Class LocalFsBackend

packages/core/src/sync/lan-server.ts:30–302

* Local filesystem backend for the LAN server. * Serves files from the device's own data directory for sync.

 * Serves files from the device's own data directory for sync.
 */
class LocalFsBackend implements ISyncBackend {
  readonly type = "lan" as const;

  private async getCurrentDeviceSnapshot(): Promise<DeviceSyncPayload> {
    return collectChanges(0);
  }

  private async getDataDir(): Promise<string> {
    const adapter = getSyncAdapter();
    return await adapter.getAppDataDir();
  }

  private async mapVirtualPath(path: string): Promise<string> {
    const adapter = getSyncAdapter();
    const dataDir = await this.getDataDir();

    // Remote structure mapping to local storage:
    // /readany/data/readany.db                    -> local DB file
    // /readany/data/books/{title-id}/{title}.ext  -> local books/{id}.ext or covers/{id}.ext
    // /readany/data/file/*                        -> local books/*    (legacy layout)
    // /readany/data/cover/*                       -> local covers/*   (legacy layout)

    if (path === "/readany/data/readany.db") {
      return await adapter.getDatabasePath();
    }

    if (path.startsWith(`${REMOTE_BOOKS_ROOT}/`)) {
      // /readany/data/books/{title-id}/{filename}
      const rest = path.substring(REMOTE_BOOKS_ROOT.length + 1);
      const slashIdx = rest.indexOf("/");
      if (slashIdx === -1) {
        // Caller asked to map the dir itself — return books root local equivalent (best-effort).
        return adapter.joinPath(dataDir, "books");
      }
      const folderName = rest.substring(0, slashIdx);
      const fileName = rest.substring(slashIdx + 1);
      const bookId = parseBookFolderName(folderName) ?? folderName.split("-").pop() ?? folderName;
      const ext = fileName.includes(".") ? fileName.split(".").pop()! : "";
      const targetSubdir = isCoverFileName(fileName) ? "covers" : "books";
      return adapter.joinPath(dataDir, targetSubdir, ext ? `${bookId}.${ext}` : bookId);
    }

    if (path.startsWith("/readany/data/file")) {
      const subPath = path.substring("/readany/data/file".length);
      return adapter.joinPath(dataDir, "books", subPath);
    }

    if (path.startsWith("/readany/data/cover")) {
      const subPath = path.substring("/readany/data/cover".length);
      return adapter.joinPath(dataDir, "covers", subPath);
    }

    if (path.startsWith("/readany/data/")) {
      const subPath = path.substring("/readany/data/".length);
      return adapter.joinPath(dataDir, subPath);
    }

    return adapter.joinPath(dataDir, path);