// Transform is used to transform the input when --with-nth option is given
func Transform(tokens []Token, withNth []Range) []Token {
transTokens := make([]Token, len(withNth))
numTokens := len(tokens)
for idx, r := range withNth {
parts := []*util.Chars{}
minIdx := 0
if r.begin == r.end {
idx := r.begin
if idx == rangeEllipsis {
chars := util.RunesToChars(joinTokens(tokens))
parts = append(parts, &chars)
} else {
if idx < 0 {
idx += numTokens + 1
}
if idx >= 1 && idx <= numTokens {
minIdx = idx - 1
parts = append(parts, tokens[idx-1].text)
}
}
} else {
var begin, end int
if r.begin == rangeEllipsis { // ..N
begin, end = 1, r.end
if end < 0 {
end += numTokens + 1
}
} else if r.end == rangeEllipsis { // N..
begin, end = r.begin, numTokens
if begin < 0 {
begin += numTokens + 1
}
} else {
begin, end = r.begin, r.end
if begin < 0 {
begin += numTokens + 1
}
if end < 0 {
end += numTokens + 1
}
}
minIdx = util.Max(0, begin-1)
for idx := begin; idx <= end; idx++ {
if idx >= 1 && idx <= numTokens {
parts = append(parts, tokens[idx-1].text)
}
}
}
// Merge multiple parts
var merged util.Chars
switch len(parts) {
case 0:
merged = util.RunesToChars([]rune{})
case 1:
merged = *parts[0]
default:
runes := []rune{}
for _, part := range parts {
runes = append(runes, part.ToRunes()...)
}
merged = util.RunesToChars(runes)
}
var prefixLength int32
if minIdx < numTokens {
prefixLength = tokens[minIdx].prefixLength
} else {
prefixLength = 0
}
transTokens[idx] = Token{&merged, prefixLength, int32(merged.TrimLength())}
}
return transTokens
}
