/*
    * Copyright (C) 2017 Alberto Irurueta Carro (alberto@irurueta.com)
    *
    * Licensed 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 com.irurueta.geometry;
  
  import java.io.Serializable;
  import java.util.Objects;
  
  /**
   * Subclass of Point2D defining an homogeneous 2D point.
   * An homogeneous 2d point is defined by three coordinates: (x,y,w), where
   * x and y are the horizontal and vertical coordinates, respectively, and w
   * is a normalization (homogenization) factor. Homogeneous 2d points at
   * infinity are expressed using w=0 (x,y,0) where (x,y) describe the direction
   * of the 2d point towards infinity.
   * Inhomogeneous 2d points can be transformed into homogeneous 2d points by
   * setting the w coordinate to one (w=1, not at infinity) as follows:
   * Inhomogeneous 2d point (x,y) -< Homogeneous 2d point (x,y,1).
   */
  public class HomogeneousPoint2D extends Point2D implements Serializable {
  
      /**
       * Default threshold to consider a point is located at infinity.
       */
      private static final double DEFAULT_INFINITY_THRESHOLD = 1e-10;
  
      /**
       * Machine precision.
       */
      private static final double PRECISION = 1e-12;
  
      /**
       * Defines the X coordinate of an homogeneous 2D point.
       */
      private double x;
  
      /**
       * Defines the Y coordinate of an homogeneous 2D point.
       */
      private double y;
  
      /**
       * Defines the W coordinate of an homogeneous 2D point.
       */
      private double w;
  
      /**
       * Determines whether this point is already normalized.
       */
      private boolean normalized;
  
      /**
       * Empty constructor.
       */
      public HomogeneousPoint2D() {
          super();
          x = y = 0.0;
          w = 1.0;
          normalized = false;
      }
  
      /**
       * Constructor of this class. This constructor sets a new homogeneous
       * v array containing the coordinates X, Y and W of the given point.
       *
       * @param v Array of length 3 containing the 2D coordinates of an
       *          homogeneous point.
       * @throws IllegalArgumentException Raised when the size of the array is
       *                                  different of 3.
       */
      public HomogeneousPoint2D(final double[] v) {
          super();
          setCoordinates(v);
      }
  
      /**
       * Constructor of this class. This constructor sets a new homogeneous 2D
       * point using the coordinates X, Y and W of the given point.
       *
       * @param x X coordinate of the given 2D point.
       * @param y Y coordinate of the given 2D point.
       * @param w W coordinate of the given 2D point.
       */
      public HomogeneousPoint2D(final double x, final double y, final double w) {
          this.x = x;
          this.y = y;
         this.w = w;
         normalized = false;
     }
 
     /**
      * This constructor sets a new homogeneous 2D point using as initialization
      * provided Point2D instance.
      *
      * @param point Point to initialize new instance to.
      */
     public HomogeneousPoint2D(final Point2D point) {
         setCoordinates(point);
     }
 
     /**
      * Returns the X coordinate of the given homogeneous 2D point instance.
      *
      * @return X coordinate.
      */
     public double getX() {
         return x;
     }
 
     /**
      * Sets the X coordinate of this homogeneous point.
      *
      * @param x X coordinate.
      */
     public void setX(final double x) {
         this.x = x;
         normalized = false;
     }
 
     /**
      * Returns the Y coordinate of the given homogeneous 2D point instance.
      *
      * @return Y coordinate.
      */
     public double getY() {
         return y;
     }
 
     /**
      * Sets the Y coordinate of this homogeneous point.
      *
      * @param y Y coordinate.
      */
     public void setY(final double y) {
         this.y = y;
         normalized = false;
     }
 
     /**
      * Returns the W coordinate of the given homogeneous 2D point instance.
      *
      * @return W coordinate.
      */
     public double getW() {
         return w;
     }
 
     /**
      * Sets the W coordinate of this homogeneous point.
      *
      * @param w W coordinate.
      */
     public void setW(final double w) {
         this.w = w;
         normalized = false;
     }
 
