Interaction Entity System (#26)

* Interaction Entity System

* ye

* Update submodule

* Requires engine update to function, but doesn't use shitcode

* Fix conflicts

* Fix conflicts but for real

* Update submodule

Content.Server/GameObjects/EntitySystems/InteractionSystem.cs

@@ -0,0 +1,149 @@
+using Content.Server.Interfaces.GameObjects;
+using SS14.Server.Interfaces.GameObjects;
+using SS14.Shared.GameObjects;
+using SS14.Shared.GameObjects.System;
+using SS14.Shared.Interfaces.GameObjects;
+using SS14.Shared.Interfaces.GameObjects.Components;
+using SS14.Shared.IoC;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    /// <summary>
+    /// This interface gives components behavior when being clicked on or "attacked" by a user with an object in their hand
+    /// </summary>
+    public interface IAttackby
+    {
+        bool Attackby(IEntity user, IEntity attackwith);
+    }
+
+    /// <summary>
+    /// This interface gives components behavior when being clicked on or "attacked" by a user with an empty hand
+    /// </summary>
+    public interface IAttackHand
+    {
+        bool Attackhand(IEntity user);
+    }
+
+    public interface IUse
+    {
+        bool UseEntity(IEntity user);
+    }
+
+    /// <summary>
+    /// Governs interactions during clicking on entities
+    /// </summary>
+    public class InteractionSystem : EntitySystem
+    {
+        private const float INTERACTION_RANGE = 2;
+        private const float INTERACTION_RANGE_SQUARED = INTERACTION_RANGE * INTERACTION_RANGE;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeEvent<ClickedOnEntityEventArgs>(UserInteraction, this);
+        }
+
+        public void UserInteraction(object sender, EntityEventArgs arg)
+        {
+            ClickedOnEntityEventArgs e = (ClickedOnEntityEventArgs)arg;
+            if (e.MouseButton != Clicktype.Left)
+                return;
+
+            IEntity user = EntityManager.GetEntity(e.Clicker);
+            IEntity attacked = EntityManager.GetEntity(e.Clicked);
+
+            if (!user.TryGetComponent<IServerTransformComponent>(out var userTransform))
+            {
+                return;
+            }
+
+            var distance = (userTransform.WorldPosition - attacked.GetComponent<IServerTransformComponent>().WorldPosition).LengthSquared;
+            if (distance > INTERACTION_RANGE_SQUARED)
+            {
+                return;
+            }
+
+            if (!user.TryGetComponent<IHandsComponent>(out var hands))
+            {
+                return;
+            }
+
+            var item = hands.GetHand(hands.ActiveIndex)?.Owner;
+
+            if (item != null && attacked != item)
+            {
+                Interaction(user, item, attacked);
+            }
+            else if(attacked == item)
+            {
+                UseInteraction(user, item);
+            }
+            else
+            {
+                Interaction(user, attacked);
+            }
+        }
+
+        /// <summary>
+        /// Uses a weapon/object on an entity
+        /// </summary>
+        /// <param name="user"></param>
+        /// <param name="weapon"></param>
+        /// <param name="attacked"></param>
+        public static void Interaction(IEntity user, IEntity weapon, IEntity attacked)
+        {
+            List<IAttackby> interactables = attacked.GetComponents<IAttackby>().ToList();
+
+            for(var i = 0; i < interactables.Count; i++)
+            {
+                if (interactables[i].Attackby(user, weapon)) //If an attackby returns a status completion we finish our attack
+                {
+                    return;
+                }
+            }
+
+            //Else check damage component to see if we damage if not attackby, and if so can we attack object
+        }
+
+        /// <summary>
+        /// Uses an empty hand on an entity
+        /// </summary>
+        /// <param name="user"></param>
+        /// <param name="attacked"></param>
+        public static void Interaction(IEntity user, IEntity attacked)
+        {
+            List<IAttackHand> interactables = attacked.GetComponents<IAttackHand>().ToList();
+
+            for (var i = 0; i < interactables.Count; i++)
+            {
+                if (interactables[i].Attackhand(user)) //If an attackby returns a status completion we finish our attack
+                {
+                    return;
+                }
+            }
+
+            //Else check damage component to see if we damage if not attackby, and if so can we attack object
+        }
+
+        /// <summary>
+        /// Activates/Uses an object in control/possession of a user
+        /// </summary>
+        /// <param name="user"></param>
+        /// <param name="attacked"></param>
+        public static void UseInteraction(IEntity user, IEntity used)
+        {
+            List<IUse> usables = used.GetComponents<IUse>().ToList();
+
+            for (var i = 0; i < usables.Count; i++)
+            {
+                if (usables[i].UseEntity(user)) //If an attackby returns a status completion we finish our attack
+                {
+                    return;
+                }
+            }
+        }
+    }
+}