strcase/snake.go

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 Ian Coleman
 * Copyright (c) 2018 Ma_124, <github.com/Ma124>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, Subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or Substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package strcase

import (
	"strings"
)

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

func ToSnakeWithIgnore(s string, ignore uint8) string {
	return ToScreamingDelimited(s, '_', ignore, false)
}

// ToScreamingSnake converts a string to SCREAMING_SNAKE_CASE
func ToScreamingSnake(s string) string {
	return ToScreamingDelimited(s, '_', 0, 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, '-', 0, true)
}

// ToDelimited converts a string to delimited.snake.case
// (in this case `delimiter = '.'`)
func ToDelimited(s string, delimiter uint8) string {
	return ToScreamingDelimited(s, delimiter, 0, false)
}

// ToScreamingDelimited converts a string to SCREAMING.DELIMITED.SNAKE.CASE
// (in this case `delimiter = '.'; screaming = true`)
// or delimited.snake.case
// (in this case `delimiter = '.'; screaming = false`)
func ToScreamingDelimited(s string, delimiter uint8, ignore uint8, screaming bool) string {
	n := strings.Builder{}
	n.Grow(len(s) + 2) // nominal 2 bytes of extra space for inserted delimiters
	start := true
	spaces := 0
	for i, v := range []byte(s) {
		if v == ' ' {
			spaces++
			continue
		} else if start {
			start = false
			spaces = 0
		} else {
			for ; spaces > 0; spaces-- {
				if ignore == ' ' {
					n.WriteByte(' ')
				} else {
					n.WriteByte(delimiter)
				}
			}
		}

		vIsCap := v >= 'A' && v <= 'Z'
		vIsLow := v >= 'a' && v <= 'z'
		if vIsLow && screaming {
			v += 'A'
			v -= 'a'
		} else if vIsCap && !screaming {
			v += 'a'
			v -= 'A'
		}

		// treat acronyms as words, eg for JSONData -> JSON is a whole word
		if i+1 < len(s) {
			next := s[i+1]
			vIsNum := v >= '0' && v <= '9'
			nextIsCap := next >= 'A' && next <= 'Z'
			nextIsLow := next >= 'a' && next <= 'z'
			nextIsNum := next >= '0' && next <= '9'
			// add underscore if next letter case type is changed
			if (vIsCap && (nextIsLow || nextIsNum)) || (vIsLow && (nextIsCap || nextIsNum)) || (vIsNum && (nextIsCap || nextIsLow)) {
				if prevIgnore := ignore > 0 && i > 0 && s[i-1] == ignore; !prevIgnore {
					if vIsCap && nextIsLow {
						if prevIsCap := i > 0 && s[i-1] >= 'A' && s[i-1] <= 'Z'; prevIsCap {
							n.WriteByte(delimiter)
						}
					}
					n.WriteByte(v)
					if vIsLow || vIsNum || nextIsNum {
						n.WriteByte(delimiter)
					}
					continue
				}
			}
		}

		if (v == ' ' || v == '_' || v == '-') && uint8(v) != ignore {
			// replace space/underscore/hyphen with delimiter
			n.WriteByte(delimiter)
		} else {
			n.WriteByte(v)
		}
	}

	return n.String()
}