     /**
      * Sets the coordinates of this homogeneous 2D point by using provided X,
      * Y and W coordinates.
      *
      * @param x X coordinate.
      * @param y Y coordinate.
      * @param w W coordinate.
      */
     public void setCoordinates(final double x, final double y, final double w) {
         this.x = x;
         this.y = y;
         this.w = w;
         normalized = false;
     }
 
     /**
      * Sets the coordinates of a 2d point using an array containing its
      * coordinates.
      *
      * @param v Array containing the coordinates of the point.
      * @throws IllegalArgumentException Raised if provided array does not have
      *                                  a valid size.
      */
     @Override
     public final void setCoordinates(final double[] v) {
         if (v.length != POINT2D_HOMOGENEOUS_COORDINATES_LENGTH) {
             throw new IllegalArgumentException();
         } else {
             x = v[0];
             y = v[1];
             w = v[2];
             normalized = false;
         }
     }
 
     /**
      * Sets coordinates of this instance using the coordinates of provided 2D
      * point.
      *
      * @param point Input point.
      */
     @Override
     public final void setCoordinates(final Point2D point) {
         switch (point.getType()) {
             case INHOMOGENEOUS_COORDINATES:
                 final var inhomPoint = (InhomogeneousPoint2D) point;
                 x = inhomPoint.getX();
                 y = inhomPoint.getY();
                 w = 1.0;
                 normalized = false;
                 break;
 
             case HOMOGENEOUS_COORDINATES:
             default:
                 final var homPoint = (HomogeneousPoint2D) point;
                 x = homPoint.getX();
                 y = homPoint.getY();
                 w = homPoint.getW();
                 normalized = false;
                 break;
         }
     }
 
     /**
      * Returns X homogeneous coordinate of this 2d point.
      *
      * @return X homogeneous coordinate.
      */
     @Override
     public double getHomX() {
         return getX();
     }
 
     /**
      * Returns Y homogeneous coordinate of this 2d point.
      *
      * @return Y homogeneous coordinate.
      */
     @Override
     public double getHomY() {
         return getY();
     }
 
     /**
      * Returns W homogeneous coordinate of this 2d point.
      *
      * @return W homogeneous coordinate.
      */
     @Override
     public double getHomW() {
         return getW();
     }
 
     /**
      * Sets coordinates of this 2d point instance using provided homogeneous
      * coordinates.
      *
      * @param homX x homogeneous coordinate.
      * @param homY y homogeneous coordinate.
      * @param homW w homogeneous coordinate.
      */
     @Override
     public void setHomogeneousCoordinates(final double homX, final double homY, final double homW) {
         setCoordinates(homX, homY, homW);
     }
 
     /**
      * Returns X inhomogeneous coordinate of this 2d point.
      *
      * @return X inhomogeneous coordinate.
      */
     @Override
     public double getInhomX() {
         return (x / w);
     }
 
     /**
      * Sets X inhomogeneous coordinate of this 2d point.
      *
      * @param inhomX inhomogeneous coordinate.
      */
     @Override
     public void setInhomX(final double inhomX) {
         x = inhomX * w;
         normalized = false;
     }
 
     /**
      * Returns Y inhomogeneous coordinate of this 2d point.
      *
      * @return Y inhomogeneous coordinate.
      */
     @Override
     public double getInhomY() {
         return (y / w);
     }
 
     /**
      * Sets Y inhomogeneous coordinate of this 2d point.
      *
      * @param inhomY Y inhomogeneous coordinate.
      */
     @Override
     public void setInhomY(final double inhomY) {
         y = inhomY * w;
         normalized = false;
     }
 
     /**
      * Sets coordinates of this 2d point instance using provided inhomogeneous
      * coordinates.
      *
      * @param inhomX x inhomogeneous coordinate.
      * @param inhomY y inhomogeneous coordinate.
      */
     @Override
     public void setInhomogeneousCoordinates(final double inhomX, final double inhomY) {
         x = inhomX;
         y = inhomY;
         w = 1.0;
         normalized = false;
     }
 
