progress: show multiple downloads as a bar table

lineMany crammed every download onto one line as name+percent, dropping
the speed column that answers "which one is stalled" and producing ugly
double brackets for names like "[Gecko]". render N>1 as a redrawn block:
one row each (name, bar, percent, DL speed, ETA/stalled), a header with
the active count and totals, falling back to a single summary line when
the table would overflow the window. one download keeps its dashboard.

progress/progress.go

@@ -25,8 +25,10 @@ type Reporter struct {
 	w        io.Writer
 	tty      bool
 	width    int
+	height   int
 
 	win       map[string]*speedWindow // keyed by Stat.ID
+	prevLines int                     // lines drawn in the previous TTY frame, redrawn in place
 	lastLog   time.Time               // last non-TTY line emitted
 }
 
@@ -62,6 +64,7 @@ func New(snap func() []download.Stat, human bool) *Reporter {
 		w:        os.Stdout,
 		tty:      term.IsTerminal(int(os.Stdout.Fd())),
 		width:    80,
+		height:   24,
 		win:      map[string]*speedWindow{},
 	}
 }
@@ -103,29 +106,21 @@ func (r *Reporter) render(final bool) {
 		}
 	}
 
-	var line string
-	switch len(stats) {
-	case 0:
-		if !final && r.tty {
-			return // nothing active; leave the line as-is
-		}
-	case 1:
-		line = r.lineOne(stats[0])
-	default:
-		line = r.lineMany(stats)
-	}
-
 	if r.tty {
 		r.width = termWidth(r.width)
-		line = clampRunes(line, r.width)
+		r.height = termHeight(r.height)
-		fmt.Fprint(r.w, "\r"+line+"\x1b[K")
+		r.redraw(r.block(stats), final)
-		if final {
-			fmt.Fprintln(r.w)
-		}
 		return
 	}
-	// Not a TTY: can't redraw one line, so print sparingly (and always the
+	// Not a TTY: no cursor control, so emit a single line sparingly (and always
-	// final line) to keep redirected output and logs readable.
+	// the final one) to keep redirected output and logs readable.
+	var line string
+	switch {
+	case len(stats) == 1:
+		line = r.lineOne(stats[0])
+	case len(stats) > 1:
+		line = r.summary(stats)
+	}
 	if line != "" && (final || now.Sub(r.lastLog) >= logEvery) {
 		fmt.Fprintln(r.w, line)
 		r.lastLog = now
@@ -165,27 +160,161 @@ func (r *Reporter) lineOne(s download.Stat) string {
 	return b.String()
 }
 
