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package cwriter
import (
"bytes"
"errors"
"io"
"os"
"strconv"
)
// ErrNotTTY not a TeleTYpewriter error.
var ErrNotTTY = errors.New("not a terminal")
// https://github.com/dylanaraps/pure-sh-bible#cursor-movement
const (
escOpen = "\x1b["
cuuAndEd = "A\x1b[J"
)
// 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
lines int // how much lines to clear before flushing new ones
fd int
terminal bool
termSize func(int) (int, int, error)
}
// New returns a new Writer with defaults.
func New(out io.Writer) *Writer {
w := &Writer{
out: out,
termSize: func(_ int) (int, int, error) {
return -1, -1, ErrNotTTY
},
}
if f, ok := out.(*os.File); ok {
w.fd = int(f.Fd())
if IsTerminal(w.fd) {
w.terminal = true
w.termSize = func(fd int) (int, int, error) {
return GetSize(fd)
}
}
}
return w
}
// Flush flushes the underlying buffer.
func (w *Writer) Flush(lines int) (err error) {
// some terminals interpret 'cursor up 0' as 'cursor up 1'
if w.lines > 0 {
err = w.clearLines()
if err != nil {
return
}
}
w.lines = lines
_, err = w.buf.WriteTo(w.out)
return
}
// 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)
}
// GetTermSize returns WxH of underlying terminal.
func (w *Writer) GetTermSize() (width, height int, err error) {
return w.termSize(w.fd)
}
func (w *Writer) ansiCuuAndEd() error {
buf := make([]byte, 8)
buf = strconv.AppendInt(buf[:copy(buf, escOpen)], int64(w.lines), 10)
_, err := w.out.Write(append(buf, cuuAndEd...))
return err
}
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