termstatus: move cursor handling to terminal package

internal/terminal/terminal_unix.go

@@ -0,0 +1,36 @@
+//go:build !windows
+// +build !windows
+
+package terminal
+
+import (
+	"io"
+	"os"
+
+	"golang.org/x/term"
+)
+
+// clearCurrentLine removes all characters from the current line and resets the
+// cursor position to the first column.
+func ClearCurrentLine(_ uintptr) func(io.Writer, uintptr) {
+	return PosixClearCurrentLine
+}
+
+// moveCursorUp moves the cursor to the line n lines above the current one.
+func MoveCursorUp(_ uintptr) func(io.Writer, uintptr, int) {
+	return PosixMoveCursorUp
+}
+
+// CanUpdateStatus returns true if status lines can be printed, the process
+// output is not redirected to a file or pipe.
+func CanUpdateStatus(fd uintptr) bool {
+	if !term.IsTerminal(int(fd)) {
+		return false
+	}
+	term := os.Getenv("TERM")
+	if term == "" {
+		return false
+	}
+	// TODO actually read termcap db and detect if terminal supports what we need
+	return term != "dumb"
+}