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)

3 files changed, 65 insertions, 73 deletions

diff --git a/src/server/scripts/Spells/spell_hunter.cpp b/src/server/scripts/Spells/spell_hunter.cpp
index 45a8e390b9c..ed8f1eb38d5 100644
--- a/src/server/scripts/Spells/spell_hunter.cpp
+++ b/src/server/scripts/Spells/spell_hunter.cpp
@@ -38,6 +38,7 @@ enum HunterSpells
     SPELL_HUNTER_EXHILARATION_R2                    = 231546,
     SPELL_HUNTER_LONE_WOLF                          = 155228,
     SPELL_HUNTER_MASTERS_CALL_TRIGGERED             = 62305,
+    SPELL_HUNTER_MISDIRECTION                       = 34477,
     SPELL_HUNTER_MISDIRECTION_PROC                  = 35079,
     SPELL_HUNTER_MULTI_SHOT_FOCUS                   = 213363,
     SPELL_HUNTER_PET_LAST_STAND_TRIGGERED           = 53479,
@@ -297,12 +298,7 @@ class spell_hun_misdirection : public SpellScriptLoader
                     return;
 
                 if (!GetTarget()->HasAura(SPELL_HUNTER_MISDIRECTION_PROC))
-                    GetTarget()->ResetRedirectThreat();
-            }
-
-            bool CheckProc(ProcEventInfo& /*eventInfo*/)
-            {
-                return GetTarget()->GetRedirectThreatTarget() != nullptr;
+                    GetTarget()->GetThreatManager().UnregisterRedirectThreat(SPELL_HUNTER_MISDIRECTION);
             }
 
             void HandleProc(AuraEffect* aurEff, ProcEventInfo& /*eventInfo*/)
@@ -314,7 +310,6 @@ class spell_hun_misdirection : public SpellScriptLoader
             void Register() override
             {
                 AfterEffectRemove += AuraEffectRemoveFn(spell_hun_misdirection_AuraScript::OnRemove, EFFECT_1, SPELL_AURA_DUMMY, AURA_EFFECT_HANDLE_REAL);
-                DoCheckProc += AuraCheckProcFn(spell_hun_misdirection_AuraScript::CheckProc);
                 OnEffectProc += AuraEffectProcFn(spell_hun_misdirection_AuraScript::HandleProc, EFFECT_1, SPELL_AURA_DUMMY);
             }
         };
@@ -337,7 +332,7 @@ class spell_hun_misdirection_proc : public SpellScriptLoader
 
             void OnRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
             {
-                GetTarget()->ResetRedirectThreat();
+                GetTarget()->GetThreatManager().UnregisterRedirectThreat(SPELL_HUNTER_MISDIRECTION);
             }
 
             void Register() override
diff --git a/src/server/scripts/Spells/spell_rogue.cpp b/src/server/scripts/Spells/spell_rogue.cpp
index 003b55c260e..25ba6f0006d 100644
--- a/src/server/scripts/Spells/spell_rogue.cpp
+++ b/src/server/scripts/Spells/spell_rogue.cpp
@@ -51,6 +51,7 @@ enum RogueSpells
     SPELL_ROGUE_STEALTH_STEALTH_AURA                = 158185,
     SPELL_ROGUE_STEALTH_SHAPESHIFT_AURA             = 158188,
     SPELL_ROGUE_VANISH_AURA                         = 11327,
+    SPELL_ROGUE_TRICKS_OF_THE_TRADE                 = 57934,
     SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC            = 59628,
     SPELL_ROGUE_HONOR_AMONG_THIEVES_ENERGIZE        = 51699,
     SPELL_ROGUE_T5_2P_SET_BONUS                     = 37169
@@ -507,82 +508,78 @@ class spell_rog_vanish_aura : public SpellScriptLoader
 };
 
 // 57934 - Tricks of the Trade
-class spell_rog_tricks_of_the_trade : public SpellScriptLoader
+class spell_rog_tricks_of_the_trade_aura : public AuraScript
 {
-    public:
-        spell_rog_tricks_of_the_trade() : SpellScriptLoader("spell_rog_tricks_of_the_trade") { }
+    PrepareAuraScript(spell_rog_tricks_of_the_trade_aura);
 
