fix: loop error condition and edge design (#5869)

* Changed math to show better edge when loop source is on the left side of the target

* Added logic to only allow loops if it comes from a loop edge

* Removed unused console log

src/frontend/src/CustomEdges/index.tsx

@@ -24,10 +24,25 @@ export function DefaultEdge({
     (sourceNode?.position.x ?? 0) + (sourceNode?.measured?.width ?? 0);
   const targetXNew = targetNode?.position.x ?? 0;
 
-  const distance = 200 + 0.1 * (Math.abs(sourceXNew - targetXNew) / 2);
-  const distanceY = 200 + 0.3 * Math.abs(sourceY - targetY);
+  const distance = 200 + 0.1 * ((sourceXNew - targetXNew) / 2);
 
-  const edgePathLoop = `M ${sourceXNew} ${sourceY} C ${sourceXNew + distance} ${sourceY + distanceY}, ${targetXNew - distance} ${targetY + distanceY}, ${targetXNew} ${targetY}`;
+  const zeroOnNegative =
+    (1 +
+      (1 - Math.exp(-0.01 * Math.abs(sourceXNew - targetXNew))) *
+        (sourceXNew - targetXNew >= 0 ? 1 : -1)) /
+    2;
+
+  const distanceY =
+    200 -
+    200 * (1 - zeroOnNegative) +
+    0.3 * Math.abs(targetY - sourceY) * zeroOnNegative;
+
+  const sourceDistanceY =
+    200 -
+    200 * (1 - zeroOnNegative) +
+    0.3 * Math.abs(sourceY - targetY) * zeroOnNegative;
+
+  const edgePathLoop = `M ${sourceXNew} ${sourceY} C ${sourceXNew + distance} ${sourceY + sourceDistanceY}, ${targetXNew - distance} ${targetY + distanceY}, ${targetXNew} ${targetY}`;
 
   const [edgePath] = getBezierPath({
     sourceX: sourceXNew,

src/frontend/src/utils/reactflowUtils.ts

@@ -581,14 +581,29 @@ function hasLoop(
   // Check if this connection would create a cycle
   const targetNode = nodes.find((n) => n.id === target);
 
-  const hasCycle = (node, visited = new Set()): boolean => {
+  const hasCycle = (
+    node,
+    visited = new Set(),
+    firstEdge: EdgeType | null = null,
+  ): boolean => {
     if (visited.has(node.id)) return false;
 
     visited.add(node.id);
 
     for (const outgoer of getOutgoers(node, nodes, edges)) {
-      if (outgoer.id === source) return true;
-      if (hasCycle(outgoer, visited)) return true;
+      const edge = edges.find(
+        (e) => e.source === node.id && e.target === outgoer.id,
+      );
+      if (outgoer.id === source) {
+        const sourceHandleObject = scapeJSONParse(
+          firstEdge?.sourceHandle ?? edge?.sourceHandle ?? "",
+        );
+        const sourceHandleParsed = scapedJSONStringfy(sourceHandleObject);
+        if (sourceHandleParsed === e.targetHandle) {
+          return true;
+        }
+      }
+      if (hasCycle(outgoer, visited, firstEdge || edge)) return true;
     }
     return false;
   };