/** One piece of a streamed input: a string, or a UTF-8 `Uint8Array` decoded as a
 * stream (so a multi-byte sequence may split across chunks). */
export type Chunk = string | Uint8Array;

export interface Options {
  /** `"erase"` (default): erasable syntax only, every offset preserved. `"downlevel"`:
   * also down-levels `enum`, instantiated `namespace`, parameter properties, `import =`
   * and `export =`; lines are preserved, columns only outside converted constructs. */
  mode?: "erase" | "downlevel";
  /** Receives `{start, end}` (UTF-16 units) for syntax `mode` cannot erase. Without it,
   * the first such construct throws (or, for a generator, throws from `next()`) an
   * `UnsupportedSyntaxError`. */
  onError?: (error: { start: number; end: number }) => void;
}

/** Transforms a whole string, asynchronously. */
export function transform(src: string, opts?: Options): Promise<string>;
/** Transforms a stream of chunks, asynchronously. Concatenating every yielded string
 * equals the string-input result for the same total input. */
export function transform(src: Iterable<Chunk> | AsyncIterable<Chunk>, opts?: Options): AsyncGenerator<string>;

/** Transforms a whole string, synchronously. */
export function transformSync(src: string, opts?: Options): string;
/** Transforms a stream of chunks, synchronously. Concatenating every yielded string
 * equals the string-input result for the same total input. */
export function transformSync(src: Iterable<Chunk>, opts?: Options): Generator<string>;

/** Lazily instantiates and returns the first pooled instance of the wasm engine for
 * `mode`, compiling it at most once per engine. Kept for tests/profiling. */
export function engine(mode?: "erase" | "downlevel"): {
  memory: WebAssembly.Memory;
  [export_: string]: unknown;
};

/** Thrown for syntax the mode cannot erase when no `onError` is given, like Node's
 * `ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX`. */
export class UnsupportedSyntaxError extends SyntaxError {
  code: "ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX";
  start: number;
  end: number;
  constructor(start: number, end: number);
}