Core/Spells: implemented SpellPriority field from SpellEntry to cleanup charged mod proc behaviour

- Only one charged mod will be consumed per SpellMod apply, and it'll be compared against other mod priority
- This is proper way of handling Backdraft/Backlash and Deathchill/Killing Machine

Thanks to killerwife for info

6 files changed, 33 insertions, 91 deletions

diff --git a/src/server/game/DataStores/DBCStructure.h b/src/server/game/DataStores/DBCStructure.h
index b0bea8ca81c..8c84e4596cf 100644
--- a/src/server/game/DataStores/DBCStructure.h
+++ b/src/server/game/DataStores/DBCStructure.h
@@ -1404,7 +1404,7 @@ struct SpellEntry
     uint32    SpellVisual[2];                               // 131-132  m_spellVisualID
     uint32    SpellIconID;                                  // 133      m_spellIconID
     uint32    activeIconID;                                 // 134      m_activeIconID
-    //uint32    spellPriority;                              // 135 not used
+    uint32    SpellPriority;                                // 135      m_spellPriority
     char*     SpellName[16];                                // 136-151  m_name_lang
     //uint32    SpellNameFlag;                              // 152 not used
     char*     Rank[16];                                     // 153-168  m_nameSubtext_lang
diff --git a/src/server/game/DataStores/DBCfmt.h b/src/server/game/DataStores/DBCfmt.h
index dd74cffb51e..6651270848b 100644
--- a/src/server/game/DataStores/DBCfmt.h
+++ b/src/server/game/DataStores/DBCfmt.h
@@ -113,7 +113,7 @@ char const SpellDifficultyfmt[] = "niiii";
 const std::string CustomSpellDifficultyfmt = "ppppp";
 const std::string CustomSpellDifficultyIndex = "id";
 char const SpellDurationfmt[] = "niii";
-char const SpellEntryfmt[] = "niiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiifxiiiiiiiiiiiiiiiiiiiiiiiiiiiifffiiiiiiiiiiiiiiiiiiiiifffiiiiiiiiiiiiiiifffiiiiiiiiiiiiixssssssssssssssssxssssssssssssssssxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxiiiiiiiiiiixfffxxxiiiiixxfffxx";
+char const SpellEntryfmt[] = "niiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiifxiiiiiiiiiiiiiiiiiiiiiiiiiiiifffiiiiiiiiiiiiiiiiiiiiifffiiiiiiiiiiiiiiifffiiiiiiiiiiiiiissssssssssssssssxssssssssssssssssxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxiiiiiiiiiiixfffxxxiiiiixxfffxx";
 const std::string CustomSpellEntryfmt = "papppppppppppapapaaaaaaaaaaapaaapapppppppaaaaapaapaaaaaaaaaaaaaaaaaappppppppppppppppppppppppppppppppppppaaappppppppppppaaapppppppppaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaappppppppapppaaaaappaaaaaaa";
 const std::string CustomSpellEntryIndex = "Id";
 char const SpellFocusObjectfmt[] = "nxxxxxxxxxxxxxxxxx";
diff --git a/src/server/game/Entities/Player/Player.cpp b/src/server/game/Entities/Player/Player.cpp
index 266259b8257..6874c6a1f77 100644
--- a/src/server/game/Entities/Player/Player.cpp
+++ b/src/server/game/Entities/Player/Player.cpp
@@ -20869,6 +20869,10 @@ bool Player::IsAffectedBySpellmod(SpellInfo const* spellInfo, SpellModifier* mod
     if (mod->op == SPELLMOD_DURATION && spellInfo->GetDuration() == -1)
         return false;
 
+    // mod crit to spells that can't crit
+    if (mod->op == SPELLMOD_CRITICAL_CHANCE && !spellInfo->HasAttribute(SPELL_ATTR0_CU_CAN_CRIT))
+        return false;
+
     return spellInfo->IsAffectedBySpellMod(mod);
 }
 
@@ -20882,103 +20886,48 @@ void Player::ApplySpellMod(uint32 spellId, SpellModOp op, T& basevalue, Spell* s
     float totalmul = 1.0f;
     int32 totalflat = 0;
 
