name.go

Documentation: github.com/GoogleCloudPlatform/k8s-config-connector/pkg/k8s

     1  // Copyright 2022 Google LLC
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package k8s
    16  
    17  import (
    18  	"fmt"
    19  	"regexp"
    20  	"strings"
    21  	"unicode"
    22  )
    23  
    24  const maxSubdomainLength = 253
    25  
    26  var notLegalRegex = regexp.MustCompile("[^a-z0-9\\-\\.]+")
    27  
    28  func ValueToDNSSubdomainName(value string) string {
    29  	// As per https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-subdomain-names, the
    30  	// following rules apply:
    31  	// * contain no more than 253 characters
    32  	// * contain only lowercase alphanumeric characters, '-' or '.'
    33  	// * start with an alphanumeric character
    34  	// * end with an alphanumeric character
    35  	value = strings.ToLower(value)
    36  	value = replaceIllegalPunctuation(value)
    37  	value = toAlphaNumeric(value)
    38  	value = ensureFirstAndLastCharactersAreAlphaNumeric(value)
    39  	if len(value) > maxSubdomainLength {
    40  		value = value[0:maxSubdomainLength]
    41  	}
    42  	return value
    43  }
    44  
    45  func replaceIllegalPunctuation(value string) string {
    46  	sb := strings.Builder{}
    47  	for _, runeValue := range value {
    48  		if unicode.IsPunct(runeValue) {
    49  			if !isLegalPunctuation(runeValue) {
    50  				runeValue = '-'
    51  			}
    52  		}
    53  		sb.WriteRune(runeValue)
    54  	}
    55  	return sb.String()
    56  }
    57  
    58  func isLegalPunctuation(r rune) bool {
    59  	return r == '-' || r == '.'
    60  }
    61  
    62  func toAlphaNumeric(value string) string {
    63  	return notLegalRegex.ReplaceAllString(value, "")
    64  }
    65  
    66  func ensureFirstAndLastCharactersAreAlphaNumeric(value string) string {
    67  	defaultCharValue := "a"
    68  	if value == "" {
    69  		return defaultCharValue
    70  	}
    71  	runes := []rune(value)
    72  	if !isAlphaNumeric(runes[0]) {
    73  		value = fmt.Sprintf("%v%v", defaultCharValue, value)
    74  	}
    75  	if !isAlphaNumeric(runes[len(runes)-1]) {
    76  		value = fmt.Sprintf("%v%v", value, defaultCharValue)
    77  	}
    78  	return value
    79  }
    80  
    81  func isAlphaNumeric(r rune) bool {
    82  	return unicode.IsLetter(r) || unicode.IsNumber(r)
    83  }
    84
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