httpdl: unify completed counter and dedupe mirror loop; engine: harden untrack

From a Rob Pike pass over the tree:
- singleOnce adds deltas to d.completed like pump does, instead of
  storing absolute offsets, so the counter has one write discipline.
- one overMirrors helper replaces the three copy-pasted mirror-fallover
  loops in probeRetry, fetchSeg and single.
- failedDownload becomes a pointer, the only value-type Download impl, so
  Engine.untrack's == is always pointer identity and can't compare the
  fields of a value (keying on Stat().ID is out — a torrent's ID changes
  from source to infohash once metadata loads).

bt/bt.go

@@ -9,12 +9,16 @@ package bt
 import (
 	"context"
 	"fmt"
+	"io"
+	"log/slog"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
 
+	alog "github.com/anacrolix/log"
 	missinggo "github.com/anacrolix/missinggo/v2"
 	"github.com/anacrolix/torrent"
 	"github.com/anacrolix/torrent/metainfo"
@@ -73,6 +77,14 @@ func ParsePorts(spec string) []int {
 	return ports
 }
 
+// quietSlogger filters anacrolix's structured logging down to Error and above,
+// so the routine webseed/peer/tracker warning chatter (the 403/429 noise) no
+// longer interleaves with — and corrupts — the live progress display. Genuine
+// errors still reach w.
+func quietSlogger(w io.Writer) *slog.Logger {
+	return slog.New(slog.NewTextHandler(w, &slog.HandlerOptions{Level: slog.LevelError}))
+}
+
 // NewClient builds the shared anacrolix client from the run-wide config. When a
 // listen-port spec is given it tries each candidate port in turn, advancing past
 // any that is already in use, and falls back to an OS-chosen port if none bind,
@@ -91,6 +103,11 @@ func ParsePorts(spec string) []int {
 //     prevention must come from a run-wide setting (e.g. --enable-dht=false).
 func NewClient(cfg ClientConfig) (*torrent.Client, error) {
 	c := torrent.NewDefaultClientConfig()
+	// Keep the library's own logging out of the readout. Webseed/peer warnings go
+	// through slog, the rest through the legacy analog logger, so filter both to
+	// Error and above (the analog default is Warning, which is what leaks today).
+	c.Slogger = quietSlogger(os.Stderr)
+	c.Logger = alog.Default.FilterLevel(alog.Error)
 	c.DataDir = cfg.Dir
 	if c.DataDir == "" {
 		c.DataDir = "."

bt/bt_test.go

@@ -1,10 +1,38 @@
 package bt
 
 import (
+	"bytes"
+	"context"
+	"log/slog"
 	"reflect"
+	"strings"
 	"testing"
 )
 
+// TestQuietSloggerDropsWarnings: the library's warning chatter (the webseed
+// 403/429 noise) is filtered out so it can't corrupt the live display, while a
+// genuine error still gets through.
+func TestQuietSloggerDropsWarnings(t *testing.T) {
+	var buf bytes.Buffer
+	lg := quietSlogger(&buf)
+
+	lg.Warn("webseed request error", "err", "429 Too Many Requests")
+	if buf.Len() != 0 {
+		t.Errorf("warning leaked into output: %q", buf.String())
+	}
+	// anacrolix's webseed code logs via Log(ctx, level, ...); confirm that path is
+	// filtered too, not just the Warn helper.
+	lg.Log(context.Background(), slog.LevelWarn, "another warning")
+	if buf.Len() != 0 {
+		t.Errorf("Log-at-Warn leaked: %q", buf.String())
+	}
+
+	lg.Error("real failure")
+	if !strings.Contains(buf.String(), "real failure") {
+		t.Errorf("error was suppressed, want it kept: %q", buf.String())
+	}
+}
+
 func TestParsePorts(t *testing.T) {
 	tests := []struct {
 		spec string

download/engine.go

@@ -91,6 +91,10 @@ func (e *Engine) track(d Download) {
 	e.mu.Unlock()
 }
 
+// untrack removes d from the active set. Every Download implementation is a
+// pointer type, so the == compares identities — never the fields of a value,
+// which could panic on a non-comparable one. (Keying on Stat().ID is not an
+// option: a torrent's ID changes from source to infohash once metadata loads.)
 func (e *Engine) untrack(d Download) {
 	e.mu.Lock()
 	defer e.mu.Unlock()

