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package cwriter
import (
"bytes"
"errors"
"fmt"
"io"
"os"
isatty "github.com/mattn/go-isatty"
"golang.org/x/crypto/ssh/terminal"
)
// ESC is the ASCII code for escape character
const ESC = 27
var NotATTY = errors.New("not a terminal")
var (
cursorUp = fmt.Sprintf("%c[%dA", ESC, 1)
clearLine = fmt.Sprintf("%c[2K\r", ESC)
clearCursorAndLine = cursorUp + clearLine
)
// Writer is a buffered the writer that updates the terminal. The
// contents of writer will be flushed when Flush is called.
type Writer struct {
out io.Writer
buf bytes.Buffer
isTerminal bool
fd int
lineCount int
}
// New returns a new Writer with defaults
func New(out io.Writer) *Writer {
w := &Writer{out: out}
if f, ok := out.(*os.File); ok {
fd := f.Fd()
w.isTerminal = isatty.IsTerminal(fd)
w.fd = int(fd)
}
return w
}
// Flush flushes the underlying buffer
func (w *Writer) Flush(lineCount int) error {
err := w.clearLines()
w.lineCount = lineCount
// WriteTo takes care of w.buf.Reset
if _, e := w.buf.WriteTo(w.out); err == nil {
err = e
}
return err
}
// Write appends the contents of p to the underlying buffer
func (w *Writer) Write(p []byte) (n int, err error) {
return w.buf.Write(p)
}
// WriteString writes string to the underlying buffer
func (w *Writer) WriteString(s string) (n int, err error) {
return w.buf.WriteString(s)
}
// ReadFrom reads from the provided io.Reader and writes to the
// underlying buffer.
func (w *Writer) ReadFrom(r io.Reader) (n int64, err error) {
return w.buf.ReadFrom(r)
}
// GetWidth returns width of underlying terminal.
func (w *Writer) GetWidth() (int, error) {
if w.isTerminal {
tw, _, err := terminal.GetSize(w.fd)
return tw, err
}
return -1, NotATTY
}
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