifndef _PLAYERBOT_LAZYCALCULATEDVALUE_H
+#define _PLAYERBOT_LAZYCALCULATEDVALUE_H
+
+template <class TValue, class TOwner>
+class LazyCalculatedValue
+{
+    public:
+        typedef TValue (TOwner::*Calculator)();
+
+    public:
+        LazyCalculatedValue(TOwner* owner, Calculator calculator) : calculator(calculator), owner(owner)
+        {
+            Reset();
+        }
+
+    public:
+        TValue GetValue()
+        {
+            if (!calculated)
+            {
+                value = (owner->*calculator)();
+                calculated = true;
+            }
+
+            return value;
+        }
+
+        void Reset()
+        {
+            calculated = false;
+        }
+
+    protected:
+        Calculator calculator;
+        TOwner* owner;
+        bool calculated;
+        TValue value;
+};
+
+#endif