/**
 * Measure what an audio backend actually delivered.
 *
 * Every backend returns a `durationMs` that is the REQUEST, not the result:
 *
 *   native-lyria3.ts        durationSec * 1000        (what we asked for)
 *   native-elevenlabs-sfx   durationSec * 1000        (what we asked for)
 *   native-elevenlabs-tts   estimateDurationMs(text)  (~14 chars/sec guess)
 *
 * Consumers read the field as delivered length, and it is routinely wrong:
 *
 *   soundtrack.json said 64000ms   the mp3 was 30.77s   (four films running)
 *   narration.json  said 54357ms   the mp3 was 60.14s
 *   narration.json  said 65643ms   the mp3 was 69.01s
 *
 * The soundtrack case is the expensive one. A 30.7s bed under a 64.1s film gets
 * looped by the mixer, and the loop seam lands wherever it lands — on one
 * delivered film, 6.7s into the climax shot. Nothing reported that, because the
 * artifact said the bed was 64 seconds long.
 *
 * `native-lyria3.ts` records the reasoning that produced this: "MP3 duration
 * parsing is out of scope — Lyria 3 returns audio/mpeg without a trivial header
 * read." True, and beside the point: ffprobe is already a hard dependency of
 * this repo, and `ffprobeDuration` already exists. No header parsing needed.
 *
 * A failed probe keeps the estimate rather than inventing a number — the file
 * is still on disk and still playable, and a wrong-but-close duration beats
 * refusing to write the artifact at all.
 */
import { existsSync } from 'node:fs';
import { ffprobeDuration } from '../assemble/ffmpeg.js';

export interface MeasureDurationOptions {
  /** Dry runs never wrote a file; keep the planned figure. */
  dryRun?: boolean;
  ffprobeBin?: string;
}

/**
 * The delivered duration of `path` in ms, falling back to `plannedMs` when the
 * file cannot be probed (missing, dry run, or ffprobe unavailable).
 */
export async function measureDeliveredDurationMs(
  path: string,
  plannedMs: number,
  options: MeasureDurationOptions = {},
): Promise<number> {
  if (options.dryRun) return plannedMs;
  if (!path || !existsSync(path)) return plannedMs;
  try {
    // ffprobeDuration returns MILLISECONDS despite the bare name — its own doc
    // says so, and stitch.ts divides by 1000 to get seconds. Converting again
    // here reported a 30-second bed as 30,694 seconds, which is exactly the
    // sort of thing a "measured" figure is supposed to stop.
    const ms = await ffprobeDuration(path, {
      ...(options.ffprobeBin ? { ffprobeBin: options.ffprobeBin } : {}),
    });
    if (!Number.isFinite(ms) || ms <= 0) return plannedMs;
    return Math.round(ms);
  } catch {
    return plannedMs;
  }
}