Core/Spells: Implemented SpellValueMod duration

Port From (https://github.com/TrinityCore/TrinityCore/commit/a048475cb037a3a3672723c1f2ab32a343142927)

Source/Framework/Constants/UnitConst.cs

@@ -396,7 +396,8 @@ namespace Framework.Constants
         MaxTargets,
         AuraStack,
         CritChance,
-        DurationPct
+        DurationPct,
+        Duration
     }
 
     public enum CombatRating

Source/Game/Spells/Spell.cs

@@ -2048,7 +2048,9 @@ namespace Game.Spells
 
                             spellAura.SetDiminishGroup(hitInfo.DRGroup);
 
-                            hitInfo.AuraDuration = caster.ModSpellDuration(m_spellInfo, unit, hitInfo.AuraDuration, hitInfo.Positive, spellAura.GetEffectMask());
+                            if (!m_spellValue.Duration.HasValue)
+                            {
+                                hitInfo.AuraDuration *= caster.ModSpellDuration(m_spellInfo, unit, hitInfo.AuraDuration, hitInfo.Positive, spellAura.GetEffectMask());
 
                                 if (hitInfo.AuraDuration > 0)
                                 {
@@ -2076,6 +2078,9 @@ namespace Game.Spells
                                             hitInfo.AuraDuration = (int)(origDuration * m_originalCaster.m_unitData.ModCastingSpeed);
                                     }
                                 }
+                            }
+                            else
+                                hitInfo.AuraDuration = m_spellValue.Duration.Value;
 
                             if (hitInfo.AuraDuration != spellAura.GetMaxDuration())
                             {
@@ -2799,7 +2804,9 @@ namespace Game.Spells
             if (m_spellInfo.IsChanneled())
             {
                 int duration = m_spellInfo.GetDuration();
-                if (duration > 0)
+                if (duration > 0 || m_spellValue.Duration.HasValue)
+                {
+                    if (!m_spellValue.Duration.HasValue)
                     {
                         // First mod_duration then haste - see Missile Barrage
                         // Apply duration mod
@@ -2811,11 +2818,15 @@ namespace Game.Spells
 
                         // Apply haste mods
                         m_caster.ModSpellDurationTime(m_spellInfo, ref duration, this);
+                    }
+                    else
+                        duration = m_spellValue.Duration.Value;
 
+                    m_channeledDuration = duration;
                     SendChannelStart((uint)duration);
                 }
                 else if (duration == -1)
-                    SendChannelStart((uint)duration);
+                    SendChannelStart(unchecked((uint)duration));
 
                 if (duration != 0)
                 {
@@ -6424,7 +6435,10 @@ namespace Game.Spells
                 return;
 
             //check pushback reduce
-            int delaytime = MathFunctions.CalculatePct(m_spellInfo.GetDuration(), 25); // channeling delay is normally 25% of its time per hit
+            // should be affected by modifiers, not take the dbc duration.
+            int duration = ((m_channeledDuration > 0) ? m_channeledDuration : m_spellInfo.GetDuration());
+
+            int delaytime = MathFunctions.CalculatePct(duration, 25); // channeling delay is normally 25% of its time per hit
             int delayReduce = 100;                                    // must be initialized to 100 for percent modifiers
 
             Player player = unitCaster.GetSpellModOwner();
@@ -6879,6 +6893,9 @@ namespace Game.Spells
                 case SpellValueMod.DurationPct:
                     m_spellValue.DurationMul = (float)value / 100.0f;
                     break;
+                case SpellValueMod.Duration:
+                    m_spellValue.Duration.Set(value);
+                    break;
             }
         }
 
@@ -7415,6 +7432,7 @@ namespace Game.Spells
 
         List<SpellPowerCost> m_powerCost = new();
         int m_casttime;                                   // Calculated spell cast time initialized only in Spell.prepare
+        int m_channeledDuration;                          // Calculated channeled spell duration in order to calculate correct pushback.
         bool m_canReflect;                                  // can reflect this spell?
         bool m_autoRepeat;
         byte m_runesState;
@@ -8073,6 +8091,7 @@ namespace Game.Spells
         public int AuraStackAmount;
         public float DurationMul;
         public float CriticalChance;
+        public Optional<int> Duration;
     }
 
     // Spell modifier (used for modify other spells)