     /**
      * Checks if provided object equals current 2D point.
      *
      * @param obj Object to compare.
      * @return True if both objects are considered to be equal, false otherwise.
      */
     @Override
     public boolean equals(final Object obj) {
         if (!(obj instanceof Point2D point)) {
             return false;
         }
         if (obj == this) {
             return true;
         }
 
         return equals(point);
     }
 
     /**
      * Returns hash code value.
      *
      * @return Hash code value.
      */
     @Override
     public int hashCode() {
         return Objects.hash(x, y, w);
     }
 
     /**
      * Checks if the homogeneous 2d point described by this instance equals the
      * input {@link Point2D} (using a comparison threshold).
      *
      * @param point     Point that will be compared to.
      * @param threshold threshold grade of tolerance to determine whether the
      *                  points are equal or not. It is used because due to machine precision, the
      *                  values might not be exactly equal (if not provided
      *                  DEFAULT_COMPARISON_THRESHOLD is used).
      * @return True if current point and input point are the same, false
      * otherwise.
      * @throws IllegalArgumentException Raised if threshold is negative.
      */
     @Override
     public boolean equals(final Point2D point, final double threshold) {
         if (point.getType() == CoordinatesType.INHOMOGENEOUS_COORDINATES) {
             return equals((InhomogeneousPoint2D) point, threshold);
         } else {
             return equals((HomogeneousPoint2D) point, threshold);
         }
     }
 
     /**
      * Checks if the homogeneous 2d point described by this instance equals the
      * input HomogeneousPoint2d (using a comparison threshold).
      *
      * @param point     Point that will be compared to.
      * @param threshold threshold grade of tolerance to determine whether the
      *                  points are equal or not. It is used because due to machine precision, the
      *                  values might not be exactly equal (if not provided
      *                  DEFAULT_COMPARISON_THRESHOLD is used).
      * @return True if current point and input point are the same, false
      * otherwise.
      * @throws IllegalArgumentException Raised if threshold is negative.
      */
     public boolean equals(final HomogeneousPoint2D point, final double threshold) {
         if (threshold < MIN_THRESHOLD) {
             throw new IllegalArgumentException();
         }
 
         normalize();
         point.normalize();
 
         // compute sign for the case when points have different sign
         final var signThis = (w > 0.0) ? 1.0 : -1.0;
         final var signPoint = (point.w > 0.0) ? 1.0 : -1.0;
 
         final var normThis = Math.sqrt(x * x + y * y + w * w) * signThis;
         final var normPoint = Math.sqrt(point.x * point.x + point.y * point.y + point.w * point.w) * signPoint;
 
         final var validX = Math.abs(x / normThis - point.x / normPoint) <= threshold;
         final var validY = Math.abs(y / normThis - point.y / normPoint) <= threshold;
         final var validW = Math.abs(w / normThis - point.w / normPoint) <= threshold;
 
         return (validX && validY && validW);
     }
 
     /**
      * Checks if the homogeneous 2d point described by this instance equals the
      * input HomogeneousPoint2d (using a comparison threshold).
      *
      * @param point Point that will be compared to.
      * @return True if current point and input point are the same, false
      * otherwise.
      */
     public boolean equals(final HomogeneousPoint2D point) {
         return equals(point, DEFAULT_COMPARISON_THRESHOLD);
     }
 
     /**
      * Checks if the homogeneous 2d point described by this instance equals the
      * input InhomogeneousPoint2d (using a comparison threshold).
      *
      * @param point     Point that will be compared to.
      * @param threshold threshold grade of tolerance to determine whether the
      *                  points are equal or not. It is used because due to machine precision, the
      *                  values might not be exactly equal (if not provided
      *                  DEFAULT_COMPARISON_THRESHOLD is used).
      * @return True if current point and input point are the same, false
      * otherwise.
      * @throws IllegalArgumentException Raised if threshold is negative.
      */
     public boolean equals(final InhomogeneousPoint2D point, final double threshold) {
         if (threshold < MIN_THRESHOLD) {
             throw new IllegalArgumentException();
         }
 
         final var dX = Math.abs(point.getX() - (x / w)) <= threshold;
         final var dY = Math.abs(point.getY() - (y / w)) <= threshold;
         return (dX && dY);
     }
 
