import {compose, EventEmitter} from '@avocado/core';

const decorate = compose(
  EventEmitter,
);

export class InputNormalizer extends decorate(class{}) {

  constructor() {
    super();
    // Track events.
    this.target = undefined;
    this.targetForKeyUp = undefined;
    // Handle lame OS input event behavior. See: https://mzl.la/2Ob0WQE
    this.keysDown = {};
    this.keyUpDelays = {};
    // Bind event handlers.
    this.onBlur = this.onBlur.bind(this);
    this.onKeyDown = this.onKeyDown.bind(this);
    this.onKeyUp = this.onKeyUp.bind(this);
  }

  actionForKey(key) {
    return this.mapKeyToAction[key];
  }

  listen(target = window.document, targetForKeyUp = window.document) {
    // Only listen once.
    if (this.target) {
      return;
    }
    this.target = target;
    this.targetForKeyUp = targetForKeyUp;
    this.target.addEventListener('blur', this.onBlur);
    this.target.addEventListener('keydown', this.onKeyDown);
    this.targetForKeyUp.addEventListener('keyup', this.onKeyUp);
  }

  onBlur(event) {
    this.setAllKeysUp();
  }

  onKeyDown(event) {
    const {key} = event;
    if (this.keysDown[key]) {
      if (this.keyUpDelays[key]) {
        clearTimeout(this.keyUpDelays[key]);
        delete this.keyUpDelays[key];
      }
      return;
    }
    this.keysDown[key] = true;
    this.emit('keyDown', key);
  }

  onKeyUp(event) {
    const {key} = event;
    this.keyUpDelays[key] = setTimeout(() => {
      delete this.keyUpDelays[key];
      delete this.keysDown[key];
      this.emit('keyUp', key);
    }, 20);
  }

  setAllKeysUp() {
    this.keysDown = {};
    for (const key in this.keyUpDelays) {
      const handle = this.keyUpDelays[key];
      clearTimeout(handle);
      this.emit('keyUp', key);
    }
    this.keyUpDelays = {};
  }

  stopListening() {
    this.setAllKeysUp();
    if (!this.target) {
      return;
    }
    this.target.removeEventListener('blur', this.onBlur);
    this.target.removeEventListener('keydown', this.onKeyDown);
    this.targetForKeyUp.removeEventListener('keyup', this.onKeyUp);
    this.target = undefined;
    this.targetForKeyUp = undefined;
  }

}