import FileSaver from 'file-saver';
import { downloadMedia } from './matrix';
import { getCurrentAccessToken } from './auth';

export type MediaSaver = (blob: Blob, filename: string) => void | Promise<void>;

let customMediaSaver: MediaSaver | null = null;

const defaultMediaSaver: MediaSaver = (blob, filename) => {
  FileSaver.saveAs(blob, filename);
};

/**
 * Register a platform-specific media saver (Android MediaStore, Electron dialog, etc.).
 * Pass null to restore the default FileSaver path.
 *
 * Platforms should call this once at startup (mobile overlay / desktop shell entry).
 */
export const registerMediaSaver = (saver: MediaSaver | null): void => {
  customMediaSaver = saver;
};

/**
 * Persist a Blob to disk via the registered platform saver, or FileSaver by default.
 */
export const saveMediaBlob = async (blob: Blob, filename: string): Promise<void> => {
  const saver = customMediaSaver ?? defaultMediaSaver;
  await saver(blob, filename);
};

/**
 * Fetch media (auth download or blob:/data:/http URL) and save it via [saveMediaBlob].
 */
export const downloadAndSaveMedia = async (
  src: string,
  filename: string,
  accessToken?: string | null
): Promise<void> => {
  let blob: Blob;
  try {
    if (src.startsWith('blob:') || src.startsWith('data:')) {
      const res = await fetch(src);
      if (!res.ok) throw new Error(`Failed to fetch ${src}`);
      blob = await res.blob();
    } else {
      blob = await downloadMedia(src, accessToken ?? getCurrentAccessToken());
    }
  } catch (error) {
    console.warn('[saveMedia] downloadMedia failed, trying fetch fallback:', error);
    const res = await fetch(src);
    if (!res.ok) throw error;
    blob = await res.blob();
  }
  await saveMediaBlob(blob, filename);
};