refactor(youtube): extract subtitle generation pipeline

launcher/youtube/whisper.ts

@@ -0,0 +1,60 @@
+import fs from 'node:fs';
+
+import type { Args } from '../types.js';
+import { runExternalCommand } from '../util.js';
+
+export interface BuildWhisperArgsOptions {
+  modelPath: string;
+  audioPath: string;
+  outputPrefix: string;
+  language: string;
+  translate: boolean;
+  threads: number;
+  vadModelPath?: string;
+}
+
+export function buildWhisperArgs(options: BuildWhisperArgsOptions): string[] {
+  const args = [
+    '-m',
+    options.modelPath,
+    '-f',
+    options.audioPath,
+    '--output-srt',
+    '--output-file',
+    options.outputPrefix,
+    '--language',
+    options.language,
+    '--threads',
+    String(options.threads),
+  ];
+  if (options.translate) args.push('--translate');
+  if (options.vadModelPath) {
+    args.push('-vm', options.vadModelPath, '--vad');
+  }
+  return args;
+}
+
+export async function runWhisper(
+  whisperBin: string,
+  args: Args,
+  options: Omit<BuildWhisperArgsOptions, 'threads' | 'vadModelPath'>,
+): Promise<string> {
+  const vadModelPath =
+    args.whisperVadModel.trim() && fs.existsSync(args.whisperVadModel.trim())
+      ? args.whisperVadModel.trim()
+      : undefined;
+  const whisperArgs = buildWhisperArgs({
+    ...options,
+    threads: args.whisperThreads,
+    vadModelPath,
+  });
+  await runExternalCommand(whisperBin, whisperArgs, {
+    commandLabel: 'whisper',
+    streamOutput: true,
+  });
+  const outputPath = `${options.outputPrefix}.srt`;
+  if (!fs.existsSync(outputPath)) {
+    throw new Error(`whisper output not found: ${outputPath}`);
+  }
+  return outputPath;
+}