feat(composites): new selector random node

Selects the first node to return success and shuffles ever time it's run. Optimized for performance.

Assets/FluidBehaviorTree/Runtime/BehaviorTree/Builder/BehaviorTreeBuilder.cs

@@ -70,6 +70,15 @@ public BehaviorTreeBuilder Selector (string name = "selector") {
             return ParentTask<Selector>(name);
         }
 
+        /// <summary>
+        /// Selects the first node to return success
+        /// </summary>
+        /// <param name="name"></param>
+        /// <returns></returns>
+        public BehaviorTreeBuilder SelectorRandom (string name = "selector random") {
+            return ParentTask<SelectorRandom>(name);
+        }
+
         public BehaviorTreeBuilder Parallel (string name = "parallel") {
             return ParentTask<Parallel>(name);
         }

Assets/FluidBehaviorTree/Runtime/TaskParents/Composites/SelectorRandom.cs

@@ -0,0 +1,51 @@
+using Adnc.FluidBT.Tasks;
+using Random = System.Random;
+
+namespace Adnc.FluidBT.TaskParents.Composites {
+    /// <summary>
+    /// Randomly selects a child node with a shuffle algorithm
+    /// </summary>
+    public class SelectorRandom : CompositeBase {
+        private bool _init;
+
+        protected override TaskStatus OnUpdate () {
+            if (!_init) {
+                ShuffleChildren();
+                _init = true;
+            }
+
+            for (var i = ChildIndex; i < Children.Count; i++) {
+                var child = Children[ChildIndex];
+
+                switch (child.Update()) {
+                    case TaskStatus.Success:
+                        return TaskStatus.Success;
+                    case TaskStatus.Continue:
+                        return TaskStatus.Continue;
+                }
+
+                ChildIndex++;
+            }
+
+            return TaskStatus.Failure;
+        }
+
+        public override void Reset () {
+            base.Reset();
+
+            ShuffleChildren();
+        }
+
+        private void ShuffleChildren () {
+            var rng = new Random();
+            var n = Children.Count;  
+            while (n > 1) {  
+                n--;  
+                var k = rng.Next(n + 1);  
+                var value = Children[k];  
+                Children[k] = Children[n];  
+                Children[n] = value;  
+            }
+        }
+    }
+}

Assets/FluidBehaviorTree/Tests/Editor/BehaviorTrees/Builders/BehaviorTreeBuilderTest.cs

@@ -14,6 +14,18 @@ public void BeforeEach () {
             _invokeCount = 0;
             _builder = new BehaviorTreeBuilder(null);
         }
+
+        public class SelectorRandomMethod : BehaviorTreeBuilderTest {
+            public void It_should_add_a_random_selector () {
+                var tree = _builder
+                    .SelectorRandom("random selector")
+                    .Build();
+
+                var selectorRandom = tree.Root.Children[0] as SelectorRandom;
+
+                Assert.IsNotNull(selectorRandom);
+            }
+        }
 
         public class SequenceMethod : BehaviorTreeBuilderTest {
             [Test]

Assets/FluidBehaviorTree/Tests/Editor/TaskParents/Composites/SelectorRandomTest.cs

@@ -0,0 +1,45 @@
+using Adnc.FluidBT.Tasks;
+using Adnc.FluidBT.Testing;
+using NUnit.Framework;
+
+namespace Adnc.FluidBT.TaskParents.Composites.Editors.Tests {
+    public class SelectorRandomTest {
+        public class UpdateMethod {
+            [Test]
+            public void It_should_return_success_if_a_child_returns_success () {
+                var child = A.TaskStub().WithUpdateStatus(TaskStatus.Success).Build();
+                var selectorRandom = new SelectorRandom();
+                selectorRandom.AddChild(child);
+
+                Assert.AreEqual(TaskStatus.Success, selectorRandom.Update());
+            }
+
+            [Test]
+            public void It_should_return_continue_if_a_child_returns_continue () {
+                var child = A.TaskStub().WithUpdateStatus(TaskStatus.Continue).Build();
+                var selectorRandom = new SelectorRandom();
+                selectorRandom.AddChild(child);
+
+                Assert.AreEqual(TaskStatus.Continue, selectorRandom.Update());
+            }
+
+            [Test]
+            public void It_should_return_failure_if_empty () {
+                var selectorRandom = new SelectorRandom();
+
+                Assert.AreEqual(TaskStatus.Failure, selectorRandom.Update());
+
+            }
+
+            [Test]
+            public void It_should_return_failure_if_child_returns_failure () {
+                var child = A.TaskStub().WithUpdateStatus(TaskStatus.Failure).Build();
+                var selectorRandom = new SelectorRandom();
+                selectorRandom.AddChild(child);
+
+                Assert.AreEqual(TaskStatus.Failure, selectorRandom.Update());
+
+            }
+        }
+    }
+}