Core/Misc: Add new centralized location for generic predicates (PR #23607)

(cherry picked from commit 6e2ca481e5)

src/server/game/Miscellaneous/CommonPredicates.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2008-2019 TrinityCore <https://www.trinitycore.org/>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "CommonPredicates.h"
+#include "Common.h"
+#include "Unit.h"
+#include "SharedDefines.h"
+
+Trinity::Predicates::IsVictimOf::IsVictimOf(Unit const* attacker) : _victim(attacker ? attacker->GetVictim() : nullptr) { }

src/server/game/Miscellaneous/CommonPredicates.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2008-2019 TrinityCore <https://www.trinitycore.org/>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TRINITY_COMMONPREDICATES_H
+#define TRINITY_COMMONPREDICATES_H
+
+#include "Define.h"
+#include <utility>
+
+class Unit;
+class WorldObject;
+
+namespace Trinity
+{
+    namespace Predicates
+    {
+        /// Only returns true for the given attacker's current victim, if any
+        class TC_GAME_API IsVictimOf
+        {
+            public:
+                IsVictimOf(Unit const* attacker);
+                bool operator()(WorldObject const* obj) const { return obj && (_victim == obj); }
+            private:
+                WorldObject const* _victim;
+        };
+
+        template <typename PRED>
+        class TC_GAME_API Inverter
+        {
+            public:
+                Inverter(PRED&& p) : _child(std::move(p)) { }
+
+                template <typename... Args>
+                bool operator()(Args&&... args)
+                {
+                    return !_child(std::forward<Args>(args)...);
+                }
+
+                template <typename... Args>
+                bool operator()(Args&&... args) const
+                {
+                    return !_child(std::forward<Args>(args)...);
+                }
+
+            private:
+                PRED _child;
+        };
+
+        template <typename PRED>
+        /// Inverts the given predicate to return the opposite result
+        Inverter<PRED> Invert(PRED&& p) { return Inverter<PRED>(std::forward<PRED>(p)); }
+    }
+}
+
+
+#endif //TRINITY_COMMONPREDICATES_H