[Feature] Implemented /shield ability and related affects (#1494)

* shield ability initial work

* updates

* update

* updates

* Update client_process.cpp

* major updates

optimized
pet support
perl support

* updates

* minor update

* fix merge error

* requested changes

* variable fix

* optimization

* minor update

* Revert "optimization"

This reverts commit 27e11e758b.

* fix

reset variables on shield_target if shielder dies or zones during shielding.

* edge case fix

Catch and fix situations where shield target doesn't have shielder variable cleared. Can occur if shielder . uses ability when target is not in combat then zones.

* combined packet and mob function

Shield now uses a common pathway through ShieldAbility, added parameters to perl function

* Addressing formatting for Kayen

* Fix function typo

Co-authored-by: Akkadius <akkadius1@gmail.com>

zone/mob.cpp

@@ -261,7 +261,6 @@ Mob::Mob(
 	MR                = CR = FR = DR = PR = Corrup = PhR = 0;
 	ExtraHaste        = 0;
 	bEnraged          = false;
-	shield_target     = nullptr;
 	current_mana      = 0;
 	max_mana          = 0;
 	hp_regen          = in_hp_regen;
@@ -376,11 +375,13 @@ Mob::Mob(
 	silenced       = false;
 	amnesiad       = false;
 	inWater        = false;
-	int m;
-	for (m = 0; m < MAX_SHIELDERS; m++) {
-		shielder[m].shielder_id    = 0;
-		shielder[m].shielder_bonus = 0;
-	}
+
+	shield_timer.Disable();
+	m_shield_target_id = 0;
+	m_shielder_id = 0;
+	m_shield_target_mitigation = 0;
+	m_shielder_mitigation = 0;
+	m_shielder_max_distance = 0;
 
 	destructibleobject = false;
 	wandertype         = 0;
@@ -3144,7 +3145,7 @@ int32 Mob::GetActSpellCasttime(uint16 spell_id, int32 casttime)
 	cast_reducer += cast_reducer_no_limit;
 	casttime = casttime * (100 - cast_reducer) / 100;
 	casttime -= cast_reducer_amt;
-	
+
 	return std::max(casttime, 0);
 
 }
@@ -4944,11 +4945,11 @@ int16 Mob::GetPositionalDmgAmt(Mob* defender)
 
 	if (back_arc_dmg_amt || front_arc_dmg_amt) {
 		if (BehindMob(defender, GetX(), GetY()))
-			total_amt = back_arc_dmg_amt; 
+			total_amt = back_arc_dmg_amt;
 		else
 			total_amt = front_arc_dmg_amt;
 	}
-	
+
 	return total_amt;
 }
 
@@ -6196,6 +6197,122 @@ float Mob::GetDefaultRaceSize() const {
 	return GetRaceGenderDefaultHeight(race, gender);
 }
 
+bool Mob::ShieldAbility(uint32 target_id, int shielder_max_distance, int shield_duration, int shield_target_mitigation, int shielder_mitigation, bool use_aa, bool can_shield_npc)
+{
+	Mob* shield_target = entity_list.GetMob(target_id);
+	if (!shield_target) {
+		return false;
+	}
+
+	if (!can_shield_npc && shield_target->IsNPC()) {
+		if (IsClient()) {
+			MessageString(Chat::White, SHIELD_TARGET_NPC);
+		}
+		return false;
+	}
+
+	if (shield_target->GetID() == GetID()) { //Client will give message "You can not shield yourself"
+		return false;
+	}
+
+	//Edge case situations. If 'Shield Target' still has Shielder set but Shielder is not in zone. Catch and fix here.
+	if (shield_target->GetShielderID() && !entity_list.GetMob(shield_target->GetShielderID())) {
+		shield_target->SetShielderID(0);
+	}
+
+	if (GetShielderID() && !entity_list.GetMob(GetShielderID())) {
+		SetShielderID(0);
+	}
+
+	//You have a shielder, or your 'Shield Target' already has a 'Shielder'
+	if (GetShielderID() || shield_target->GetShielderID()) {
+		if (IsClient()) {
+			MessageString(Chat::White, ALREADY_SHIELDED);
+		}
+		return false;
+	}
+
+	//You are being shielded or already have a 'Shield Target'
+	if (GetShieldTargetID() || shield_target->GetShieldTargetID()) {
+		if (IsClient()) {
+			MessageString(Chat::White, ALREADY_SHIELDING);
+		}
+		return false;
+	}
+
+	//AA to increase SPA 230 extended shielding (default live is 15 distance units)
+	if (use_aa) {
+		shielder_max_distance += aabonuses.ExtendedShielding + itembonuses.ExtendedShielding + spellbonuses.ExtendedShielding;
+		shielder_max_distance = std::max(shielder_max_distance, 0);
+	}
+
+	if (shield_target->CalculateDistance(GetX(), GetY(), GetZ()) > static_cast<float>(shielder_max_distance)) {
+		return false; //Live does not give a message when out of range.
+	}
+
+	entity_list.MessageCloseString(this, false, 100, 0, START_SHIELDING, GetCleanName(), shield_target->GetCleanName());
+
+	SetShieldTargetID(shield_target->GetID());
+	SetShielderMitigation(shield_target_mitigation);
+	SetShielderMaxDistance(shielder_max_distance);
+
+	shield_target->SetShielderID(GetID());
+	shield_target->SetShieldTargetMitigation(shield_target_mitigation);
+
+	//Calculate AA for adding time SPA 255 extend shield duration (Baseline ability is 12 seconds)
+	if (use_aa) {
+		shield_duration += (aabonuses.ShieldDuration + itembonuses.ShieldDuration + spellbonuses.ShieldDuration) * 1000;
+		shield_duration = std::max(shield_duration, 1); //Incase of negative modifiers lets just make min duration 1 ms.
+	}
+
+	shield_timer.Start(static_cast<uint32>(shield_duration));
+	return true;
+}
+
+void Mob::ShieldAbilityFinish()
+{
+	Mob* shield_target = entity_list.GetMob(GetShieldTargetID());
+
+	if (shield_target) {
+		entity_list.MessageCloseString(this, false, 100, 0, END_SHIELDING, GetCleanName(), shield_target->GetCleanName());
+		shield_target->SetShielderID(0);
+		shield_target->SetShieldTargetMitigation(0);
+	}
+	SetShieldTargetID(0);
+	SetShielderMitigation(0);
+	SetShielderMaxDistance(0);
+	shield_timer.Disable();
+}
+
+void Mob::ShieldAbilityClearVariables()
+{
+	//If 'shield target' dies
+	if (GetShielderID()){
+		Mob* shielder = entity_list.GetMob(GetShielderID());
+		if (shielder) {
+			shielder->SetShieldTargetID(0);
+			shielder->SetShielderMitigation(0);
+			shielder->SetShielderMaxDistance(0);
+			shielder->shield_timer.Disable();
+		}
+		SetShielderID(0);
+		SetShieldTargetMitigation(0);
+	}
+
+	//If 'shielder' dies
+	if (GetShieldTargetID()) {
+		Mob* shield_target = entity_list.GetMob(GetShieldTargetID());
+		if (shield_target) {
+			shield_target->SetShielderID(0);
+			shield_target->SetShieldTargetMitigation(0);
+		}
+		SetShieldTargetID(0);
+		SetShielderMitigation(0);
+		SetShielderMaxDistance(0);
+		shield_timer.Disable();
+	}
+}
+
 #ifdef BOTS
 bool Mob::JoinHealRotationTargetPool(std::shared_ptr<HealRotation>* heal_rotation)
 {