export default class AsyncTask extends Promise {

  constructor(executor) {
    let rejectFunc;

    super((resolve, reject) => {
      rejectFunc = reject;

      if(executor.constructor === Promise) {
        executor.then(resolve, reject);
      } else {
        executor(resolve, reject);
      }
    });

    this.state = 'pending';
    this.cancel = rejectFunc.bind(null, {cancelled: true});
  }

  then(onFulfilled, onRejected) {
    const fulfill = (result) => {
      this.state = 'fulfilled';

      if(typeof onFulfilled === 'function') {
        return onFulfilled(result);
      }
    };

    const reject = (error) => {
      this.state = 'rejected';

      if(typeof onRejected === 'function') {
        return onRejected(error);
      }
    };

    return super.then(fulfill, reject);
  }
}