import { hasBlob, saveBlob } from '@/lib/offline-db'

/**
 * Pre-cache a track's audio blob into IndexedDB.
 * Only stores the blob (no metadata) so pre-cached tracks don't appear
 * in the offline library, but the player still finds them via getTrackBlob().
 * Best-effort — errors are silently swallowed.
 */
export async function precacheTrack(
  trackId: string,
  signal?: AbortSignal
): Promise<void> {
  if (await hasBlob(trackId)) return
  if (signal?.aborted) return

  const res = await fetch(`/api/music/stream/${trackId}`, { signal })
  if (!res.ok) return

  const blob = await res.blob()
  if (signal?.aborted) return

  await saveBlob(trackId, blob)
}

/**
 * Pre-cache the next N tracks in a queue sequentially.
 * Sequential to avoid flooding bandwidth on mobile connections.
 */
export async function precacheUpcoming(
  queue: { id: string }[],
  currentIndex: number,
  count: number,
  signal: AbortSignal
): Promise<void> {
  const upcoming = queue.slice(currentIndex + 1, currentIndex + 1 + count)
  for (const track of upcoming) {
    if (signal.aborted) return
    try {
      await precacheTrack(track.id, signal)
    } catch {
      // best-effort — continue with next track
    }
  }
}