/**
 * Small helpers around the Origin Private File System, used to stream muxer
 * output into a real file with random access instead of hand-assembling
 * chunks in memory. Browser-only; every function is a no-op when OPFS is not
 * available.
 */

const PREFIX = "j621-optimize-";
const STALE_MS = 60 * 60 * 1000; // purge leftovers after an hour

function directory(): Promise<FileSystemDirectoryHandle> | null {
  if (typeof navigator === "undefined") return null;
  const storage = navigator.storage as StorageManager | undefined;
  if (!storage?.getDirectory) return null;
  return storage.getDirectory();
}

export function opfsSupported(): boolean {
  return (
    typeof navigator !== "undefined" &&
    Boolean((navigator.storage as StorageManager | undefined)?.getDirectory)
  );
}

export async function createStoredFile(
  extension: string,
): Promise<{ name: string; handle: FileSystemFileHandle } | null> {
  const root = await directory();
  if (!root) return null;
  const name = `${PREFIX}${crypto.randomUUID()}.${extension}`;
  const handle = await root.getFileHandle(name, { create: true });
  return { name, handle };
}

export async function deleteStoredFile(name: string): Promise<void> {
  try {
    const root = await directory();
    if (!root) return;
    await root.removeEntry(name);
  } catch {
    // Best effort: stale entries are purged on the next run anyway.
  }
}

export async function purgeStaleStoredFiles(): Promise<void> {
  try {
    const root = await directory();
    if (!root) return;
    const now = Date.now();
    const entries = (
      root as unknown as {
        entries(): AsyncIterableIterator<[string, FileSystemHandle]>;
      }
    ).entries();
    for await (const [name, handle] of entries) {
      if (!name.startsWith(PREFIX) || handle.kind !== "file") continue;
      try {
        const file = await (handle as FileSystemFileHandle).getFile();
        if (now - file.lastModified > STALE_MS) {
          await root.removeEntry(name);
        }
      } catch {
        // Ignore entries that vanish underneath us.
      }
    }
  } catch {
    // OPFS iteration is best effort.
  }
}