Prevent cyclical dependencies from occuring.

Fixes #81.

Author: Jcparkyn

Nodexr/Nodexr.xml

@@ -7,7 +7,7 @@
 
 @foreach (var node in Nodes)
 {
-    var inputsWithNoodles = node.GetInputsRecursive()
+    var inputsWithNoodles = node.GetAllInputs()
         .OfType<InputProcedural>()
         .Where(input => input.ConnectedNode != null);
 

Nodexr/Shared/Components/NoodleCollection.razor

@@ -7,6 +7,7 @@ namespace Nodexr.Shared.NodeInputs
     public class InputProcedural : NodeInput, INoodleData
     {
         private INodeOutput connectedNode;
+
         public INodeOutput ConnectedNode
         {
             get => connectedNode;

Nodexr/Shared/NodeInputs/InputProcedural.cs

@@ -6,7 +6,6 @@
 using Nodexr.Shared.NodeInputs;
 using Nodexr.Shared;
 
-
 namespace Nodexr.Shared.Nodes
 {
     public interface INodeOutput
@@ -27,12 +26,27 @@ public interface INode : IPositionable, INodeOutput
 
         IEnumerable<NodeInput> NodeInputs { get; }
         InputProcedural Previous { get; }
+
+        /// <summary>
+        /// The node connected to the 'Previous' input.
+        /// </summary>
         INodeOutput PreviousNode { get; set; }
 
         void CalculateInputsPos();
+
+        /// <summary>
+        /// Get the height of the node, in pixels. Disabled inputs do not contribute to the height.
+        /// </summary>
         int GetHeight();
-        IEnumerable<NodeInput> GetInputsRecursive();
+
+        /// <summary>
+        /// Get all of the inputs to the node, including the 'previous' input and the sub-inputs of any InputCollections.
+        /// InputCollections themselves are not returned.
+        /// </summary>
+        IEnumerable<NodeInput> GetAllInputs();
         void OnLayoutChanged(object sender, EventArgs e);
+        bool IsDependentOn(INodeInput childInput);
+
         event EventHandler LayoutChanged;
     }
 
@@ -49,14 +63,16 @@ public Vector2L Pos
                 CalculateInputsPos();
             }
         }
+
         public InputProcedural Previous { get; } = new InputProcedural();
+
         public INodeOutput PreviousNode
         {
             get => Previous.ConnectedNode;
             set => Previous.ConnectedNode = value;
         }
 
-        public IEnumerable<NodeInput> NodeInputs { get; private set; }
+        public IEnumerable<NodeInput> NodeInputs { get; }
         public abstract string Title { get; }
         public abstract string NodeInfo { get; }
 
@@ -77,7 +93,7 @@ protected virtual void OnOutputChanged(EventArgs e)
         public void OnLayoutChanged(object sender, EventArgs e)
         {
             CalculateInputsPos();
-            foreach(var input in GetInputsRecursive().OfType<InputProcedural>())
+            foreach(var input in GetAllInputs().OfType<InputProcedural>())
             {
                 input.Refresh();
             }
@@ -168,11 +184,8 @@ public void CalculateInputsPos()
             }
         }
 
-        /// <summary>
-        /// Get all of the inputs to the node, including the 'previous' input and the sub-inputs of any InputCollections.
-        /// InputCollections themselves are not returned.
-        /// </summary>
-        public IEnumerable<NodeInput> GetInputsRecursive()
+        /// <inheritdoc/>
+        public IEnumerable<NodeInput> GetAllInputs()
         {
             yield return Previous;
             foreach(var input in NodeInputs)
@@ -189,9 +202,28 @@ public IEnumerable<NodeInput> GetInputsRecursive()
             }
         }
 
+        public bool IsDependentOn(INodeInput childInput)
+        {
+            return GetAllProceduralInputsRecursive(this).Any(input => input == childInput);
+
+            static IEnumerable<InputProcedural> GetAllProceduralInputsRecursive(INode parent)
+            {
+                foreach(var input in parent.GetAllInputs().OfType<InputProcedural>())
+                {
+                    yield return input;
+
+                    if (input.ConnectedNode is INode childNode)
+                    {
+                        foreach (var input2 in GetAllProceduralInputsRecursive(childNode))
+                            yield return input2;
+                    }
+                }
+            }
+        }
+
         public int GetHeight()
         {
-            int baseHeight = 28;
+            const int baseHeight = 28;
 
             int inputHeight = NodeInputs
                 .Where(input => input.IsEnabled())

