Predict PickRandom verb (#39326)

Co-authored-by: ArtisticRoomba <145879011+ArtisticRoomba@users.noreply.github.com>

Content.Shared/Storage/EntitySystems/PickRandomSystem.cs

@@ -0,0 +1,72 @@
+using System.Linq;
+using Content.Shared.Database;
+using Content.Shared.Hands.EntitySystems;
+using Content.Shared.Storage.Components;
+using Content.Shared.Verbs;
+using Content.Shared.Whitelist;
+using Robust.Shared.Containers;
+using Robust.Shared.Network;
+using Robust.Shared.Random;
+
+namespace Content.Shared.Storage.EntitySystems;
+
+public sealed class PickRandomSystem : EntitySystem
+{
+    [Dependency] private readonly EntityWhitelistSystem _whitelistSystem = default!;
+    [Dependency] private readonly INetManager _net = default!;
+    [Dependency] private readonly IRobustRandom _random = default!;
+    [Dependency] private readonly SharedContainerSystem _container = default!;
+    [Dependency] private readonly SharedHandsSystem _hands = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<PickRandomComponent, GetVerbsEvent<AlternativeVerb>>(OnGetAlternativeVerbs);
+    }
+
+    private void OnGetAlternativeVerbs(EntityUid uid, PickRandomComponent comp, GetVerbsEvent<AlternativeVerb> args)
+    {
+        if (!args.CanAccess || !args.CanInteract || !TryComp<StorageComponent>(uid, out var storage))
+            return;
+
+        var user = args.User;
+
+        var enabled = storage.Container.ContainedEntities.Any(item => _whitelistSystem.IsWhitelistPassOrNull(comp.Whitelist, item));
+
+        // alt-click / alt-z to pick an item
+        args.Verbs.Add(new AlternativeVerb
+        {
+            Act = () =>
+            {
+                TryPick(uid, comp, storage, user);
+            },
+            Impact = LogImpact.Low,
+            Text = Loc.GetString(comp.VerbText),
+            Disabled = !enabled,
+            Message = enabled ? null : Loc.GetString(comp.EmptyText, ("storage", uid))
+        });
+    }
+
+    private void TryPick(EntityUid uid, PickRandomComponent comp, StorageComponent storage, EntityUid user)
+    {
+        // It's hard to predict picking a random entity from a container since the contained entity list will have a different order on the server and client.
+        // One idea might be to sort them by NetEntity ID, but that is expensive if there are a lot of entities.
+        // Another option would be to make this client authorative.
+        if (_net.IsClient)
+            return;
+
+        var entities = storage.Container.ContainedEntities.Where(item => _whitelistSystem.IsWhitelistPassOrNull(comp.Whitelist, item)).ToArray();
+
+        if (entities.Length == 0)
+            return;
+
+        var picked = _random.Pick(entities);
+
+        // if it fails to go into a hand of the user, will be on the storage
+        _container.AttachParentToContainerOrGrid((picked, Transform(picked)));
+
+        // TODO: try to put in hands, failing that put it on the storage
+        _hands.TryPickupAnyHand(user, picked);
+    }
+}