-func (r *Reporter) lineMany(stats []download.Stat) string {
+// nameW is the fixed rune width of the name column in the table, matching
+// shortName's cap so a padded name lines the columns up.
+const nameW = 20
+
+// block builds the lines of the live display: the single-download dashboard for
+// one download, a name/bar/speed/ETA table for several, or a one-line summary
+// when the table would not fit the window.
+func (r *Reporter) block(stats []download.Stat) []string {
+	switch {
+	case len(stats) == 0:
+		return nil
+	case len(stats) == 1:
+		return []string{r.lineOne(stats[0])}
+	case len(stats)+1 > r.height: // header + one row each would overflow the screen
+		return []string{r.summary(stats)}
+	default:
+		out := make([]string, 0, len(stats)+1)
+		out = append(out, r.summary(stats))
+		for _, s := range stats {
+			out = append(out, r.tableRow(s))
+		}
+		return out
+	}
+}
+
+// redraw repaints the block in place: move to the top of the previous frame,
+// clear it, and print the new lines clamped to the terminal width. A stray line
+// from stderr that lands in the block is painted over on the next tick.
+func (r *Reporter) redraw(lines []string, final bool) {
+	if r.prevLines > 0 {
+		if r.prevLines > 1 {
+			fmt.Fprintf(r.w, "\x1b[%dA", r.prevLines-1) // up to the first line
+		}
+		fmt.Fprint(r.w, "\r\x1b[J") // column 0, clear to end of screen
+	}
+	for i, ln := range lines {
+		if i > 0 {
+			fmt.Fprint(r.w, "\n")
+		}
+		fmt.Fprint(r.w, clampRunes(ln, r.width))
+	}
+	r.prevLines = len(lines)
+	if final && len(lines) > 0 {
+		fmt.Fprintln(r.w) // leave the cursor below the block for the OK/FAIL lines
+		r.prevLines = 0
+	}
+}
+
+// summary is the header/aggregate line: the active count and total down/up
+// speed, plus a stalled count when any download has gone quiet.
+func (r *Reporter) summary(stats []download.Stat) string {
+	if len(stats) == 0 {
+		return ""
+	}
 	var totDL, totUL int64
+	stalled := 0
 	for _, s := range stats {
 		dl, ul := r.rates(s)
 		totDL += dl
 		totUL += ul
-	}
+		if r.isStalled(s, dl) {
-	var b strings.Builder
+			stalled++
-	fmt.Fprintf(&b, "[%d active DL:%s UL:%s]", len(stats), speed(totDL, r.human), speed(totUL, r.human))
-	for i, s := range stats {
-		if i >= 4 {
-			fmt.Fprintf(&b, "[+%d]", len(stats)-i)
-			break
-		}
-		if s.Total > 0 {
-			fmt.Fprintf(&b, "[%s %d%%]", shortName(s.Name), percent(s.Completed, s.Total))
-		} else {
-			fmt.Fprintf(&b, "[%s %s]", shortName(s.Name), humanSize(s.Completed, r.human))
 		}
 	}
-	return b.String()
+	line := fmt.Sprintf("%d active   DL:%s UL:%s", len(stats), speed(totDL, r.human), speed(totUL, r.human))
+	if stalled > 0 {
+		line += fmt.Sprintf("  (%d stalled)", stalled)
+	}
+	return line
+}
+
+// tableRow renders one download as "name |bar| pct metric tail": the bar and
+// percent for progress, then the field that answers "stalled or fast" (DL speed
+// or seeding) and a tail (ETA, upload rate, or a stalled flag).
+func (r *Reporter) tableRow(s download.Stat) string {
+	dl, ul := r.rates(s)
+	metric, tail := r.rowMetric(s, dl, ul)
+	return fmt.Sprintf("  %s  %s %s  %-9s %s", padRune(shortName(s.Name), nameW), barOf(s), pctField(s), metric, tail)
+}
+
+// rowMetric returns a table row's two trailing fields for the download's state:
+// the primary metric (DL speed, "seeding", "done", "failed") and a tail (ETA,
+// upload rate, or a "stalled" flag).
+func (r *Reporter) rowMetric(s download.Stat, dl, ul int64) (metric, tail string) {
+	switch s.Status {
+	case download.Seeding:
+		return "seeding", "UL:" + speed(ul, r.human)
+	case download.Complete:
+		return "done", ""
+	case download.Errored:
+		return "failed", ""
+	default:
+		metric = "DL:" + speed(dl, r.human)
+		switch {
+		case dl > 0 && s.Total > 0:
+			eta := time.Duration(float64(s.Total-s.Completed)/float64(dl)) * time.Second
+			tail = secfmt(eta)
+		case r.isStalled(s, dl):
+			tail = "stalled"
+		}
+		return metric, tail
+	}
+}
+
+// isStalled reports an active download that has gone a while with no new bytes,
+// so the table can flag it rather than leave the eye to read DL:0B. A download
+// too young to have a rate yet is not stalled.
+func (r *Reporter) isStalled(s download.Stat, dl int64) bool {
+	if s.Status != download.Active || dl > 0 {
+		return false
+	}
+	w := r.win[s.ID]
+	if w == nil || len(w.samples) < 2 {
+		return false
+	}
+	return w.samples[len(w.samples)-1].t.Sub(w.samples[0].t) >= 4*time.Second
+}
+
+// barOf renders a fixed-width progress bar. A seeding or complete download is
+// full; an unknown total (no Content-Length, or pre-metadata) shows empty.
+func barOf(s download.Stat) string {
+	const cells = 12
+	k := 0
+	switch {
+	case s.Status == download.Seeding || s.Status == download.Complete:
+		k = cells
+	case s.Total > 0:
+		k = int(int64(cells) * s.Completed / s.Total)
+		if k > cells {
+			k = cells
+		}
+	}
+	return "|" + strings.Repeat("#", k) + strings.Repeat("-", cells-k) + "|"
+}
+
+// pctField is the percent column: a number, full for seeding/complete, or "--"
+// when the total is unknown.
+func pctField(s download.Stat) string {
+	switch {
+	case s.Status == download.Seeding || s.Status == download.Complete:
+		return "100%"
+	case s.Total > 0:
+		return fmt.Sprintf("%3d%%", percent(s.Completed, s.Total))
+	default:
+		return "  --"
+	}
+}
+
+// padRune right-pads s with spaces to w runes (it is never longer, having been
+// through shortName) so table columns line up on rune count.
+func padRune(s string, w int) string {
+	if n := utf8.RuneCountInString(s); n < w {
+		return s + strings.Repeat(" ", w-n)
+	}
+	return s
 }
 
 // add records a sample and drops any that have fallen out of the window. A
@@ -272,3 +401,13 @@ func termWidth(prev int) int {
 	}
 	return 80
 }
+
+func termHeight(prev int) int {
+	if _, h, err := term.GetSize(int(os.Stdout.Fd())); err == nil && h > 0 {
+		return h
+	}
+	if prev > 0 {
+		return prev
+	}
+	return 24
+}

progress/progress_test.go

@@ -1,6 +1,7 @@
 package progress
 
 import (
+	"bytes"
 	"strings"
 	"testing"
 	"time"
@@ -112,6 +113,100 @@ func TestLineOneCNSD(t *testing.T) {
 	}
 }
 
