feat: download ETA on the press bar from measured Soulseek throughput

Show a live "~Xm left" countdown on the download progress bar. The slskd download
loop already polls byte transfer every 3s; measure the actual throughput (EWMA-
smoothed bytes/sec), compute seconds-remaining from the album's total bytes, and
surface it. New nullable Job.downloadEtaSeconds (migration; web entrypoint runs
prisma migrate deploy), threaded through the on_progress callback (optional 2nd arg,
so other adapters/callers are unaffected — they report no ETA). API exposes it;
queue.tsx renders etaLabel() after the track count. Null when unknown (no sample yet
or a source that doesn't report bytes). Worker 330 tests, web 214 tests, both green;
verified live-rendered as "42% · 6/14 tracks · ~4m left".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/prisma/migrations/20260720200000_add_job_download_eta/migration.sql

@@ -0,0 +1,2 @@
+-- Estimated seconds remaining for the active download (measured throughput). Nullable.
+ALTER TABLE "Job" ADD COLUMN "downloadEtaSeconds" INTEGER;

web/prisma/schema.prisma

@@ -58,6 +58,9 @@ model Job {
   createdAt        DateTime    @default(now())
   updatedAt        DateTime    @updatedAt
   downloadProgress Float       @default(0)
+  // Estimated seconds until the current download finishes, from measured throughput (slskd byte
+  // transfer rate). Null when unknown (no speed sample yet, or a source that doesn't report bytes).
+  downloadEtaSeconds Int?
   paused           Boolean     @default(false)
   candidates       Candidate[]
 }

web/src/app/_ui/status.test.ts

@@ -1,5 +1,20 @@
 import { describe, it, expect } from "vitest";
-import { describeJob, timeAgo } from "./status";
+import { describeJob, etaLabel, timeAgo } from "./status";
+
+describe("etaLabel", () => {
+  it("formats seconds, minutes, and hours", () => {
+    expect(etaLabel(45)).toBe("~45s left");
+    expect(etaLabel(240)).toBe("~4m left");
+    expect(etaLabel(3900)).toBe("~1h 5m left");
+  });
+
+  it("returns null for missing or non-positive input", () => {
+    expect(etaLabel(null)).toBeNull();
+    expect(etaLabel(undefined)).toBeNull();
+    expect(etaLabel(0)).toBeNull();
+    expect(etaLabel(-5)).toBeNull();
+  });
+});
 
 describe("describeJob", () => {
   it("maps pipeline states to literal labels + severity kind", () => {

web/src/app/_ui/status.ts

@@ -27,6 +27,16 @@ export function timeAgo(value: string | Date | null | undefined, now: number): s
   return `${Math.floor(h / 24)}d`;
 }
 
+/** Compact download ETA like "~4m left", "~45s left", "~1h 5m left". Null/≤0 → no label. */
+export function etaLabel(seconds: number | null | undefined): string | null {
+  if (seconds == null || seconds <= 0) return null;
+  if (seconds < 60) return `~${seconds}s left`;
+  const m = Math.round(seconds / 60);
+  if (m < 60) return `~${m}m left`;
+  const h = Math.floor(m / 60);
+  return `~${h}h ${m % 60}m left`;
+}
+
 export function describeJob(state: string, stage: string): { label: string; kind: Kind } {
   void stage; // stage no longer drives the label; kept for call-site compatibility
   return (

web/src/app/api/requests/route.ts

@@ -64,6 +64,7 @@ export async function GET() {
               claimedAt: r.job.claimedAt,
               updatedAt: r.job.updatedAt,
               downloadProgress: r.job.downloadProgress,
+              downloadEtaSeconds: r.job.downloadEtaSeconds,
               paused: r.job.paused,
               candidateCount: cands.length,
               chosen: chosen ? { source: chosen.source, format: chosen.format, trackCount: chosen.trackCount } : null,

web/src/app/queue.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { useEffect, useState } from "react";
-import { describeJob, timeAgo } from "./_ui/status";
+import { describeJob, etaLabel, timeAgo } from "./_ui/status";
 import { StatTiles } from "./_ui/stat-tiles";
 import { SectionHeader } from "./_ui/section-header";
 import { JobRow } from "./_ui/job-row";
@@ -46,6 +46,7 @@ type Row = {
     candidateCount: number;
     chosen: { source: string; format: string; trackCount: number } | null;
     downloadProgress: number;
+    downloadEtaSeconds: number | null;
     paused: boolean;
   } | null;
 };
@@ -62,6 +63,7 @@ function jobOf(r: Row) {
       candidateCount: 0,
       chosen: null,
       downloadProgress: 0,
+      downloadEtaSeconds: null,
       paused: false,
     }
   );
@@ -270,13 +272,9 @@ export function Queue() {
       } else {
         const total = j.chosen?.trackCount ?? 0;
         const done = total ? Math.round((pct / 100) * total) : 0;
-        bar = (
-          <ProgressBar
-            kind="working"
-            percent={pct}
-            caption={total ? `${pct}% · ${done}/${total} tracks` : `${pct}%`}
-          />
-        );
+        const base = total ? `${pct}% · ${done}/${total} tracks` : `${pct}%`;
+        const eta = etaLabel(j.downloadEtaSeconds);
+        bar = <ProgressBar kind="working" percent={pct} caption={eta ? `${base} · ${eta}` : base} />;
       }
     } else if (j.state === "tagging") {
       bar = <ProgressBar kind="verify" indeterminate caption="finishing" />;