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import type { Page } from "../core.ts";
type Listener = [EventListener, EventOptions | undefined];
/** * Class to manage the event listeners * and dispatch events */export default class Events {  listeners = new Map<EventType, Set<Listener>>();
  /** Assign a listener to an event */  addEventListener(    type: EventType,    listenerFn: EventListener,    options?: EventOptions,  ) {    const listeners = this.listeners.get(type) || new Set();    const listener: Listener = [listenerFn, options];
    listeners.add(listener);    this.listeners.set(type, listeners);
    // Remove on abort    if (options?.signal) {      options.signal.addEventListener("abort", () => {        listeners.delete(listener);      });    }
    return this;  }
  /** Dispatch an event */  async dispatchEvent(event: Event) {    const { type } = event;    const listeners = this.listeners.get(type);
    if (!listeners) {      return true;    }
    for (const listener of listeners) {      const [listenerFn, listenerOptions] = listener;
      // Remove the listener if it's a once listener      if (listenerOptions?.once) {        listeners.delete(listener);      }
      if (await listenerFn(event) === false) {        return false;      }    }
    return true;  }}
/** An event object */export interface Event {  /** The event type */  type: EventType;
  /**   * Available only in "beforeUpdate" and "afterUpdate"   * contains the files that were changed   */  files?: Set<string>;
  /**   * Available only in "beforeRenderOnDemand"   * contains the page that will be rendered   */  page?: Page;
  /**   * Available only in "afterBuild" and "afterUpdate"   * contains the list of pages that have been saved   */  pages?: Page[];}
/** The available event types */export type EventType =  | "beforeBuild"  | "afterBuild"  | "beforeUpdate"  | "afterUpdate"  | "afterRender"  | "beforeRenderOnDemand"  | "beforeSave";
/** Event listener */export type EventListener = (event: Event) => unknown;
/** The available options for events */export interface EventOptions {  /**   * To indicate that the listener should be invoked at most once   * after being added   */  once?: boolean;
  /**   * The listener will be removed   * when the given AbortSignal object's abort() method is called   */  signal?: AbortSignal;}