From 98eda3684d7dfa0da160c88539ac762336b7dc70 Mon Sep 17 00:00:00 2001
From: Jelle Meeus <sogladev@gmail.com>
Date: Tue, 29 Jul 2025 05:36:36 -0700
Subject: [PATCH] feat(Core/Spell): implement `SPELL_ATTR2_CHAIN_FROM_CASTER`
 (#22515)

Co-authored-by: Shauren <shauren.trinity@gmail.com>
---
 src/server/game/Spells/Spell.cpp  | 25 +++++++++++--------------
 src/server/shared/SharedDefines.h |  2 +-
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/src/server/game/Spells/Spell.cpp b/src/server/game/Spells/Spell.cpp
index af13154c8..a0f46e9a8 100644
--- a/src/server/game/Spells/Spell.cpp
+++ b/src/server/game/Spells/Spell.cpp
@@ -2238,21 +2238,15 @@ void Spell::SearchChainTargets(std::list<WorldObject*>& targets, uint32 chainTar
     if (isBouncingFar)
         searchRadius *= chainTargets;
 
+    WorldObject* chainSource = m_spellInfo->HasAttribute(SPELL_ATTR2_CHAIN_FROM_CASTER) ? m_caster : target;
     std::list<WorldObject*> tempTargets;
-    SearchAreaTargets(tempTargets, searchRadius, target, m_caster, objectType, selectType, condList);
+    SearchAreaTargets(tempTargets, searchRadius, chainSource, m_caster, objectType, selectType, condList);
     tempTargets.remove(target);
 
     // remove targets which are always invalid for chain spells
     // for some spells allow only chain targets in front of caster (swipe for example)
     if (!isBouncingFar)
-    {
-        for (std::list<WorldObject*>::iterator itr = tempTargets.begin(); itr != tempTargets.end();)
-        {
-            std::list<WorldObject*>::iterator checkItr = itr++;
-            if (!m_caster->HasInArc(static_cast<float>(M_PI), *checkItr))
-                tempTargets.erase(checkItr);
-        }
-    }
+        tempTargets.remove_if([this](WorldObject* target) { return !m_caster->HasInArc(static_cast<float>(M_PI), target); });
 
     while (chainTargets)
     {
@@ -2267,7 +2261,7 @@ void Spell::SearchChainTargets(std::list<WorldObject*>& targets, uint32 chainTar
                 if (Unit* unit = (*itr)->ToUnit())
                 {
                     uint32 deficit = unit->GetMaxHealth() - unit->GetHealth();
-                    if (deficit > maxHPDeficit && target->IsWithinDist(unit, jumpRadius) && target->IsWithinLOSInMap(unit, VMAP::ModelIgnoreFlags::M2))
+                    if (deficit > maxHPDeficit && chainSource->IsWithinDist(unit, jumpRadius) && chainSource->IsWithinLOSInMap(unit, VMAP::ModelIgnoreFlags::M2))
                     {
                         foundItr = itr;
                         maxHPDeficit = deficit;
@@ -2282,19 +2276,22 @@ void Spell::SearchChainTargets(std::list<WorldObject*>& targets, uint32 chainTar
             {
                 if (foundItr == tempTargets.end())
                 {
-                    if ((!isBouncingFar || target->IsWithinDist(*itr, jumpRadius)) && target->IsWithinLOSInMap(*itr, VMAP::ModelIgnoreFlags::M2))
+                    if ((!isBouncingFar || chainSource->IsWithinDist(*itr, jumpRadius)) && chainSource->IsWithinLOSInMap(*itr, VMAP::ModelIgnoreFlags::M2))
                         foundItr = itr;
                 }
-                else if (target->GetDistanceOrder(*itr, *foundItr) && target->IsWithinLOSInMap(*itr, VMAP::ModelIgnoreFlags::M2))
+                else if (chainSource->GetDistanceOrder(*itr, *foundItr) && chainSource->IsWithinLOSInMap(*itr, VMAP::ModelIgnoreFlags::M2))
                     foundItr = itr;
             }
         }
         // not found any valid target - chain ends
         if (foundItr == tempTargets.end())
             break;
-        target = *foundItr;
+
+        if (!m_spellInfo->HasAttribute(SPELL_ATTR2_CHAIN_FROM_CASTER))
+            chainSource = *foundItr;
+
+        targets.push_back(*foundItr);
         tempTargets.erase(foundItr);
-        targets.push_back(target);
         --chainTargets;
     }
 }
diff --git a/src/server/shared/SharedDefines.h b/src/server/shared/SharedDefines.h
index 2788167c4..e114c997d 100644
--- a/src/server/shared/SharedDefines.h
+++ b/src/server/shared/SharedDefines.h
@@ -465,7 +465,7 @@ enum SpellAttr2 : uint32
     SPELL_ATTR2_ALWAYS_CAST_AS_UNIT                  = 0x00000200, // TITLE Unknown attribute 9@Attr2
     SPELL_ATTR2_SPECIAL_TAMING_FLAG                  = 0x00000400, // TITLE Unknown attribute 10@Attr2 DESCRIPTION Related to taming?
     SPELL_ATTR2_NO_TARGET_PER_SECOND_COST            = 0x00000800, // TITLE Health Funnel
-    SPELL_ATTR2_CHAIN_FROM_CASTER                    = 0x00001000, // TITLE Unknown attribute 12@Attr2 DESCRIPTION Cleave, Heart Strike, Maul, Sunder Armor, Swipe
+    SPELL_ATTR2_CHAIN_FROM_CASTER                    = 0x00001000, // TITLE Chain from caster DESCRIPTION Cleave, Heart Strike, Maul, Sunder Armor, Swipe
     SPELL_ATTR2_ENCHANT_OWN_ITEM_ONLY                = 0x00002000, // TITLE Enchant persists when entering arena
     SPELL_ATTR2_ALLOW_WHILE_INVISIBLE                = 0x00004000, // TITLE Unknown attribute 14@Attr2
     SPELL_ATTR2_DO_NOT_CONSUME_IF_GAINED_DURING_CAST = 0x00008000, // TITLE Unused attribute 15@Attr2 DESCRIPTION not set in 3.3.5a