cmd/streamdata: additional prompt helpers

These wrap existing helpers to implement certain retry behaviour.

Signed-off-by: Yonah <contrib@gensokyo.uk>

cmd/streamdata/prompt.go

@@ -7,6 +7,7 @@ import (
 	"math"
 	"os"
 	"strconv"
+	"strings"
 	"syscall"
 
 	"hakurei.app/ext"
@@ -50,6 +51,23 @@ func prompt(br *bufio.Reader, p string) (string, bool) {
 	return s[:len(s)-1], true
 }
 
+// promptTrimNoEmpty prompts the user until EOF or a non-empty and
+// non-whitespace-only response is read. It returns read response with leading
+// and trailing whitespaces trimmed.
+func promptTrimNoEmpty(br *bufio.Reader, p string) (string, bool) {
+invalid:
+	s, ok := prompt(br, p)
+	if !ok {
+		return "", false
+	}
+
+	s = strings.TrimSpace(s)
+	if s == "" {
+		goto invalid
+	}
+	return s, true
+}
+
 // noResponseUint is returned by promptUint when the user responds with a single
 // newline character.
 const noResponseUint = math.MaxUint64
@@ -74,6 +92,40 @@ invalid:
 	return v, true
 }
 
+// promptUintFallback is like promptUint, but returns fallback if the user
+// responds with a single newline character.
+func promptUintFallback(
+	br *bufio.Reader,
+	p string,
+	fallback uint64,
+) (uint64, bool) {
+	v, ok := promptUint(br, p+
+		"["+strconv.FormatUint(fallback, 10)+"] ")
+	if !ok && v == noResponseUint {
+		v, ok = fallback, true
+	}
+	return v, ok
+}
+
+// promptUintFallbackBounds is like promptUint, but checks input bounds and
+// returns fallback if the user responds with a single newline character.
+func promptUintFallbackBounds(
+	br *bufio.Reader,
+	p string,
+	lb, ub uint64,
+	fallback uint64,
+) (uint64, bool) {
+invalid:
+	v, ok := promptUintFallback(br, p, fallback)
+	if !ok {
+		return 0, false
+	}
+	if v < lb || v > ub {
+		goto invalid
+	}
+	return v, true
+}
+
 // require panics with an error if ok is false, and returns v otherwise.
 func require[T any](v T, ok bool) T {
 	if !ok {