class Bump {
  constructor(context, x) {
    this._context = context;
    this._x = x;
  }
  areaStart() {
    this._line = 0;
  }
  areaEnd() {
    this._line = NaN;
  }
  lineStart() {
    this._point = 0;
  }
  lineEnd() {
    if (this._line || (this._line !== 0 && this._point === 1)) this._context.closePath();
    this._line = 1 - this._line;
  }
  point(x, y) {
    x = +x, y = +y;
    switch (this._point) {
      case 0: {
        this._point = 1;
        if (this._line) this._context.lineTo(x, y);
        else this._context.moveTo(x, y);
        break;
      }
      case 1: this._point = 2; // proceed
      default: {
        if (this._x) this._context.bezierCurveTo(this._x0 = (this._x0 + x) / 2, this._y0, this._x0, y, x, y);
        else this._context.bezierCurveTo(this._x0, this._y0 = (this._y0 + y) / 2, x, this._y0, x, y);
        break;
      }
    }
    this._x0 = x, this._y0 = y;
  }
}

export function bumpX(context) {
  return new Bump(context, true);
}

export function bumpY(context) {
  return new Bump(context, false);
}