Click Drag Functionality + Refactor Interaction Interfaces (#1125)

Co-authored-by: Víctor Aguilera Puerto <6766154+Zumorica@users.noreply.github.com>
Co-authored-by: ComicIronic <comicironic@gmail.com>
Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/Interfaces/GameObjects/Components/Interaction/IAfterInteract.cs

@@ -0,0 +1,68 @@
+using System;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Map;
+
+namespace Content.Server.Interfaces.GameObjects.Components.Interaction
+{
+    /// <summary>
+    /// This interface gives components a behavior when clicking on another object and no interaction occurs,
+    /// at any range.
+    /// </summary>
+    public interface IAfterInteract
+    {
+        /// <summary>
+        /// Called when we interact with nothing, or when we interact with an entity out of range that has no behavior
+        /// </summary>
+        void AfterInteract(AfterInteractEventArgs eventArgs);
+    }
+
+    public class AfterInteractEventArgs : EventArgs
+    {
+        public IEntity User { get; set; }
+        public GridCoordinates ClickLocation { get; set; }
+        public IEntity Target { get; set; }
+    }
+
+    /// <summary>
+    ///     Raised when clicking on another object and no attack event was handled.
+    /// </summary>
+    [PublicAPI]
+    public class AfterInteractMessage : EntitySystemMessage
+    {
+        /// <summary>
+        ///     If this message has already been "handled" by a previous system.
+        /// </summary>
+        public bool Handled { get; set; }
+
+        /// <summary>
+        ///     Entity that triggered the attack.
+        /// </summary>
+        public IEntity User { get; }
+
+        /// <summary>
+        ///     Entity that the User attacked with.
+        /// </summary>
+        public IEntity ItemInHand { get; set; }
+
+        /// <summary>
+        ///     Entity that was attacked. This can be null if the attack did not click on an entity.
+        /// </summary>
+        public IEntity Attacked { get; }
+
+        /// <summary>
+        ///     Location that the user clicked outside of their interaction range.
+        /// </summary>
+        public GridCoordinates ClickLocation { get; }
+
+        public AfterInteractMessage(IEntity user, IEntity itemInHand, IEntity attacked, GridCoordinates clickLocation)
+        {
+            User = user;
+            Attacked = attacked;
+            ClickLocation = clickLocation;
+            ItemInHand = itemInHand;
+        }
+    }
+
+}