import { execSync } from 'node:child_process';
import { renameSync, statSync } from 'node:fs';
import { MAX_DURATION_S, OUTPUT_FPS, VIDEO_SIZE, WEBM_BITRATE } from './config.js';

const LEAD_IN_S = 0.12;

export function trimRecording(
  rawPath: string,
  trimmedPath: string,
  times: { recordStartMs: number; sceneStartMs: number; sceneEndMs: number }
) {
  const sceneSpan = (times.sceneEndMs - times.sceneStartMs) / 1000;
  const trimStart = Math.max(
    0,
    (times.sceneStartMs - times.recordStartMs) / 1000 - LEAD_IN_S
  );
  const trimEnd = (times.sceneEndMs - times.recordStartMs) / 1000;
  const wallDuration = trimEnd - trimStart;
  const finalDuration = wallDuration;

  if (finalDuration > MAX_DURATION_S) {
    console.log(
      `Scene output duration is ${finalDuration.toFixed(2)}s (guard ${MAX_DURATION_S.toFixed(2)}s); keeping the full take.`
    );
  }

  const filter =
    `trim=start=${trimStart.toFixed(3)}:duration=${wallDuration.toFixed(3)},` +
    `setpts=PTS-STARTPTS,fps=${OUTPUT_FPS},` +
    `trim=duration=${finalDuration.toFixed(3)},setpts=PTS-STARTPTS`;

  // Keep trimming inside the filter graph: it is frame-accurate for WebM
  // without the keyframe leakage of input seeking.
  execSync(
    `ffmpeg -y -i "${rawPath}" -vf "${filter}" ` +
      `-fps_mode cfr -r ${OUTPUT_FPS} -c:v libvpx -b:v ${WEBM_BITRATE} -deadline good -cpu-used 5 ` +
      `"${trimmedPath}"`,
    { stdio: 'inherit' }
  );

  try {
    statSync(rawPath);
    renameSync(rawPath, rawPath + '.untrimmed');
  } catch {
    /* ignore */
  }

  console.log(
    `Wrote ${trimmedPath} (${finalDuration.toFixed(2)}s, scene=${sceneSpan.toFixed(2)}s, capture=${VIDEO_SIZE.width}x${VIDEO_SIZE.height})`
  );
}