Add prediction for standing states and mob states (#1937)

Content.Server/GameObjects/Components/Mobs/State/MobStateManager.cs

@@ -0,0 +1,70 @@
+using System.Collections.Generic;
+using Content.Shared.GameObjects.Components.Damage;
+using Content.Shared.GameObjects.Components.Mobs;
+using Content.Shared.GameObjects.Components.Mobs.State;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.GameObjects.Components.Mobs.State
+{
+    [RegisterComponent]
+    [ComponentReference(typeof(SharedMobStateManagerComponent))]
+    public class MobStateManagerComponent : SharedMobStateManagerComponent
+    {
+        private readonly Dictionary<DamageState, IMobState> _behavior = new Dictionary<DamageState, IMobState>
+        {
+            {DamageState.Alive, new NormalState()},
+            {DamageState.Critical, new CriticalState()},
+            {DamageState.Dead, new DeadState()}
+        };
+
+        private DamageState _currentDamageState;
+
+        protected override IReadOnlyDictionary<DamageState, IMobState> Behavior => _behavior;
+
+        public override IMobState CurrentMobState { get; protected set; }
+
+        public override DamageState CurrentDamageState
+        {
+            get => _currentDamageState;
+            protected set
+            {
+                if (_currentDamageState == value)
+                {
+                    return;
+                }
+
+                if (_currentDamageState != DamageState.Invalid)
+                {
+                    CurrentMobState.ExitState(Owner);
+                }
+
+                _currentDamageState = value;
+                CurrentMobState = Behavior[CurrentDamageState];
+                CurrentMobState.EnterState(Owner);
+
+                Dirty();
+            }
+        }
+
+        public override void OnRemove()
+        {
+            // TODO: Might want to add an OnRemove() to IMobState since those are where these components are being used
+            base.OnRemove();
+
+            if (Owner.TryGetComponent(out ServerStatusEffectsComponent status))
+            {
+                status.RemoveStatusEffect(StatusEffect.Health);
+            }
+
+            if (Owner.TryGetComponent(out ServerOverlayEffectsComponent overlay))
+            {
+                overlay.ClearOverlays();
+            }
+        }
+
+        public override ComponentState GetComponentState()
+        {
+            return new MobStateManagerComponentState(CurrentDamageState);
+        }
+    }
+}