Core/Scripts: fix Nightfall proc chance and reduce it for victims with level above 60

Closes #15734

(cherrypicked from eac9c1f0b9)

sql/updates/world/master/2019_07_28_01_world_2017_02_21_01_world.sql

@@ -0,0 +1,3 @@
+DELETE FROM `item_script_names` WHERE  `Id`=19169;
+INSERT INTO `item_script_names` (`Id`, `ScriptName`) VALUES (19169, 'item_generic_limit_chance_above_60');
+UPDATE `item_template_addon` SET `SpellPPMChance`='2.5' WHERE  `Id`=19169;

src/server/game/Entities/Player/Player.cpp

@@ -7978,7 +7978,7 @@ void Player::CastItemCombatSpell(DamageInfo const& damageInfo, Item* item, ItemT
             else if (chance > 100.0f)
                 chance = GetWeaponProcChance();
 
-            if (roll_chance_f(chance))
+            if (roll_chance_f(chance) && sScriptMgr->OnCastItemCombatSpell(this, damageInfo.GetVictim(), spellInfo, item))
                 CastSpell(damageInfo.GetVictim(), spellInfo->Id, true, item);
         }
     }

src/server/game/Scripting/ScriptMgr.cpp

@@ -1685,6 +1685,17 @@ bool ScriptMgr::OnItemRemove(Player* player, Item* item)
     return tmpscript->OnRemove(player, item);
 }
 
+bool ScriptMgr::OnCastItemCombatSpell(Player* player, Unit* victim, SpellInfo const* spellInfo, Item* item)
+{
+    ASSERT(player);
+    ASSERT(victim);
+    ASSERT(spellInfo);
+    ASSERT(item);
+
+    GET_SCRIPT_RET(ItemScript, item->GetScriptId(), tmpscript, true);
+    return tmpscript->OnCastItemCombatSpell(player, victim, spellInfo, item);
+}
+
 bool ScriptMgr::OnDummyEffect(Unit* caster, uint32 spellId, SpellEffIndex effIndex, Creature* target)
 {
     ASSERT(caster);

src/server/game/Scripting/ScriptMgr.h

@@ -52,6 +52,7 @@ class Player;
 class Quest;
 class ScriptMgr;
 class Spell;
+class SpellInfo;
 class SpellScript;
 class SpellCastTargets;
 class Transport;
@@ -388,6 +389,9 @@ class TC_GAME_API ItemScript : public ScriptObject
 
         // Called when the item is destroyed.
         virtual bool OnRemove(Player* /*player*/, Item* /*item*/) { return false; }
+
+        // Called before casting a combat spell from this item (chance on hit spells of item template, can be used to prevent cast if returning false)
+        virtual bool OnCastItemCombatSpell(Player* /*player*/, Unit* /*victim*/, SpellInfo const* /*spellInfo*/, Item* /*item*/) { return true; }
 };
 
 class TC_GAME_API UnitScript : public ScriptObject
@@ -1028,6 +1032,7 @@ class TC_GAME_API ScriptMgr
         bool OnItemUse(Player* player, Item* item, SpellCastTargets const& targets, ObjectGuid castId);
         bool OnItemExpire(Player* player, ItemTemplate const* proto);
         bool OnItemRemove(Player* player, Item* item);
+        bool OnCastItemCombatSpell(Player* player, Unit* victim, SpellInfo const* spellInfo, Item* item);
 
     public: /* CreatureScript */
 

src/server/scripts/World/item_scripts.cpp

@@ -414,6 +414,30 @@ public:
     }
 };
 
+// Only used currently for
+// 19169: Nightfall
+class item_generic_limit_chance_above_60 : public ItemScript
+{
+    public:
+        item_generic_limit_chance_above_60() : ItemScript("item_generic_limit_chance_above_60") { }
+
+        bool OnCastItemCombatSpell(Player* player, Unit* victim, SpellInfo const* /*spellInfo*/, Item* /*item*/) override
+        {
+            // spell proc chance gets severely reduced on victims > 60 (formula unknown)
+            if (victim->getLevel() > 60)
+            {
+                // gives ~0.1% proc chance at lvl 70
+                float const lvlPenaltyFactor = 9.93f;
+                float const failureChance = (victim->GetLevelForTarget(player) - 60) * lvlPenaltyFactor;
+
+                // base ppm chance was already rolled, only roll success chance
+                return !roll_chance_f(failureChance);
+            }
+
+            return true;
+        }
+};
+
 void AddSC_item_scripts()
 {
     new item_only_for_flight();
@@ -427,4 +451,5 @@ void AddSC_item_scripts()
     new item_dehta_trap_smasher();
     new item_trident_of_nazjan();
     new item_captured_frog();
+    new item_generic_limit_chance_above_60();
 }