Core: Combat/threat system rewrite (PR #19930)

- PvE combat is now always mutual. UNIT_FLAG_IN_COMBAT is backed by actual references to the units we're in combat with.
- PvP combat is now also tracked, and almost always mutual; spells like Vanish and Feign Death can break this rule. That means we can easily determine a list of players we're fighting.
- By extension, IsInCombatWith now has sensible behavior when invoked on nonplayers.
- Threat and combat systems are no longer the same.
  - They still have an enforced relationship (threat implies combat - clearing combat clears threat)...
  - ...but we can have combat without threat. A creature (with threat list) isn't considered to be engaged until it has an entry on its threat list...
  - ...which means we can now faithfully replicate retail engage behavior. Combat on projectile launch - engagement start on projectile impact. Yay for progress!
- AI method refactor, as already ported in 6113b9d - `JustEngagedWith`, `JustEnteredCombat` and `JustExitedCombat`.
- Vehicle threat is now properly pooled on the main vehicle body (fixes #16542).
- Various edge case bug fixes for threat redirects (Misdirection "cancelling" Vigilance and similar).
- Target re-selection is now significantly faster.
- Fixed a ton of other smaller edge case bugs, probably.

Closes #7951 and #19998.

(cherry picked from commit 532ab1c7f8653d1a2e48aa1f1f8a9ba1041d4bb7)

1 files changed, 28 insertions, 38 deletions

diff --git a/src/server/game/AI/CreatureAI.cpp b/src/server/game/AI/CreatureAI.cpp
index 1b7234dd939..2c07dcd551d 100644
--- a/src/server/game/AI/CreatureAI.cpp
+++ b/src/server/game/AI/CreatureAI.cpp
@@ -67,61 +67,49 @@ void CreatureAI::DoZoneInCombat(Creature* creature /*= nullptr*/, float maxRange
     if (!creature)
         creature = me;
 
-    if (!creature->CanHaveThreatList())
-        return;
-
     Map* map = creature->GetMap();
-    if (!map->IsDungeon())                                  //use IsDungeon instead of Instanceable, in case battlegrounds will be instantiated
+    if (creature->CanHaveThreatList())
     {
-        TC_LOG_ERROR("misc", "DoZoneInCombat call for map that isn't an instance (creature entry = %d)", creature->GetTypeId() == TYPEID_UNIT ? creature->ToCreature()->GetEntry() : 0);
-        return;
-    }
+        if (!map->IsDungeon())                                  //use IsDungeon instead of Instanceable, in case battlegrounds will be instantiated
+        {
+            TC_LOG_ERROR("misc", "DoZoneInCombat call for map that isn't an instance (creature entry = %d)", creature->GetTypeId() == TYPEID_UNIT ? creature->ToCreature()->GetEntry() : 0);
+            return;
+        }
 
-    if (!creature->HasReactState(REACT_PASSIVE) && !creature->GetVictim())
-    {
-        if (Unit* nearTarget = creature->SelectNearestTarget(maxRangeToNearestTarget))
-            creature->AI()->AttackStart(nearTarget);
-        else if (creature->IsSummon())
+        if (!creature->HasReactState(REACT_PASSIVE) && !creature->GetVictim())
         {
-            if (Unit* summoner = creature->ToTempSummon()->GetSummoner())
+            if (Unit* nearTarget = creature->SelectNearestTarget(maxRangeToNearestTarget))
+                creature->AI()->AttackStart(nearTarget);
+            else if (creature->IsSummon())
             {
-                Unit* target = summoner->getAttackerForHelper();
-                if (!target && summoner->CanHaveThreatList() && !summoner->GetThreatManager().IsThreatListEmpty())
-                    target = summoner->GetThreatManager().GetAnyTarget();
-                if (target && (creature->IsFriendlyTo(summoner) || creature->IsHostileTo(target)))
-                    creature->AI()->AttackStart(target);
+                if (Unit* summoner = creature->ToTempSummon()->GetSummoner())
+                {
+                    Unit* target = summoner->getAttackerForHelper();
+                    if (!target && !summoner->GetThreatManager().IsThreatListEmpty())
+                        target = summoner->GetThreatManager().GetAnyTarget();
+                    if (target && (creature->IsFriendlyTo(summoner) || creature->IsHostileTo(target)))
+                        creature->AI()->AttackStart(target);
+                }
             }
         }
-    }
 
-    // Intended duplicated check, the code above this should select a victim
-    // If it can't find a suitable attack target then we should error out.
-    if (!creature->HasReactState(REACT_PASSIVE) && !creature->GetVictim())
-    {
-        TC_LOG_ERROR("misc.dozoneincombat", "DoZoneInCombat called for creature that has empty threat list (creature entry = %u)", creature->GetEntry());
-        return;
+        // Intended duplicated check, the code above this should select a victim
+        // If it can't find a suitable attack target then we should error out.
+        if (!creature->HasReactState(REACT_PASSIVE) && !creature->GetVictim())
+        {
+            TC_LOG_ERROR("misc.dozoneincombat", "DoZoneInCombat called for creature that has empty threat list (creature entry = %u)", creature->GetEntry());
+            return;
+        }
     }
 
     Map::PlayerList const& playerList = map->GetPlayers();
-
     if (playerList.isEmpty())
         return;
 
     for (Map::PlayerList::const_iterator itr = playerList.begin(); itr != playerList.end(); ++itr)
-    {
         if (Player* player = itr->GetSource())
-        {
-            if (player->IsGameMaster())
-                continue;
-
             if (player->IsAlive())
-            {
                 creature->SetInCombatWith(player);
-                player->SetInCombatWith(creature);
-                creature->GetThreatManager().AddThreat(player, 0.0f, nullptr, true, true);
-            }
-        }
-    }
 }
 
 // scripts does not take care about MoveInLineOfSight loops
@@ -249,11 +237,13 @@ bool CreatureAI::UpdateVictim()
 
         return me->GetVictim() != nullptr;
     }
-    else if (me->GetThreatManager().IsThreatListEmpty())
+    else if (me->GetThreatManager().IsThreatListEmpty(true))
     {
         EnterEvadeMode(EVADE_REASON_NO_HOSTILES);
         return false;
     }
+    else
+        me->AttackStop();
 
     return true;
 }