feat(uploads): the worker measures the converted audio against the limit and the claim (review F2)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/uploads/worker.go

@@ -54,6 +54,12 @@ func WithHeartbeat(beat, still time.Duration) WorkerOption {
 	return func(w *Worker) { w.beatEvery, w.stillEvery = beat, still }
 }
 
+// WithMaxDuration makes the worker measure the converted audio and fail a job whose real
+// length exceeds the limit, or falls far short of what the file claimed. Zero (the
+// default) measures nothing. The limit is first checked against the file's header, which
+// can lie (ADR-035 review).
+func WithMaxDuration(d time.Duration) WorkerOption { return func(w *Worker) { w.maxDuration = d } }
+
 // WithLogger replaces slog.Default() as the worker's logger.
 func WithLogger(l *slog.Logger) WorkerOption { return func(w *Worker) { w.log = l } }
 
@@ -88,6 +94,7 @@ type Worker struct {
 
 	log                   *slog.Logger
 	beatEvery, stillEvery time.Duration
+	maxDuration           time.Duration
 
 	mu      sync.Mutex
 	queue   []Job
@@ -191,7 +198,7 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 
 	if err := w.store.StartTranscribing(ctx, job.UserID, job.UploadID); err != nil {
 		log.Error("upload: start transcribing", "err", err)
-		w.fail(ctx, job, log)
+		w.fail(ctx, job, log, domain.UploadErrTranscriptionFailed)
 		return
 	}
 
@@ -218,17 +225,17 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 
 	// abort records where the job stopped. A shutdown (the parent context ended) is not
 	// a failure: the row is left for the start-up sweep, so the step stays as it was.
-	abort := func() {
+	abort := func(kind domain.UploadErrorKind) {
 		if ctx.Err() == nil {
 			tr.FailRunning()
 		}
-		w.fail(ctx, job, log)
+		w.fail(ctx, job, log, kind)
 	}
 
 	wav, err := w.tempWAV()
 	if err != nil {
 		log.Error("upload: temp wav", "err", err)
-		abort()
+		abort(domain.UploadErrTranscriptionFailed)
 		return
 	}
 	defer func() { _ = os.Remove(wav) }()
@@ -238,7 +245,12 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 	tr.Begin("audio", 0)
 	if err := w.conv.ToWAV(jobCtx, job.Path, wav); err != nil {
 		log.Error("upload: convert", "kind", errkind.Of(err))
-		abort()
+		abort(domain.UploadErrTranscriptionFailed)
+		return
+	}
+	if kind, bad := w.audioLengthProblem(wav, job.Duration); bad {
+		abort(kind)
+		log.Error("upload: converted audio length rejected", "kind", string(kind))
 		return
 	}
 	tr.Done("audio")
@@ -249,7 +261,7 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 	t, err := w.tr.Transcribe(progress.With(jobCtx, tr), wav)
 	if err != nil {
 		log.Error("upload: transcribe", "kind", errkind.Of(err), "elapsed", time.Since(start).Round(time.Second))
-		abort()
+		abort(domain.UploadErrTranscriptionFailed)
 		return
 	}
 	if !planned {
@@ -259,7 +271,7 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 	tr.Begin("save", 0)
 	if err := w.store.CompleteUpload(ctx, job.UserID, job.UploadID, t); err != nil {
 		log.Error("upload: store transcript", "err", err)
-		abort()
+		abort(domain.UploadErrTranscriptionFailed)
 		return
 	}
 	tr.Done("save")
@@ -270,11 +282,11 @@ func (w *Worker) Process(ctx context.Context, job Job) {
 
 // fail records a transcription failure — unless the PARENT context ended, which
 // is a shutdown, not a failure: the row is left for the start-up sweep.
-func (w *Worker) fail(ctx context.Context, job Job, log *slog.Logger) {
+func (w *Worker) fail(ctx context.Context, job Job, log *slog.Logger, kind domain.UploadErrorKind) {
 	if ctx.Err() != nil {
 		return
 	}
-	if err := w.store.FailUpload(ctx, job.UserID, job.UploadID, domain.UploadErrTranscriptionFailed); err != nil {
+	if err := w.store.FailUpload(ctx, job.UserID, job.UploadID, kind); err != nil {
 		log.Error("upload: record failure", "err", err)
 	}
 }
@@ -291,3 +303,34 @@ func (w *Worker) tempWAV() (string, error) {
 	}
 	return name, nil
 }
+
+const (
+	// tooLongSlack is how far over the limit the converted audio may be before the claim
+	// in the file's header is called a lie: ffmpeg rounds.
+	tooLongSlack = 30 * time.Second
+	// A file counts as truncated when it converts to under 80% of the length it claimed
+	// AND more than two minutes short. Probe estimates for variable-bitrate files are
+	// imprecise; refusing real recordings would be worse than the problem.
+	incompleteBelow     = 0.8
+	incompleteShortfall = 2 * time.Minute
+)
+
+// audioLengthProblem measures the converted WAV (16 kHz mono 16-bit PCM is 32,000 bytes a
+// second after a 44-byte header) against the limit and against what the file claimed.
+func (w *Worker) audioLengthProblem(wav string, claimed time.Duration) (domain.UploadErrorKind, bool) {
+	if w.maxDuration <= 0 {
+		return "", false
+	}
+	info, err := os.Stat(wav)
+	if err != nil {
+		return "", false
+	}
+	got := time.Duration(float64(max(info.Size()-44, 0)) / 32000 * float64(time.Second))
+	switch {
+	case got > w.maxDuration+tooLongSlack:
+		return domain.UploadErrTooLong, true
+	case float64(got) < incompleteBelow*float64(claimed) && claimed-got > incompleteShortfall:
+		return domain.UploadErrIncomplete, true
+	}
+	return "", false
+}