feat(workflow): handles area and connection

app/globals.css

@@ -211,14 +211,20 @@
   z-index: 20 !important;
 }
 
-/* Increase hit area on mobile without changing visual size */
+/* Invisible hit area for desktop */
+.react-flow__handle::after {
+  content: "" !important;
+  position: absolute !important;
+  top: 50% !important;
+  left: 50% !important;
+  transform: translate(-50%, -50%) !important;
+  width: 24px !important;
+  height: 24px !important;
+}
+
+/* Invisible hit area for mobile with WCAG minimum target size */
 @media (max-width: 768px) {
   .react-flow__handle::after {
-    content: "" !important;
-    position: absolute !important;
-    top: 50% !important;
-    left: 50% !important;
-    transform: translate(-50%, -50%) !important;
     width: 44px !important;
     height: 44px !important;
   }

components/workflow/workflow-canvas.tsx

@@ -101,6 +101,7 @@ export function WorkflowCanvas() {
     useReactFlow();
 
   const connectingNodeId = useRef<string | null>(null);
+  const connectingHandleType = useRef<"source" | "target" | null>(null);
   const justCreatedNodeFromConnection = useRef(false);
   const viewportInitialized = useRef(false);
   const [isCanvasReady, setIsCanvasReady] = useState(false);
@@ -227,6 +228,27 @@ export function WorkflowCanvas() {
     []
   );
 
+  const nodeHasHandle = useCallback(
+    (nodeId: string, handleType: "source" | "target") => {
+      const node = nodes.find((n) => n.id === nodeId);
+
+      if (!node) {
+        return false;
+      }
+
+      if (node.type === "add") {
+        return false;
+      }
+
+      if (handleType === "target") {
+        return node.type !== "trigger";
+      }
+
+      return true;
+    },
+    [nodes]
+  );
+
   const isValidConnection = useCallback(
     (connection: XYFlowConnection | XYFlowEdge) => {
       // Ensure we have both source and target
@@ -272,6 +294,7 @@ export function WorkflowCanvas() {
   const onConnectStart = useCallback(
     (_event: MouseEvent | TouchEvent, params: OnConnectStartParams) => {
       connectingNodeId.current = params.nodeId;
+      connectingHandleType.current = params.handleType;
     },
     []
   );
@@ -306,6 +329,125 @@ export function WorkflowCanvas() {
     []
   );
 
+  const handleConnectionToExistingNode = useCallback(
+    (nodeElement: Element) => {
+      const targetNodeId = nodeElement.getAttribute("data-id");
+      const fromSource = connectingHandleType.current === "source";
+      const requiredHandle = fromSource ? "target" : "source";
+      const connectingId = connectingNodeId.current;
+
+      if (
+        targetNodeId &&
+        connectingId &&
+        targetNodeId !== connectingId &&
+        nodeHasHandle(targetNodeId, requiredHandle)
+      ) {
+        const sourceId = fromSource ? connectingId : targetNodeId;
+        const targetId = fromSource ? targetNodeId : connectingId;
+        onConnect({
+          source: sourceId,
+          target: targetId,
+          sourceHandle: null,
+          targetHandle: null,
+        });
+      }
+    },
+    [nodeHasHandle, onConnect]
+  );
+
+  const handleConnectionToNewNode = useCallback(
+    (event: MouseEvent | TouchEvent, clientX: number, clientY: number) => {
+      const sourceNodeId = connectingNodeId.current;
+      if (!sourceNodeId) {
+        return;
+      }
+
+      const { adjustedX, adjustedY } = calculateMenuPosition(
+        event,
+        clientX,
+        clientY
+      );
+
+      // Get the action template
+      const actionTemplate = nodeTemplates.find((t) => t.type === "action");
+      if (!actionTemplate) {
+        return;
+      }
+
+      // Get the position in the flow coordinate system
+      const position = screenToFlowPosition({
+        x: adjustedX,
+        y: adjustedY,
+      });
+
+      // Center the node vertically at the cursor position
+      // Node height is 192px (h-48 in Tailwind)
+      const nodeHeight = 192;
+      position.y -= nodeHeight / 2;
+
+      const newNode: WorkflowNode = {
+        id: nanoid(),
+        type: actionTemplate.type,
+        position,
+        data: {
+          label: actionTemplate.label,
+          description: actionTemplate.description,
+          type: actionTemplate.type,
+          config: actionTemplate.defaultConfig,
+          status: "idle",
+        },
+        selected: true,
+      };
+
+      addNode(newNode);
+      setSelectedNode(newNode.id);
+      setActiveTab("properties");
+
+      // Deselect all other nodes and select only the new node
+      // Need to do this after a delay because panOnDrag will clear selection
+      setTimeout(() => {
+        setNodes((currentNodes) =>
+          currentNodes.map((n) => ({
+            ...n,
+            selected: n.id === newNode.id,
+          }))
+        );
+      }, 50);
+
+      // Create connection from the source node to the new node
+      const fromSource = connectingHandleType.current === "source";
+
+      const newEdge = {
+        id: nanoid(),
+        source: fromSource ? sourceNodeId : newNode.id,
+        target: fromSource ? newNode.id : sourceNodeId,
+        type: "animated",
+      };
+      setEdges([...edges, newEdge]);
+      setHasUnsavedChanges(true);
+      // Trigger immediate autosave for the new edge
+      triggerAutosave({ immediate: true });
+
+      // Set flag to prevent immediate deselection
+      justCreatedNodeFromConnection.current = true;
+      setTimeout(() => {
+        justCreatedNodeFromConnection.current = false;
+      }, 100);
+    },
+    [
+      calculateMenuPosition,
+      screenToFlowPosition,
+      addNode,
+      edges,
+      setEdges,
+      setNodes,
+      setSelectedNode,
+      setActiveTab,
+      setHasUnsavedChanges,
+      triggerAutosave,
+    ]
+  );
+
   const onConnectEnd = useCallback(
     (event: MouseEvent | TouchEvent) => {
       if (!connectingNodeId.current) {
@@ -327,96 +469,28 @@ export function WorkflowCanvas() {
         return;
       }
 
