feat(downloads): estimate a transcode's size so the progress bar moves

A transcode is produced as it is sent — chunked, with no Content-Length — and the worker reported progress 0.0 for its whole duration: an empty bar reading "0%" while the byte count climbed for an hour. That is the case every film whose audio must be re-encoded lands in. The backend already fetches the item to decide the audio policy, and that item carries what a prediction needs: the source's size (an `original` download copies the picture, so the output is the source give or take the audio track) and its runtime (a preset re-encodes at fixed rates, so the size is rate × runtime — from a preset table the URL builder now shares, so the two cannot drift). The prediction is made where the URL is resolved and persisted as the row's file_size. The worker uses it only when the response has no length; the server's figure always wins; an estimated bar is capped at 99% so a low prediction never shows a finished download still running; and the Completed event now carries the bytes actually written so the frontend stops persisting the row's file_size as the final size. The row renders three honest states: exact "42%", estimated "~42%" with "X / ~Y", or — with no total at all — an indeterminate band and the bytes so far, never "0%". The single-video button joins the series/season buttons on the enqueue path so all three resolve, and predict, in one place. DR-290, UT-252, UT-253, UT-254. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-09-21 11:18:29 +02:00
parent e271874b1d
commit b3228cb4f4
15 changed files with 716 additions and 105 deletions
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+/**
+ * What the progress bar on a download row should say.
+ *
+ * Extracted from `DownloadItem.svelte` so the three cases can be unit-tested:
+ * an exact total (the server sent `Content-Length`), an estimated one (a
+ * transcode sends none, so the backend predicted it from the source), and no
+ * total at all — which used to render as an empty bar reading "0%" for the
+ * whole of a transcode download. Progress with no denominator is not 0%; it
+ * is unknown, and the bar says so.
+ *
+ * TRACES: UR-071 | DR-290 | UT-254
+ */
+
+export interface ProgressSource {
+  status: "pending" | "downloading" | "completed" | "failed" | "paused";
+  /** 0..1 as the backend reports it; already capped short of 1 when estimated. */
+  progress: number;
+  bytesDownloaded: number;
+  fileSize?: number;
+  /** `fileSize` is the backend's prediction, not the server's word. */
+  fileSizeEstimated?: boolean;
+}
+
+export type ProgressKind = "exact" | "estimated" | "indeterminate";
+
+export interface ProgressView {
+  kind: ProgressKind;
+  /** Whole percent for the bar width; `null` when there is nothing to measure against. */
+  percent: number | null;
+  /** "42%" / "~42%"; empty when indeterminate. */
+  percentLabel: string;
+  /** "512 B / 1.0 KB", "420 B / ~1000 B", or just the bytes so far. */
+  label: string;
+}
+
+export function formatBytes(bytes: number): string {
+  if (bytes === 0) return "0 B";
+  const k = 1024;
+  const sizes = ["B", "KB", "MB", "GB"];
+  const i = Math.min(Math.floor(Math.log(bytes) / Math.log(k)), sizes.length - 1);
+  return `${(bytes / Math.pow(k, i)).toFixed(i === 0 ? 0 : 1)} ${sizes[i]}`;
+}
+
+export function describeProgress(d: ProgressSource): ProgressView {
+  const downloaded = formatBytes(d.bytesDownloaded);
+  if (!d.fileSize) {
+    return { kind: "indeterminate", percent: null, percentLabel: "", label: downloaded };
+  }
+  const percent = Math.round(Math.min(Math.max(d.progress, 0), 1) * 100);
+  if (d.fileSizeEstimated) {
+    return {
+      kind: "estimated",
+      percent,
+      percentLabel: `~${percent}%`,
+      label: `${downloaded} / ~${formatBytes(d.fileSize)}`,
+    };
+  }
+  return {
+    kind: "exact",
+    percent,
+    percentLabel: `${percent}%`,
+    label: `${downloaded} / ${formatBytes(d.fileSize)}`,
+  };
+}