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import { join, relative } from "../deps/path.ts";import Events from "./events.ts";
import type { Event, EventListener, EventOptions } from "../core.ts";
/** The options to configure the local server */export interface Options {  /** The folder root to watch */  root: string;
  /** Paths ignored by the watcher */  ignore?: string[];
  /** The debounce waiting time */  debounce?: number;}
/** Custom events for server */export interface WatchEvent extends Event {  /** The event type */  type: WatchEventType;
  /** The list of changed files (only for "change" events) */  files?: Set<string>;
  /** The error object (only for "error" events) */  error?: Error;}
/** The available event types */export type WatchEventType =  | "start"  | "change"  | "error";
export default class Watcher {  events: Events<WatchEvent> = new Events<WatchEvent>();  options: Options;
  constructor(options: Options) {    this.options = options;  }
  /** Add a listener to an event */  addEventListener(    type: WatchEventType,    listener: EventListener<WatchEvent>,    options?: EventOptions,  ) {    this.events.addEventListener(type, listener, options);    return this;  }
  /** Dispatch an event */  dispatchEvent(event: WatchEvent) {    return this.events.dispatchEvent(event);  }
  /** Start the file watcher */  async start() {    const { root, ignore, debounce } = this.options;    const watcher = Deno.watchFs(root);    const changes = new Set<string>();    let timer = 0;    let runningCallback = false;
    await this.dispatchEvent({ type: "start" });
    const callback = async () => {      if (!changes.size || runningCallback) {        return;      }
      const files = new Set(changes);      changes.clear();
      runningCallback = true;
      try {        const result = await this.dispatchEvent({ type: "change", files });        if (false === result) {          return watcher.close();        }      } catch (error) {        await this.dispatchEvent({ type: "error", error });      }      runningCallback = false;    };
    for await (const event of watcher) {      let { paths } = event;
      // Filter ignored paths      paths = paths.filter((path) => {        if (path.endsWith(".DS_Store")) { // macOS file          return false;        }
        return ignore          ? !ignore.some((ignore) => path.startsWith(join(root, ignore, "/")))          : true;      });
      if (!paths.length) {        continue;      }
      paths.forEach((path) => changes.add(join("/", relative(root, path))));
      // Debounce      clearTimeout(timer);      timer = setTimeout(callback, debounce ?? 100);    }  }}