import mlfn from '../common/mlfn';
import e0fn from '../common/e0fn';
import e1fn from '../common/e1fn';
import e2fn from '../common/e2fn';
import e3fn from '../common/e3fn';
import gN from '../common/gN';
import adjust_lon from '../common/adjust_lon';
import adjust_lat from '../common/adjust_lat';
import imlfn from '../common/imlfn';
import {HALF_PI, EPSLN} from '../constants/values';

export function init() {
  if (!this.sphere) {
    this.e0 = e0fn(this.es);
    this.e1 = e1fn(this.es);
    this.e2 = e2fn(this.es);
    this.e3 = e3fn(this.es);
    this.ml0 = this.a * mlfn(this.e0, this.e1, this.e2, this.e3, this.lat0);
  }
}

/* Cassini forward equations--mapping lat,long to x,y
  -----------------------------------------------------------------------*/
export function forward(p) {

  /* Forward equations
      -----------------*/
  var x, y;
  var lam = p.x;
  var phi = p.y;
  lam = adjust_lon(lam - this.long0);

  if (this.sphere) {
    x = this.a * Math.asin(Math.cos(phi) * Math.sin(lam));
    y = this.a * (Math.atan2(Math.tan(phi), Math.cos(lam)) - this.lat0);
  }
  else {
    //ellipsoid
    var sinphi = Math.sin(phi);
    var cosphi = Math.cos(phi);
    var nl = gN(this.a, this.e, sinphi);
    var tl = Math.tan(phi) * Math.tan(phi);
    var al = lam * Math.cos(phi);
    var asq = al * al;
    var cl = this.es * cosphi * cosphi / (1 - this.es);
    var ml = this.a * mlfn(this.e0, this.e1, this.e2, this.e3, phi);

    x = nl * al * (1 - asq * tl * (1 / 6 - (8 - tl + 8 * cl) * asq / 120));
    y = ml - this.ml0 + nl * sinphi / cosphi * asq * (0.5 + (5 - tl + 6 * cl) * asq / 24);


  }

  p.x = x + this.x0;
  p.y = y + this.y0;
  return p;
}

/* Inverse equations
  -----------------*/
export function inverse(p) {
  p.x -= this.x0;
  p.y -= this.y0;
  var x = p.x / this.a;
  var y = p.y / this.a;
  var phi, lam;

  if (this.sphere) {
    var dd = y + this.lat0;
    phi = Math.asin(Math.sin(dd) * Math.cos(x));
    lam = Math.atan2(Math.tan(x), Math.cos(dd));
  }
  else {
    /* ellipsoid */
    var ml1 = this.ml0 / this.a + y;
    var phi1 = imlfn(ml1, this.e0, this.e1, this.e2, this.e3);
    if (Math.abs(Math.abs(phi1) - HALF_PI) <= EPSLN) {
      p.x = this.long0;
      p.y = HALF_PI;
      if (y < 0) {
        p.y *= -1;
      }
      return p;
    }
    var nl1 = gN(this.a, this.e, Math.sin(phi1));

    var rl1 = nl1 * nl1 * nl1 / this.a / this.a * (1 - this.es);
    var tl1 = Math.pow(Math.tan(phi1), 2);
    var dl = x * this.a / nl1;
    var dsq = dl * dl;
    phi = phi1 - nl1 * Math.tan(phi1) / rl1 * dl * dl * (0.5 - (1 + 3 * tl1) * dl * dl / 24);
    lam = dl * (1 - dsq * (tl1 / 3 + (1 + 3 * tl1) * tl1 * dsq / 15)) / Math.cos(phi1);

  }

  p.x = adjust_lon(lam + this.long0);
  p.y = adjust_lat(phi);
  return p;

}

export var names = ["Cassini", "Cassini_Soldner", "cass"];
export default {
  init: init,
  forward: forward,
  inverse: inverse,
  names: names
};