termstatus: move cursor handling to terminal package

internal/terminal/terminal_posix.go

@@ -0,0 +1,36 @@
+package terminal
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+)
+
+const (
+	PosixControlMoveCursorHome = "\r"
+	PosixControlMoveCursorUp   = "\x1b[1A"
+	PosixControlClearLine      = "\x1b[2K"
+)
+
+// posixClearCurrentLine removes all characters from the current line and resets the
+// cursor position to the first column.
+func PosixClearCurrentLine(wr io.Writer, _ uintptr) {
+	// clear current line
+	_, err := wr.Write([]byte(PosixControlMoveCursorHome + PosixControlClearLine))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
+		return
+	}
+}
+
+// posixMoveCursorUp moves the cursor to the line n lines above the current one.
+func PosixMoveCursorUp(wr io.Writer, _ uintptr, n int) {
+	data := []byte(PosixControlMoveCursorHome)
+	data = append(data, bytes.Repeat([]byte(PosixControlMoveCursorUp), n)...)
+	_, err := wr.Write(data)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "write failed: %v\n", err)
+		return
+	}
+}