alphabetic.go

package sorting

import (
	"unicode"
)

type AlphabetSorter func([]string) func(i, j int) bool

// LessIgnoreCase returns true if first is alphabetically less than second.
func LessIgnoreCase(first string, second string) bool {
	iRunes := []rune(first)
	jRunes := []rune(second)

	max := len(iRunes)
	if max > len(jRunes) {
		max = len(jRunes)
	}

	for idx := 0; idx < max; idx++ {
		ir := iRunes[idx]
		jr := jRunes[idx]

		lir := unicode.ToLower(ir)
		ljr := unicode.ToLower(jr)

		if lir == ljr {
			continue
		}

		return lir < ljr
	}

	return false
}

// SortAlphabeticFunc returns a `less()` comparator for sorting strings while
// respecting case.
func SortAlphabeticFunc(list []string) func(i, j int) bool {
	return func(i, j int) bool {
		return LessIgnoreCase(list[i], list[j])
	}
}