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|
// +build windows linux darwin openbsd freebsd netbsd
package liner
import (
"container/ring"
"errors"
"fmt"
"io"
"strings"
"unicode"
"unicode/utf8"
)
type action int
const (
left action = iota
right
up
down
home
end
insert
del
pageUp
pageDown
f1
f2
f3
f4
f5
f6
f7
f8
f9
f10
f11
f12
altB
altF
altY
shiftTab
wordLeft
wordRight
winch
unknown
)
const (
ctrlA = 1
ctrlB = 2
ctrlC = 3
ctrlD = 4
ctrlE = 5
ctrlF = 6
ctrlG = 7
ctrlH = 8
tab = 9
lf = 10
ctrlK = 11
ctrlL = 12
cr = 13
ctrlN = 14
ctrlO = 15
ctrlP = 16
ctrlQ = 17
ctrlR = 18
ctrlS = 19
ctrlT = 20
ctrlU = 21
ctrlV = 22
ctrlW = 23
ctrlX = 24
ctrlY = 25
ctrlZ = 26
esc = 27
bs = 127
)
const (
beep = "\a"
)
type tabDirection int
const (
tabForward tabDirection = iota
tabReverse
)
func (s *State) refresh(prompt []rune, buf []rune, pos int) error {
if s.multiLineMode {
return s.refreshMultiLine(prompt, buf, pos)
} else {
return s.refreshSingleLine(prompt, buf, pos)
}
}
func (s *State) refreshSingleLine(prompt []rune, buf []rune, pos int) error {
s.cursorPos(0)
_, err := fmt.Print(string(prompt))
if err != nil {
return err
}
pLen := countGlyphs(prompt)
bLen := countGlyphs(buf)
pos = countGlyphs(buf[:pos])
if pLen+bLen < s.columns {
_, err = fmt.Print(string(buf))
s.eraseLine()
s.cursorPos(pLen + pos)
} else {
// Find space available
space := s.columns - pLen
space-- // space for cursor
start := pos - space/2
end := start + space
if end > bLen {
end = bLen
start = end - space
}
if start < 0 {
start = 0
end = space
}
pos -= start
// Leave space for markers
if start > 0 {
start++
}
if end < bLen {
end--
}
startRune := len(getPrefixGlyphs(buf, start))
line := getPrefixGlyphs(buf[startRune:], end-start)
// Output
if start > 0 {
fmt.Print("{")
}
fmt.Print(string(line))
if end < bLen {
fmt.Print("}")
}
// Set cursor position
s.eraseLine()
s.cursorPos(pLen + pos)
}
return err
}
func (s *State) refreshMultiLine(prompt []rune, buf []rune, pos int) error {
promptColumns := countMultiLineGlyphs(prompt, s.columns, 0)
totalColumns := countMultiLineGlyphs(buf, s.columns, promptColumns)
totalRows := (totalColumns + s.columns - 1) / s.columns
maxRows := s.maxRows
if totalRows > s.maxRows {
s.maxRows = totalRows
}
cursorRows := s.cursorRows
if cursorRows == 0 {
cursorRows = 1
}
/* First step: clear all the lines used before. To do so start by
* going to the last row. */
if maxRows-cursorRows > 0 {
s.moveDown(maxRows - cursorRows)
}
/* Now for every row clear it, go up. */
for i := 0; i < maxRows-1; i++ {
s.cursorPos(0)
s.eraseLine()
s.moveUp(1)
}
/* Clean the top line. */
s.cursorPos(0)
s.eraseLine()
/* Write the prompt and the current buffer content */
if _, err := fmt.Print(string(prompt)); err != nil {
return err
}
if _, err := fmt.Print(string(buf)); err != nil {
return err
}
/* If we are at the very end of the screen with our prompt, we need to
* emit a newline and move the prompt to the first column. */
cursorColumns := countMultiLineGlyphs(buf[:pos], s.columns, promptColumns)
if cursorColumns == totalColumns && totalColumns%s.columns == 0 {
s.emitNewLine()
s.cursorPos(0)
totalRows++
if totalRows > s.maxRows {
s.maxRows = totalRows
}
}
/* Move cursor to right position. */
cursorRows = (cursorColumns + s.columns) / s.columns
if s.cursorRows > 0 && totalRows-cursorRows > 0 {
s.moveUp(totalRows - cursorRows)
}
/* Set column. */
s.cursorPos(cursorColumns % s.columns)
s.cursorRows = cursorRows
return nil
}
func (s *State) resetMultiLine(prompt []rune, buf []rune, pos int) {
columns := countMultiLineGlyphs(prompt, s.columns, 0)
