Core/Unit: Fix movement hiccups in water

* Core/Unit: Allow to define Units which can enter water but cannot swim

Allow to define Units which can enter water but cannot swim, i.e. crabs walking at the bottom of a sea.

* Add UNIT_FLAG_SWIMMING to creatures when entering combat

* Fix charmed creatures not entering water

* Always allow Creatures controlled by players to enter water

* Add swimming flag when possessing a unit and remove it properly at the end, even if the creature engaged combat before and after.
When adding/removing UNIT_FLAG_SWIMMING manually calling Creature::RefreshSwimmingFlag(true) might be required.

src/server/game/Entities/Creature/Creature.cpp

@@ -267,7 +267,7 @@ m_respawnDelay(300), m_corpseDelay(60), m_respawnradius(0.0f), m_boundaryCheckTi
 m_defaultMovementType(IDLE_MOTION_TYPE), m_spawnId(0), m_equipmentId(0), m_originalEquipmentId(0), m_AlreadyCallAssistance(false),
 m_AlreadySearchedAssistance(false), m_regenHealth(true), m_cannotReachTarget(false), m_cannotReachTimer(0), m_AI_locked(false), m_meleeDamageSchoolMask(SPELL_SCHOOL_MASK_NORMAL),
 m_originalEntry(0), m_homePosition(), m_transportHomePosition(), m_creatureInfo(nullptr), m_creatureData(nullptr), _waypointPathId(0), _currentWaypointNodeInfo(0, 0), _cyclicSplinePathId(0),
-m_formation(nullptr), m_triggerJustAppeared(true), m_respawnCompatibilityMode(false)
+m_formation(nullptr), m_triggerJustAppeared(true), m_respawnCompatibilityMode(false), _isMissingSwimmingFlagOutOfCombat(false)
 {
     m_valuesCount = UNIT_END;
 
@@ -2722,6 +2722,36 @@ CreatureMovementData const& Creature::GetMovementTemplate() const
     return GetCreatureTemplate()->Movement;
 }
 
+bool Creature::CanSwim() const
+{
+    if (Unit::CanSwim())
+        return true;
+
+    if (IsPet())
+        return true;
+
+    return false;
+}
+
+bool Creature::CanEnterWater() const
+{
+    if (CanSwim())
+        return true;
+
+    return GetMovementTemplate().IsSwimAllowed();
+}
+
+void Creature::RefreshSwimmingFlag(bool recheck)
+{
+    if (!_isMissingSwimmingFlagOutOfCombat || recheck)
+        _isMissingSwimmingFlagOutOfCombat = !HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING);
+
+    // Check if the creature has UNIT_FLAG_SWIMMING and add it if it's missing
+    // Creatures must be able to chase a target in water if they can enter water
+    if (_isMissingSwimmingFlagOutOfCombat && CanEnterWater())
+        SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING);
+}
+
 void Creature::AllLootRemovedFromCorpse()
 {
     if (loot.loot_type != LOOT_SKINNING && !IsPet() && GetCreatureTemplate()->SkinLootId && hasLootRecipient())
@@ -3014,8 +3044,7 @@ void Creature::UpdateMovementFlags()
     if (!isInAir)
         RemoveUnitMovementFlag(MOVEMENTFLAG_FALLING);
 
-    if (GetMovementTemplate().IsSwimAllowed())
-        SetSwim(IsInWater());
+    SetSwim(CanSwim() && IsInWater());
 }
 
 void Creature::SetObjectScale(float scale)
@@ -3250,6 +3279,8 @@ void Creature::AtEngage(Unit* target)
     if (!(GetCreatureTemplate()->type_flags & CREATURE_TYPE_FLAG_MOUNTED_COMBAT_ALLOWED))
         Dismount();
 
