string-to-snake-case.go

package tdd

import (
	"regexp"
	"strings"
)

func StringToSnakeCase(str string) string {
	var matchFirstCap = regexp.MustCompile("(.)([A-Z][a-z]+)")
	var matchAllCap = regexp.MustCompile("([a-z0-9])([A-Z])")
	snake := matchFirstCap.ReplaceAllString(str, "${1}_${2}")
	snake = matchAllCap.ReplaceAllString(snake, "${1}_${2}")
	return strings.ToLower(snake)
}

// ToSnake converts a string to snake_case
func ToSnake(s string) string {
	return ToDelimited(s, '_')
}

// ToScreamingSnake converts a string to SCREAMING_SNAKE_CASE
func ToScreamingSnake(s string) string {
	return ToScreamingDelimited(s, '_', true)
}

// ToKebab converts a string to kebab-case
func ToKebab(s string) string {
	return ToDelimited(s, '-')
}

// ToScreamingKebab converts a string to SCREAMING-KEBAB-CASE
func ToScreamingKebab(s string) string {
	return ToScreamingDelimited(s, '-', true)
}

// ToDelimited converts a string to delimited.snake.case (in this case `del = '.'`)
func ToDelimited(s string, del uint8) string {
	return ToScreamingDelimited(s, del, false)
}

// ToScreamingDelimited converts a string to SCREAMING.DELIMITED.SNAKE.CASE (in this case `del = '.'; screaming = true`) or delimited.snake.case (in this case `del = '.'; screaming = false`)
func ToScreamingDelimited(s string, del uint8, screaming bool) string {
	s = addWordBoundariesToNumbers(s)
	s = strings.Trim(s, " ")
	n := ""
	for i, v := range s {
		// treat acronyms as words, eg for JSONData -> JSON is a whole word
		nextCaseIsChanged := false
		if i+1 < len(s) {
			next := s[i+1]
			if (v >= 'A' && v <= 'Z' && next >= 'a' && next <= 'z') || (v >= 'a' && v <= 'z' && next >= 'A' && next <= 'Z') {
				nextCaseIsChanged = true
			}
		}

		if i > 0 && n[len(n)-1] != del && nextCaseIsChanged {
			// add underscore if next letter case type is changed
			if v >= 'A' && v <= 'Z' {
				n += string(del) + string(v)
			} else if v >= 'a' && v <= 'z' {
				n += string(v) + string(del)
			}
		} else if v == ' ' || v == '_' || v == '-' {
			// replace spaces/underscores with delimiters
			n += string(del)
		} else {
			n = n + string(v)
		}
	}

	if screaming {
		n = strings.ToUpper(n)
	} else {
		n = strings.ToLower(n)
	}
	return n
}