Nodexr/Shared/Nodes/Node.cs

@@ -77,7 +77,7 @@ private void DeleteOutputNoodles(INode nodeToRemove)
         {
             foreach (var node in nodes)
             {
-                foreach (var input in node.GetInputsRecursive().OfType<InputProcedural>())
+                foreach (var input in node.GetAllInputs().OfType<InputProcedural>())
                 {
                     DeleteNoodlesBetween(nodeToRemove, input);
                 }

Nodexr/Shared/Nodes/NodeTree.cs

@@ -43,7 +43,7 @@ void FillColumns(Node endNode)
 
         private static List<Node> GetChildren(Node node)
         {
-            var inputs = node.GetInputsRecursive().OfType<InputProcedural>();
+            var inputs = node.GetAllInputs().OfType<InputProcedural>();
             var children = inputs.Select(input => input.ConnectedNode).OfType<Node>().ToList();
             return children;
         }

Nodexr/Shared/RegexParsers/NodeTreeBuilder.cs

@@ -8,6 +8,7 @@
 using System;
 using System.Threading.Tasks;
 using System.Linq;
+using Blazored.Toast.Services;
 
 namespace Nodexr.Shared.Services
 {
@@ -24,13 +25,14 @@ public interface INoodleDragService
     public class NoodleDragService : INoodleDragService
     {
         public INode NodeToDrag { get; set; }
-        public NoodleDataCustom TempNoodle { get; private set; } = new NoodleDataCustom() { Enabled = false };
+        public NoodleDataCustom TempNoodle { get; } = new NoodleDataCustom() { Enabled = false };
 
-        readonly INodeHandler nodeHandler;
-        readonly IJSRuntime jsRuntime;
-        public NoodleDragService(INodeHandler nodeHandler, IJSRuntime jsRuntime)
+        private readonly IToastService toastService;
+        private readonly IJSRuntime jsRuntime;
+
+        public NoodleDragService(IToastService toastService, IJSRuntime jsRuntime)
         {
-            this.nodeHandler = nodeHandler;
+            this.toastService = toastService;
             this.jsRuntime = jsRuntime;
         }
 
@@ -46,9 +48,7 @@ public void OnStartNoodleDrag(INodeOutput nodeToDrag, DragEventArgs e, Vector2L
             {
                 NodeToDrag = node;
                 TempNoodle.Enabled = true;
-                //nodeHandler.OnRequireNoodleRefresh?.Invoke();
 
-                //Console.WriteLine("Start Noodle Drag");
                 jsRuntime.InvokeAsync<object>("tempNoodle.startNoodleDrag",
                     nodeToDrag.OutputPos.x, nodeToDrag.OutputPos.y,
                     noodleEndPos.x, noodleEndPos.y);
@@ -59,14 +59,20 @@ public void OnStartNoodleDrag(INodeOutput nodeToDrag, DragEventArgs e, Vector2L
 
         public void OnDropNoodle(InputProcedural nodeInput)
         {
-            Console.WriteLine("Drop noodle");
             TempNoodle.Enabled = false;
 
-            //TODO: Properly check for cyclic dependencies
-            if (NodeToDrag != null && !NodeToDrag.GetInputsRecursive().Contains(nodeInput))
+            if (NodeToDrag is null) return;
+
+            if (NodeToDrag.IsDependentOn(nodeInput))
+            {
+                toastService.ShowError(
+                    "Cyclical dependencies would create a rift in the space-time continuum and are therefore not allowed. " +
+                    "If you want to use the same node multiple times in a row, connect it to multiple inputs of a 'Concatenate' node.",
+                    "Can't connect these nodes");
+            }
+            else
             {
                 nodeInput.ConnectedNode = NodeToDrag;
-                //nodeHandler.OnRequireNodeGraphRefresh?.Invoke();
             }
 
             NodeToDrag = null;