/*
    * 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.commons.geometry.spherical.oned;
  
  import java.util.Comparator;
  
  import org.apache.commons.geometry.core.Point;
  import org.apache.commons.geometry.core.internal.DoubleFunction1N;
  import org.apache.commons.geometry.core.internal.SimpleTupleFormat;
  import org.apache.commons.geometry.euclidean.twod.PolarCoordinates;
  import org.apache.commons.geometry.euclidean.twod.Vector2D;
  import org.apache.commons.numbers.angle.Angle;
  import org.apache.commons.numbers.core.Precision;
  
  /** This class represents a point on the 1-sphere, or in other words, an
   * azimuth angle on a circle. The value of the azimuth angle is not normalized
   * by default, meaning that instances can be constructed representing negative
   * values or values greater than {@code 2pi}. However, instances separated by a
   * multiple of {@code 2pi} are considered equivalent for most methods, with the
   * exceptions being {@link #equals(Object)} and {@link #hashCode()}, where the
   * azimuth values must match exactly in order for instances to be considered
   * equal.
   *
   * <p>Instances of this class are guaranteed to be immutable.</p>
   */
  public final class Point1S implements Point<Point1S> {
  
      /** A point with coordinates set to {@code 0*pi}. */
      public static final Point1S ZERO = Point1S.of(0.0);
  
      /** A point with coordinates set to {@code pi}. */
      public static final Point1S PI = Point1S.of(Math.PI);
  
      /** A point with all coordinates set to NaN. */
      public static final Point1S NaN = Point1S.of(Double.NaN);
  
      /** Comparator that sorts points by normalized azimuth in ascending order.
       * Points are only considered equal if their normalized azimuths match exactly.
       * Null arguments are evaluated as being greater than non-null arguments.
       * @see #getNormalizedAzimuth()
       */
      public static final Comparator<Point1S> NORMALIZED_AZIMUTH_ASCENDING_ORDER = (a, b) -> {
          int cmp = 0;
  
          if (a != null && b != null) {
              cmp = Double.compare(a.getNormalizedAzimuth(), b.getNormalizedAzimuth());
          } else if (a != null) {
              cmp = -1;
          } else if (b != null) {
              cmp = 1;
          }
  
          return cmp;
      };
  
      /** Azimuthal angle in radians. */
      private final double azimuth;
  
      /** Normalized azimuth value in the range {@code [0, 2pi)}. */
      private final double normalizedAzimuth;
  
      /** Build a point from its internal components.
       * @param azimuth azimuth angle
       * @param normalizedAzimuth azimuth angle normalized to the range {@code [0, 2pi)}
       */
      private Point1S(final double azimuth, final double normalizedAzimuth) {
          this.azimuth  = azimuth;
          this.normalizedAzimuth = normalizedAzimuth;
      }
  
      /** Get the azimuth angle in radians. This value is not normalized and
       * can be any floating point number.
       * @return azimuth angle
       * @see Point1S#of(double)
       */
      public double getAzimuth() {
          return azimuth;
      }
  
      /** Get the azimuth angle normalized to the range {@code [0, 2pi)}.
       * @return the azimuth angle normalized to the range {@code [0, 2pi)}.
       */
      public double getNormalizedAzimuth() {
          return normalizedAzimuth;
      }
 
     /** Get the normalized vector corresponding to this azimuth angle in 2D Euclidean space.
      * @return normalized vector
      */
     public Vector2D getVector() {
         if (isFinite()) {
             return PolarCoordinates.toCartesian(1, azimuth);
         }
 
         return null;
     }
 
     /** {@inheritDoc} */
     @Override
     public int getDimension() {
         return 1;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isNaN() {
         return Double.isNaN(azimuth);
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isInfinite() {
         return !isNaN() && Double.isInfinite(azimuth);
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isFinite() {
         return Double.isFinite(azimuth);
     }
 
     /** {@inheritDoc}
      *
      * <p>The returned value is the shortest angular distance between
      * the two points, in the range {@code [0, pi]}.</p>
      */
     @Override
     public double distance(final Point1S point) {
         return distance(this, point);
     }
 
