/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.spatial3d.geom;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * This class represents a point on the surface of a sphere or ellipsoid.
 *
 * @lucene.experimental
 */
public class GeoPoint extends Vector implements SerializableObject {

  // By making lazily-evaluated variables be "volatile", we guarantee atomicity when they
  // are updated.  This is necessary if we are using these classes in a multi-thread fashion,
  // because we don't try to synchronize for the lazy computation.

  /**
   * This is the lazily-evaluated magnitude. Some constructors include it, but others don't, and we
   * try not to create extra computation by always computing it. Does not need to be synchronized
   * for thread safety, because depends wholly on immutable variables of this class.
   */
  protected volatile double magnitude = Double.NEGATIVE_INFINITY;

  /**
   * Lazily-evaluated latitude. Does not need to be synchronized for thread safety, because depends
   * wholly on immutable variables of this class.
   */
  protected volatile double latitude = Double.NEGATIVE_INFINITY;

  /**
   * Lazily-evaluated longitude. Does not need to be synchronized for thread safety, because depends
   * wholly on immutable variables of this class.
   */
  protected volatile double longitude = Double.NEGATIVE_INFINITY;

  /**
   * Construct a GeoPoint from the trig functions of a lat and lon pair.
   *
   * @param planetModel is the planetModel to put the point on.
   * @param sinLat is the sin of the latitude.
   * @param sinLon is the sin of the longitude.
   * @param cosLat is the cos of the latitude.
   * @param cosLon is the cos of the longitude.
   * @param lat is the latitude.
   * @param lon is the longitude.
   */
  public GeoPoint(
      final PlanetModel planetModel,
      final double sinLat,
      final double sinLon,
      final double cosLat,
      final double cosLon,
      final double lat,
      final double lon) {
    this(
        computeDesiredEllipsoidMagnitude(planetModel, cosLat * cosLon, cosLat * sinLon, sinLat),
        cosLat * cosLon,
        cosLat * sinLon,
        sinLat,
        lat,
        lon);
  }

  /**
   * Construct a GeoPoint from the trig functions of a lat and lon pair.
   *
   * @param planetModel is the planetModel to put the point on.
   * @param sinLat is the sin of the latitude.
   * @param sinLon is the sin of the longitude.
   * @param cosLat is the cos of the latitude.
   * @param cosLon is the cos of the longitude.
   */
  public GeoPoint(
      final PlanetModel planetModel,
      final double sinLat,
      final double sinLon,
      final double cosLat,
      final double cosLon) {
    this(
        computeDesiredEllipsoidMagnitude(planetModel, cosLat * cosLon, cosLat * sinLon, sinLat),
        cosLat * cosLon,
        cosLat * sinLon,
        sinLat);
  }

  /**
   * Construct a GeoPoint from a latitude/longitude pair.
   *
   * @param planetModel is the planetModel to put the point on.
   * @param lat is the latitude.
   * @param lon is the longitude.
   */
  public GeoPoint(final PlanetModel planetModel, final double lat, final double lon) {
    this(planetModel, Math.sin(lat), Math.sin(lon), Math.cos(lat), Math.cos(lon), lat, lon);
  }

  /**
   * Construct a GeoPoint from an input stream.
   *
   * @param planetModel is the planet model
   * @param inputStream is the input stream
   */
  public GeoPoint(final PlanetModel planetModel, final InputStream inputStream) throws IOException {
    this(inputStream);
  }

  /**
   * Construct a GeoPoint from an input stream with no planet model.
   *
   * @param inputStream is the input stream
   */
  public GeoPoint(final InputStream inputStream) throws IOException {
    // Note: this relies on left-right parameter execution order!!  Much code depends on that though
    // and it is apparently in a java spec:
    // https://stackoverflow.com/questions/2201688/order-of-execution-of-parameters-guarantees-in-java
    this(
        SerializableObject.readDouble(inputStream),
        SerializableObject.readDouble(inputStream),
        SerializableObject.readDouble(inputStream),
        SerializableObject.readDouble(inputStream),
        SerializableObject.readDouble(inputStream));
  }

  /**
   * Construct a GeoPoint from five unchecked parameters: lat, lon, x, y, z. This is primarily used
   * for deserialization, but can also be used to fully initialize a point externally.
   *
   * @param lat is the latitude in radians
   * @param lon is the longitude in radians
   * @param x is the unit x value
   * @param y is the unit y value
   * @param z is the unit z value
   */
  public GeoPoint(
      final double lat, final double lon, final double x, final double y, final double z) {
    super(x, y, z);
    this.latitude = lat;
    this.longitude = lon;
  }