     /**
      * Checks if the homogeneous 2d point described by this instance equals the
      * input InhomogeneousPoint2d (using a comparison threshold).
      *
      * @param point Point that will be compared to.
      * @return True if current point and input point are the same, false
      * otherwise.
      */
     public boolean equals(final InhomogeneousPoint2D point) {
         return equals(point, DEFAULT_COMPARISON_THRESHOLD);
     }
 
     /**
      * Checks whether this Point2D is at infinity or not.
      *
      * @return True if the point is at infinity. False otherwise.
      */
     @Override
     public boolean isAtInfinity() {
         return isAtInfinity(DEFAULT_INFINITY_THRESHOLD);
     }
 
     /**
      * Checks whether this homogeneous 2D point is at infinity or not. An
      * homogeneous 2D point is at infinity when W coordinates are equal or close
      * to zero.
      *
      * @param threshold Grade of tolerance to determine whether the point is at
      *                  infinity or not. It is used because due to machine precision, the values
      *                  might not be exactly equal.
      * @return True if point is at infinity, false otherwise.
      * @throws IllegalArgumentException Raised if threshold is negative.
      */
     public boolean isAtInfinity(final double threshold) {
         if (threshold < MIN_THRESHOLD) {
             throw new IllegalArgumentException();
         }
 
         return (Math.abs(w) <= threshold);
     }
 
     /**
      * Returns the type of coordinates used to represent a Point2D.
      *
      * @return Type of coordinates of this 2d point.
      */
     @Override
     public CoordinatesType getType() {
         return CoordinatesType.HOMOGENEOUS_COORDINATES;
     }
 
     /**
      * Method to normalize a 2d point by dividing all homogeneous components by
      * its norm. This only applies to homogeneous 2d points, because they are
      * defined up to scale.
      */
     @SuppressWarnings("DuplicatedCode")
     @Override
     public void normalize() {
         if (!normalized) {
             final var norm = Math.sqrt(x * x + y * y + w * w);
             if (norm > PRECISION) {
                 x /= norm;
                 y /= norm;
                 w /= norm;
                 normalized = true;
             }
         }
     }
 
     /**
      * Returns boolean indicating whether this point has already been mNormalized
      *
      * @return True if mNormalized, false otherwise.
      */
     @Override
     public boolean isNormalized() {
         return normalized;
     }
 
     /**
      * Converts this instance into an inhomogeneous 2D point and returns the
      * result as a new inhomogeneous 2D point instance.
      *
      * @return Converts and returns this point as an inhomogeneous 2D point.
      */
     public InhomogeneousPoint2D toInhomogeneous() {
         return new InhomogeneousPoint2D(x / w, y / w);
     }
 
     /**
      * Returns an array containing the coordinates of this Point2D.
      *
      * @return Array containing coordinates of this Point2D.
      */
     @Override
     public double[] asArray() {
         final var out = new double[POINT2D_HOMOGENEOUS_COORDINATES_LENGTH];
         asArray(out);
         return out;
     }
 
     /**
      * Uses provided array to store the coordinates of this HomogeneousPoint2D
      *
      * @param array Array where coordinates will be stored.
      * @throws IllegalArgumentException Raised if length of array is not 3.
      */
     @Override
     public void asArray(double[] array) {
         if (array.length != POINT2D_HOMOGENEOUS_COORDINATES_LENGTH) {
             throw new IllegalArgumentException();
         }
         array[0] = x;
         array[1] = y;
         array[2] = w;
     }
 }