package liner

import "unicode"

// These character classes are mostly zero width (when combined).
// A few might not be, depending on the user's font. Fixing this
// is non-trivial, given that some terminals don't support
// ANSI DSR/CPR
var zeroWidth = []*unicode.RangeTable{
	unicode.Mn,
	unicode.Me,
	unicode.Cc,
	unicode.Cf,
}

func countGlyphs(s []rune) int {
	n := 0
	for _, r := range s {
		if !unicode.IsOneOf(zeroWidth, r) {
			n++
		}
	}
	return n
}

func getPrefixGlyphs(s []rune, num int) []rune {
	p := 0
	for n := 0; n < num && p < len(s); p++ {
		if !unicode.IsOneOf(zeroWidth, s[p]) {
			n++
		}
	}
	for p < len(s) && unicode.IsOneOf(zeroWidth, s[p]) {
		p++
	}
	return s[:p]
}

func getSuffixGlyphs(s []rune, num int) []rune {
	p := len(s)
	for n := 0; n < num && p > 0; p-- {
		if !unicode.IsOneOf(zeroWidth, s[p-1]) {
			n++
		}
	}
	return s[p:]
}