Decouple shared functions between controllers (#8829)

* Decouple shared functions between controllers

* Apply suggestions from code review

Co-authored-by: Jintao Zhang <tao12345666333@163.com>

* Fix package names and fmt

Co-authored-by: Jintao Zhang <tao12345666333@163.com>

pkg/util/file/structure.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package file
+
+import (
+	"fmt"
+	"os"
+)
+
+const (
+	// AuthDirectory default directory used to store files
+	// to authenticate request
+	AuthDirectory = "/etc/ingress-controller/auth"
+
+	// DefaultSSLDirectory defines the location where the SSL certificates will be generated
+	// This directory contains all the SSL certificates that are specified in Ingress rules.
+	// The name of each file is <namespace>-<secret name>.pem. The content is the concatenated
+	// certificate and key.
+	DefaultSSLDirectory = "/etc/ingress-controller/ssl"
+)
+
+var (
+	directories = []string{
+		DefaultSSLDirectory,
+		AuthDirectory,
+	}
+)
+
+// CreateRequiredDirectories verifies if the required directories to
+// start the ingress controller exist and creates the missing ones.
+func CreateRequiredDirectories() error {
+	for _, directory := range directories {
+		_, err := os.Stat(directory)
+		if err != nil {
+			if os.IsNotExist(err) {
+				err = os.MkdirAll(directory, ReadWriteByUser)
+				if err != nil {
+					return fmt.Errorf("creating directory %s: %w", directory, err)
+				}
+
+				continue
+			}
+
+			return fmt.Errorf("checking directory %s: %w", directory, err)
+		}
+	}
+
+	return nil
+}