exports.Poly = function(n) {
  this.n = n == undefined ? 128 : n * 2;
  this.midScreenX = Bangle.appRect.w / 2; // g.getWidth() / 2;
  this.midScreenY = Bangle.appRect.h / 2; // g.getHeight() / 2;
  this.points = new Int32Array(this.n);
  this._index = 0;
  this.minX = undefined;
  this.maxX = undefined;
  this.minY = undefined;
  this.maxY = undefined;
  this.width = 0;
  this.height = 0;

  this.getPoints = function() {
  return this.points.subarray(0, this._index+1);
  };

  this.addPoint = function(x, y) {
		this.points[this._index] = x;
		this._index++;
		this.points[this._index] = y;
		this._index++;
    if (this.minX === undefined) {
      this.minX = x;
      this.maxX = x;
      this.minY = y;
      this.maxY = y;
    }
    this.minX = Math.min(this.minX, x);
    this.maxX = Math.max(this.maxX, x);

    this.minY = Math.min(this.minY, y);
    this.maxY = Math.max(this.maxY, y);

    this.width = this.maxX - this.minX + 1;
    this.height = this.maxY - this.minY + 1;

    this.midX = Math.round(this.width / 2);
    this.midY = Math.round(this.height / 2);

    this.centerX = this.minX + this.midX + 1;
    this.centerY = this.minY + this.midY + 1;

    return this;
  };

  this.p = this.addPoint;

  this.getWidth = function() {
    return this.width;
  };

  this.getHeight = function() {
    return this.height;
  };

  this.getmidY = function() {
    return this.midY;
  };

  this.getmidX = function() {
    return this.midX;
  };

  /**
  * Convert an angle and radius into x and y cooridinates
  * @param a angle in radians
  * @param r radius, defaults to half screen width
  * @param x x cooridinate, defaults to center
  * @param y y coordinate, defaults to center
  */
  this.addRadialPoint = function(a, r, x, y) {
    r = r === undefined ? this.midScreenX : r;
    x = x === undefined ? this.midScreenX : x;
    y = y === undefined ? this.midScreenY : y;
    this.addPoint(Math.round((Math.cos(a) * r)) + x, Math.round((Math.sin(a) * r)) + y);
    return this;
  };

  this.makeArc = function(a1, a2, r, x, y) {
    const aS = a1; // < a2 ? a1 : a2;
    const aE = a2; // > a1 ? a2 + 0.001: a1 + 0.001;
    if (a1 < a2) {
      for (let a = aS; a <= aE; a+=0.1) {
        this.addRadialPoint(a, r, x, y);
      }
    } else {
      for (let a = aS; a >= aE; a-=0.1) {
        this.addRadialPoint(a, r, x, y);
      }
    }
    this.addRadialPoint(a2, r, x, y);  // make sure we actually have a point at the end angle
   // this.addPoint(x, y); // center point
    return this;
  };

  this.makeSeg = function(a1, a2, r1, r2, x, y) {
    this.makeArc(a1 , a2, r1, x, y);
    this.makeArc(a2, a1, r2, x, y);
    return this;
  };

}