strcase/snake.go

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 Ian Coleman
 *
 * 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 converts strings to snake_case or CamelCase
package strcase

import (
	"strings"
)

// Converts a string to snake_case
func ToSnake(s string) 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] != '_' && nextCaseIsChanged {
			// add underscore if next letter case type is changed
			if v >= 'A' && v <= 'Z' {
				n += "_" + string(v)
			} else if v >= 'a' && v <= 'z' {
				n += string(v) + "_"
			}
		} else if v == ' ' {
			// replace spaces with underscores
			n += "_"
		} else {
			n = n + string(v)
		}
	}
	n = strings.ToLower(n)
	return n
}