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/*
 * Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
 *
 *   Portions of this software were developed by the Unidata Program at the
 *   University Corporation for Atmospheric Research.
 *
 *   Access and use of this software shall impose the following obligations
 *   and understandings on the user. The user is granted the right, without
 *   any fee or cost, to use, copy, modify, alter, enhance and distribute
 *   this software, and any derivative works thereof, and its supporting
 *   documentation for any purpose whatsoever, provided that this entire
 *   notice appears in all copies of the software, derivative works and
 *   supporting documentation.  Further, UCAR requests that the user credit
 *   UCAR/Unidata in any publications that result from the use of this
 *   software or in any product that includes this software. The names UCAR
 *   and/or Unidata, however, may not be used in any advertising or publicity
 *   to endorse or promote any products or commercial entity unless specific
 *   written permission is obtained from UCAR/Unidata. The user also
 *   understands that UCAR/Unidata is not obligated to provide the user with
 *   any support, consulting, training or assistance of any kind with regard
 *   to the use, operation and performance of this software nor to provide
 *   the user with any updates, revisions, new versions or "bug fixes."
 *
 *   THIS SOFTWARE IS PROVIDED BY UCAR/UNIDATA "AS IS" AND ANY EXPRESS OR
 *   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 *   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *   DISCLAIMED. IN NO EVENT SHALL UCAR/UNIDATA BE LIABLE FOR ANY SPECIAL,
 *   INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 *   FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 *   NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 *   WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
 */

package ucar.unidata.geoloc;

import net.jcip.annotations.Immutable;

import java.io.Serializable;
import java.util.Formatter;

/**
 * Defines the shape of the earth ellipsoid.
 *
 * @author Russ Rew
 */
@Immutable
public class Earth implements Serializable {
  private static final double earthRadius = 6371229.;  // canonical radius of the spherical earth in meters

  /**
   * Get canonical radius of spherical earth, in meters
   *
   * @return canonical radius of spherical earth in meters
   */
  public static double getRadius() {
    return earthRadius;
  }

  ///////////////////////////////////////////////////////////////////////////////////
  protected final double eccentricity; // eccentricity
  protected final double eccentricitySquared; // eccentricity squared
  protected final double equatorRadius; // equatorial radius (semimajor axis)
  protected final double poleRadius; // polar radius (semiminor axis)
  protected final double flattening; // flattening
  protected final String name;

  /**
   * Spherical earth with canonical radius.
   */
  public Earth() {
    this(earthRadius);
  }

  /**
   * Create a spherical earth.
   *
   * @param radius radius of spherical earth.
   */
  public Earth(double radius) {
    this.equatorRadius = radius;
    this.poleRadius = radius;
    this.flattening = 0.0;
    this.eccentricity = 1.0;
    this.eccentricitySquared = 1.0;
    this.name = "spherical_earth";
  }

  /**
   * Create an ellipsoidal earth.
   * The reciprocalFlattening is used if not zero, else the poleRadius is used.
   *
   * @param equatorRadius        equatorial radius (semimajor axis) in meters, must be specified
   * @param poleRadius           polar radius (semiminor axis) in meters
   * @param reciprocalFlattening inverse flattening = 1/flattening = a / (a-b)
   */
  public Earth(double equatorRadius, double poleRadius, double reciprocalFlattening) {
    this(equatorRadius, poleRadius, reciprocalFlattening, "ellipsoidal_earth");
  }