columns = countMultiLineGlyphs(buf[:pos], s.columns, columns)
columns += 2 // ^C
cursorRows := (columns + s.columns) / s.columns
if s.maxRows-cursorRows > 0 {
for i := 0; i < s.maxRows-cursorRows; i++ {
fmt.Println() // always moves the cursor down or scrolls the window up as needed
}
}
s.maxRows = 1
s.cursorRows = 0
}
func longestCommonPrefix(strs []string) string {
if len(strs) == 0 {
return ""
}
longest := strs[0]
for _, str := range strs[1:] {
for !strings.HasPrefix(str, longest) {
longest = longest[:len(longest)-1]
}
}
// Remove trailing partial runes
longest = strings.TrimRight(longest, "\uFFFD")
return longest
}
func (s *State) circularTabs(items []string) func(tabDirection) (string, error) {
item := -1
return func(direction tabDirection) (string, error) {
if direction == tabForward {
if item < len(items)-1 {
item++
} else {
item = 0
}
} else if direction == tabReverse {
if item > 0 {
item--
} else {
item = len(items) - 1
}
}
return items[item], nil
}
}
func calculateColumns(screenWidth int, items []string) (numColumns, numRows, maxWidth int) {
for _, item := range items {
if len(item) >= screenWidth {
return 1, len(items), screenWidth - 1
}
if len(item) >= maxWidth {
maxWidth = len(item) + 1
}
}
numColumns = screenWidth / maxWidth
numRows = len(items) / numColumns
if len(items)%numColumns > 0 {
numRows++
}
if len(items) <= numColumns {
maxWidth = 0
}
return
}
func (s *State) printedTabs(items []string) func(tabDirection) (string, error) {
numTabs := 1
prefix := longestCommonPrefix(items)
return func(direction tabDirection) (string, error) {
if len(items) == 1 {
return items[0], nil
}
if numTabs == 2 {
if len(items) > 100 {
fmt.Printf("\nDisplay all %d possibilities? (y or n) ", len(items))
prompt:
for {
next, err := s.readNext()
if err != nil {
return prefix, err
}
if key, ok := next.(rune); ok {
switch key {
case 'n', 'N':
return prefix, nil
case 'y', 'Y':
break prompt
case ctrlC, ctrlD, cr, lf:
s.restartPrompt()
}
}
}
}
fmt.Println("")
numColumns, numRows, maxWidth := calculateColumns(s.columns, items)
for i := 0; i < numRows; i++ {
for j := 0; j < numColumns*numRows; j += numRows {
if i+j < len(items) {
if maxWidth > 0 {
fmt.Printf("%-*.[1]*s", maxWidth, items[i+j])
} else {
fmt.Printf("%v ", items[i+j])
}
}
}
fmt.Println("")
}
} else {
numTabs++
}
return prefix, nil
}
}
func (s *State) tabComplete(p []rune, line []rune, pos int) ([]rune, int, interface{}, error) {
if s.completer == nil {
return line, pos, rune(esc), nil
}
head, list, tail := s.completer(string(line), pos)
if len(list) <= 0 {
return line, pos, rune(esc), nil
}
hl := utf8.RuneCountInString(head)
if len(list) == 1 {
s.refresh(p, []rune(head+list[0]+tail), hl+utf8.RuneCountInString(list[0]))
return []rune(head + list[0] + tail), hl + utf8.RuneCountInString(list[0]), rune(esc), nil
}
direction := tabForward
tabPrinter := s.circularTabs(list)
if s.tabStyle == TabPrints {
tabPrinter = s.printedTabs(list)
}
for {
pick, err := tabPrinter(direction)
if err != nil {
return line, pos, rune(esc), err
}
s.refresh(p, []rune(head+pick+tail), hl+utf8.RuneCountInString(pick))
next, err := s.readNext()
if err != nil {
return line, pos, rune(esc), err
}
if key, ok := next.(rune); ok {
if key == tab {
direction = tabForward
continue
}
if key == esc {
return line, pos, rune(esc), nil
}
}
if a, ok := next.(action); ok && a == shiftTab {
direction = tabReverse
continue
}
return []rune(head + pick + tail), hl + utf8.RuneCountInString(pick), next, nil
}
// Not reached
return line, pos, rune(esc), nil
}
// reverse intelligent search, implements a bash-like history search.
