implemented input node resolver and major refactoring over execution function

Examples/Nodify.Calculator/Execution/Handlers/NodeHandlers.cs

@@ -346,11 +346,21 @@ namespace Nodify.Calculator.Execution.Handlers
 
     internal sealed class ApiRequestHandler : INodeExecutionHandler
     {
+        // Matches {name} placeholders in URL templates (e.g., /api/Pizza/{id})
+        private static readonly System.Text.RegularExpressions.Regex PlaceholderRegex =
+            new System.Text.RegularExpressions.Regex(@"\{([^{}]+)\}",
+                System.Text.RegularExpressions.RegexOptions.Compiled);
+
         public bool CanHandle(OperationViewModel node, ExecutionContext ctx) => true; // final fallback
 
         public void Execute(OperationViewModel node, ExecutionContext ctx)
         {
-            var url = node.Title ?? "";
+            var urlTemplate = node.Title ?? "";
+            var url = ResolveUrlPlaceholders(urlTemplate, node, ctx);
+
+            if (!string.Equals(url, urlTemplate, StringComparison.Ordinal))
+                ctx.Log($"URL resolved: {urlTemplate} → {url}");
+
             ctx.Log($"Starting Execution : {url}");
 
             var httpMethod = (node is APIOperationViewModel apiVm)
@@ -369,5 +379,42 @@ namespace Nodify.Calculator.Execution.Handlers
             }
             ctx.Log($"Response Result : {res}");
         }
+
+        /// <summary>
+        /// Replaces {name} tokens in the URL template with values read from the
+        /// matching input connector on the node. Connector titles may include a
+        /// trailing " (type)" suffix (e.g., "id (int)") which is stripped for matching.
+        /// </summary>
+        private static string ResolveUrlPlaceholders(string template, OperationViewModel node, ExecutionContext ctx)
+        {
+            if (string.IsNullOrEmpty(template) || template.IndexOf('{') < 0)
+                return template;
+
+            // Build lookup: normalized connector name → value
+            var inputMap = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var inp in node.Input)
+            {
+                if (inp.Shape == ConnectorShape.Triangle) continue;
+                var name = inp.Title ?? "";
+                var parenIdx = name.IndexOf(" (", StringComparison.Ordinal);
+                if (parenIdx > 0) name = name.Substring(0, parenIdx);
+                name = name.Trim();
+                if (string.IsNullOrEmpty(name)) continue;
+
+                var value = ctx.ReadInput(inp);
+                if (value != null)
+                    inputMap[name] = value;
+            }
+
+            return PlaceholderRegex.Replace(template, m =>
+            {
+                var key = m.Groups[1].Value.Trim();
+                if (inputMap.TryGetValue(key, out var val))
+                    return Uri.EscapeDataString(val);
+
+                ctx.Log($"URL placeholder '{{{key}}}' has no matching input value; leaving as-is.", logType.Warning);
+                return m.Value;
+            });
+        }
     }
 }

Examples/Nodify.Calculator/Execution/INodeValueResolver.cs

@@ -0,0 +1,43 @@
+namespace Nodify.Calculator.Execution
+{
+    /// <summary>
+    /// Strategy for lazily producing a value from a <em>non-flow</em> (sideband) node when
+    /// downstream code asks for a value on one of its output connectors.
+    ///
+    /// The <see cref="Executor"/>'s value-reading pipeline walks this list (first match wins)
+    /// whenever an upstream source has not populated <c>outputs[nodeId]</c>. This lets us
+    /// transparently support chains like:
+    ///   ForEach.CurrentItem → Split.Id → API.id
+    /// without ever needing Split (or Copy, Take, Knot, GET-variable, Parse-JSON, …) to be in
+    /// the flow chain.
+    /// </summary>
+    public interface INodeValueResolver
+    {
+        /// <summary>Return true if this resolver knows how to produce a value for the source connector.</summary>
+        bool CanResolve(OperationViewModel sourceNode, ConnectorViewModel sourceConnector);
+
+        /// <summary>
+        /// Produce the value. May call <paramref name="readUpstream"/> recursively to resolve
+        /// any of the source node's own inputs (common case for Split/Copy/Take).
+        /// Returns null when no value can be produced.
+        /// </summary>
+        string Resolve(OperationViewModel sourceNode,
+                       ConnectorViewModel sourceConnector,
+                       IValueResolutionContext context);
+    }
+
+    /// <summary>
+    /// Services provided to resolvers so they can recursively evaluate the graph.
+    /// </summary>
+    public interface IValueResolutionContext
+    {
+        System.Collections.Generic.ICollection<ConnectionViewModel> Connections { get; }
+        System.Collections.Generic.Dictionary<string, string> Outputs { get; }
+        System.Collections.Generic.Dictionary<string, dynamic> Variables { get; }
+
+        /// <summary>Recursively read the value feeding any input connector.</summary>
+        string Read(ConnectorViewModel input);
+
+        void Log(string message, logType level = logType.Information);
+    }
+}

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;
+        }
+    }
+}