Allow txt export with timestampts

src/lib/export.ts

@@ -59,10 +59,39 @@ export function transcriptToSrt(chunks: TranscriptChunk[]): string {
   return cues.length === 0 ? "" : `${cues.join("\n\n")}\n`;
 }
 
+/** Seconds → compact clock timestamp, e.g. 3.21 → "00:03.2" (mm:ss.s). */
+export function formatClockTimestamp(seconds: number): string {
+  const totalTenths = Math.max(0, Math.round(seconds * 10));
+  const tenths = totalTenths % 600;
+  const m = (totalTenths - tenths) / 600;
+  return `${String(m).padStart(2, "0")}:${(tenths / 10).toFixed(1).padStart(4, "0")}`;
+}
+
+/**
+ * Timestamped chunks → plain text, one line per chunk:
+ * "[00:03.2 – 00:07.9] text". A null end time — Whisper sometimes never
+ * closes the last segment — omits the range end: "[00:03.2] text".
+ * Empty-text chunks are skipped, mirroring transcriptToSrt.
+ */
+export function transcriptToTimestampedTxt(chunks: TranscriptChunk[]): string {
+  const lines = chunks
+    .filter((chunk) => chunk.text.trim() !== "")
+    .map((chunk) => {
+      const [start, end] = chunk.timestamp;
+      const range =
+        end === null
+          ? formatClockTimestamp(start)
+          : `${formatClockTimestamp(start)} – ${formatClockTimestamp(end)}`;
+      return `[${range}] ${chunk.text.trim()}`;
+    });
+  return lines.length === 0 ? "" : `${lines.join("\n")}\n`;
+}
+
 /**
  * Download filename for an export: the source file's base name with the
  * extension swapped ("talk.m4a" → "talk.srt"), or "transcript.<ext>" when no
- * usable source name is known.
+ * usable source name is known. `ext` may be compound ("timestamps.txt") so
+ * sibling exports of the same format get distinct names.
  */
 export function exportFilename(sourceName: string | null | undefined, ext: string): string {
   const trimmed = sourceName?.trim() ?? "";