func (s *State) reverseISearch(origLine []rune, origPos int) ([]rune, int, interface{}, error) {
p := "(reverse-i-search)`': "
s.refresh([]rune(p), origLine, origPos)
line := []rune{}
pos := 0
foundLine := string(origLine)
foundPos := origPos
getLine := func() ([]rune, []rune, int) {
search := string(line)
prompt := "(reverse-i-search)`%s': "
return []rune(fmt.Sprintf(prompt, search)), []rune(foundLine), foundPos
}
history, positions := s.getHistoryByPattern(string(line))
historyPos := len(history) - 1
for {
next, err := s.readNext()
if err != nil {
return []rune(foundLine), foundPos, rune(esc), err
}
switch v := next.(type) {
case rune:
switch v {
case ctrlR: // Search backwards
if historyPos > 0 && historyPos < len(history) {
historyPos--
foundLine = history[historyPos]
foundPos = positions[historyPos]
} else {
fmt.Print(beep)
}
case ctrlS: // Search forward
if historyPos < len(history)-1 && historyPos >= 0 {
historyPos++
foundLine = history[historyPos]
foundPos = positions[historyPos]
} else {
fmt.Print(beep)
}
case ctrlH, bs: // Backspace
if pos <= 0 {
fmt.Print(beep)
} else {
n := len(getSuffixGlyphs(line[:pos], 1))
line = append(line[:pos-n], line[pos:]...)
pos -= n
// For each char deleted, display the last matching line of history
history, positions := s.getHistoryByPattern(string(line))
historyPos = len(history) - 1
if len(history) > 0 {
foundLine = history[historyPos]
foundPos = positions[historyPos]
} else {
foundLine = ""
foundPos = 0
}
}
case ctrlG: // Cancel
return origLine, origPos, rune(esc), err
case tab, cr, lf, ctrlA, ctrlB, ctrlD, ctrlE, ctrlF, ctrlK,
ctrlL, ctrlN, ctrlO, ctrlP, ctrlQ, ctrlT, ctrlU, ctrlV, ctrlW, ctrlX, ctrlY, ctrlZ:
fallthrough
case 0, ctrlC, esc, 28, 29, 30, 31:
return []rune(foundLine), foundPos, next, err
default:
line = append(line[:pos], append([]rune{v}, line[pos:]...)...)
pos++
// For each keystroke typed, display the last matching line of history
history, positions = s.getHistoryByPattern(string(line))
historyPos = len(history) - 1
if len(history) > 0 {
foundLine = history[historyPos]
foundPos = positions[historyPos]
} else {
foundLine = ""
foundPos = 0
}
}
case action:
return []rune(foundLine), foundPos, next, err
}
s.refresh(getLine())
}
}
// addToKillRing adds some text to the kill ring. If mode is 0 it adds it to a
// new node in the end of the kill ring, and move the current pointer to the new
// node. If mode is 1 or 2 it appends or prepends the text to the current entry
// of the killRing.
func (s *State) addToKillRing(text []rune, mode int) {
// Don't use the same underlying array as text
killLine := make([]rune, len(text))
copy(killLine, text)
// Point killRing to a newNode, procedure depends on the killring state and
// append mode.
if mode == 0 { // Add new node to killRing
if s.killRing == nil { // if killring is empty, create a new one
s.killRing = ring.New(1)
} else if s.killRing.Len() >= KillRingMax { // if killring is "full"
s.killRing = s.killRing.Next()
} else { // Normal case
s.killRing.Link(ring.New(1))
s.killRing = s.killRing.Next()
}
} else {
if s.killRing == nil { // if killring is empty, create a new one
s.killRing = ring.New(1)
s.killRing.Value = []rune{}
}
if mode == 1 { // Append to last entry
killLine = append(s.killRing.Value.([]rune), killLine...)
} else if mode == 2 { // Prepend to last entry
killLine = append(killLine, s.killRing.Value.([]rune)...)
