implemented input node resolver and major refactoring over execution function

Examples/Nodify.Calculator/Execution/Resolvers/NodeValueResolvers.cs

@@ -0,0 +1,178 @@
+using System;
+using System.Linq;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Nodify.Calculator.Execution.Resolvers
+{
+    /// <summary>Utilities shared by resolvers.</summary>
+    internal static class ResolverUtils
+    {
+        /// <summary>Strip " (type)" suffix from a connector title. "Id (int)" → "Id".</summary>
+        public static string NormalizeConnectorName(string title)
+        {
+            if (string.IsNullOrEmpty(title)) return string.Empty;
+            var parenIdx = title.IndexOf(" (", StringComparison.Ordinal);
+            return parenIdx > 0 ? title.Substring(0, parenIdx).Trim() : title.Trim();
+        }
+
+        /// <summary>Pick a named property from a JSON string (case-insensitive). Returns null if not parseable or not an object.</summary>
+        public static string ExtractJsonProperty(string json, string propertyName)
+        {
+            if (string.IsNullOrWhiteSpace(json) || string.IsNullOrEmpty(propertyName)) return null;
+            try
+            {
+                var token = JToken.Parse(json);
+                if (token is JObject obj)
+                {
+                    var prop = obj.Properties()
+                        .FirstOrDefault(p => string.Equals(p.Name, propertyName, StringComparison.OrdinalIgnoreCase));
+                    if (prop != null)
+                    {
+                        return prop.Value.Type == JTokenType.String
+                            ? prop.Value.ToString()
+                            : prop.Value.ToString(Formatting.None);
+                    }
+                }
+            }
+            catch { /* not JSON */ }
+            return null;
+        }
+
+        /// <summary>Find the single non-flow (non-Triangle) input connector.</summary>
+        public static ConnectorViewModel FirstDataInput(OperationViewModel node)
+            => node.Input.FirstOrDefault(i => i.Shape != ConnectorShape.Triangle);
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // SPLIT: expose properties of an incoming JSON object as individual outputs.
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class SplitNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+            => node is SystemOperationViewModel sys && sys.SystemOperationType == SystemOperations.SPLIT;
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            // Split's model input is the Square-shaped connector
+            var modelInput = node.Input.FirstOrDefault(i => i.Shape == ConnectorShape.Square);
+            if (modelInput == null) return null;
+
+            var modelJson = ctx.Read(modelInput);
+            if (string.IsNullOrWhiteSpace(modelJson)) return null;
+
+            var propName = ResolverUtils.NormalizeConnectorName(outputConnector.Title);
+            return ResolverUtils.ExtractJsonProperty(modelJson, propName);
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // COPY: N identical outputs = whatever feeds the single input.
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class CopyNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+            => node is SystemOperationViewModel sys && sys.SystemOperationType == SystemOperations.COPY;
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            var input = ResolverUtils.FirstDataInput(node);
+            return input == null ? null : ctx.Read(input);
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // KNOT / reroute: passthrough of the single data input.
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class KnotNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+            => node is KnotOperationViewModel;
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            var input = ResolverUtils.FirstDataInput(node);
+            return input == null ? null : ctx.Read(input);
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // TAKE: pick the Nth (or random) element from an incoming JSON array.
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class TakeNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+            => node is TakeOperationViewModel;
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            var takeOp = (TakeOperationViewModel)node;
+            var listInput = node.Input.FirstOrDefault(i => i.IsTakeListConnector)
+                            ?? ResolverUtils.FirstDataInput(node);
+            if (listInput == null) return null;
+
+            var json = ctx.Read(listInput);
+            if (string.IsNullOrWhiteSpace(json)) return null;
+
+            try
+            {
+                var token = JToken.Parse(json);
+                if (token is JArray arr && arr.Count > 0)
+                {
+                    int idx = takeOp.IsRandom
+                        ? new Random().Next(arr.Count)
+                        : Math.Max(0, Math.Min(takeOp.NthIndex, arr.Count - 1));
+                    var item = arr[idx];
+                    return item.Type == JTokenType.String ? item.ToString() : item.ToString(Formatting.None);
+                }
+            }
+            catch (Exception ex)
+            {
+                ctx.Log($"[TAKE] Failed to parse list JSON: {ex.Message}", logType.Warning);
+            }
+            return null;
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // PARSEJSON: passthrough (output = parsed form of input). For value-reading
+    // purposes we just forward the raw JSON downstream.
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class ParseJsonNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+            => node is SystemOperationViewModel sys && sys.SystemOperationType == SystemOperations.PARSEJSON;
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            var input = ResolverUtils.FirstDataInput(node);
+            return input == null ? null : ctx.Read(input);
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────────
+    // GET variable (GET_SET non-flow node): resolve from the variables dictionary.
+    // Titles look like "GET myVar (string)" or "GET ClassName".
+    // ─────────────────────────────────────────────────────────────────────────────
+    internal sealed class GetVariableNodeValueResolver : INodeValueResolver
+    {
+        public bool CanResolve(OperationViewModel node, ConnectorViewModel c)
+        {
+            if (!(node is SystemOperationViewModel sys) || sys.SystemOperationType != SystemOperations.GET_SET)
+                return false;
+            var t = node.Title ?? string.Empty;
+            return t.StartsWith("GET ", StringComparison.OrdinalIgnoreCase);
+        }
+
+        public string Resolve(OperationViewModel node, ConnectorViewModel outputConnector, IValueResolutionContext ctx)
+        {
+            var parts = (node.Title ?? string.Empty)
+                .Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
+            if (parts.Length < 2) return null;
+            var varName = parts[1];
+            if (ctx.Variables.TryGetValue(varName, out var val))
+                return val?.ToString();
+            return null;
+        }
+    }
+}