web/src/shims-fs.d.ts

export interface FileSystemGetFileOptions {
  create?: boolean;
}

interface FileSystemCreateWritableOptions {
  keepExistingData?: boolean;
}

interface FileSystemRemoveOptions {
  recursive?: boolean;
}

interface FileSystemFileHandle {
  getFile(): Promise<File>;

  createWritable(options?: FileSystemCreateWritableOptions): Promise<FileSystemWritableFileStream>;
}

enum WriteCommandType {
  write = 'write',
  seek = 'seek',
  truncate = 'truncate',
}

interface WriteParams {
  type: WriteCommandType;
  size?: number;
  position?: number;
  data: BufferSource | Blob | string;
}

type FileSystemWriteChunkType = BufferSource | Blob | string | WriteParams;

interface FileSystemWritableFileStream extends WritableStream {
  write(data: FileSystemWriteChunkType): Promise<undefined>;

  seek(position: number): Promise<undefined>;

  truncate(size: number): Promise<undefined>;

  close(): Promise<undefined>; // should be implemented in WritableStream
}

export declare interface FileSystemDirectoryHandle {
  getFileHandle(name: string, options?: FileSystemGetFileOptions): Promise<FileSystemFileHandle>;

  removeEntry(name: string, options?: FileSystemRemoveOptions): Promise<undefined>;
}

declare global {
  interface Window {
    showDirectoryPicker?(): Promise<FileSystemDirectoryHandle>;
  }
}