+func TestBarOf(t *testing.T) {
+	tests := []struct {
+		name string
+		s    download.Stat
+		want string
+	}{
+		{"empty", download.Stat{Status: download.Active, Total: 100, Completed: 0}, "|------------|"},
+		{"half", download.Stat{Status: download.Active, Total: 100, Completed: 50}, "|######------|"},
+		{"full by complete", download.Stat{Status: download.Complete}, "|############|"},
+		{"full by seeding", download.Stat{Status: download.Seeding}, "|############|"},
+		{"unknown total is empty", download.Stat{Status: download.Active, Total: -1, Completed: 9}, "|------------|"},
+	}
+	for _, tc := range tests {
+		if got := barOf(tc.s); got != tc.want {
+			t.Errorf("%s: barOf = %q, want %q", tc.name, got, tc.want)
+		}
+	}
+}
+
+func TestPctField(t *testing.T) {
+	if got := pctField(download.Stat{Status: download.Active, Total: 100, Completed: 50}); got != " 50%" {
+		t.Errorf("active 50%% = %q, want ' 50%%'", got)
+	}
+	if got := pctField(download.Stat{Status: download.Seeding}); got != "100%" {
+		t.Errorf("seeding = %q, want 100%%", got)
+	}
+	if got := pctField(download.Stat{Status: download.Active, Total: -1}); got != "  --" {
+		t.Errorf("unknown total = %q, want '  --'", got)
+	}
+}
+
+// TestRowMetric: the two trailing fields per download state.
+func TestRowMetric(t *testing.T) {
+	r := newReporter(true)
+	if m, tail := r.rowMetric(download.Stat{Status: download.Active, Total: 100, Completed: 50}, 10, 0); !strings.HasPrefix(m, "DL:") || tail == "" {
+		t.Errorf("active downloading: metric=%q tail=%q, want DL:… + an ETA", m, tail)
+	}
+	if m, tail := r.rowMetric(download.Stat{Status: download.Seeding}, 0, 128<<10); m != "seeding" || !strings.HasPrefix(tail, "UL:") {
+		t.Errorf("seeding: metric=%q tail=%q, want seeding + UL:…", m, tail)
+	}
+	if m, _ := r.rowMetric(download.Stat{Status: download.Complete}, 0, 0); m != "done" {
+		t.Errorf("complete metric=%q, want done", m)
+	}
+}
+
+// TestBlockTableAndFallback: several downloads render as header+rows when they
+// fit, and collapse to a single summary line when the window is too short.
+func TestBlockTableAndFallback(t *testing.T) {
+	r := newReporter(true)
+	stats := []download.Stat{
+		{ID: "a", Name: "a", Status: download.Active, Total: 100, Completed: 50},
+		{ID: "b", Name: "b", Status: download.Active, Total: 100, Completed: 10},
+	}
+	r.height = 24
+	if got := r.block(stats); len(got) != 3 { // header + 2 rows
+		t.Errorf("table block = %d lines, want 3:\n%v", len(got), got)
+	}
+	r.height = 2 // header + 2 rows = 3 > 2
+	if got := r.block(stats); len(got) != 1 {
+		t.Errorf("overflow block = %d lines, want 1 summary:\n%v", len(got), got)
+	}
+}
+
+// TestRenderRedraw: the TTY path draws the block, then on the next frame moves
+// the cursor up over the previous frame and clears it before repainting.
+func TestRenderRedraw(t *testing.T) {
+	snap := []download.Stat{
+		{ID: "a", Name: "alpha", IsBT: true, Status: download.Active, Total: 100, Completed: 50},
+		{ID: "b", Name: "beta", IsBT: true, Status: download.Seeding, Total: 100, Completed: 100, Uploaded: 200},
+	}
+	var buf bytes.Buffer
+	r := &Reporter{
+		snap:  func() []download.Stat { return snap },
+		human: true, w: &buf, tty: true, width: 200, height: 24,
+		win: map[string]*speedWindow{},
+	}
+	r.render(false)
+	first := buf.String()
+	for _, want := range []string{"2 active", "alpha", "seeding", "|"} {
+		if !strings.Contains(first, want) {
+			t.Fatalf("first frame missing %q:\n%q", want, first)
+		}
+	}
+	buf.Reset()
+	r.render(false)
+	second := buf.String()
+	if !strings.Contains(second, "\x1b[2A") { // up prevLines-1 = 3-1
+		t.Errorf("second frame should move cursor up 2 lines:\n%q", second)
+	}
+	if !strings.Contains(second, "\x1b[J") {
+		t.Errorf("second frame should clear to end of screen:\n%q", second)
+	}
+}
+
 // TestShortNameRune ensures CJK names are truncated on runes, not bytes.
 func TestShortNameRune(t *testing.T) {
 	name := strings.Repeat("あ", 30) // 30 runes, 90 bytes