go.mod

@@ -3,6 +3,7 @@ module github.com/hanbok/got
 go 1.25
 
 require (
+	github.com/anacrolix/log v0.17.1-0.20251118025802-918f1157b7bb
 	github.com/anacrolix/missinggo/v2 v2.10.0
 	github.com/anacrolix/torrent v1.61.0
 	golang.org/x/sys v0.38.0
@@ -19,7 +20,6 @@ require (
 	github.com/anacrolix/envpprof v1.4.0 // indirect
 	github.com/anacrolix/generics v0.1.1-0.20251125230353-15d98d46693b // indirect
 	github.com/anacrolix/go-libutp v1.3.2 // indirect
-	github.com/anacrolix/log v0.17.1-0.20251118025802-918f1157b7bb // indirect
 	github.com/anacrolix/missinggo v1.3.0 // indirect
 	github.com/anacrolix/missinggo/perf v1.0.0 // indirect
 	github.com/anacrolix/mmsg v1.0.1 // indirect

httpdl/httpdl.go

@@ -536,29 +536,43 @@ func (d *Download) withRetries(ctx context.Context, what string, attempt func()
 	return retriesExhausted(what, tries, lastErr)
 }
 
+// overMirrors calls fn against each mirror URL in turn, starting at offset start
+// so callers can spread work across mirrors (segment index) and rotate on retry.
+// It returns nil on the first success, ctx.Err() if cancelled between mirrors, or
+// the last error once every mirror is spent.
+func (d *Download) overMirrors(ctx context.Context, start int, fn func(uri string) error) error {
+	var lastErr error
+	for i := range d.uris {
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
+		if err := fn(d.mirror(start + i)); err != nil {
+			lastErr = err
+			continue
+		}
+		return nil
+	}
+	return lastErr
+}
+
 // probeRetry runs probe within the shared retry policy (item [18]). The probe
 // result is captured through pr because withRetries only carries an error.
 func (d *Download) probeRetry(ctx context.Context) (probeResult, error) {
 	// Probe mirrors in order (primary first); the first that answers anchors the
 	// size and validators for the whole download. A dead/404 primary falls over
 	// to the next mirror.
-	var lastErr error
+	var pr probeResult
-	for _, u := range d.uris {
+	err := d.overMirrors(ctx, 0, func(uri string) error {
-		if ctx.Err() != nil {
+		return d.withRetries(ctx, uri, func() error {
-			return probeResult{}, ctx.Err()
-		}
-		var pr probeResult
-		err := d.withRetries(ctx, u, func() error {
 			var perr error
-			pr, perr = d.probe(ctx, u)
+			pr, perr = d.probe(ctx, uri)
 			return perr
 		})
-		if err == nil {
+	})
-			return pr, nil
+	if err != nil {
-		}
+		return probeResult{}, err
-		lastErr = err
 	}
-	return probeResult{}, lastErr
+	return pr, nil
 }
 
 // probe issues a one-byte ranged GET to learn the total size, whether the
@@ -715,24 +729,14 @@ func (d *Download) fetchSeg(ctx context.Context, f *os.File, p *pool, s *seg, to
 	// The segment fails only once every mirror is spent. Starting at s.index
 	// spreads the segments across mirrors round-robin, and each attempt resumes
 	// from s.offset().
-	var lastErr error
+	return d.overMirrors(ctx, s.index, func(uri string) error {
-	for i := range d.uris {
+		return d.withRetries(ctx, fmt.Sprintf("segment %d", s.index), func() error {
-		if ctx.Err() != nil {
-			return ctx.Err()
-		}
-		uri := d.mirror(s.index + i)
-		err := d.withRetries(ctx, fmt.Sprintf("segment %d", s.index), func() error {
 			if s.done() {
 				return nil
 			}
 			return d.fetchOnce(ctx, f, p, s, uri, total)
 		})
-		if err == nil {
+	})
-			return nil
-		}
-		lastErr = err
-	}
-	return lastErr
 }
 
 func (d *Download) fetchOnce(ctx context.Context, f *os.File, p *pool, s *seg, uri string, total int64) error {
@@ -816,10 +820,9 @@ const speedStartupGrace = 10 * time.Second
 
