Add Dify integration and enhance workflow node specifications

- Introduce new fields `dify_api_url` and `dify_api_key` in `AssistantConfig` for Dify API integration.
- Update `requirements.txt` to include `dify-client-python` for Dify SDK support.
- Modify `config_resolver` to handle Dify connection information.
- Add a new `globalNode` type in workflow specifications to provide unified settings across workflows.
- Enhance node specifications with additional constraints and default values for better configuration management.
- Update frontend components to support the new `globalNode` type and its properties, improving workflow editor functionality.

frontend/src/components/workflow/WorkflowEditor.tsx

@@ -90,6 +90,14 @@ export type WorkflowEditorProps = {
 let nodeSeq = 0;
 const NONE = "__none__";
 
+function defaultNodeData(spec: RuntimeNodeSpec): WorkflowNodeData {
+  const data: WorkflowNodeData = { name: spec.displayName };
+  for (const field of spec.fields) {
+    if (field.default !== undefined) data[field.key] = field.default;
+  }
+  return data;
+}
+
 function toFlow(graph: WorkflowGraph): { nodes: Node[]; edges: Edge[] } {
   return {
     nodes: graph.nodes.map((n) => ({
@@ -179,12 +187,34 @@ function Canvas({
   const isValidConnection = useCallback(
     (c: Connection | Edge) => {
       if (c.source === c.target) return false;
+      const source = nodes.find((n) => n.id === c.source);
       const target = nodes.find((n) => n.id === c.target);
-      if (!target) return false;
-      const spec = specsByType[target.type as string];
-      return !!spec?.hasTarget;
+      if (!source || !target) return false;
+
+      const sourceSpec = specsByType[source.type as string];
+      const targetSpec = specsByType[target.type as string];
+      if (!sourceSpec?.hasSource || !targetSpec?.hasTarget) return false;
+      if (edges.some((e) => e.source === c.source && e.target === c.target)) {
+        return false;
+      }
+
+      const sourceLimit = sourceSpec.constraints.maxOutgoing;
+      if (
+        sourceLimit !== undefined &&
+        edges.filter((e) => e.source === c.source).length >= sourceLimit
+      ) {
+        return false;
+      }
+      const targetLimit = targetSpec.constraints.maxIncoming;
+      if (
+        targetLimit !== undefined &&
+        edges.filter((e) => e.target === c.target).length >= targetLimit
+      ) {
+        return false;
+      }
+      return true;
     },
-    [nodes, specsByType],
+    [edges, nodes, specsByType],
   );
 
   const addNode = useCallback(
@@ -195,11 +225,7 @@ function Canvas({
         x: window.innerWidth / 2,
         y: window.innerHeight / 2,
       });
-      const data: WorkflowNodeData = { name: spec.displayName };
-      if (spec.type === "agentNode") {
-        data.allowInterrupt = true;
-        data.prompt = "";
-      }
+      const data = defaultNodeData(spec);
       setNodes((ns) => [...ns, { id, type: spec.type, position, data }]);
       setAddOpen(false);
       setEditingId(id);
@@ -281,6 +307,14 @@ function Canvas({
   const editingSpec = editingNode ? specsByType[editingNode.type as string] : null;
   const editingEdge = edges.find((e) => e.id === editingEdgeId);
   const addableSpecs = Object.values(specsByType).filter((s) => s.addable);
+  const canAddSpec = useCallback(
+    (spec: RuntimeNodeSpec) => {
+      const limit = spec.constraints.maxInstances;
+      if (limit === undefined) return true;
+      return nodes.filter((node) => node.type === spec.type).length < limit;
+    },
+    [nodes],
+  );
 
   return (
     <NodeSpecsContext.Provider value={specsByType}>
@@ -398,11 +432,13 @@ function Canvas({
                   ) : null}
                   {addableSpecs.map((spec) => {
                     const Icon = spec.icon;
+                    const canAdd = canAddSpec(spec);
                     return (
                       <button
                         key={spec.type}
                         type="button"
-                        className="group relative flex items-start gap-4 overflow-hidden rounded-2xl border border-hairline bg-card p-4 text-left shadow-sm transition-[border-color,box-shadow,transform] hover:-translate-y-0.5 hover:border-hairline-strong hover:shadow-md"
+                        disabled={!canAdd}
+                        className="group relative flex items-start gap-4 overflow-hidden rounded-2xl border border-hairline bg-card p-4 text-left shadow-sm transition-[border-color,box-shadow,transform] hover:-translate-y-0.5 hover:border-hairline-strong hover:shadow-md disabled:cursor-not-allowed disabled:opacity-55 disabled:hover:translate-y-0 disabled:hover:border-hairline disabled:hover:shadow-sm"
                         onClick={() => addNode(spec)}
                       >
                         <span
@@ -421,8 +457,13 @@ function Canvas({
                           <Icon size={17} />
                         </div>
                         <div className="min-w-0 flex-1">
-                          <div className="text-sm font-medium text-foreground">
-                            {spec.displayName}
+                          <div className="flex items-center gap-2 text-sm font-medium text-foreground">
+                            <span>{spec.displayName}</span>
+                            {!canAdd && (
+                              <span className="rounded-full bg-surface-strong px-2 py-0.5 text-[10px] font-normal text-muted-foreground">
+                                已添加
+                              </span>
+                            )}
                           </div>
                           <div className="mt-1 text-xs leading-5 text-muted-foreground">
                             {spec.description}
@@ -610,6 +651,11 @@ function NodeForm({
   const [draft, setDraft] = useState<WorkflowNodeData>({ ...data });
   const set = (key: string, val: unknown) =>
     setDraft((d) => ({ ...d, [key]: val }));
+  const missingRequired = spec.fields.some((field) => {
+    if (!field.required) return false;
+    const value = draft[field.key];
+    return typeof value === "string" ? !value.trim() : value == null;
+  });
 
   return (
     <>
@@ -677,7 +723,9 @@ function NodeForm({
         ) : (
           <span />
         )}
-        <Button onClick={() => onSave(draft)}>保存</Button>
+        <Button disabled={missingRequired} onClick={() => onSave(draft)}>
+          保存
+        </Button>
       </DialogFooter>
     </>
   );