Adding progress bar to milestone report and outfile so you can watch the progress bar easier and still manipulate w/ grep after (#46354)

tools/github-manage/pkg/util/progress.go

@@ -0,0 +1,82 @@
+package util
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/mattn/go-isatty"
+)
+
+// ProgressBar renders an inline progress bar to stderr for long per-item loops
+// (e.g. fetching metadata for each issue in a milestone report). It writes only
+// to stderr, so it never corrupts report output sent to stdout or a file. When
+// stderr is not a terminal the bar stays silent to avoid polluting piped or
+// redirected output.
+type ProgressBar struct {
+	label   string
+	total   int
+	width   int
+	start   time.Time
+	enabled bool
+}
+
+// NewProgressBar creates a progress bar for total steps with the given label.
+func NewProgressBar(label string, total int) *ProgressBar {
+	fd := os.Stderr.Fd()
+	return &ProgressBar{
+		label:   label,
+		total:   total,
+		width:   30,
+		start:   time.Now(),
+		enabled: isatty.IsTerminal(fd) || isatty.IsCygwinTerminal(fd),
+	}
+}
+
+// Update redraws the bar at the given 1-based step. detail is shown after the
+// counter, e.g. the issue number currently being fetched ("#46029").
+func (p *ProgressBar) Update(current int, detail string) {
+	if p == nil || !p.enabled || p.total <= 0 {
+		return
+	}
+	if current < 0 {
+		current = 0
+	}
+	if current > p.total {
+		current = p.total
+	}
+	frac := float64(current) / float64(p.total)
+	filled := int(frac * float64(p.width))
+	bar := strings.Repeat("█", filled) + strings.Repeat("░", p.width-filled)
+
+	line := fmt.Sprintf("%s [%s] %d/%d (%.0f%%)", p.label, bar, current, p.total, frac*100)
+	if detail != "" {
+		line += " " + detail
+	}
+	if eta := p.eta(current); eta != "" {
+		line += " " + eta
+	}
+
+	// \r returns to column 0; \033[K clears leftovers from a longer prior line.
+	fmt.Fprintf(os.Stderr, "\r\033[K%s", line)
+}
+
+// eta estimates remaining time from the average duration per completed step.
+func (p *ProgressBar) eta(current int) string {
+	if current <= 0 || current >= p.total {
+		return ""
+	}
+	per := time.Since(p.start) / time.Duration(current)
+	remaining := (per * time.Duration(p.total-current)).Round(time.Second)
+	return fmt.Sprintf("ETA %s", remaining)
+}
+
+// Done terminates the bar's line so subsequent output starts cleanly. It is a
+// no-op when the bar is disabled.
+func (p *ProgressBar) Done() {
+	if p == nil || !p.enabled {
+		return
+	}
+	fmt.Fprintln(os.Stderr)
+}