RandomTriggerOnTriggerComponent (#41422)

* commit

* rename

* prevent recusion

---------

Co-authored-by: iaada <iaada@users.noreply.github.com>

Content.Shared/Trigger/Components/Effects/RandomTriggerOnTriggerComponent.cs

@@ -0,0 +1,21 @@
+using Content.Shared.Random;
+using Content.Shared.Trigger.Components.Triggers;
+using Robust.Shared.GameStates;
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Trigger.Components.Effects;
+
+/// <summary>
+/// When triggered this component will choose a key and send a new trigger.
+/// Trigger is sent to user if <see cref="BaseXOnTriggerComponent.TargetUser"/> is true.
+/// </summary>
+/// <remarks>Does not support recursive loops where this component triggers itself. Use <see cref="RepeatingTriggerComponent"/> instead.</remarks>
+[RegisterComponent, NetworkedComponent, AutoGenerateComponentState]
+public sealed partial class RandomTriggerOnTriggerComponent : BaseXOnTriggerComponent
+{
+    /// <summary>
+    /// The trigger keys and their weights.
+    /// </summary>
+    [DataField(required: true), AutoNetworkedField]
+    public ProtoId<WeightedRandomPrototype> RandomKeyOut;
+}

Content.Shared/Trigger/Systems/RandomTriggerOnTriggerSystem.cs

@@ -0,0 +1,38 @@
+using Content.Shared.Random.Helpers;
+using Content.Shared.Trigger.Components.Effects;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Timing;
+
+namespace Content.Shared.Trigger.Systems;
+
+public sealed class RandomTriggerOnTriggerSystem : XOnTriggerSystem<RandomTriggerOnTriggerComponent>
+{
+    [Dependency] private readonly TriggerSystem _trigger = default!;
+    [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
+    [Dependency] private readonly IGameTiming _timing = default!;
+
+    protected override void OnTrigger(Entity<RandomTriggerOnTriggerComponent> ent, EntityUid target, ref TriggerEvent args)
+    {
+        // TODO: Replace with RandomPredicted once the engine PR is merged
+        var hash = new List<int>
+        {
+            (int)_timing.CurTick.Value,
+            GetNetEntity(ent).Id,
+            args.User == null ? 0 : GetNetEntity(args.User.Value).Id,
+        };
+        var seed = SharedRandomExtensions.HashCodeCombine(hash);
+        var rand = new System.Random(seed);
+
+        var keyOut = _prototypeManager.Index(ent.Comp.RandomKeyOut).Pick(rand);
+
+        // Prevent recursive triggers
+        if (target == ent.Owner && ent.Comp.KeysIn.Contains(keyOut))
+        {
+            Log.Warning($"{ToPrettyString(ent)} attempted to recursively trigger itself using RandomTriggerOnTriggerComponent.");
+            return;
+        }
+
+        _trigger.Trigger(target, args.User, keyOut);
+        args.Handled = true;
+    }
+}