Simple knockback implementation

Scripts/Components/FSM/Enemy/EnemyKnockbackProvider.cs

@@ -0,0 +1,60 @@
+using Cirno.Scripts.Components.Actors;
+using Cirno.Scripts.Enums;
+using Godot;
+
+namespace Cirno.Scripts.Components.FSM.Enemy;
+
+public partial class EnemyKnockbackProvider : ModuleBase<EnemyState, CharacterBody2D>
+{
+    [Export] public GenericDamageReceiver DamageReceiver { get; private set; }
+    [Export] public EnemyStorageModule StorageModule { get; private set; }
+    
+    [Export] public float KnockbackDecayRate = 800f; // pixels per second^2, tweak this
+
+    private Vector2 KnockbackVelocity
+    {
+        get => StorageModule.KnockbackVelocity;
+        set => StorageModule.KnockbackVelocity = value;
+    }
+
+    private bool IsKnockbackActive => KnockbackVelocity.LengthSquared() > 1f;
+    
+    private IStateMachine<EnemyState, CharacterBody2D> _machine;
+    private bool _enabled = false;
+    public override void EnterState(EnemyState state)
+    {
+        _enabled = true;
+        DamageReceiver.BulletHit += DamageReceiverOnBulletHit;
+    }
+
+    private void DamageReceiverOnBulletHit(Bullet bullet, Vector2 position, Vector2 direction)
+    {
+        var knockbackVelocity = direction * bullet.BulletInfo.Knockback;
+        
+        KnockbackVelocity = knockbackVelocity;
+    }
+
+    public override void ExitState(EnemyState state)
+    {
+        _enabled = false;
+        DamageReceiver.BulletHit -= DamageReceiverOnBulletHit;
+    }
+
+    public override void Init(IStateMachine<EnemyState, CharacterBody2D> machine)
+    {
+        _machine = machine;
+    }
+
+    public override void Process(double delta)
+    {
+        
+    }
+
+    public override void PhysicsProcess(double delta)
+    {
+        if (IsKnockbackActive)
+        {
+            KnockbackVelocity = KnockbackVelocity.MoveToward(Vector2.Zero, KnockbackDecayRate * (float)delta);
+        }
+    }
+}