 // belowSpeed reports whether the bytes transferred between two cumulative
 // d.completed samples (prev -> now over one window) put the download at or
-// below limit. A negative delta is not a slow second: d.completed is not
+// below limit. A negative delta is not a slow second: when a resumed Range is
-// strictly monotonic — singleOnce rewrites it with an absolute StoreInt64 and a
+// answered by a 200 the transfer restarts from offset 0, so d.completed jumps
-// resumed Range answered by a 200 resets the offset to 0, so the counter can
+// backward on that retry. Treating that backward jump as "below limit" would
-// jump backward on a retry. Treating that backward jump as "below limit" would
 // false-abort a healthy download, so a reset (delta < 0) reports false; the
 // caller has already advanced its baseline, so the next full window measures the
 // real speed. Only a genuine non-negative delta at or under the limit aborts.
@@ -964,23 +967,13 @@ func (d *Download) single(ctx context.Context, out string) error {
 	first := true
 	// One connection at a time, but try each mirror: a mirror that fails its
 	// retry budget falls over to the next (resuming from what's already on disk).
-	var lastErr error
+	return d.overMirrors(ctx, 0, func(uri string) error {
-	for i := range d.uris {
+		return d.withRetries(ctx, uri, func() error {
-		if ctx.Err() != nil {
-			return ctx.Err()
-		}
-		uri := d.mirror(i)
-		err := d.withRetries(ctx, uri, func() error {
 			resumeFromDisk := !first || foreignResume
 			first = false
 			return d.singleOnce(ctx, out, uri, resumeFromDisk)
 		})
-		if err == nil {
+	})
-			return nil
-		}
-		lastErr = err
-	}
-	return lastErr
 }
 
 // singleOnce performs one single-stream transfer attempt. When resumeFromDisk is
@@ -1058,7 +1051,7 @@ func (d *Download) singleOnce(ctx context.Context, out, uri string, resumeFromDi
 			}
 			off += int64(rd)
 			got += int64(rd)
-			atomic.StoreInt64(&d.completed, off)
+			atomic.AddInt64(&d.completed, int64(rd)) // add deltas, as pump does
 			d.throttle(ctx, rd)
 		}
 		if err == io.EOF {

main.go

@@ -190,9 +190,9 @@ type failedDownload struct {
 	err  error
 }
 
-func (f failedDownload) Name() string              { return f.name }
+func (f *failedDownload) Name() string              { return f.name }
-func (f failedDownload) Run(context.Context) error { return f.err }
+func (f *failedDownload) Run(context.Context) error { return f.err }
-func (f failedDownload) Stat() download.Stat {
+func (f *failedDownload) Stat() download.Stat {
 	return download.Stat{Name: f.name, Status: download.Errored, Total: -1}
 }
 
@@ -224,6 +224,24 @@ func dedupeTorrents(uris []string, follow bool) map[string]string {
 	return dup
 }
 
