source.go

// Copyright 2019 Authors of Cilium
//
// 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 source

// Source describes the source of a definition
type Source string

const (
	// Unspec is used when the source is unspecified
	Unspec Source = "unspec"

	// Local is the source used for state derived from local agent state.
	// Local state has the strongest ownership and can only be overwritten
	// by other local state.
	Local Source = "local"

	// KVStore is the source used for state derived from a key value store.
	// State in the key value stored takes precendence over orchestration
	// system state such as Kubernetes.
	KVStore Source = "kvstore"

	// Kubernetes is the source used for state derived from Kubernetes
	Kubernetes Source = "k8s"

	// CustomResource is the source used for state derived from Kubernetes
	// custom resources
	CustomResource Source = "custom-resource"

	// Generated is the source used for generated state which can be
	// overwritten by all other sources
	Generated Source = "generated"
)

// AllowOverwrite returns true if new state from a particular source is allowed
// to overwrite existing state from another source
func AllowOverwrite(existing, new Source) bool {
	switch existing {

	// Kubernetes state can be overwritten by everything except generated
	// and unspecified state
	case Kubernetes:
		return new != Generated && new != Unspec

	// Custom-resource state can be overwritten everything except
	// generated, unspecified and Kuberntes (non-CRD) state
	case CustomResource:
		return new != Generated && new != Unspec && new != Kubernetes

	// KVStore can be overwritten by other kvstore or local state
	case KVStore:
		return new == KVStore || new == Local

	// local state can only be overwritten by other local state
	case Local:
		return new == Local

	// Generated and unspecified state can be overwritten by everything
	case Generated:
		return new != Unspec

	// Unspecified state can be overwritten by everything
	case Unspec:
		return true
	}

	return true
}