class EventEmitter {
  events: {};
  constructor() {
    this.events = {};
  }
  on(name, fn) {
    if (!this.events[name]) {
      this.events[name] = [];
    }
    this.events[name].push(fn);
  }

  once(name, fn) {
    const once = (...args) => {
      fn(...args);
      this.off(name, once);
    };

    this.on(name, once);
  }

  emit(name, ...args) {
    if (this.events[name]) {
      this.events[name].forEach((fn) => fn(...args));
    }
  }

  off(name, fn) {
    if (this.events[name]) {
      this.events[name] = this.events[name].filter((f) => f !== fn);
    }
  }
}
declare global {
  interface Window {
    HMRRegisterMap$: Record<string, EventEmitter>;
  }
}

const processEvent = new EventEmitter();

function getEventEmitter(file) {
  if (!window.HMRRegisterMap$) {
    window.HMRRegisterMap$ = {};
  }
  if (undefined === window.HMRRegisterMap$[file]) {
    const emiter = new EventEmitter();
    window.HMRRegisterMap$[file] = emiter;
    processEvent.emit("new", file, emiter);
  }
  return window.HMRRegisterMap$[file];
}

export function waitForOneFile() {
  return new Promise((resolve) =>
    processEvent.once("new", (file) => {
      resolve(accept(file));
    })
  );
}

export function accept(file) {
  const emitter = getEventEmitter(file);

  return {
    emit(newModule) {
      emitter.emit("update", newModule);
    },
    on(cb) {
      emitter.on("update", cb);
      return () => emitter.off("update", cb);
    },
  };
}