restic/internal/ui/termstatus/status.go

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package termstatus
import (
"bufio"
"bytes"
"context"
"fmt"
"io"
"os"
"strings"
"unicode"
"golang.org/x/crypto/ssh/terminal"
"golang.org/x/text/width"
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)
// Terminal is used to write messages and display status lines which can be
// updated. When the output is redirected to a file, the status lines are not
// printed.
type Terminal struct {
wr *bufio.Writer
fd uintptr
errWriter io.Writer
buf *bytes.Buffer
msg chan message
status chan status
canUpdateStatus bool
// will be closed when the goroutine which runs Run() terminates, so it'll
// yield a default value immediately
closed chan struct{}
clearCurrentLine func(io.Writer, uintptr)
moveCursorUp func(io.Writer, uintptr, int)
}
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type message struct {
line string
err bool
}
type status struct {
lines []string
}
type fder interface {
Fd() uintptr
}
// New returns a new Terminal for wr. A goroutine is started to update the
// terminal. It is terminated when ctx is cancelled. When wr is redirected to
// a file (e.g. via shell output redirection) or is just an io.Writer (not the
// open *os.File for stdout), no status lines are printed. The status lines and
// normal output (via Print/Printf) are written to wr, error messages are
// written to errWriter. If disableStatus is set to true, no status messages
// are printed even if the terminal supports it.
func New(wr io.Writer, errWriter io.Writer, disableStatus bool) *Terminal {
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t := &Terminal{
wr: bufio.NewWriter(wr),
errWriter: errWriter,
buf: bytes.NewBuffer(nil),
msg: make(chan message),
status: make(chan status),
closed: make(chan struct{}),
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}
if disableStatus {
return t
}
if d, ok := wr.(fder); ok && CanUpdateStatus(d.Fd()) {
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// only use the fancy status code when we're running on a real terminal.
t.canUpdateStatus = true
t.fd = d.Fd()
t.clearCurrentLine = clearCurrentLine(wr, t.fd)
t.moveCursorUp = moveCursorUp(wr, t.fd)
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}
return t
}
// CanUpdateStatus return whether the status output is updated in place.
func (t *Terminal) CanUpdateStatus() bool {
return t.canUpdateStatus
}
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// Run updates the screen. It should be run in a separate goroutine. When
// ctx is cancelled, the status lines are cleanly removed.
func (t *Terminal) Run(ctx context.Context) {
defer close(t.closed)
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if t.canUpdateStatus {
t.run(ctx)
return
}
t.runWithoutStatus(ctx)
}
// run listens on the channels and updates the terminal screen.
func (t *Terminal) run(ctx context.Context) {
var status []string
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for {
select {
case <-ctx.Done():
if !IsProcessBackground(t.fd) {
t.undoStatus(len(status))
}
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return
case msg := <-t.msg:
if IsProcessBackground(t.fd) {
// ignore all messages, do nothing, we are in the background process group
continue
}
t.clearCurrentLine(t.wr, t.fd)
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var dst io.Writer
if msg.err {
dst = t.errWriter
// assume t.wr and t.errWriter are different, so we need to
// flush clearing the current line
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err := t.wr.Flush()
if err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
} else {
dst = t.wr
}
if _, err := io.WriteString(dst, msg.line); err != nil {
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fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
continue
}
t.writeStatus(status)
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if err := t.wr.Flush(); err != nil {
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fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
case stat := <-t.status:
if IsProcessBackground(t.fd) {
// ignore all messages, do nothing, we are in the background process group
continue
}
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status = status[:0]
status = append(status, stat.lines...)
t.writeStatus(status)
}
}
}
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func (t *Terminal) writeStatus(status []string) {
for _, line := range status {
t.clearCurrentLine(t.wr, t.fd)
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_, err := t.wr.WriteString(line)
if err != nil {
fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
}
// flush is needed so that the current line is updated
err = t.wr.Flush()
if err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
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}
}
if len(status) > 0 {
t.moveCursorUp(t.wr, t.fd, len(status)-1)
}
err := t.wr.Flush()
if err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
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}
// runWithoutStatus listens on the channels and just prints out the messages,
// without status lines.
func (t *Terminal) runWithoutStatus(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
case msg := <-t.msg:
var flush func() error
var dst io.Writer
if msg.err {
dst = t.errWriter
} else {
dst = t.wr
flush = t.wr.Flush
}
if _, err := io.WriteString(dst, msg.line); err != nil {
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fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
}
if flush == nil {
continue
}
if err := flush(); err != nil {
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fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
case stat := <-t.status:
for _, line := range stat.lines {
// Ensure that each message ends with exactly one newline.
fmt.Fprintln(t.wr, strings.TrimRight(line, "\n"))
}
if err := t.wr.Flush(); err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
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}
}
}
func (t *Terminal) undoStatus(lines int) {
for i := 0; i < lines; i++ {
t.clearCurrentLine(t.wr, t.fd)
_, err := t.wr.WriteRune('\n')
if err != nil {
fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
}
// flush is needed so that the current line is updated
err = t.wr.Flush()
if err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
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}
t.moveCursorUp(t.wr, t.fd, lines)
err := t.wr.Flush()
if err != nil {
fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
}
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}
func (t *Terminal) print(line string, isErr bool) {
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// make sure the line ends with a line break
if line[len(line)-1] != '\n' {
line += "\n"
}
select {
case t.msg <- message{line: line, err: isErr}:
case <-t.closed:
}
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}
// Print writes a line to the terminal.
func (t *Terminal) Print(line string) {
t.print(line, false)
}
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// Printf uses fmt.Sprintf to write a line to the terminal.
func (t *Terminal) Printf(msg string, args ...interface{}) {
s := fmt.Sprintf(msg, args...)
t.Print(s)
}
// Error writes an error to the terminal.
func (t *Terminal) Error(line string) {
t.print(line, true)
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}
// Errorf uses fmt.Sprintf to write an error line to the terminal.
func (t *Terminal) Errorf(msg string, args ...interface{}) {
s := fmt.Sprintf(msg, args...)
t.Error(s)
}
// Truncate s to fit in width (number of terminal cells) w.
// If w is negative, returns the empty string.
func Truncate(s string, w int) string {
if len(s) < w {
// Since the display width of a character is at most 2
// and all of ASCII (single byte per rune) has width 1,
// no character takes more bytes to encode than its width.
return s
}
for i, r := range s {
w--
if r > unicode.MaxASCII && wideRune(r) {
w--
}
if w < 0 {
return s[:i]
}
}
return s
}
// Guess whether r would occupy two terminal cells instead of one.
// This cannot be determined exactly without knowing the terminal font,
// so we treat all ambigous runes as full-width, i.e., two cells.
func wideRune(r rune) bool {
kind := width.LookupRune(r).Kind()
return kind != width.Neutral && kind != width.EastAsianNarrow
}
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// SetStatus updates the status lines.
func (t *Terminal) SetStatus(lines []string) {
if len(lines) == 0 {
return
}
// only truncate interactive status output
var width int
if t.canUpdateStatus {
var err error
width, _, err = terminal.GetSize(int(t.fd))
if err != nil || width <= 0 {
// use 80 columns by default
width = 80
}
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}
// make sure that all lines have a line break and are not too long
for i, line := range lines {
line = strings.TrimRight(line, "\n")
if width > 0 {
line = Truncate(line, width-2)
}
lines[i] = line + "\n"
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}
// make sure the last line does not have a line break
last := len(lines) - 1
lines[last] = strings.TrimRight(lines[last], "\n")
select {
case t.status <- status{lines: lines}:
case <-t.closed:
}
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}