/*
 * Copyright ©2019 Hal Perkins.  All rights reserved.  Permission is
 * hereby granted to students registered for University of Washington
 * CSE 331 for use solely during Spring Quarter 2019 for purposes of
 * the course.  No other use, copying, distribution, or modification
 * is permitted without prior written consent. Copyrights for
 * third-party components of this work must be honored.  Instructors
 * interested in reusing these course materials should contact the
 * author.
 */

package pathfinder.datastructures;

/**
 * Represents an immutable cartesian coordinate point.
 */
public class Point {

  // AF(this) =
  //      the x coordinate -> x
  //      the y coordinate -> y;

  // Rep Invariant:
  //      Double.isFinite(x) &&
  //      Double.isFinite(y)
  //   In other words, both x and y are not infinite and not NaN

  /**
   * The left object in the pair.
   */
  private final double x;

  /**
   * The right object in the pair.
   */
  private final double y;

  /**
   * Constructs a new ordered pair using the provided coordinates. Neither coordinate
   * may be NaN or infinite.
   *
   * @param x The x coordinate.
   * @param y The y coordinate.
   * @throws IllegalArgumentException if x or y are NaN or infinite.
   */
  public Point(double x, double y) {
    if(!Double.isFinite(x) || !Double.isFinite(y)) {
      throw new IllegalArgumentException("x and y cannot be NaN or infinite.");
    }
    this.x = x;
    this.y = y;
    // checkRep not necessary, the representation fields are final and immutable.
  }

  /**
   * @return The x coordinate of this point.
   */
  public double getX() {
    return x;
  }

  /**
   * @return The y coordinate of this point.
   */
  public double getY() {
    return y;
  }

  /**
   * @param obj An object to compare {@code this} to for equality.
   * @return {@literal true} if and only if {@code obj} is a point representing the same
   * location in cartesian space.
   */
  @Override
  public boolean equals(Object obj) {
    if(!(obj instanceof Point)) {
      return false;
    }
    Point other = (Point) obj;
    return (Double.compare(this.x, other.x) == 0) && (Double.compare(this.y, other.y) == 0);
  }

  @Override
  public String toString() {
    return "(" + x + ", " + y + ")";
  }

  @Override
  public int hashCode() {
    return (31 * Double.hashCode(x)) + Double.hashCode(y);
  }
}