From ffc05d0bf17979b14a913a2a0e9393e564c1913b Mon Sep 17 00:00:00 2001
From: Ovahlord <dreadkiller@gmx.de>
Date: Fri, 26 Feb 2021 11:30:44 +0100
Subject: [PATCH] Core/Spells: implement helper to filter mechanic immunities
 in packets to reflect sniff behavior and removed pct heal effects from heal
 prediction

Despite being able to send all mechanic immunities in spell_start and channel_start, sniffs confirm that only relevant immunities are being sent which in most cases are silence and interrupt immunities. Further sniff analysis may reveal even more possible interrupt flags
---
 src/server/game/Spells/Spell.cpp     | 14 ++++++--------
 src/server/game/Spells/SpellInfo.cpp | 19 +++++++++++++++++++
 src/server/game/Spells/SpellInfo.h   |  2 ++
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/src/server/game/Spells/Spell.cpp b/src/server/game/Spells/Spell.cpp
index 28b23fb6fbb..544a96c2e15 100644
--- a/src/server/game/Spells/Spell.cpp
+++ b/src/server/game/Spells/Spell.cpp
@@ -4279,8 +4279,9 @@ void Spell::SendSpellStart()
     //TC_LOG_DEBUG("spells", "Sending SMSG_SPELL_START id=%u", m_spellInfo->Id);
 
     uint32 castFlags = CAST_FLAG_HAS_TRAJECTORY;
-    uint32 schoolImmunityMask = m_caster->GetSchoolImmunityMask();
-    uint32 mechanicImmunityMask = m_caster->GetMechanicImmunityMask();
+    uint32 schoolImmunityMask = m_casttime != 0 ? m_caster->GetSchoolImmunityMask() : 0;
+    uint32 mechanicImmunityMask = m_casttime != 0 ? m_spellInfo->GetMechanicImmunityMask(m_caster, false) : 0;
+
     if (schoolImmunityMask || mechanicImmunityMask)
         castFlags |= CAST_FLAG_IMMUNITY;
 
@@ -4298,8 +4299,7 @@ void Spell::SendSpellStart()
     if (m_spellInfo->RuneCostID && m_spellInfo->PowerType == POWER_RUNE)
         castFlags |= CAST_FLAG_NO_GCD; // not needed, but Blizzard sends it
 
-    if ((m_casttime && m_spellInfo->HasEffect(SPELL_EFFECT_HEAL)) || m_spellInfo->HasEffect(SPELL_EFFECT_HEAL_PCT) ||
-        m_spellInfo->HasAura(SPELL_AURA_PERIODIC_HEAL))
+    if ((m_casttime && m_spellInfo->HasEffect(SPELL_EFFECT_HEAL)) || m_spellInfo->HasAura(SPELL_AURA_PERIODIC_HEAL))
         castFlags |= CAST_FLAG_HEAL_PREDICTION;
 
     WorldPackets::Spells::SpellStart packet;
@@ -4317,8 +4317,6 @@ void Spell::SendSpellStart()
     castData.CastFlagsEx = m_castFlagsEx;
     castData.CastTime = m_casttime;
 
-    //data << uint32(m_timer);                                // delay?
-
     m_targets.Write(castData.Target);
 
     if (castFlags & CAST_FLAG_POWER_LEFT_SELF)
@@ -4806,7 +4804,7 @@ void Spell::SendChannelStart(uint32 duration)
 
     uint32 castFlags = CAST_FLAG_HAS_TRAJECTORY;
     uint32 schoolImmunityMask = m_caster->GetSchoolImmunityMask();
-    uint32 mechanicImmunityMask = m_caster->GetMechanicImmunityMask();
+    uint32 mechanicImmunityMask = m_spellInfo->GetMechanicImmunityMask(m_caster, true);
 
     if (schoolImmunityMask || mechanicImmunityMask)
         castFlags |= CAST_FLAG_IMMUNITY;
@@ -4824,7 +4822,7 @@ void Spell::SendChannelStart(uint32 duration)
 
         for (uint8 j = 0; j < MAX_SPELL_EFFECTS; j++)
         {
-            if (spell->Effects[j].Effect == SPELL_EFFECT_HEAL || spell->Effects[j].Effect == SPELL_EFFECT_HEAL_PCT)
+            if (spell->Effects[j].Effect == SPELL_EFFECT_HEAL)
             {
                 Unit* target = m_targets.GetUnitTarget() ? m_targets.GetUnitTarget() : m_caster;
                 int32 heal = spell->Effects[j].CalcValue(m_caster);
diff --git a/src/server/game/Spells/SpellInfo.cpp b/src/server/game/Spells/SpellInfo.cpp
index 3444f103f75..f382b0802fd 100644
--- a/src/server/game/Spells/SpellInfo.cpp
+++ b/src/server/game/Spells/SpellInfo.cpp
@@ -3253,6 +3253,25 @@ uint32 SpellInfo::GetAllowedMechanicMask() const
     return _allowedMechanicMask;
 }
 
+uint32 SpellInfo::GetMechanicImmunityMask(Unit* caster, bool channeled) const
+{
+    uint32 casterMechanicImmunityMask = caster->GetMechanicImmunityMask();
+    uint32 mechanicImmunityMask = 0;
+    uint32 flags = channeled ? ChannelInterruptFlags : InterruptFlags;
+
+    // @todo: research other interrupt flags
+    if (flags & SPELL_INTERRUPT_FLAG_INTERRUPT)
+    {
+        if (casterMechanicImmunityMask & (1 << MECHANIC_SILENCE))
+            mechanicImmunityMask |= (1 << MECHANIC_SILENCE);
+
+        if (casterMechanicImmunityMask & (1 << MECHANIC_INTERRUPT))
+            mechanicImmunityMask |= (1 << MECHANIC_INTERRUPT);
+    }
+
+    return mechanicImmunityMask;
+}
+
 float SpellInfo::GetMinRange(bool positive) const
 {
     if (!RangeEntry)
diff --git a/src/server/game/Spells/SpellInfo.h b/src/server/game/Spells/SpellInfo.h
index 9bb59173a9d..5c768e7a0b1 100644
--- a/src/server/game/Spells/SpellInfo.h
+++ b/src/server/game/Spells/SpellInfo.h
@@ -593,6 +593,8 @@ class TC_GAME_API SpellInfo
 
         uint32 GetAllowedMechanicMask() const;
 
+        uint32 GetMechanicImmunityMask(Unit* caster, bool channeled) const;
+
     private:
         // loading helpers
         void _InitializeExplicitTargetMask();