camelcase.go

package sflags

// This part was taken from the https://github.com/fatih/camelcase package.
// The only fix is for integers, they stay with previous words.
//
// The MIT License (MIT)
//
// Copyright (c) 2015 Fatih Arslan
//
// 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.

import (
	"unicode"
	"unicode/utf8"
)

const (
	classLower = 1
	classUpper = 2
	classDigit = 3
	classOther = 4
)

// split splits the camelcase word and returns a list of words. It also
// supports digits. Both lower camel case and upper camel case are supported.
// For more info please check: http://en.wikipedia.org/wiki/CamelCase
//
// Examples
//
//   "" =>                     [""]
//   "lowercase" =>            ["lowercase"]
//   "Class" =>                ["Class"]
//   "MyClass" =>              ["My", "Class"]
//   "MyC" =>                  ["My", "C"]
//   "HTML" =>                 ["HTML"]
//   "PDFLoader" =>            ["PDF", "Loader"]
//   "AString" =>              ["A", "String"]
//   "SimpleXMLParser" =>      ["Simple", "XML", "Parser"]
//   "vimRPCPlugin" =>         ["vim", "RPC", "Plugin"]
//   "GL11Version" =>          ["GL11", "Version"]
//   "99Bottles" =>            ["99", "Bottles"]
//   "May5" =>                 ["May5"]
//   "BFG9000" =>              ["BFG9000"]
//   "BöseÜberraschung" =>     ["Böse", "Überraschung"]
//   "Two  spaces" =>          ["Two", "  ", "spaces"]
//   "BadUTF8\xe2\xe2\xa1" =>  ["BadUTF8\xe2\xe2\xa1"]
//
// Splitting rules
//
//  1) If string is not valid UTF-8, return it without splitting as
//     single item array.
//  2) Assign all unicode characters into one of 4 sets: lower case
//     letters, upper case letters, numbers, and all other characters.
//  3) Iterate through characters of string, introducing splits
//     between adjacent characters that belong to different sets.
//  4) Iterate through array of split strings, and if a given string
//     is upper case:
//       if subsequent string is lower case:
//         move last character of upper case string to beginning of
//         lower case string
func split(src string) (entries []string) {
	// don't split invalid utf8
	if !utf8.ValidString(src) {
		return []string{src}
	}
	entries = []string{}
	var runes [][]rune
	var class int
	lastClass := 0
	// split into fields based on class of unicode character
	for _, r := range src {
		switch true {
		case unicode.IsLower(r):
			class = classLower
		case unicode.IsUpper(r):
			class = classUpper
		case unicode.IsDigit(r):
			class = classDigit
		default:
			class = classOther
		}
		if lastClass != 0 && (class == lastClass || class == classDigit) {
			runes[len(runes)-1] = append(runes[len(runes)-1], r)
		} else {
			runes = append(runes, []rune{r})
		}
		lastClass = class
	}
	// handle upper case -> lower case sequences, e.g.
	// "PDFL", "oader" -> "PDF", "Loader"
	for i := 0; i < len(runes)-1; i++ {
		if unicode.IsUpper(runes[i][0]) && unicode.IsLower(runes[i+1][0]) {
			runes[i+1] = append([]rune{runes[i][len(runes[i])-1]}, runes[i+1]...)
			runes[i] = runes[i][:len(runes[i])-1]
		}
	}
	// construct []string from results
	for _, s := range runes {
		if len(s) > 0 {
			entries = append(entries, string(s))
		}
	}
	return
}