feat: flow design & page query refactor

server/internal/flow/application/node_start.go

@@ -0,0 +1,31 @@
+package application
+
+import (
+	"context"
+	"errors"
+	"mayfly-go/internal/flow/domain/entity"
+)
+
+/******************* 开始节点处理器 *******************/
+
+const FlowNodeTypeStart entity.FlowNodeType = "start" // 开始节点
+
+// StartNodeBehavior 开始节点处理器
+type StartNodeBehavior struct {
+	DefaultNodeBehavior
+}
+
+var _ NodeBehavior = (*StartNodeBehavior)(nil)
+
+func (h *StartNodeBehavior) GetType() entity.FlowNodeType {
+	return FlowNodeTypeStart
+}
+
+func (h *StartNodeBehavior) Validate(ctx context.Context, flowDef *entity.FlowDef, node *entity.FlowNode) error {
+	// 检查开始节点是否有一个连线指出去
+	edgesFromStartNode := flowDef.GetEdgeBySourceNode(node.Key)
+	if len(edgesFromStartNode) == 0 {
+		return errors.New("start node not has outgoing edge")
+	}
+	return nil
+}