-    // Drop charges for triggering spells instead of triggered ones
-    if (m_spellModTakingSpell)
-        spell = m_spellModTakingSpell;
-
-    switch (op)
+    auto calculateSpellMod = [&](SpellModifier* mod)
     {
-        // special case, if a mod makes spell instant, only consume that mod
-        case SPELLMOD_CASTING_TIME:
-        {
-            SpellModifier* modInstantSpell = nullptr;
-            for (SpellModifier* mod : m_spellMods[op])
-            {
-                if (!IsAffectedBySpellmod(spellInfo, mod, spell))
-                    continue;
-
-                if (mod->type == SPELLMOD_PCT && basevalue < T(10000) && mod->value <= -100)
-                {
-                    modInstantSpell = mod;
-                    break;
-                }
-            }
-
-            if (modInstantSpell)
-            {
-                Player::ApplyModToSpell(modInstantSpell, spell);
-                basevalue = T(0);
-                return;
-            }
-            break;
-        }
-        // special case if two mods apply 100% critical chance, only consume one
-        case SPELLMOD_CRITICAL_CHANCE:
-        {
-            SpellModifier* modCritical = nullptr;
-            for (SpellModifier* mod : m_spellMods[op])
-            {
-                if (!IsAffectedBySpellmod(spellInfo, mod, spell))
-                    continue;
-
-                if (mod->type == SPELLMOD_FLAT && mod->value >= 100)
-                {
-                    modCritical = mod;
-                    break;
-                }
-            }
-
-            if (modCritical)
-            {
-                Player::ApplyModToSpell(modCritical, spell);
-                basevalue = T(100);
-                return;
-            }
-            break;
-        }
-        default:
-            break;
-    }
-
-    for (SpellModifier* mod : m_spellMods[op])
-    {
-        if (!IsAffectedBySpellmod(spellInfo, mod, spell))
-            continue;
-
         switch (mod->type)
         {
             case SPELLMOD_FLAT:
                 totalflat += mod->value;
                 break;
             case SPELLMOD_PCT:
-            {
-                // skip percent mods with null basevalue (most important for spell mods with charges)
-                if (basevalue == T(0))
-                    continue;
-
                 // special case (skip > 10sec spell casts for instant cast setting)
                 if (op == SPELLMOD_CASTING_TIME && mod->value <= -100 && basevalue >= T(10000))
-                    continue;
-                else if (!Player::HasSpellModApplied(mod, spell))
-                {
-                    // special case for Surge of Light, don't apply critical chance reduction if other mods not applied (ie procs while casting another spell)
-                    // (Surge of Light is the only PCT_MOD on critical chance)
-                    if (op == SPELLMOD_CRITICAL_CHANCE)
-                        continue;
-                    // special case for Backdraft, dont' apply GCD reduction if cast time reduction wasn't applied (ie when Backlash is consumed first)
-                    // (Backdraft is the only PCT_MOD on global cooldown)
-                    else if (op == SPELLMOD_GLOBAL_COOLDOWN)
-                        continue;
-                }
+                    return;
 
                 totalmul += CalculatePct(1.0f, mod->value);
                 break;
-            }
         }
 
         Player::ApplyModToSpell(mod, spell);
+    };
+
+    // Drop charges for triggering spells instead of triggered ones
+    if (m_spellModTakingSpell)
+        spell = m_spellModTakingSpell;
+
+    SpellModifier* chargedMod = nullptr;
+    for (SpellModifier* mod : m_spellMods[op])
+    {
+        if (!IsAffectedBySpellmod(spellInfo, mod, spell))
+            continue;
+
+        if (mod->ownerAura->IsUsingCharges())
+        {
+            if (!chargedMod || (chargedMod->ownerAura->GetSpellInfo()->Priority < mod->ownerAura->GetSpellInfo()->Priority))
+                chargedMod = mod;
+            continue;
+        }
+
+        calculateSpellMod(mod);
     }
 
+    if (chargedMod)
+        calculateSpellMod(chargedMod);
+
     basevalue = T(float(basevalue + totalflat) * totalmul);
 }
 
@@ -21023,14 +20972,6 @@ void Player::AddSpellMod(SpellModifier* mod, bool apply)
         m_spellMods[mod->op].erase(mod);
 }
 
-bool Player::HasSpellModApplied(SpellModifier* mod, Spell* spell)
-{
-    if (!spell)
-        return false;
-
-    return spell->m_appliedMods.count(mod->ownerAura) != 0;
-}
-
 void Player::ApplyModToSpell(SpellModifier* mod, Spell* spell)
 {
     if (!spell)
diff --git a/src/server/game/Entities/Player/Player.h b/src/server/game/Entities/Player/Player.h
index fd9c4230ca9..e828bdb5488 100644
--- a/src/server/game/Entities/Player/Player.h
+++ b/src/server/game/Entities/Player/Player.h
@@ -1454,7 +1454,6 @@ class TC_GAME_API Player : public Unit, public GridObject<Player>
         template <class T>
         void ApplySpellMod(uint32 spellId, SpellModOp op, T& basevalue, Spell* spell = nullptr) const;
         static void ApplyModToSpell(SpellModifier* mod, Spell* spell);
-        static bool HasSpellModApplied(SpellModifier* mod, Spell* spell);
         void SetSpellModTakingSpell(Spell* spell, bool apply);
 
         void RemoveArenaSpellCooldowns(bool removeActivePetCooldowns = false);
diff --git a/src/server/game/Spells/SpellInfo.cpp b/src/server/game/Spells/SpellInfo.cpp
index 873bfbefdcf..88958e97fd3 100644
--- a/src/server/game/Spells/SpellInfo.cpp
+++ b/src/server/game/Spells/SpellInfo.cpp
@@ -841,6 +841,7 @@ SpellInfo::SpellInfo(SpellEntry const* spellEntry)
 
     SpellIconID = spellEntry->SpellIconID;
     ActiveIconID = spellEntry->activeIconID;
+    Priority = spellEntry->SpellPriority;
     for (uint8 i = 0; i < 16; ++i)
         SpellName[i] = spellEntry->SpellName[i];
 
diff --git a/src/server/game/Spells/SpellInfo.h b/src/server/game/Spells/SpellInfo.h
index e117319a7f1..5670a9052a2 100644
--- a/src/server/game/Spells/SpellInfo.h
+++ b/src/server/game/Spells/SpellInfo.h
@@ -386,6 +386,7 @@ class TC_GAME_API SpellInfo
         uint32 SpellVisual[2];
         uint32 SpellIconID;
         uint32 ActiveIconID;
+        uint32 Priority;
         char* SpellName[16];
         char* Rank[16];
         uint32 MaxTargetLevel;