}
}
// Save text in the current killring node
s.killRing.Value = killLine
}
func (s *State) yank(p []rune, text []rune, pos int) ([]rune, int, interface{}, error) {
if s.killRing == nil {
return text, pos, rune(esc), nil
}
lineStart := text[:pos]
lineEnd := text[pos:]
var line []rune
for {
value := s.killRing.Value.([]rune)
line = make([]rune, 0)
line = append(line, lineStart...)
line = append(line, value...)
line = append(line, lineEnd...)
pos = len(lineStart) + len(value)
s.refresh(p, line, pos)
next, err := s.readNext()
if err != nil {
return line, pos, next, err
}
switch v := next.(type) {
case rune:
return line, pos, next, nil
case action:
switch v {
case altY:
s.killRing = s.killRing.Prev()
default:
return line, pos, next, nil
}
}
}
return line, pos, esc, nil
}
// Prompt displays p and returns a line of user input, not including a trailing
// newline character. An io.EOF error is returned if the user signals end-of-file
// by pressing Ctrl-D. Prompt allows line editing if the terminal supports it.
func (s *State) Prompt(prompt string) (string, error) {
if s.inputRedirected || !s.terminalSupported {
return s.promptUnsupported(prompt)
}
if s.outputRedirected {
return "", ErrNotTerminalOutput
}
s.historyMutex.RLock()
defer s.historyMutex.RUnlock()
fmt.Print(prompt)
p := []rune(prompt)
var line []rune
pos := 0
historyEnd := ""
prefixHistory := s.getHistoryByPrefix(string(line))
historyPos := len(prefixHistory)
historyAction := false // used to mark history related actions
killAction := 0 // used to mark kill related actions
defer s.stopPrompt()
restart:
s.startPrompt()
s.getColumns()
mainLoop:
for {
next, err := s.readNext()
haveNext:
if err != nil {
if s.shouldRestart != nil && s.shouldRestart(err) {
goto restart
}
return "", err
}
historyAction = false
switch v := next.(type) {
case rune:
switch v {
case cr, lf:
if s.multiLineMode {
s.resetMultiLine(p, line, pos)
}
fmt.Println()
break mainLoop
case ctrlA: // Start of line
pos = 0
s.refresh(p, line, pos)
case ctrlE: // End of line
pos = len(line)
s.refresh(p, line, pos)
case ctrlB: // left
if pos > 0 {
pos -= len(getSuffixGlyphs(line[:pos], 1))
s.refresh(p, line, pos)
} else {
fmt.Print(beep)
}
case ctrlF: // right
if pos < len(line) {
pos += len(getPrefixGlyphs(line[pos:], 1))
s.refresh(p, line, pos)
} else {
fmt.Print(beep)
}
case ctrlD: // del
if pos == 0 && len(line) == 0 {
// exit
return "", io.EOF
}
// ctrlD is a potential EOF, so the rune reader shuts down.
// Therefore, if it isn't actually an EOF, we must re-startPrompt.
s.restartPrompt()
if pos >= len(line) {
fmt.Print(beep)
} else {
n := len(getPrefixGlyphs(line[pos:], 1))
line = append(line[:pos], line[pos+n:]...)
s.refresh(p, line, pos)
}
case ctrlK: // delete remainder of line
if pos >= len(line) {
fmt.Print(beep)
} else {
if killAction > 0 {
s.addToKillRing(line[pos:], 1) // Add in apend mode
} else {
s.addToKillRing(line[pos:], 0) // Add in normal mode
}
killAction = 2 // Mark that there was a kill action
line = line[:pos]
s.refresh(p, line, pos)
}
case ctrlP: // up
historyAction = true
if historyPos > 0 {
if historyPos == len(prefixHistory) {
historyEnd = string(line)
}
historyPos--
line = []rune(prefixHistory[historyPos])
pos = len(line)
s.refresh(p, line, pos)
} else {
fmt.Print(beep)
}
case ctrlN: // down
historyAction = true
if historyPos < len(prefixHistory) {
historyPos++
if historyPos == len(prefixHistory) {
line = []rune(historyEnd)
} else {
line = []rune(prefixHistory[historyPos])
}
pos = len(line)
s.refresh(p, line, pos)
} else {
fmt.Print(beep)
}
case ctrlT: // transpose prev glyph with glyph under cursor
if len(line) < 2 || pos < 1 {
fmt.Print(beep)
} else {
if pos == len(line) {
pos -= len(getSuffixGlyphs(line, 1))
}
prev := getSuffixGlyphs(line[:pos], 1)
next := getPrefixGlyphs(line[pos:], 1)
scratch := make([]rune, len(prev))
copy(scratch, prev)
copy(line[pos-len(prev):], next)
copy(line[pos-len(prev)+len(next):], scratch)
pos += len(next)
s.refresh(p, line, pos)
}
case ctrlL: // clear screen
s.eraseScreen()
s.refresh(p, line, pos)
case ctrlC: // reset
fmt.Println("^C")
if s.multiLineMode {
s.resetMultiLine(p, line, pos)
}
if s.ctrlCAborts {
return "", ErrPromptAborted
}
line = line[:0]
pos = 0
fmt.Print(prompt)
s.restartPrompt()
case ctrlH, bs: // Backspace
if pos <= 0 {
fmt.Print(beep)
} else {
n := len(getSuffixGlyphs(line[:pos], 1))
line = append(line[:pos-n], line[pos:]...)