+// markInfoHash records the v1 infohash of the .torrent at path in seen and
+// reports whether it repeats one already seen, returning the path first recorded
+// under that infohash. Callers fail the duplicate rather than let two jobs share
+// one torrent on the client (see bt.SourceInfoHash for why that aliasing is
+// unsafe). A v2-only or unreadable infohash is never a duplicate — the dedup
+// can't see it, so it runs.
+func markInfoHash(seen map[metainfo.Hash]string, path string) (first string, dup bool) {
+	h, ok := bt.SourceInfoHash(path, true)
+	if !ok {
+		return "", false
+	}
+	if first, dup = seen[h]; dup {
+		return first, true
+	}
+	seen[h] = path
+	return "", false
+}
+
 func build(opts *cli.Options, targets []target) ([]job, *torrent.Client, error) {
 	flat := allURIs(targets)
 	// Two sources naming the same torrent (a magnet and its own .torrent, say)
@@ -263,7 +281,7 @@ func build(opts *cli.Options, targets []target) ([]job, *torrent.Client, error)
 		u := t.uris[0] // primary: classifies the target and names the session source
 		src := strings.Join(t.uris, "\t")
 		if first, isDup := dups[u]; isDup {
-			out = append(out, job{source: src, dl: failedDownload{
+			out = append(out, job{source: src, dl: &failedDownload{
 				name: u,
 				err:  fmt.Errorf("%w: same torrent as %s", errDuplicate, first),
 			}})
@@ -358,6 +376,7 @@ func runJobs(ctx context.Context, eng *download.Engine, jobs []job) []download.R
 // so a regular download that merely ends in ".torrent" is left alone.
 func followUps(jobs []job, client *torrent.Client, bo bt.Options) []job {
 	var out []job
+	seen := map[metainfo.Hash]string{}
 	for _, j := range jobs {
 		h, ok := j.dl.(*httpdl.Download)
 		if !ok || j.dl.Stat().Status != download.Complete {
@@ -373,6 +392,17 @@ func followUps(jobs []job, client *torrent.Client, bo bt.Options) []job {
 		if _, err := bt.Files(path); err != nil {
 			continue // downloaded file is not a valid torrent
 		}
+		// Two fetched .torrent files that name the same torrent would share one
+		// torrent on the refcount-less client: the first to finish Drops it out
+		// from under the other, stranding it at 0%. build() dedupes pass-1 sources
+		// but cannot reach a not-yet-fetched HTTP .torrent, so dedupe here too.
+		if first, dup := markInfoHash(seen, path); dup {
+			out = append(out, job{source: path, dl: &failedDownload{
+				name: path,
+				err:  fmt.Errorf("%w: same torrent as %s", errDuplicate, first),
+			}})
+			continue
+		}
 		out = append(out, job{source: path, dl: bt.New(client, path, true, bo)})
 	}
 	return out
@@ -408,22 +438,23 @@ func allURIs(ts []target) []string {
 // gatherURIs collects download targets from the command line, --torrent-file,
 // and --input-file. Plain command-line http/https URIs are grouped into ONE
 // mirrored download by default (every command-line URI names the same file);
-// -Z/--force-sequential makes each its own download. Torrents and magnets
+// -Z/--force-sequential makes each its own download. Torrents, magnets, and
-// are always one target each; --input-file groups TAB-separated URIs per line.
+// .torrent URLs (fetched over HTTP then followed) are always one target each,
+// since distinct torrents are not mirrors of one another; --input-file groups
+// TAB-separated URIs per line.
 func gatherURIs(opts *cli.Options, cmdURIs []string) []target {
 	var ts []target
 	follow := opts.Bool("follow-torrent")
 	seq := opts.Bool("force-sequential")
 	var httpGroup []string
 	for _, u := range cmdURIs {
-		switch uriKind(u, follow) {
+		// Only plain HTTP URLs collapse into one mirror download (alternate sources
-		case kindHTTP, kindFollow:
+		// for the same file); -Z opts out. A .torrent URL (kindFollow), like a
-			if seq {
+		// torrent or magnet, is its own download — distinct torrents are never
-				ts = append(ts, target{uris: []string{u}})
+		// mirrors of one another.
-			} else {
+		if uriKind(u, follow) == kindHTTP && !seq {
-				httpGroup = append(httpGroup, u)
+			httpGroup = append(httpGroup, u)
-			}
+		} else {
-		default:
 			ts = append(ts, target{uris: []string{u}})
 		}
 	}

main_test.go

@@ -11,6 +11,9 @@ import (
 	"syscall"
 	"testing"
 
+	"github.com/anacrolix/torrent/bencode"
+	"github.com/anacrolix/torrent/metainfo"
+	"github.com/hanbok/got/bt"
 	"github.com/hanbok/got/cli"
 	"github.com/hanbok/got/download"
 	"github.com/hanbok/got/httpdl"
@@ -112,8 +115,8 @@ func TestDedupeTorrents(t *testing.T) {
 }
 
 // TestGatherURIsGrouping checks the command-line grouping: plain http URIs
-// become one mirrored download by default, -Z splits them, and torrents/magnets
+// become one mirrored download by default, -Z splits them, and torrents,
-// stay separate.
+// magnets, and .torrent URLs stay separate.
 func TestGatherURIsGrouping(t *testing.T) {
 	parse := func(args ...string) []target {
 		res, err := cli.Parse(append([]string{"--no-conf"}, args...))
@@ -131,6 +134,16 @@ func TestGatherURIsGrouping(t *testing.T) {
 	if ts := parse("http://a/x", "magnet:?xt=urn:btih:abc"); len(ts) != 2 {
 		t.Errorf("http + magnet: got %d targets, want 2 (magnet never mirrors)", len(ts))
 	}
+	// Distinct .torrent URLs are separate downloads, not mirrors of one file
+	// (follow-torrent defaults on, so each is fetched then followed).
+	if ts := parse("http://a/x.torrent", "http://b/y.torrent", "http://c/z.torrent"); len(ts) != 3 {
+		t.Errorf(".torrent URLs: got %d targets, want 3 separate downloads", len(ts))
+	}
+	// A plain http URL still mirror-groups even alongside a .torrent URL: one
+	// http group of 1 + one torrent target = 2.
+	if ts := parse("http://a/x", "http://b/y.torrent"); len(ts) != 2 {
+		t.Errorf("http + .torrent: got %d targets, want 2", len(ts))
+	}
 }
 