+    RefreshSwimmingFlag();
+
     MovementGeneratorType const movetype = GetMotionMaster()->GetCurrentMovementGeneratorType();
     if (movetype == WAYPOINT_MOTION_TYPE || movetype == POINT_MOTION_TYPE || (IsAIEnabled && AI()->IsEscorted()))
         SetHomePosition(GetPosition());

src/server/game/Entities/Creature/Creature.h

@@ -95,7 +95,8 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
 
         CreatureMovementData const& GetMovementTemplate() const;
         bool CanWalk() const { return GetMovementTemplate().IsGroundAllowed(); }
-        bool CanSwim() const override { return GetMovementTemplate().IsSwimAllowed() || IsPet(); }
+        bool CanSwim() const override;
+        bool CanEnterWater() const override;
         bool CanFly()  const override { return GetMovementTemplate().IsFlightAllowed() || IsFlying(); }
         bool CanHover() const { return GetMovementTemplate().Ground == CreatureGroundMovementType::Hover || IsHovering(); }
         bool SetDisableGravity(bool disable, bool packetOnly = false, bool updateAnimationTier = true) override;
@@ -366,6 +367,12 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
         void AtEngage(Unit* target) override;
         void AtDisengage() override;
 
+        bool HasSwimmingFlagOutOfCombat() const
+        {
+            return !_isMissingSwimmingFlagOutOfCombat;
+        }
+        void RefreshSwimmingFlag(bool recheck = false);
+
     protected:
         bool CreateFromProto(ObjectGuid::LowType guidlow, uint32 entry, CreatureData const* data = nullptr, uint32 vehId = 0);
         bool InitEntry(uint32 entry, CreatureData const* data = nullptr);
@@ -446,6 +453,8 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
         } _spellFocusInfo;
 
         CreatureTextRepeatGroup m_textRepeat;
+
+        bool _isMissingSwimmingFlagOutOfCombat;
 };
 
 class TC_GAME_API AssistDelayEvent : public BasicEvent

src/server/game/Entities/Player/Player.h

@@ -2374,6 +2374,7 @@ class TC_GAME_API Player : public Unit, public GridObject<Player>
         void SendMovementSetCollisionHeight(float height, UpdateCollisionHeightReason reason);
 
         bool CanFly() const override { return m_movementInfo.HasMovementFlag(MOVEMENTFLAG_CAN_FLY); }
+        bool CanEnterWater() const override { return true; }
 
         std::string GetMapAreaAndZoneString() const;
         std::string GetCoordsMapAreaAndZoneString() const;

src/server/game/Entities/Unit/Unit.cpp

@@ -3130,7 +3130,7 @@ bool Unit::isInBackInMap(Unit const* target, float distance, float arc) const
 bool Unit::isInAccessiblePlaceFor(Creature const* c) const
 {
     if (IsInWater())
-        return c->CanSwim();
+        return c->CanEnterWater();
     else
         return c->CanWalk() || c->CanFly();
 }
@@ -13271,9 +13271,9 @@ bool Unit::CanSwim() const
         return true;
     if (HasFlag(UNIT_FIELD_FLAGS_2, 0x1000000))
         return false;
-    if (IsPet() && HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_PET_IN_COMBAT))
+    if (HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_PET_IN_COMBAT))
         return true;
-    return HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_RENAME | UNIT_FLAG_UNK_15);
+    return HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_RENAME | UNIT_FLAG_SWIMMING);
 }
 
 void Unit::NearTeleportTo(Position const& pos, bool casting /*= false*/)

src/server/game/Entities/Unit/Unit.h

@@ -1672,6 +1672,7 @@ class TC_GAME_API Unit : public WorldObject
         virtual bool CanFly() const = 0;
         bool IsFlying() const   { return m_movementInfo.HasMovementFlag(MOVEMENTFLAG_FLYING | MOVEMENTFLAG_DISABLE_GRAVITY); }
         bool IsFalling() const;
+        virtual bool CanEnterWater() const = 0;
         virtual bool CanSwim() const;
 
         float GetHoverOffset() const

src/server/game/Entities/Unit/UnitDefines.h

@@ -135,7 +135,7 @@ enum UnitFlags : uint32
     UNIT_FLAG_PVP                   = 0x00001000,           // changed in 3.0.3
     UNIT_FLAG_SILENCED              = 0x00002000,           // silenced, 2.1.1
     UNIT_FLAG_CANNOT_SWIM           = 0x00004000,           // 2.0.8
-    UNIT_FLAG_UNK_15                = 0x00008000,
+    UNIT_FLAG_SWIMMING              = 0x00008000,           // shows swim animation in water
     UNIT_FLAG_NOT_ATTACKABLE_2      = 0x00010000,
     UNIT_FLAG_PACIFIED              = 0x00020000,           // 3.0.3 ok
     UNIT_FLAG_STUNNED               = 0x00040000,           // 3.0.3 ok

