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package text
import (
"strings"
"unicode/utf8"
)
// EscapeItem hold the description of terminal escapes in a line.
// 'item' is the actual escape command
// 'pos' is the index in the rune array where the 'item' shall be inserted back.
// For example, the escape item in "F\x1b33mox" is {"\x1b33m", 1}.
type EscapeItem struct {
Item string
Pos int
}
// ExtractTermEscapes extract terminal escapes out of a line and returns a new
// line without terminal escapes and a slice of escape items. The terminal escapes
// can be inserted back into the new line at rune index 'item.pos' to recover the
// original line.
//
// Required: The line shall not contain "\n"
func ExtractTermEscapes(line string) (string, []EscapeItem) {
var termEscapes []EscapeItem
var line1 strings.Builder
pos := 0
item := ""
occupiedRuneCount := 0
inEscape := false
for i, r := range []rune(line) {
if r == '\x1b' {
pos = i
item = string(r)
inEscape = true
continue
}
if inEscape {
item += string(r)
if r == 'm' {
termEscapes = append(termEscapes, EscapeItem{item, pos - occupiedRuneCount})
occupiedRuneCount += utf8.RuneCountInString(item)
inEscape = false
}
continue
}
line1.WriteRune(r)
}
return line1.String(), termEscapes
}
// ApplyTermEscapes apply the extracted terminal escapes to the edited line.
// Escape sequences need to be ordered by their position.
// If the position is < 0, the escape is applied at the beginning of the line.
// If the position is > len(line), the escape is applied at the end of the line.
func ApplyTermEscapes(line string, escapes []EscapeItem) string {
if len(escapes) == 0 {
return line
}
var out strings.Builder
currPos := 0
currItem := 0
for _, r := range line {
for currItem < len(escapes) && currPos >= escapes[currItem].Pos {
out.WriteString(escapes[currItem].Item)
currItem++
}
out.WriteRune(r)
currPos++
}
// Don't forget the trailing escapes, if any.
for currItem < len(escapes) {
out.WriteString(escapes[currItem].Item)
currItem++
}
return out.String()
}
// OffsetEscapes is a utility function to offset the position of a
// collection of EscapeItem.
func OffsetEscapes(escapes []EscapeItem, offset int) []EscapeItem {
result := make([]EscapeItem, len(escapes))
for i, e := range escapes {
result[i] = EscapeItem{
Item: e.Item,
Pos: e.Pos + offset,
}
}
return result
}
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