NPC utility queries (#15843)

Content.Server/NPC/HTN/PrimitiveTasks/Operators/UtilityOperator.cs

@@ -0,0 +1,47 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Content.Server.NPC.Queries;
+using Content.Server.NPC.Systems;
+using Robust.Shared.Map;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype;
+
+namespace Content.Server.NPC.HTN.PrimitiveTasks.Operators;
+
+/// <summary>
+/// Utilises a <see cref="UtilityQueryPrototype"/> to determine the best target and sets it to the Key.
+/// </summary>
+public sealed class UtilityOperator : HTNOperator
+{
+    [Dependency] private readonly IEntityManager _entManager = default!;
+
+    [DataField("key")] public string Key = "CombatTarget";
+
+    /// <summary>
+    /// The EntityCoordinates of the specified target.
+    /// </summary>
+    [DataField("keyCoordinates")]
+    public string KeyCoordinates = "CombatTargetCoordinates";
+
+    [DataField("proto", required: true, customTypeSerializer:typeof(PrototypeIdSerializer<UtilityQueryPrototype>))]
+    public string Prototype = string.Empty;
+
+    public override async Task<(bool Valid, Dictionary<string, object>? Effects)> Plan(NPCBlackboard blackboard,
+        CancellationToken cancelToken)
+    {
+        var result = _entManager.System<NPCUtilitySystem>().GetEntities(blackboard, Prototype);
+        var target = result.GetHighest();
+
+        if (!target.IsValid())
+        {
+            return (false, new Dictionary<string, object>());
+        }
+
+        var effects = new Dictionary<string, object>()
+        {
+            {Key, target},
+            {KeyCoordinates, new EntityCoordinates(target, Vector2.Zero)}
+        };
+
+        return (true, effects);
+    }
+}