Bring elemental-cli code into the agent (#13)

pkg/utils/cleanstack.go

@@ -0,0 +1,66 @@
+/*
+Copyright © 2022 SUSE LLC
+
+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 utils
+
+import (
+	"github.com/hashicorp/go-multierror"
+)
+
+type CleanJob func() error
+
+// NewCleanStack returns a new stack.
+func NewCleanStack() *CleanStack {
+	return &CleanStack{}
+}
+
+// Stack is a basic LIFO stack that resizes as needed.
+type CleanStack struct {
+	jobs  []CleanJob
+	count int
+}
+
+// Push adds a node to the stack
+func (clean *CleanStack) Push(job CleanJob) {
+	clean.jobs = append(clean.jobs[:clean.count], job)
+	clean.count++
+}
+
+// Pop removes and returns a node from the stack in last to first order.
+func (clean *CleanStack) Pop() CleanJob {
+	if clean.count == 0 {
+		return nil
+	}
+	clean.count--
+	return clean.jobs[clean.count]
+}
+
+// Cleanup runs the whole cleanup stack. In case of error it runs all jobs
+// and returns the first error occurrence.
+func (clean *CleanStack) Cleanup(err error) error {
+	var errs error
+	if err != nil {
+		errs = multierror.Append(errs, err)
+	}
+	for clean.count > 0 {
+		job := clean.Pop()
+		err = job()
+		if err != nil {
+			errs = multierror.Append(errs, err)
+		}
+	}
+	return errs
+}