Module split: extract audio I/O helpers to server/audio.js

• getAudioDuration(path)         — ffprobe wrapper, returns seconds | null
  • splitAudioFile(in, dir, secs)  — ffmpeg -acodec copy chunking
  • downloadPodcastAudio(url, dst) — streams HTTP audio to disk

Also moved fetchUrl into util.js (alongside the other stateless
helpers) — it's a generic HTTP-GET-with-redirects used by RSS parsing
and channel discovery, not strictly audio.

server/index.js: 2758 → 2694 lines.

Smoke tested: server boots; /api/license-status, /api/health, /
respond. No behavior change.

server/index.js

@@ -17,8 +17,14 @@ import {
   parseTimestampedTranscript,
   safeText,
   retryGemini,
+  fetchUrl,
 } from "./util.js";
 import { calcCost, buildAnalysisPrompt } from "./gemini-helpers.js";
+import {
+  getAudioDuration,
+  splitAudioFile,
+  downloadPodcastAudio,
+} from "./audio.js";
 
 const execFileAsync = promisify(execFile);
 const app = express();
@@ -949,19 +955,7 @@ async function fetchUploadDates(videoIds) {
 // ── RSS-based date fetching (bypasses bot detection) ─────────────────────
 
 // Fetch a URL and return the response body as a string
-function fetchUrl(url) {
-  return new Promise((resolve, reject) => {
-    https.get(url, (res) => {
-      if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
-        return fetchUrl(res.headers.location).then(resolve, reject);
-      }
-      let data = "";
-      res.on("data", (chunk) => (data += chunk));
-      res.on("end", () => resolve(data));
-      res.on("error", reject);
-    }).on("error", reject);
-  });
-}
+// fetchUrl moved to ./util.js
 
 // Get channel_id from a YouTube channel/playlist URL using yt-dlp
 async function getChannelId(url) {
@@ -1086,26 +1080,7 @@ async function parsePodcastRSS(feedUrl, limit = 200) {
 }
 
 // Download a podcast episode audio file via HTTP(S) to a local path
-function downloadPodcastAudio(audioUrl, destPath) {
-  return new Promise((resolve, reject) => {
-    const doFetch = (url) => {
-      const getter = url.startsWith("https") ? https : http;
-      getter.get(url, (res) => {
-        if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
-          return doFetch(res.headers.location);
-        }
-        if (res.statusCode !== 200) {
-          return reject(new Error(`HTTP ${res.statusCode} downloading podcast audio`));
-        }
-        const fileStream = createWriteStream(destPath);
-        res.pipe(fileStream);
-        fileStream.on("finish", () => fileStream.close(resolve));
-        fileStream.on("error", reject);
-      }).on("error", reject);
-    };
-    doFetch(audioUrl);
-  });
-}
+// downloadPodcastAudio moved to ./audio.js
 
 // Get channel name from URL
 async function fetchChannelName(url) {
@@ -2638,46 +2613,7 @@ Return ONLY the timestamped transcript, nothing else.`;
 
 // ── Helpers ────────────────────────────────────────────────────────────────
 
-// ── Audio duration helper (ffprobe) ─────────────────────────────────────
-async function getAudioDuration(filePath) {
-  try {
-    const { stdout } = await execFileAsync("ffprobe", [
-      "-v", "error",
-      "-show_entries", "format=duration",
-      "-of", "default=noprint_wrappers=1:nokey=1",
-      filePath,
-    ], { timeout: 15000 });
-    const dur = parseFloat(stdout.trim());
-    return isNaN(dur) ? null : dur;
-  } catch {
-    return null;
-  }
-}
-
-// ── Split audio into chunks with ffmpeg ─────────────────────────────────
-async function splitAudioFile(inputPath, outputDir, chunkSeconds = 2700) {
-  const duration = await getAudioDuration(inputPath);
-  if (!duration || duration <= chunkSeconds) return null; // no split needed
-
-  const chunks = [];
-  let startSec = 0;
-  let i = 0;
-  while (startSec < duration) {
-    const chunkPath = path.join(outputDir, `chunk_${i}.mp3`);
-    const segLen = Math.min(chunkSeconds, duration - startSec);
-    await execFileAsync("ffmpeg", [
-      "-y", "-i", inputPath,
-      "-ss", String(startSec),
-      "-t", String(segLen),
-      "-acodec", "copy",
-      chunkPath,
-    ], { timeout: 120000 });
-    chunks.push({ path: chunkPath, startOffset: startSec, index: i });
-    startSec += chunkSeconds;
-    i++;
-  }
-  return chunks;
-}
+// getAudioDuration + splitAudioFile moved to ./audio.js
 
 // sendEvent / extractVideoId / formatTime / parseTimestampedTranscript moved to ./util.js