-        class spell_rog_tricks_of_the_trade_AuraScript : public AuraScript
-        {
-            PrepareAuraScript(spell_rog_tricks_of_the_trade_AuraScript);
+    bool Validate(SpellInfo const* /*spellInfo*/) override
+    {
+        return ValidateSpellInfo({ SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC });
+    }
 
-            bool Validate(SpellInfo const* /*spellInfo*/) override
-            {
-                return ValidateSpellInfo({ SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC });
-            }
+    void OnRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
+    {
+        if (GetTargetApplication()->GetRemoveMode() != AURA_REMOVE_BY_DEFAULT || !GetTarget()->HasAura(SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC))
+            GetTarget()->GetThreatManager().UnregisterRedirectThreat(SPELL_ROGUE_TRICKS_OF_THE_TRADE);
+    }
 
-            void OnRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
-            {
-                if (GetTargetApplication()->GetRemoveMode() != AURA_REMOVE_BY_DEFAULT)
-                    GetTarget()->ResetRedirectThreat();
-            }
+    void HandleProc(AuraEffect* aurEff, ProcEventInfo& /*eventInfo*/)
+    {
+        PreventDefaultAction();
 
-            bool CheckProc(ProcEventInfo& /*eventInfo*/)
-            {
-                _redirectTarget = GetTarget()->GetRedirectThreatTarget();
-                return _redirectTarget != nullptr;
-            }
+        Unit* rogue = GetTarget();
+        if (ObjectAccessor::GetUnit(*rogue, _redirectTarget))
+            rogue->CastSpell(rogue, SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC, aurEff);
+        Remove(AURA_REMOVE_BY_DEFAULT);
+    }
 
-            void HandleProc(AuraEffect* /*aurEff*/, ProcEventInfo& /*eventInfo*/)
-            {
-                PreventDefaultAction();
+    void Register() override
+    {
+        AfterEffectRemove += AuraEffectRemoveFn(spell_rog_tricks_of_the_trade_aura::OnRemove, EFFECT_1, SPELL_AURA_DUMMY, AURA_EFFECT_HANDLE_REAL);
+        OnEffectProc += AuraEffectProcFn(spell_rog_tricks_of_the_trade_aura::HandleProc, EFFECT_1, SPELL_AURA_DUMMY);
+    }
 
-                Unit* target = GetTarget();
-                target->CastSpell(target, SPELL_ROGUE_TRICKS_OF_THE_TRADE_PROC, true);
-                Remove(AURA_REMOVE_BY_DEFAULT); // maybe handle by proc charges
-            }
+    ObjectGuid _redirectTarget;
+public:
+    void SetRedirectTarget(ObjectGuid guid) { _redirectTarget = guid; }
+};
 
-            void Register() override
+class spell_rog_tricks_of_the_trade : public SpellScript
+{
+    PrepareSpellScript(spell_rog_tricks_of_the_trade);
+
+    void DoAfterHit()
+    {
+        if (Aura* aura = GetHitAura())
+            if (auto* script = aura->GetScript<spell_rog_tricks_of_the_trade_aura>("spell_rog_tricks_of_the_trade"))
             {
-                AfterEffectRemove += AuraEffectRemoveFn(spell_rog_tricks_of_the_trade_AuraScript::OnRemove, EFFECT_1, SPELL_AURA_DUMMY, AURA_EFFECT_HANDLE_REAL);
-                DoCheckProc += AuraCheckProcFn(spell_rog_tricks_of_the_trade_AuraScript::CheckProc);
-                OnEffectProc += AuraEffectProcFn(spell_rog_tricks_of_the_trade_AuraScript::HandleProc, EFFECT_1, SPELL_AURA_DUMMY);
+                if (Unit* explTarget = GetExplTargetUnit())
+                    script->SetRedirectTarget(explTarget->GetGUID());
+                else
+                    script->SetRedirectTarget(ObjectGuid::Empty);
             }
+    }
 
-            Unit* _redirectTarget = nullptr;
-        };
-
-        AuraScript* GetAuraScript() const override
-        {
-            return new spell_rog_tricks_of_the_trade_AuraScript();
-        }
+    void Register() override
+    {
+        AfterHit += SpellHitFn(spell_rog_tricks_of_the_trade::DoAfterHit);
+    }
 };
 