pos -= n
s.refresh(p, line, pos)
}
case ctrlU: // Erase line before cursor
if killAction > 0 {
s.addToKillRing(line[:pos], 2) // Add in prepend mode
} else {
s.addToKillRing(line[:pos], 0) // Add in normal mode
}
killAction = 2 // Mark that there was some killing
line = line[pos:]
pos = 0
s.refresh(p, line, pos)
case ctrlW: // Erase word
if pos == 0 {
fmt.Print(beep)
break
}
// Remove whitespace to the left
var buf []rune // Store the deleted chars in a buffer
for {
if pos == 0 || !unicode.IsSpace(line[pos-1]) {
break
}
buf = append(buf, line[pos-1])
line = append(line[:pos-1], line[pos:]...)
pos--
}
// Remove non-whitespace to the left
for {
if pos == 0 || unicode.IsSpace(line[pos-1]) {
break
}
buf = append(buf, line[pos-1])
line = append(line[:pos-1], line[pos:]...)
pos--
}
// Invert the buffer and save the result on the killRing
var newBuf []rune
for i := len(buf) - 1; i >= 0; i-- {
newBuf = append(newBuf, buf[i])
}
if killAction > 0 {
s.addToKillRing(newBuf, 2) // Add in prepend mode
} else {
s.addToKillRing(newBuf, 0) // Add in normal mode
}
killAction = 2 // Mark that there was some killing
s.refresh(p, line, pos)
case ctrlY: // Paste from Yank buffer
line, pos, next, err = s.yank(p, line, pos)
goto haveNext
case ctrlR: // Reverse Search
line, pos, next, err = s.reverseISearch(line, pos)
s.refresh(p, line, pos)
goto haveNext
case tab: // Tab completion
line, pos, next, err = s.tabComplete(p, line, pos)
goto haveNext
// Catch keys that do nothing, but you don't want them to beep
case esc:
// DO NOTHING
// Unused keys
case ctrlG, ctrlO, ctrlQ, ctrlS, ctrlV, ctrlX, ctrlZ:
fallthrough
// Catch unhandled control codes (anything <= 31)
case 0, 28, 29, 30, 31:
fmt.Print(beep)
default:
if pos == len(line) && !s.multiLineMode && countGlyphs(p)+countGlyphs(line) < s.columns-1 {
line = append(line, v)
fmt.Printf("%c", v)
pos++
} else {
line = append(line[:pos], append([]rune{v}, line[pos:]...)...)
pos++
s.refresh(p, line, pos)
}
}
case action:
switch v {
case del:
if pos >= len(line) {
fmt.Print(beep)
} else {
n := len(getPrefixGlyphs(line[pos:], 1))
line = append(line[:pos], line[pos+n:]...)