-      const isNode = target.closest(".react-flow__node");
+      const nodeElement = target.closest(".react-flow__node");
       const isHandle = target.closest(".react-flow__handle");
 
-      if (!(isNode || isHandle)) {
-        const { adjustedX, adjustedY } = calculateMenuPosition(
-          event,
-          clientX,
-          clientY
-        );
-
-        // Get the action template
-        const actionTemplate = nodeTemplates.find((t) => t.type === "action");
-        if (!actionTemplate) {
-          return;
-        }
-
-        // Get the position in the flow coordinate system
-        const position = screenToFlowPosition({
-          x: adjustedX,
-          y: adjustedY,
-        });
-
-        // Center the node vertically at the cursor position
-        // Node height is 192px (h-48 in Tailwind)
-        const nodeHeight = 192;
-        position.y -= nodeHeight / 2;
+      // Create connection on edge dragged over node release
+      if (nodeElement && !isHandle && connectingHandleType.current) {
+        handleConnectionToExistingNode(nodeElement);
+        connectingNodeId.current = null;
+        connectingHandleType.current = null;
+        return;
+      }
 
-        // Create new action node
-        const newNode: WorkflowNode = {
-          id: nanoid(),
-          type: actionTemplate.type,
-          position,
-          data: {
-            label: actionTemplate.label,
-            description: actionTemplate.description,
-            type: actionTemplate.type,
-            config: actionTemplate.defaultConfig,
-            status: "idle",
-          },
-          selected: true,
-        };
-
-        addNode(newNode);
-        setSelectedNode(newNode.id);
-        setActiveTab("properties");
-
-        // Deselect all other nodes and select only the new node
-        // Need to do this after a delay because panOnDrag will clear selection
-        setTimeout(() => {
-          setNodes((currentNodes) =>
-            currentNodes.map((n) => ({
-              ...n,
-              selected: n.id === newNode.id,
-            }))
-          );
-        }, 50);
-
-        // Create connection from the source node to the new node
-        const newEdge = {
-          id: nanoid(),
-          source: connectingNodeId.current,
-          target: newNode.id,
-          type: "animated",
-        };
-        setEdges([...edges, newEdge]);
-        setHasUnsavedChanges(true);
-        // Trigger immediate autosave for the new edge
-        triggerAutosave({ immediate: true });
-
-        // Set flag to prevent immediate deselection
-        justCreatedNodeFromConnection.current = true;
-        setTimeout(() => {
-          justCreatedNodeFromConnection.current = false;
-        }, 100);
+      if (!(nodeElement || isHandle)) {
+        handleConnectionToNewNode(event, clientX, clientY);
       }
 
       connectingNodeId.current = null;
+      connectingHandleType.current = null;
     },
     [
       getClientPosition,
-      calculateMenuPosition,
-      screenToFlowPosition,
-      addNode,
-      edges,
-      setEdges,
-      setNodes,
-      setSelectedNode,
-      setActiveTab,
-      setHasUnsavedChanges,
-      triggerAutosave,
+      handleConnectionToExistingNode,
+      handleConnectionToNewNode,
     ]
   );