import { existsSync, mkdirSync, readdirSync, linkSync, copyFileSync, writeFileSync } from 'node:fs'
import { dirname, join } from 'node:path'

/** Each saved clip owns its sources, so deleting a parent cannot break extensions. */
export function videoSourcePaths(videoPath: string) {
  const dir = join(dirname(videoPath), 'sources')
  if (existsSync(dir)) {
    const paths = readdirSync(dir).filter(name => /^\d{6}\.mp4$/.test(name)).sort().map(name => join(dir, name))
    if (paths.length) return paths
  }
  // Legacy clips become a fixed baseline; their past compression is irreversible.
  return [videoPath]
}

export function preserveVideoSources(videoPath: string, parents: string[], segment: Buffer) {
  const dir = join(dirname(videoPath), 'sources')
  mkdirSync(dir, { recursive: true })
  parents.forEach((source, index) => {
    const dest = join(dir, `${String(index).padStart(6, '0')}.mp4`)
    try { linkSync(source, dest) } catch { copyFileSync(source, dest) }
  })
  writeFileSync(join(dir, `${String(parents.length).padStart(6, '0')}.mp4`), segment)
}