labels.go

/*
Copyright 2014 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 labels

import (
	"sort"
	"strings"
)

// Labels allows you to present labels independently from their storage.
type Labels interface {
	// Has returns whether the provided label exists.
	Has(label string) (exists bool)

	// Get returns the value for the provided label.
	Get(label string) (value string)
}

// Set is a map of label:value. It implements Labels.
type Set map[string]string

// String returns all labels listed as a human readable string.
// Conveniently, exactly the format that ParseSelector takes.
func (ls Set) String() string {
	selector := make([]string, 0, len(ls))
	for key, value := range ls {
		selector = append(selector, key+"="+value)
	}
	// Sort for determinism.
	sort.StringSlice(selector).Sort()
	return strings.Join(selector, ",")
}

// Has returns whether the provided label exists in the map.
func (ls Set) Has(label string) bool {
	_, exists := ls[label]
	return exists
}

// Get returns the value in the map for the provided label.
func (ls Set) Get(label string) string {
	return ls[label]
}

// AsSelector converts labels into a selectors.
func (ls Set) AsSelector() Selector {
	return SelectorFromSet(ls)
}

// AsSelectorPreValidated converts labels into a selector, but
// assumes that labels are already validated and thus don't
// preform any validation.
// According to our measurements this is significantly faster
// in codepaths that matter at high sccale.
func (ls Set) AsSelectorPreValidated() Selector {
	return SelectorFromValidatedSet(ls)
}

// FormatLables convert label map into plain string
func FormatLabels(labelMap map[string]string) string {
	l := Set(labelMap).String()
	if l == "" {
		l = "<none>"
	}
	return l
}