Wieldable/two-handed weapons (#4554)

* wielding kinda works

* rough out all the edges, wielding works nicely

* popups + loc

* increase damage & extra damage against whitelist

* small fixes

* forgot to actually do that

* reviews

* reviews + thing

* use resistances and not extradamageagainstwhitelist

* slashy

* make increasedamageonwield and melee hit events work with modifiersets

* Silly individual

Content.Server/Hands/Systems/HandVirtualItemSystem.cs

@@ -0,0 +1,106 @@
+using Content.Server.Hands.Components;
+using Content.Server.Pulling;
+using Content.Shared.Hands;
+using Content.Shared.Hands.Components;
+using Content.Shared.Interaction;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.Hands.Systems
+{
+    [UsedImplicitly]
+    public sealed class HandVirtualItemSystem : EntitySystem
+    {
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<HandVirtualItemComponent, DroppedEvent>(HandleItemDropped);
+            SubscribeLocalEvent<HandVirtualItemComponent, UnequippedHandEvent>(HandleItemUnequipped);
+
+            SubscribeLocalEvent<HandVirtualItemComponent, BeforeInteractEvent>(HandleBeforeInteract);
+        }
+
+        public bool TrySpawnVirtualItemInHand(EntityUid blockingEnt, EntityUid user)
+        {
+            if (ComponentManager.TryGetComponent<HandsComponent>(user, out var hands))
+            {
+                foreach (var handName in hands.ActivePriorityEnumerable())
+                {
+                    var hand = hands.GetHand(handName);
+                    if (!hand.IsEmpty)
+                        continue;
+
+                    var pos = hands.Owner.Transform.Coordinates;
+                    var virtualItem = EntityManager.SpawnEntity("HandVirtualItem", pos);
+                    var virtualItemComp = virtualItem.GetComponent<HandVirtualItemComponent>();
+                    virtualItemComp.BlockingEntity = blockingEnt;
+                    hands.PutEntityIntoHand(hand, virtualItem);
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static void HandleBeforeInteract(
+            EntityUid uid,
+            HandVirtualItemComponent component,
+            BeforeInteractEvent args)
+        {
+            // No interactions with a virtual item, please.
+            args.Handled = true;
+        }
+
+        // If the virtual item gets removed from the hands for any reason, cancel the pull and delete it.
+        private void HandleItemUnequipped(EntityUid uid, HandVirtualItemComponent component, UnequippedHandEvent args)
+        {
+            Delete(component, args.User.Uid);
+        }
+
+        private void HandleItemDropped(EntityUid uid, HandVirtualItemComponent component, DroppedEvent args)
+        {
+            Delete(component, args.User.Uid);
+        }
+
+        /// <summary>
+        ///     Queues a deletion for a virtual item and notifies the blocking entity and user.
+        /// </summary>
+        public void Delete(HandVirtualItemComponent comp, EntityUid user)
+        {
+            var userEv = new VirtualItemDeletedEvent(comp.BlockingEntity, user);
+            RaiseLocalEvent(user, userEv, false);
+            var targEv = new VirtualItemDeletedEvent(comp.BlockingEntity, user);
+            RaiseLocalEvent(comp.BlockingEntity, targEv, false);
+
+            comp.Owner.QueueDelete();
+        }
+
+        /// <summary>
+        ///     Deletes all virtual items in a user's hands with
+        ///     the specified blocked entity.
+        /// </summary>
+        public void DeleteInHandsMatching(EntityUid user, EntityUid matching)
+        {
+            if (ComponentManager.TryGetComponent<HandsComponent>(user, out var hands))
+            {
+                foreach (var handName in hands.ActivePriorityEnumerable())
+                {
+                    var hand = hands.GetHand(handName);
+                    if (hand.IsEmpty)
+                        continue;
+
+                    if (hand.HeldEntity != null)
+                    {
+                        if (ComponentManager.TryGetComponent<HandVirtualItemComponent>(hand.HeldEntity.Uid,
+                            out var virt)
+                        && virt.BlockingEntity == matching)
+                        {
+                            Delete(virt, user);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}