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 (
	"fmt"
	"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
}

// Conflicts takes 2 maps and returns true if there a key match between
// the maps but the value doesn't match, and returns false in other cases
func Conflicts(labels1, labels2 Set) bool {
	small := labels1
	big := labels2
	if len(labels2) < len(labels1) {
		small = labels2
		big = labels1
	}

	for k, v := range small {
		if val, match := big[k]; match {
			if val != v {
				return true
			}
		}
	}

	return false
}

// Merge combines given maps, and does not check for any conflicts
// between the maps. In case of conflicts, second map (labels2) wins
func Merge(labels1, labels2 Set) Set {
	mergedMap := Set{}

	for k, v := range labels1 {
		mergedMap[k] = v
	}
	for k, v := range labels2 {
		mergedMap[k] = v
	}
	return mergedMap
}

// Equals returns true if the given maps are equal
func Equals(labels1, labels2 Set) bool {
	if len(labels1) != len(labels2) {
		return false
	}

	for k, v := range labels1 {
		value, ok := labels2[k]
		if !ok {
			return false
		}
		if value != v {
			return false
		}
	}
	return true
}

// AreLabelsInWhiteList verifies if the provided label list
// is in the provided whitelist and returns true, otherwise false.
func AreLabelsInWhiteList(labels, whitelist Set) bool {
	if len(whitelist) == 0 {
		return true
	}

	for k, v := range labels {
		value, ok := whitelist[k]
		if !ok {
			return false
		}
		if value != v {
			return false
		}
	}
	return true
}

// ConvertSelectorToLabelsMap converts selector string to labels map
// and validates keys and values
func ConvertSelectorToLabelsMap(selector string) (Set, error) {
	labelsMap := Set{}

	if len(selector) == 0 {
		return labelsMap, nil
	}

	labels := strings.Split(selector, ",")
	for _, label := range labels {
		l := strings.Split(label, "=")
		if len(l) != 2 {
			return labelsMap, fmt.Errorf("invalid selector: %s", l)
		}
		key := strings.TrimSpace(l[0])
		if err := validateLabelKey(key); err != nil {
			return labelsMap, err
		}
		value := strings.TrimSpace(l[1])
		if err := validateLabelValue(value); err != nil {
			return labelsMap, err
		}
		labelsMap[key] = value
	}
	return labelsMap, nil
}