  /**
   * Construct a GeoPoint from a unit (x,y,z) vector and a magnitude.
   *
   * @param magnitude is the desired magnitude, provided to put the point on the ellipsoid.
   * @param x is the unit x value.
   * @param y is the unit y value.
   * @param z is the unit z value.
   * @param lat is the latitude.
   * @param lon is the longitude.
   */
  public GeoPoint(
      final double magnitude,
      final double x,
      final double y,
      final double z,
      double lat,
      double lon) {
    super(x * magnitude, y * magnitude, z * magnitude);
    this.magnitude = magnitude;
    if (lat > Math.PI * 0.5 || lat < -Math.PI * 0.5) {
      throw new IllegalArgumentException(
          "Latitude " + lat + " is out of range: must range from -Math.PI/2 to Math.PI/2");
    }
    if (lon < -Math.PI || lon > Math.PI) {
      throw new IllegalArgumentException(
          "Longitude " + lon + " is out of range: must range from -Math.PI to Math.PI");
    }
    this.latitude = lat;
    this.longitude = lon;
  }

  /**
   * Construct a GeoPoint from a unit (x,y,z) vector and a magnitude.
   *
   * @param magnitude is the desired magnitude, provided to put the point on the ellipsoid.
   * @param x is the unit x value.
   * @param y is the unit y value.
   * @param z is the unit z value.
   */
  public GeoPoint(final double magnitude, final double x, final double y, final double z) {
    super(x * magnitude, y * magnitude, z * magnitude);
    this.magnitude = magnitude;
  }

  /**
   * Construct a GeoPoint from an (x,y,z) value. The (x,y,z) tuple must be on the desired ellipsoid.
   *
   * @param x is the ellipsoid point x value.
   * @param y is the ellipsoid point y value.
   * @param z is the ellipsoid point z value.
   */
  public GeoPoint(final double x, final double y, final double z) {
    super(x, y, z);
  }

  @Override
  public void write(final OutputStream outputStream) throws IOException {
    SerializableObject.writeDouble(outputStream, getLatitude());
    SerializableObject.writeDouble(outputStream, getLongitude());
    SerializableObject.writeDouble(outputStream, x);
    SerializableObject.writeDouble(outputStream, y);
    SerializableObject.writeDouble(outputStream, z);
  }

  /**
   * Compute an arc distance between two points. Note: this is an angular distance, and not a
   * surface distance, and is therefore independent of planet model. For surface distance, see
   * {@link PlanetModel#surfaceDistance(GeoPoint, GeoPoint)}
   *
   * @param v is the second point.
   * @return the angle, in radians, between the two points.
   */
  public double arcDistance(final Vector v) {
    return Tools.safeAcos(dotProduct(v) / (magnitude() * v.magnitude()));
  }

  /**
   * Compute an arc distance between two points.
   *
   * @param x is the x part of the second point.
   * @param y is the y part of the second point.
   * @param z is the z part of the second point.
   * @return the angle, in radians, between the two points.
   */
  public double arcDistance(final double x, final double y, final double z) {
    return Tools.safeAcos(dotProduct(x, y, z) / (magnitude() * Vector.magnitude(x, y, z)));
  }

  /**
   * Compute the latitude for the point.
   *
   * @return the latitude.
   */
  public double getLatitude() {
    double lat = this.latitude; // volatile-read once
    if (lat == Double.NEGATIVE_INFINITY) {
      this.latitude = lat = Math.asin(z / magnitude());
    }
    return lat;
  }

  /**
   * Compute the longitude for the point.
   *
   * @return the longitude value. Uses 0.0 if there is no computable longitude.
   */
  public double getLongitude() {
    double lon = this.longitude; // volatile-read once
    if (lon == Double.NEGATIVE_INFINITY) {
      if (Math.abs(x) < MINIMUM_RESOLUTION && Math.abs(y) < MINIMUM_RESOLUTION) {
        this.longitude = lon = 0.0;
      } else {
        this.longitude = lon = Math.atan2(y, x);
      }
    }
    return lon;
  }

  /**
   * Compute the linear magnitude of the point.
   *
   * @return the magnitude.
   */
  @Override
  public double magnitude() {
    double mag = this.magnitude; // volatile-read once
    if (mag == Double.NEGATIVE_INFINITY) {
      this.magnitude = mag = super.magnitude();
    }
    return mag;
  }

  /**
   * Compute whether point matches another.
   *
   * @param p is the other point.
   * @return true if the same.
   */
  public boolean isIdentical(final GeoPoint p) {
    return isIdentical(p.x, p.y, p.z);
  }

  /**
   * Compute whether point matches another.
   *
   * @param x is the x value
   * @param y is the y value
   * @param z is the z value
   * @return true if the same.
   */
  public boolean isIdentical(final double x, final double y, final double z) {
    return Math.abs(this.x - x) < MINIMUM_RESOLUTION
        && Math.abs(this.y - y) < MINIMUM_RESOLUTION
        && Math.abs(this.z - z) < MINIMUM_RESOLUTION;
  }

  @Override
  public String toString() {
    if (this.longitude == Double.NEGATIVE_INFINITY) {
      return super.toString();
    }
    return "[lat=" + getLatitude() + ", lon=" + getLongitude() + "(" + super.toString() + ")]";
  }
}
