textui: Add some utilities for human-friendly text

1 files changed, 85 insertions, 0 deletions

diff --git a/lib/textui/text.go b/lib/textui/text.go
new file mode 100644
index 0000000..f628eab
--- /dev/null
+++ b/lib/textui/text.go
@@ -0,0 +1,85 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package textui
+
+import (
+	"fmt"
+	"io"
+
+	"golang.org/x/exp/constraints"
+	"golang.org/x/text/language"
+	"golang.org/x/text/message"
+	"golang.org/x/text/number"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/fmtutil"
+)
+
+var printer = message.NewPrinter(language.English)
+
+// Fprintf is like `fmt.Fprintf`, but (1) includes the extensions of
+// `golang.org/x/text/message.Printer`, and (2) is useful for marking
+// when a print call is part of the UI, rather than something
+// internal.
+func Fprintf(w io.Writer, key string, a ...any) (n int, err error) {
+	return printer.Fprintf(w, key, a...)
+}
+
+// Sprintf is like `fmt.Sprintf`, but (1) includes the extensions of
+// `golang.org/x/text/message.Printer`, and (2) is useful for marking
+// when a sprint call is part of the UI, rather than something
+// internal.
+func Sprintf(key string, a ...any) string {
+	return printer.Sprintf(key, a...)
+}
+
+// Humanized wraps a value such that formatting of it can make use of
+// the `golang.org/x/text/message.Printer` extensions even when used
+// with plain-old `fmt`.
+func Humanized(x any) any {
+	return humanized{val: x}
+}
+
+type humanized struct {
+	val any
+}
+
+var (
+	_ fmt.Formatter = humanized{}
+	_ fmt.Stringer  = humanized{}
+)
+
+// String implements fmt.Formatter.
+func (h humanized) Format(f fmt.State, verb rune) {
+	printer.Fprintf(f, fmtutil.FmtStateString(f, verb), h.val)
+}
+
+// String implements fmt.Stringer.
+func (h humanized) String() string {
+	return fmt.Sprint(h)
+}
+
+// Portion renders a fraction N/D as both a percentage and
+// parenthetically as the exact fractional value, rendered with
+// human-friendly commas.
+//
+// For example:
+//
+//	fmt.Sprint(Portion[int]{N: 1, D: 12345}) ⇒ "0% (1/12,345)"
+type Portion[T constraints.Integer] struct {
+	N, D T
+}
+
+var (
+	_ fmt.Stringer = Portion[int]{}
+)
+
+// String implements fmt.Stringer.
+func (p Portion[T]) String() string {
+	pct := float64(1)
+	if p.D > 0 {
+		pct = float64(p.N) / float64(p.D)
+	}
+	return printer.Sprintf("%v (%v/%v)", number.Percent(pct), uint64(p.N), uint64(p.D))
+}