     /** Return the signed distance (angular separation) between this instance and the
      * given point in the range {@code [-pi, pi)}. If {@code p1} is the current instance,
      * {@code p2} the given point, and {@code d} the signed distance, then
      * {@code p1.getAzimuth() + d} is an angle equivalent to {@code p2.getAzimuth()}.
      * @param point point to compute the signed distance to
      * @return the signed distance between this instance and the given point in the range
      *      {@code [-pi, pi)}
      */
     public double signedDistance(final Point1S point) {
         return signedDistance(this, point);
     }
 
     /** Return an equivalent point with an azimuth value at or above the given base
      * value in radians. The returned point has an azimuth value in the range
      * {@code [base, base + 2pi)}.
      * @param base base azimuth to place this instance's azimuth value above
      * @return a point equivalent to the current instance but with an azimuth
      *      value in the range {@code [base, base + 2pi)}
      * @throws IllegalArgumentException if the azimuth value is NaN or infinite and
      *      cannot be normalized
      */
     public Point1S above(final double base) {
         if (isFinite()) {
             final double az = Angle.Rad.normalizer(base).applyAsDouble(azimuth);
             return new Point1S(az, normalizedAzimuth);
         }
         throw new IllegalArgumentException("Cannot normalize azimuth value: " + azimuth);
     }
 
     /** Return an equivalent point with an azimuth value at or above the given base.
      * The returned point has an azimuth value in the range {@code [base, base + 2pi)}.
      * @param base point to place this instance's azimuth value above
      * @return a point equivalent to the current instance but with an azimuth
      *      value in the range {@code [base, base + 2pi)}
      * @throws IllegalArgumentException if the azimuth value is NaN or infinite and
      *      cannot be normalized
      */
     public Point1S above(final Point1S base) {
         return above(base.getAzimuth());
     }
 
     /** Get the point exactly opposite this point on the circle, {@code pi} distance away.
      * The azimuth of the antipodal point is in the range {@code [0, 2pi)}.
      * @return the point exactly opposite this point on the circle
      */
     public Point1S antipodal() {
         double az = normalizedAzimuth + Math.PI;
         if (az >= Angle.TWO_PI) {
             az -= Angle.TWO_PI;
         }
 
         return Point1S.of(az);
     }
 
     /** Return true if this instance is equivalent to the argument. The points are
      * considered equivalent if the shortest angular distance between them is equal to
      * zero as evaluated by the given precision context. This means that points that differ
      * in azimuth by multiples of {@code 2pi} are considered equivalent.
      * @param other point to compare with
      * @param precision precision context used for floating point comparisons
      * @return true if this instance is equivalent to the argument
      */
     public boolean eq(final Point1S other, final Precision.DoubleEquivalence precision) {
         final double dist = signedDistance(other);
         return precision.eqZero(dist);
     }
 
     /**
      * Get a hashCode for the point. Points normally must have exactly the
      * same azimuth angles in order to have the same hash code. Points
      * will angles that differ by multiples of {@code 2pi} will not
      * necessarily have the same hash code.
      *
      * <p>All NaN values have the same hash code.</p>
      *
      * @return a hash code value for this object
      */
     @Override
     public int hashCode() {
         if (isNaN()) {
             return 542;
         }
         return (Double.hashCode(azimuth) >> 17) ^
                 Double.hashCode(normalizedAzimuth);
     }
 
     /** Test for the exact equality of two points on the 1-sphere.
      *
      * <p>If all coordinates of the given points are exactly the same, and none are
      * <code>Double.NaN</code>, the points are considered to be equal. Points with
      * azimuth values separated by multiples of {@code 2pi} are <em>not</em> considered
      * equal.</p>
      *
      * <p><code>NaN</code> coordinates are considered to affect globally the vector
      * and be equals to each other - i.e, if either (or all) coordinates of the
      * point are equal to <code>Double.NaN</code>, the point is equal to
      * {@link #NaN}.</p>
      *
      * @param other Object to test for equality to this
      * @return true if two points on the 1-sphere objects are exactly equal, false if
      *         object is null, not an instance of Point1S, or
      *         not equal to this Point1S instance
      *
      */
     @Override
     public boolean equals(final Object other) {
         if (this == other) {
             return true;
         }
 
