Interactable component system. (#9)

* InteractableComponent v1. Broken edition

* It works!

Content.Server/GameObjects/Components/Interactable/InteractableComponent.cs

@@ -0,0 +1,80 @@
+using Content.Server.Interfaces.GameObjects;
+using SS14.Server.Interfaces.GameObjects;
+using SS14.Shared.GameObjects;
+using SS14.Shared.Interfaces.GameObjects.Components;
+using SS14.Shared.Log;
+using System;
+
+namespace Content.Server.GameObjects
+{
+    public class InteractableComponent : Component, IInteractableComponent
+    {
+        public override string Name => "Interactable";
+
+        /// <inheritdoc />
+        public event EventHandler<AttackHandEventArgs> OnAttackHand;
+
+        /// <inheritdoc />
+        public event EventHandler<AttackByEventArgs> OnAttackBy;
+
+        private IClickableComponent clickableComponent;
+        private IServerTransformComponent transform;
+        private const float INTERACTION_RANGE = 2;
+        private const float INTERACTION_RANGE_SQUARED = INTERACTION_RANGE * INTERACTION_RANGE;
+
+        public override void Initialize()
+        {
+            transform = Owner.GetComponent<IServerTransformComponent>();
+            if (Owner.TryGetComponent<IClickableComponent>(out var component))
+            {
+                clickableComponent = component;
+                clickableComponent.OnClick += ClickableComponent_OnClick;
+            }
+            else
+            {
+                Logger.Error($"Interactable component must also have a clickable component to function! Prototype: {Owner.Prototype.ID}");
+            }
+            base.Initialize();
+        }
+
+        public override void Shutdown()
+        {
+            if (clickableComponent != null)
+            {
+                clickableComponent.OnClick -= ClickableComponent_OnClick;
+                clickableComponent = null;
+            }
+            transform = null;
+            base.Shutdown();
+        }
+
+        private void ClickableComponent_OnClick(object sender, ClickEventArgs e)
+        {
+            if (!e.User.TryGetComponent<IServerTransformComponent>(out var userTransform))
+            {
+                return;
+            }
+
+            var distance = (userTransform.WorldPosition - transform.WorldPosition).LengthSquared;
+            if (distance > INTERACTION_RANGE_SQUARED)
+            {
+                return;
+            }
+
+            if (!e.User.TryGetComponent<IHandsComponent>(out var hands))
+            {
+                return;
+            }
+
+            var item = hands.GetHand(hands.ActiveIndex);
+            if (item != null)
+            {
+                OnAttackBy?.Invoke(this, new AttackByEventArgs(Owner, e.User, item, hands.ActiveIndex));
+            }
+            else
+            {
+                OnAttackHand?.Invoke(this, new AttackHandEventArgs(Owner, e.User, hands.ActiveIndex));
+            }
+        }
+    }
+}