NPC refactor (#10122)

Co-authored-by: metalgearsloth <metalgearsloth@gmail.com>

Content.Server/NPC/HTN/PrimitiveTasks/Operators/Melee/PickMeleeTargetOperator.cs

@@ -0,0 +1,33 @@
+using Robust.Shared.Map;
+
+namespace Content.Server.NPC.HTN.PrimitiveTasks.Operators.Melee;
+
+/// <summary>
+/// Selects a target for melee.
+/// </summary>
+public sealed class PickMeleeTargetOperator : NPCCombatOperator
+{
+    protected override float GetRating(NPCBlackboard blackboard, EntityUid uid, EntityUid existingTarget, bool canMove, EntityQuery<TransformComponent> xformQuery)
+    {
+        var ourCoordinates = blackboard.GetValueOrDefault<EntityCoordinates>(NPCBlackboard.OwnerCoordinates);
+
+        if (!xformQuery.TryGetComponent(uid, out var targetXform))
+            return -1f;
+
+        var targetCoordinates = targetXform.Coordinates;
+
+        if (!ourCoordinates.TryDistance(EntManager, targetCoordinates, out var distance))
+            return -1f;
+
+        var rating = 0f;
+
+        if (existingTarget == uid)
+        {
+            rating += 3f;
+        }
+
+        rating += 1f / distance * 4f;
+
+        return rating;
+    }
+}