import './styles.css';

const DEFAULT_TIMEOUT = 2750;

export interface SnackOptions {
  message: string;
  timeout?: number;
  actionText?: string;
  actionHandler?: () => boolean | null;
}

export interface SnackShowResult {
  action: boolean;
}

class Snack {
  private _onremove: ((result: SnackShowResult) => void)[] = [];
  private _options: SnackOptions;
  private _element: Element = document.createElement('div');
  private _text: Element = document.createElement('div');
  private _button: Element = document.createElement('button');
  private _showing = false;
  private _closeTimer?: number;
  private _result: SnackShowResult = {
    action: false,
  };

  constructor (options: SnackOptions, callback?: (result: SnackShowResult) => void) {
    this._options = options;

    this._element.className = 'snackbar';
    this._element.setAttribute('aria-live', 'assertive');
    this._element.setAttribute('aria-atomic', 'true');
    this._element.setAttribute('aria-hidden', 'true');

    this._text.className = 'snackbar--text';
    this._text.textContent = options.message;
    this._element.appendChild(this._text);

    if (options.actionText) {
      this._button.className = 'snackbar--button';
      this._button.textContent = options.actionText;
      this._button.addEventListener('click', () => {
        if (this._showing) {
          if (options.actionHandler && options.actionHandler() === false) return;
          this._result.action = true;
        }
        this.hide();
      });
      this._element.appendChild(this._button);
    }

    if (callback) {
      this._onremove.push(callback);
    }
  }

  cancelTimer () {
    if (this._closeTimer != null) clearTimeout(this._closeTimer);
  }

  show (parent: Element): Promise<SnackShowResult> {
    if (this._showing) return Promise.resolve(this._result);
    this._showing = true;
    this.cancelTimer();
    if (parent !== this._element.parentNode) {
      parent.appendChild(this._element);
    }
    this._element.removeAttribute('aria-hidden');
    this._closeTimer = setTimeout(this.hide.bind(this), this._options.timeout || DEFAULT_TIMEOUT);
    return new Promise((resolve) => {
      this._onremove.push(resolve);
    });
  }

  hide () {
    if (!this._showing) return;
    this._showing = false;
    this.cancelTimer();
    this._element.addEventListener('animationend', this.remove.bind(this));
    this._element.setAttribute('aria-hidden', 'true');
  }

  remove () {
    this.cancelTimer();
    const parent = this._element.parentNode;
    if (parent) parent.removeChild(this._element);
    this._onremove.forEach(f => f(this._result));
    this._onremove = [];
  }
}

export default class SnackBarElement extends HTMLElement {
  private _snackbars: Snack[] = [];
  private _processingStack = false;

  showSnackbar (options: SnackOptions): Promise<SnackShowResult> {
    return new Promise((resolve) => {
      const snack = new Snack(options, resolve);
      this._snackbars.push(snack);
      this._processStack();
    });
  }

  private async _processStack () {
    if (this._processingStack === true || this._snackbars.length === 0) return;
    this._processingStack = true;
    await this._snackbars[0].show(this);
    this._snackbars.shift();
    this._processingStack = false;
    this._processStack();
  }
}

customElements.define('snack-bar', SnackBarElement);