// within rangeResult.ts
// @ts-ignore
export class RangeResult implements IteratorResult<number> {
  done: boolean;
  value: number;

  constructor(value: number | undefined, done: boolean) {
    this.done = done;
    this.value = value ?? 0;
  }
}

export class RangeIterator implements Iterator<number> {
  private _first: number;
  private _current: number;
  private _last: number;
  private _step: number;

  constructor(first: number, last: number, step: number) {
    this._current = this._first = first;
    this._last = last;
    this._step = step;
  }

  next(value?: any): IteratorResult<number> {
    let r: RangeResult;
    if (this._first < this._last && this._current < this._last) {
      r = new RangeResult(this._current, false);
      this._current += this._step;
    } else if (this._first < this._last && this._current === this._last) {
      r = new RangeResult(this._current, false);
      this._current += this._step;
    } else if (this._first > this._last && this._current > this._last) {
      r = new RangeResult(this._current, false);
      this._current -= this._step;
    } else if (this._first > this._last && this._current === this._last) {
      r = new RangeResult(this._current, false);
      this._current -= this._step;
    } else if (this._current === this._last) {
      r = new RangeResult(this._current, false);
      this._current -= this._step;
    } else {
      r = new RangeResult(undefined, true);
    }
    return r;
  }
}

export class Range implements Iterable<number> {
  public readonly isRange = true;

  constructor(
    public first: number,
    public last: number,
    public step: number = 1
  ) {
  }

  [Symbol.iterator](): Iterator<number> {
    return new RangeIterator(this.first, this.last, this.step);
  }

  map<U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any): U[] {
    return Array.from(this).map(callbackfn);
  }

  public static range(first: number | string, last?: number, step: number = 1): Range {
    if (typeof first === 'number' && last === undefined) {
      return new Range(0, first, step);
    } else if (typeof first === 'string') {
      const [_first, _last = '0'] = first.split('..');
      const [__last, _step = '1'] = _last.split(',');
      return new Range(Number(_first.trim()), Number(__last.trim()), Number(_step.trim()));
    } else {
      return new Range(first, last ?? 0, step);
    }
  }
}