Core/Spells: Fixed spell effect value truncation when value is a large integer

Port From (https://github.com/TrinityCore/TrinityCore/commit/2d205506bfd3a2bb253db73b121fd147928811ba)

Source/Game/Entities/Object/WorldObject.cs

@@ -1827,7 +1827,7 @@ namespace Game.Entities
             return spellInfo.GetMinRange(!IsHostileTo(target));
         }
 
-        public float ApplyEffectModifiers(SpellInfo spellInfo, uint effIndex, float value)
+        public double ApplyEffectModifiers(SpellInfo spellInfo, uint effIndex, double value)
         {
             Player modOwner = GetSpellModOwner();
             if (modOwner != null)

Source/Game/Entities/Player/Player.Spells.cs

@@ -2765,6 +2765,16 @@ namespace Game.Entities
             basevalue = (float)(basevalue + totalflat) * totalmul;
         }
 
+        public void ApplySpellMod(SpellInfo spellInfo, SpellModOp op, ref double basevalue, Spell spell = null)
+        {
+            float totalmul = 1.0f;
+            int totalflat = 0;
+
+            GetSpellModValues(spellInfo, op, spell, basevalue, ref totalflat, ref totalmul);
+
+            basevalue = (double)(basevalue + totalflat) * totalmul;
+        }
+
         public void GetSpellModValues<T>(SpellInfo spellInfo, SpellModOp op, Spell spell, T baseValue, ref int flat, ref float pct) where T : IComparable
         {
             flat = 0;

Source/Game/Spells/SpellInfo.cs

@@ -4171,11 +4171,11 @@ namespace Game.Spells
         public int CalcValue(out float variance, WorldObject caster = null, int? bp = null, Unit target = null, uint castItemId = 0, int itemLevel = -1)
         {
             variance = 0.0f;
-            float basePointsPerLevel = RealPointsPerLevel;
+            double basePointsPerLevel = RealPointsPerLevel;
             // TODO: this needs to be a float, not rounded
             int basePoints = CalcBaseValue(caster, target, castItemId, itemLevel);
-            float value = bp.HasValue ? bp.Value : basePoints;
-            float comboDamage = PointsPerResource;
+            double value = bp.HasValue ? bp.Value : basePoints;
+            double comboDamage = PointsPerResource;
 
             Unit casterUnit = null;
             if (caster != null)
@@ -4184,9 +4184,9 @@ namespace Game.Spells
             if (Scaling.Variance != 0)
             {
                 float delta = Math.Abs(Scaling.Variance * 0.5f);
-                float valueVariance = RandomHelper.FRand(-delta, delta);
-                value += basePoints * valueVariance;
-                variance = valueVariance;
+                double valueVariance = RandomHelper.FRand(-delta, delta);
+                value += (double)basePoints * valueVariance;
+                variance = (float)valueVariance;
             }
 
             // base amount modification based on spell lvl vs caster lvl