 // 59628 - Tricks of the Trade (Proc)
-class spell_rog_tricks_of_the_trade_proc : public SpellScriptLoader
+class spell_rog_tricks_of_the_trade_proc : public AuraScript
 {
-    public:
-        spell_rog_tricks_of_the_trade_proc() : SpellScriptLoader("spell_rog_tricks_of_the_trade_proc") { }
+    PrepareAuraScript(spell_rog_tricks_of_the_trade_proc);
 
-        class spell_rog_tricks_of_the_trade_proc_AuraScript : public AuraScript
-        {
-            PrepareAuraScript(spell_rog_tricks_of_the_trade_proc_AuraScript);
-
-            void HandleRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
-            {
-                GetTarget()->ResetRedirectThreat();
-            }
-
-            void Register() override
-            {
-                AfterEffectRemove += AuraEffectRemoveFn(spell_rog_tricks_of_the_trade_proc_AuraScript::HandleRemove, EFFECT_0, SPELL_AURA_DUMMY, AURA_EFFECT_HANDLE_REAL);
-            }
-        };
+    void HandleRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
+    {
+        GetTarget()->GetThreatManager().UnregisterRedirectThreat(SPELL_ROGUE_TRICKS_OF_THE_TRADE);
+    }
 
-        AuraScript* GetAuraScript() const override
-        {
-            return new spell_rog_tricks_of_the_trade_proc_AuraScript();
-        }
+    void Register() override
+    {
+        AfterEffectRemove += AuraEffectRemoveFn(spell_rog_tricks_of_the_trade_proc::HandleRemove, EFFECT_0, SPELL_AURA_DUMMY, AURA_EFFECT_HANDLE_REAL);
+    }
 };
 
 // 198031 - Honor Among Thieves
@@ -704,8 +701,8 @@ void AddSC_rogue_spell_scripts()
     new spell_rog_stealth();
     new spell_rog_vanish();
     new spell_rog_vanish_aura();
-    new spell_rog_tricks_of_the_trade();
-    new spell_rog_tricks_of_the_trade_proc();
+    RegisterSpellAndAuraScriptPair(spell_rog_tricks_of_the_trade, spell_rog_tricks_of_the_trade_aura);
+    RegisterAuraScript(spell_rog_tricks_of_the_trade_proc);
     new spell_rog_honor_among_thieves();
     new spell_rog_eviscerate();
     new spell_rog_envenom();
diff --git a/src/server/scripts/Spells/spell_warlock.cpp b/src/server/scripts/Spells/spell_warlock.cpp
index 163c867d71d..1740f3291f9 100644
--- a/src/server/scripts/Spells/spell_warlock.cpp
+++ b/src/server/scripts/Spells/spell_warlock.cpp
@@ -51,7 +51,7 @@ enum WarlockSpells
     SPELL_WARLOCK_RAIN_OF_FIRE_DAMAGE               = 42223,
     SPELL_WARLOCK_SEED_OF_CORRUPTION_DAMAGE         = 27285,
     SPELL_WARLOCK_SEED_OF_CORRUPTION_GENERIC        = 32865,
-    SPELL_WARLOCK_SOULSHATTER                       = 32835,
+    SPELL_WARLOCK_SOULSHATTER_EFFECT                = 32835,
     SPELL_WARLOCK_SOUL_SWAP_CD_MARKER               = 94229,
     SPELL_WARLOCK_SOUL_SWAP_OVERRIDE                = 86211,
     SPELL_WARLOCK_SOUL_SWAP_MOD_COST                = 92794,
@@ -815,15 +815,15 @@ class spell_warl_soulshatter : public SpellScriptLoader
 
             bool Validate(SpellInfo const* /*spellInfo*/) override
             {
-                return ValidateSpellInfo({ SPELL_WARLOCK_SOULSHATTER });
+                return ValidateSpellInfo({ SPELL_WARLOCK_SOULSHATTER_EFFECT });
             }
 
             void HandleDummy(SpellEffIndex /*effIndex*/)
             {
                 Unit* caster = GetCaster();
                 if (Unit* target = GetHitUnit())
-                    if (target->CanHaveThreatList() && target->GetThreatManager().IsThreatenedBy(caster, true))
-                        caster->CastSpell(target, SPELL_WARLOCK_SOULSHATTER, true);
+                    if (target->GetThreatManager().IsThreatenedBy(caster, true))
+                        caster->CastSpell(target, SPELL_WARLOCK_SOULSHATTER_EFFECT, true);
             }
 
             void Register() override