Deathgasp + last words / succumbing / fake deathgasp as crit actions (#18993)

Content.Shared/Mobs/Systems/MobStateActionsSystem.cs

@@ -0,0 +1,54 @@
+using Content.Shared.Actions;
+using Content.Shared.Actions.ActionTypes;
+using Content.Shared.Mobs.Components;
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Mobs.Systems;
+
+/// <summary>
+///     Adds and removes defined actions when a mob's <see cref="MobState"/> changes.
+/// </summary>
+public sealed class MobStateActionsSystem : EntitySystem
+{
+    [Dependency] private readonly IPrototypeManager _proto = default!;
+    [Dependency] private readonly SharedActionsSystem _actions = default!;
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<MobStateActionsComponent, MobStateChangedEvent>(OnMobStateChanged);
+    }
+
+    private void OnMobStateChanged(EntityUid uid, MobStateActionsComponent component, MobStateChangedEvent args)
+    {
+        if (!TryComp<ActionsComponent>(uid, out var action))
+            return;
+
+        foreach (var (state, acts) in component.Actions)
+        {
+            if (state != args.NewMobState && state != args.OldMobState)
+                continue;
+
+            foreach (var item in acts)
+            {
+                if (!_proto.TryIndex<InstantActionPrototype>(item, out var proto))
+                    continue;
+
+                var instance = new InstantAction(proto);
+                if (state == args.OldMobState)
+                {
+                    // Don't remove actions that would be getting readded anyway
+                    if (component.Actions.TryGetValue(args.NewMobState, out var value)
+                        && value.Contains(item))
+                        continue;
+
+                    _actions.RemoveAction(uid, instance, action);
+                }
+                else if (state == args.NewMobState)
+                {
+                    _actions.AddAction(uid, instance, null, action);
+                }
+            }
+        }
+    }
+}