  /**
   * Create an ellipsoidal earth with a name.
   *
   * @param equatorRadius        equatorial radius (semimajor axis) in meters, must be specified
   * @param poleRadius           polar radius (semiminor axis) in meters; if reciprocalFlattening != 0 then this is ignored
   * @param reciprocalFlattening inverse flattening = 1/flattening = a / (a-b); if 0 use the poleRadius to calculate
   * @param name                 name of the Earth
   */
  public Earth(double equatorRadius, double poleRadius, double reciprocalFlattening, String name) {
    this.equatorRadius = equatorRadius;
    this.name = name;
    if (reciprocalFlattening != 0) {
      flattening = 1.0 / reciprocalFlattening;
      eccentricitySquared = 2 * flattening - flattening * flattening;
      this.poleRadius = equatorRadius * Math.sqrt(1.0 - eccentricitySquared);
    } else {
      this.poleRadius = poleRadius;
      eccentricitySquared = 1.0 - (poleRadius * poleRadius) / (equatorRadius * equatorRadius);
      flattening = 1.0 - poleRadius / equatorRadius;
    }
    eccentricity = Math.sqrt(eccentricitySquared);
  }

  public boolean isSpherical() {
    return flattening == 0.0;
  }

  /**
   * Specify earth with equatorial and polar radius.
   *
   * @param a semimajor (equatorial) radius, in meters.
   * @param b semiminor (polar) radius, in meters.
   *
   * Earth(double a, double b) {
   * this.equatorRadius = a;
   * this.poleRadius = b;
   * eccentricitySquared = 1.0 - (b * b) / (a * a);
   * flattening = 1.0 - b / a;
   * }
   *
   *
   * Specify earth with semimajor radius a, and flattening f.
   * b = a(1-flattening)
   *
   * @param a    semimajor (equatorial) radius, in meters.
   * @param f    flattening.
   * @param fake fake
   *
   * Earth(double a, double f, boolean fake) {
   * this.equatorRadius = a;
   * this.flattening = flattening;
   * poleRadius = a * (1.0 - flattening);
   * eccentricitySquared = 1.0 - (poleRadius * poleRadius) / (a * a);
   * }
   *
   * @return _more_
   */


  /**
   * Get the equatorial radius (semimajor axis) of the earth, in meters.
   *
   * @return equatorial radius (semimajor axis) in meters
   */
  public double getMajor() {
    return equatorRadius;
  }

  /**
   * Get the polar radius (semiminor axis) of the earth, in meters.
   *
   * @return polar radius (semiminor axis) in meters
   */
  public double getMinor() {
    return poleRadius;
  }

  /**
   * Get the Name property.
   *
   * @return The Name
   */
  public String getName() {
    return name;
  }

  /**
   * Get the Eccentricity property.
   *
   * @return The Eccentricity
   */
  public double getEccentricity() {
    return eccentricity;
  }

  /**
   * Get the EccentricitySquared property.
   *
   * @return The EccentricitySquared
   */
  public double getEccentricitySquared() {
    return eccentricitySquared;
  }

  /**
   * Get the EquatorRadius property.
   *
   * @return The EquatorRadius
   */
  public double getEquatorRadius() {
    return equatorRadius;
  }

  /**
   * Get the PoleRadius property.
   *
   * @return The PoleRadius
   */
  public double getPoleRadius() {
    return poleRadius;
  }

  /**
   * Get the Flattening property.
   *
   * @return The Flattening
   */
  public double getFlattening() {
    return flattening;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;

    Earth earth = (Earth) o;

    if (Double.compare(earth.equatorRadius, equatorRadius) != 0) return false;
    if (Double.compare(earth.poleRadius, poleRadius) != 0) return false;
    // if (name != null ? !name.equals(earth.name) : earth.name != null) return false;

    return true;
  }

  @Override
  public int hashCode() {
    int result;
    long temp;
    temp = equatorRadius != +0.0d ? Double.doubleToLongBits(equatorRadius) : 0L;
    result = (int) (temp ^ (temp >>> 32));
    temp = poleRadius != +0.0d ? Double.doubleToLongBits(poleRadius) : 0L;
    result = 31 * result + (int) (temp ^ (temp >>> 32));
    result = 31 * result + (name != null ? name.hashCode() : 0);
    return result;
  }

  @Override
  public String toString() {
    Formatter ff = new Formatter();
    ff.format("equatorRadius=%f inverseFlattening=%f", equatorRadius,
            (1.0 / flattening));
    return ff.toString();
  }

}