type CapacitorFilesystemModule = typeof import('@capacitor/filesystem');
type CapacitorCoreModule = typeof import('@capacitor/core');

/**
 * Minimal Capacitor Filesystem surface the attachment store depends on, plus the
 * `Directory` enum and `convertFileSrc` helper. Loaded lazily so the desktop and
 * browser builds never statically import `@capacitor/*` (see LESSONS:
 * "Lazy-load Capacitor modules on Electron/desktop").
 */
export interface CapacitorAttachmentFilesystem {
  filesystem: CapacitorFilesystemModule['Filesystem'];
  directory: CapacitorFilesystemModule['Directory'][keyof CapacitorFilesystemModule['Directory']];
  /** User-visible directory (`Documents`) used when exporting attachments out of app storage. */
  exportDirectory: CapacitorFilesystemModule['Directory'][keyof CapacitorFilesystemModule['Directory']];
  convertFileSrc: (url: string) => string;
}

let cachedFilesystem: Promise<CapacitorAttachmentFilesystem | null> | null = null;

/**
 * Resolve the Capacitor Filesystem plugin (scoped to the app `Data` directory)
 * on native shells. Returns `null` on web/Electron or when the plugin is
 * unavailable.
 */
export function loadCapacitorAttachmentFilesystem(): Promise<CapacitorAttachmentFilesystem | null> {
  cachedFilesystem ??= resolveCapacitorAttachmentFilesystem();

  return cachedFilesystem;
}

async function resolveCapacitorAttachmentFilesystem(): Promise<CapacitorAttachmentFilesystem | null> {
  if (typeof window === 'undefined') {
    return null;
  }

  try {
    const filesystemModule: CapacitorFilesystemModule = await import('@capacitor/filesystem');
    const coreModule: CapacitorCoreModule = await import('@capacitor/core');

    if (!coreModule.Capacitor.isNativePlatform()) {
      return null;
    }

    return {
      filesystem: filesystemModule.Filesystem,
      directory: filesystemModule.Directory.Data,
      exportDirectory: filesystemModule.Directory.Documents,
      convertFileSrc: (url: string) => coreModule.Capacitor.convertFileSrc(url)
    };
  } catch {
    return null;
  }
}