         if (other instanceof Point1S) {
             final Point1S rhs = (Point1S) other;
 
             if (rhs.isNaN()) {
                 return this.isNaN();
             }
 
             return Double.compare(azimuth, rhs.azimuth) == 0 &&
                     Double.compare(normalizedAzimuth, rhs.normalizedAzimuth) == 0;
         }
 
         return false;
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString() {
         return SimpleTupleFormat.getDefault().format(getAzimuth());
     }
 
     /** Create a new point instance from the given azimuth angle.
      * @param azimuth azimuth angle in radians
      * @return point instance with the given azimuth angle
      * @see #getAzimuth()
      */
     public static Point1S of(final double azimuth) {
         final double normalizedAzimuth = PolarCoordinates.normalizeAzimuth(azimuth);
 
         return new Point1S(azimuth, normalizedAzimuth);
     }
 
     /** Create a new point instance from the given azimuth angle.
      * @param azimuth azimuth azimuth angle
      * @return point instance with the given azimuth angle
      * @see #getAzimuth()
      */
     public static Point1S of(final Angle azimuth) {
         return of(azimuth.toRad().getAsDouble());
     }
 
     /** Create a new point instance from the given Euclidean 2D vector. The returned point
      * will have an azimuth value equal to the angle between the positive x-axis and the
      * given vector, measured in a counter-clockwise direction.
      * @param vector 3D vector to create the point from
      * @return a new point instance with an azimuth value equal to the angle between the given
      *      vector and the positive x-axis, measured in a counter-clockwise direction
      */
     public static Point1S from(final Vector2D vector) {
         final PolarCoordinates polar = PolarCoordinates.fromCartesian(vector);
         final double az = polar.getAzimuth();
 
         return new Point1S(az, az);
     }
 
     /** Create a new point instance containing an azimuth value equal to that of the
      * given set of polar coordinates.
      * @param polar polar coordinates to convert to a point
      * @return a new point instance containing an azimuth value equal to that of
      *      the given set of polar coordinates.
      */
     public static Point1S from(final PolarCoordinates polar) {
         final double az = polar.getAzimuth();
 
         return new Point1S(az, az);
     }
 
     /** Parse the given string and returns a new point instance. The expected string
      * format is the same as that returned by {@link #toString()}.
      * @param str the string to parse
      * @return point instance represented by the string
      * @throws IllegalArgumentException if the given string has an invalid format
      */
     public static Point1S parse(final String str) {
         return SimpleTupleFormat.getDefault().parse(str, (DoubleFunction1N<Point1S>) Point1S::of);
     }
 
     /** Compute the signed shortest distance (angular separation) between two points. The return
      * value is in the range {@code [-pi, pi)} and is such that {@code p1.getAzimuth() + d}
      * (where {@code d} is the signed distance) is an angle equivalent to {@code p2.getAzimuth()}.
      * @param p1 first point
      * @param p2 second point
      * @return the signed angular separation between p1 and p2, in the range {@code [-pi, pi)}.
      */
     public static double signedDistance(final Point1S p1, final Point1S p2) {
         double dist = p2.normalizedAzimuth - p1.normalizedAzimuth;
         if (dist < -Math.PI) {
             dist += Angle.TWO_PI;
         }
         if (dist >= Math.PI) {
             dist -= Angle.TWO_PI;
         }
         return dist;
     }
 
     /** Compute the shortest distance (angular separation) between two points. The returned
      * value is in the range {@code [0, pi]}. This method is equal to the absolute value of
      * the {@link #signedDistance(Point1S, Point1S) signed distance}.
      * @param p1 first point
      * @param p2 second point
      * @return the angular separation between p1 and p2, in the range {@code [0, pi]}.
      * @see #signedDistance(Point1S, Point1S)
      */
     public static double distance(final Point1S p1, final Point1S p2) {
         return Math.abs(signedDistance(p1, p2));
     }
 }