import adjust_lon from '../common/adjust_lon';

export function init() {
  this.a = 6377397.155;
  this.es = 0.006674372230614;
  this.e = Math.sqrt(this.es);
  if (!this.lat0) {
    this.lat0 = 0.863937979737193;
  }
  if (!this.long0) {
    this.long0 = 0.7417649320975901 - 0.308341501185665;
  }
  /* if scale not set default to 0.9999 */
  if (!this.k0) {
    this.k0 = 0.9999;
  }
  this.s45 = 0.785398163397448; /* 45 */
  this.s90 = 2 * this.s45;
  this.fi0 = this.lat0;
  this.e2 = this.es;
  this.e = Math.sqrt(this.e2);
  this.alfa = Math.sqrt(1 + (this.e2 * Math.pow(Math.cos(this.fi0), 4)) / (1 - this.e2));
  this.uq = 1.04216856380474;
  this.u0 = Math.asin(Math.sin(this.fi0) / this.alfa);
  this.g = Math.pow((1 + this.e * Math.sin(this.fi0)) / (1 - this.e * Math.sin(this.fi0)), this.alfa * this.e / 2);
  this.k = Math.tan(this.u0 / 2 + this.s45) / Math.pow(Math.tan(this.fi0 / 2 + this.s45), this.alfa) * this.g;
  this.k1 = this.k0;
  this.n0 = this.a * Math.sqrt(1 - this.e2) / (1 - this.e2 * Math.pow(Math.sin(this.fi0), 2));
  this.s0 = 1.37008346281555;
  this.n = Math.sin(this.s0);
  this.ro0 = this.k1 * this.n0 / Math.tan(this.s0);
  this.ad = this.s90 - this.uq;
}

/* ellipsoid */
/* calculate xy from lat/lon */
/* Constants, identical to inverse transform function */
export function forward(p) {
  var gfi, u, deltav, s, d, eps, ro;
  var lon = p.x;
  var lat = p.y;
  var delta_lon = adjust_lon(lon - this.long0);
  /* Transformation */
  gfi = Math.pow(((1 + this.e * Math.sin(lat)) / (1 - this.e * Math.sin(lat))), (this.alfa * this.e / 2));
  u = 2 * (Math.atan(this.k * Math.pow(Math.tan(lat / 2 + this.s45), this.alfa) / gfi) - this.s45);
  deltav = -delta_lon * this.alfa;
  s = Math.asin(Math.cos(this.ad) * Math.sin(u) + Math.sin(this.ad) * Math.cos(u) * Math.cos(deltav));
  d = Math.asin(Math.cos(u) * Math.sin(deltav) / Math.cos(s));
  eps = this.n * d;
  ro = this.ro0 * Math.pow(Math.tan(this.s0 / 2 + this.s45), this.n) / Math.pow(Math.tan(s / 2 + this.s45), this.n);
  p.y = ro * Math.cos(eps) / 1;
  p.x = ro * Math.sin(eps) / 1;

  if (!this.czech) {
    p.y *= -1;
    p.x *= -1;
  }
  return (p);
}

/* calculate lat/lon from xy */
export function inverse(p) {
  var u, deltav, s, d, eps, ro, fi1;
  var ok;

  /* Transformation */
  /* revert y, x*/
  var tmp = p.x;
  p.x = p.y;
  p.y = tmp;
  if (!this.czech) {
    p.y *= -1;
    p.x *= -1;
  }
  ro = Math.sqrt(p.x * p.x + p.y * p.y);
  eps = Math.atan2(p.y, p.x);
  d = eps / Math.sin(this.s0);
  s = 2 * (Math.atan(Math.pow(this.ro0 / ro, 1 / this.n) * Math.tan(this.s0 / 2 + this.s45)) - this.s45);
  u = Math.asin(Math.cos(this.ad) * Math.sin(s) - Math.sin(this.ad) * Math.cos(s) * Math.cos(d));
  deltav = Math.asin(Math.cos(s) * Math.sin(d) / Math.cos(u));
  p.x = this.long0 - deltav / this.alfa;
  fi1 = u;
  ok = 0;
  var iter = 0;
  do {
    p.y = 2 * (Math.atan(Math.pow(this.k, - 1 / this.alfa) * Math.pow(Math.tan(u / 2 + this.s45), 1 / this.alfa) * Math.pow((1 + this.e * Math.sin(fi1)) / (1 - this.e * Math.sin(fi1)), this.e / 2)) - this.s45);
    if (Math.abs(fi1 - p.y) < 0.0000000001) {
      ok = 1;
    }
    fi1 = p.y;
    iter += 1;
  } while (ok === 0 && iter < 15);
  if (iter >= 15) {
    return null;
  }

  return (p);
}

export var names = ["Krovak", "krovak"];
export default {
  init: init,
  forward: forward,
  inverse: inverse,
  names: names
};