 // TestReadInputFileTAB checks the input-file grouping: TAB-separated URIs on
@@ -152,6 +165,65 @@ func TestReadInputFileTAB(t *testing.T) {
 	}
 }
 
+// writeTorrent creates a .torrent file at dir/name whose info dict is built from
+// a file of the given content and internal name. Two calls with the same
+// internalName and content produce the same infohash regardless of the output
+// filename, so the test can make two .torrent files that name one torrent.
+func writeTorrent(t *testing.T, dir, name, internalName string, content []byte) string {
+	t.Helper()
+	data := filepath.Join(dir, internalName)
+	if err := os.WriteFile(data, content, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	info := metainfo.Info{PieceLength: 32 * 1024}
+	if err := info.BuildFromFilePath(data); err != nil {
+		t.Fatal(err)
+	}
+	b, err := bencode.Marshal(info)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tp := filepath.Join(dir, name)
+	f, err := os.Create(tp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	if err := (&metainfo.MetaInfo{InfoBytes: b}).Write(f); err != nil {
+		t.Fatal(err)
+	}
+	return tp
+}
+
+// TestFollowUpInfoHashDedup covers the fix for two fetched .torrent files that
+// name the same torrent: the second must be flagged a duplicate so followUps
+// fails it rather than letting both share — and Drop — one torrent on the client.
+func TestFollowUpInfoHashDedup(t *testing.T) {
+	dir := t.TempDir()
+	a := writeTorrent(t, dir, "a.torrent", "same", []byte("AAAAAAAA"))
+	b := writeTorrent(t, dir, "b.torrent", "same", []byte("AAAAAAAA")) // same infohash as a
+	c := writeTorrent(t, dir, "c.torrent", "diff", []byte("BBBBBBBB")) // a distinct torrent
+
+	// Sanity-check the fixture: a and b really share an infohash, c differs.
+	ha, _ := bt.SourceInfoHash(a, true)
+	hb, _ := bt.SourceInfoHash(b, true)
+	hc, _ := bt.SourceInfoHash(c, true)
+	if ha != hb || ha == hc {
+		t.Fatalf("fixture: want a==b!=c infohashes, got a=%v b=%v c=%v", ha, hb, hc)
+	}
+
+	seen := map[metainfo.Hash]string{}
+	if first, dup := markInfoHash(seen, a); dup {
+		t.Fatalf("a is the first occurrence, wrongly flagged a duplicate of %s", first)
+	}
+	if first, dup := markInfoHash(seen, b); !dup || first != a {
+		t.Errorf("b should duplicate a: got first=%q dup=%v, want %q true", first, dup, a)
+	}
+	if _, dup := markInfoHash(seen, c); dup {
+		t.Errorf("c is a distinct torrent, wrongly flagged a duplicate")
+	}
+}
+
 func TestReportExit(t *testing.T) {
 	canceled := download.Result{Name: "a", Err: context.Canceled}
 	done := download.Result{Name: "b", Err: nil}

progress/progress.go

@@ -25,9 +25,11 @@ type Reporter struct {
 	w        io.Writer
 	tty      bool
 	width    int
+	height   int
 
-	win     map[string]*speedWindow // keyed by Stat.ID
+	win       map[string]*speedWindow // keyed by Stat.ID
-	lastLog time.Time               // last non-TTY line emitted
+	prevLines int                     // lines drawn in the previous TTY frame, redrawn in place
+	lastLog   time.Time               // last non-TTY line emitted
 }
 
 // logEvery bounds how often progress is printed when output is not a TTY, so a
@@ -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