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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.import { basename } from "../path.ts";import { EventEmitter } from "../events.ts";import { notImplemented } from "../_utils.ts";import { getValidatedPath } from "../internal/fs/utils.mjs";
export function asyncIterableIteratorToCallback<T>(  iterator: AsyncIterableIterator<T>,  callback: (val: T, done?: boolean) => void,) {  function next() {    iterator.next().then((obj) => {      if (obj.done) {        callback(obj.value, true);        return;      }      callback(obj.value);      next();    });  }  next();}
export function asyncIterableToCallback<T>(  iter: AsyncIterable<T>,  callback: (val: T, done?: boolean) => void,  errCallback: (e: unknown) => void,) {  const iterator = iter[Symbol.asyncIterator]();  function next() {    iterator.next().then((obj) => {      if (obj.done) {        callback(obj.value, true);        return;      }      callback(obj.value);      next();    }, errCallback);  }  next();}
type watchOptions = {  persistent?: boolean;  recursive?: boolean;  encoding?: string;};
type watchListener = (eventType: string, filename: string) => void;
export function watch(  filename: string | URL,  options: watchOptions,  listener: watchListener,): FSWatcher;export function watch(  filename: string | URL,  listener: watchListener,): FSWatcher;export function watch(  filename: string | URL,  options: watchOptions,): FSWatcher;export function watch(filename: string | URL): FSWatcher;export function watch(  filename: string | URL,  optionsOrListener?: watchOptions | watchListener,  optionsOrListener2?: watchOptions | watchListener,) {  const listener = typeof optionsOrListener === "function"    ? optionsOrListener    : typeof optionsOrListener2 === "function"    ? optionsOrListener2    : undefined;  const options = typeof optionsOrListener === "object"    ? optionsOrListener    : typeof optionsOrListener2 === "object"    ? optionsOrListener2    : undefined;
  const watchPath = getValidatedPath(filename).toString();
  let iterator: Deno.FsWatcher;  // Start the actual watcher in the next event loop  // to avoid error in compat test case (parallel/test-fs-watch.js)  const timer = setTimeout(() => {    iterator = Deno.watchFs(watchPath, {      recursive: options?.recursive || false,    });
    asyncIterableToCallback<Deno.FsEvent>(iterator, (val, done) => {      if (done) return;      fsWatcher.emit(        "change",        convertDenoFsEventToNodeFsEvent(val.kind),        basename(val.paths[0]),      );    }, (e) => {      fsWatcher.emit("error", e);    });  }, 0);
  const fsWatcher = new FSWatcher(() => {    clearTimeout(timer);    try {      iterator?.close();    } catch (e) {      if (e instanceof Deno.errors.BadResource) {        // already closed        return;      }      throw e;    }  });
  if (listener) {    fsWatcher.on("change", listener);  }
  return fsWatcher;}
export { watch as watchFile };
class FSWatcher extends EventEmitter {  #closer: () => void;  #closed = false;  constructor(closer: () => void) {    super();    this.#closer = closer;  }  close() {    if (this.#closed) {      return;    }    this.#closed = true;    this.emit("close");    this.#closer();  }  ref() {    notImplemented("FSWatcher.ref() is not implemented");  }  unref() {    notImplemented("FSWatcher.unref() is not implemented");  }}
type NodeFsEventType = "rename" | "change";
function convertDenoFsEventToNodeFsEvent(  kind: Deno.FsEvent["kind"],): NodeFsEventType {  if (kind === "create" || kind === "remove") {    return "rename";  } else {    return "change";  }}