src/server/game/Movement/MovementGenerators/HomeMovementGenerator.cpp

@@ -81,6 +81,9 @@ void HomeMovementGenerator<Creature>::DoFinalize(Creature* owner)
 {
     if (_arrived)
     {
+        if (!owner->HasSwimmingFlagOutOfCombat())
+            owner->RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING);
+
         owner->ClearUnitState(UNIT_STATE_EVADE);
         owner->SetWalk(true);
         owner->LoadCreaturesAddon();

src/server/game/Movement/PathGenerator.cpp

@@ -658,7 +658,7 @@ void PathGenerator::CreateFilter()
             includeFlags |= NAV_GROUND;          // walk
 
         // creatures don't take environmental damage
-        if (creature->CanSwim())
+        if (creature->CanEnterWater())
             includeFlags |= (NAV_WATER | NAV_MAGMA_SLIME);                 // swim
     }
     else // assume Player

src/server/scripts/Commands/cs_npc.cpp

@@ -135,7 +135,7 @@ EnumName<UnitFlags> const unitFlags[MAX_UNIT_FLAGS] =
     CREATE_NAMED_ENUM(UNIT_FLAG_PVP),
     CREATE_NAMED_ENUM(UNIT_FLAG_SILENCED),
     CREATE_NAMED_ENUM(UNIT_FLAG_CANNOT_SWIM),
-    CREATE_NAMED_ENUM(UNIT_FLAG_UNK_15),
+    CREATE_NAMED_ENUM(UNIT_FLAG_SWIMMING),
     CREATE_NAMED_ENUM(UNIT_FLAG_NOT_ATTACKABLE_2),
     CREATE_NAMED_ENUM(UNIT_FLAG_PACIFIED),
     CREATE_NAMED_ENUM(UNIT_FLAG_STUNNED),

src/server/scripts/EasternKingdoms/ScarletEnclave/the_scarlet_enclave_chapter_1.cpp

@@ -533,7 +533,7 @@ public:
 
             me->RestoreFaction();
             CombatAI::Reset();
-            me->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_15);
+            me->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING);
         }
 
         void SpellHit(Unit* pCaster, SpellInfo const* pSpell) override
@@ -628,7 +628,7 @@ public:
                 }
 
                 me->SetImmuneToPC(false);
-                me->RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_15);
+                me->RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING);
 
                 player->CastSpell(me, SPELL_DUEL, false);
                 player->CastSpell(player, SPELL_DUEL_FLAG, true);

src/server/scripts/Northrend/Nexus/Oculus/boss_varos.cpp

@@ -280,10 +280,10 @@ class spell_varos_centrifuge_shield : public SpellScriptLoader
                 if (Unit* caster = GetCaster())
                 {
                     // flags taken from sniffs
-                    if (caster->HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_15|UNIT_FLAG_IMMUNE_TO_NPC|UNIT_FLAG_IMMUNE_TO_PC|UNIT_FLAG_UNK_6))
+                    if (caster->HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING | UNIT_FLAG_IMMUNE_TO_NPC | UNIT_FLAG_IMMUNE_TO_PC | UNIT_FLAG_UNK_6))
                     {
                         caster->ToCreature()->SetReactState(REACT_PASSIVE);
-                        caster->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_15|UNIT_FLAG_UNK_6);
+                        caster->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING | UNIT_FLAG_UNK_6);
                         caster->SetImmuneToAll(true, true);
                     }
                 }
@@ -294,7 +294,7 @@ class spell_varos_centrifuge_shield : public SpellScriptLoader
                 if (Unit* caster = GetCaster())
                 {
                     caster->ToCreature()->SetReactState(REACT_AGGRESSIVE);
-                    caster->RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_15|UNIT_FLAG_UNK_6);
+                    caster->RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_SWIMMING | UNIT_FLAG_UNK_6);
                     caster->SetImmuneToAll(false);
                 }
             }