}
case left:
if pos > 0 {
pos -= len(getSuffixGlyphs(line[:pos], 1))
} else {
fmt.Print(beep)
}
case wordLeft, altB:
if pos > 0 {
var spaceHere, spaceLeft, leftKnown bool
for {
pos--
if pos == 0 {
break
}
if leftKnown {
spaceHere = spaceLeft
} else {
spaceHere = unicode.IsSpace(line[pos])
}
spaceLeft, leftKnown = unicode.IsSpace(line[pos-1]), true
if !spaceHere && spaceLeft {
break
}
}
} else {
fmt.Print(beep)
}
case right:
if pos < len(line) {
pos += len(getPrefixGlyphs(line[pos:], 1))
} else {
fmt.Print(beep)
}
case wordRight, altF:
if pos < len(line) {
var spaceHere, spaceLeft, hereKnown bool
for {
pos++
if pos == len(line) {
break
}
if hereKnown {
spaceLeft = spaceHere
} else {
spaceLeft = unicode.IsSpace(line[pos-1])
}
spaceHere, hereKnown = unicode.IsSpace(line[pos]), true
if spaceHere && !spaceLeft {
break
}
}
} else {
fmt.Print(beep)
}
case up:
historyAction = true
if historyPos > 0 {
if historyPos == len(prefixHistory) {
historyEnd = string(line)
}
historyPos--
line = []rune(prefixHistory[historyPos])
pos = len(line)
} else {
fmt.Print(beep)
}
case down:
historyAction = true
if historyPos < len(prefixHistory) {
historyPos++
if historyPos == len(prefixHistory) {
line = []rune(historyEnd)
} else {
line = []rune(prefixHistory[historyPos])
}
pos = len(line)
} else {
fmt.Print(beep)
}
case home: // Start of line
pos = 0
case end: // End of line
pos = len(line)
case winch: // Window change
if s.multiLineMode {
if s.maxRows-s.cursorRows > 0 {
s.moveDown(s.maxRows - s.cursorRows)
}
for i := 0; i < s.maxRows-1; i++ {
s.cursorPos(0)
s.eraseLine()
s.moveUp(1)
}
s.maxRows = 1
s.cursorRows = 1
}
}
s.refresh(p, line, pos)
}
if !historyAction {
prefixHistory = s.getHistoryByPrefix(string(line))
historyPos = len(prefixHistory)
}
if killAction > 0 {
killAction--
}
}
return string(line), nil
}
// PasswordPrompt displays p, and then waits for user input. The input typed by
// the user is not displayed in the terminal.
func (s *State) PasswordPrompt(prompt string) (string, error) {
if !s.terminalSupported {
return "", errors.New("liner: function not supported in this terminal")
}
if s.inputRedirected {
return s.promptUnsupported(prompt)
}
if s.outputRedirected {
return "", ErrNotTerminalOutput
}
defer s.stopPrompt()
restart:
s.startPrompt()
s.getColumns()
fmt.Print(prompt)
p := []rune(prompt)
var line []rune
pos := 0
mainLoop:
for {
next, err := s.readNext()
if err != nil {
if s.shouldRestart != nil && s.shouldRestart(err) {
goto restart
}
return "", err
}
switch v := next.(type) {
case rune:
switch v {
case cr, lf:
if s.multiLineMode {
s.resetMultiLine(p, line, pos)
}
fmt.Println()
break mainLoop
case ctrlD: // del
if pos == 0 && len(line) == 0 {
// exit
return "", io.EOF
}
// ctrlD is a potential EOF, so the rune reader shuts down.
// Therefore, if it isn't actually an EOF, we must re-startPrompt.
s.restartPrompt()
case ctrlL: // clear screen
s.eraseScreen()
s.refresh(p, []rune{}, 0)
case ctrlH, bs: // Backspace
if pos <= 0 {
fmt.Print(beep)
} else {
n := len(getSuffixGlyphs(line[:pos], 1))
line = append(line[:pos-n], line[pos:]...)
pos -= n
}
case ctrlC:
fmt.Println("^C")
if s.multiLineMode {
s.resetMultiLine(p, line, pos)
}
if s.ctrlCAborts {
return "", ErrPromptAborted
}
line = line[:0]
pos = 0
fmt.Print(prompt)
s.restartPrompt()
// Unused keys
case esc, tab, ctrlA, ctrlB, ctrlE, ctrlF, ctrlG, ctrlK, ctrlN, ctrlO, ctrlP, ctrlQ, ctrlR, ctrlS,
ctrlT, ctrlU, ctrlV, ctrlW, ctrlX, ctrlY, ctrlZ:
fallthrough
// Catch unhandled control codes (anything <= 31)
case 0, 28, 29, 30, 31:
fmt.Print(beep)
default:
line = append(line[:pos], append([]rune{v}, line[pos:]...)...)
pos++
}
}
}
return string(line), nil
}
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