/**
 * Copyright (c) 2001-2017 Mathew A. Nelson and Robocode contributors
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://robocode.sourceforge.net/license/epl-v10.html
 */
package samplesentry;


import robocode.*;
import robocode.util.Utils;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Point2D;
import java.util.*;


/**
 * BorderGuard - is a sample robot that demonstrates how the BorderSentry interface can be used for
 * creating a robot that guards the border area of the battle field, and which is efficient against
 * robots trying to hide at corners and robots sneaking around near the borders.
 * <p>
 * This robot is somewhat advanced due to:<br>
 * 1) it uses linear targeting for predicting how to hit robots that moves in straight lines.<br>
 * 2) it will only fire at a robot, if it figures out that its bullets will do damage to that
 * particular robot, e.g. when the robots predicted future position will be within the sentry border
 * attack range.<br>
 * 3) it has an efficient scanner that keeps the scan angle as little as possible to get as new
 * scanned data for enemy robots as possible.<br>
 * 4) it picks a target robot to fire at, which is the nearest robot our robot will be able to
 * damage (by predicting its future position using linear targeting).<br>
 * 5) it only moves along the borders of the battle field and constantly changes its direction, so
 * it is not an easy target, and it will try to get as close to its target robot as possible.<br>
 * <p>
 * Lots of improvements can be made to this robot by copying it - making it even stronger. The
 * intention with of this sample robot is to serve as a more advanced example of how a AdvancedRobot
 * can be made, and how it can be structured as most sample robots are far simpler.
 * <p>
 * 
 * Credits goes to the hard working Robocoders at the RoboWiki. :-)
 * <p>
 * 
 * This robot makes use of the Oldest Scanned melee scanner from the RoboWiki:<br>
 * http://robowiki.net/wiki/Melee_Radar
 * <p>
 * 
 * In addition, it makes use of the Exact Non-iterative Solution for Linear Targeting from the
 * RoboWiki:<br>
 * http://robowiki.net/wiki/Linear_Targeting
 * 
 * @author Flemming N. Larsen
 * 
 * @version 1.0
 * 
 * @since 1.9.0.0
 */
public class BorderGuard extends AdvancedRobot implements BorderSentry {

	// Constants
	final double FIREPOWER = 3; // Max. power => violent as this robot can afford it!
	final double HALF_ROBOT_SIZE = 18; // Robot size is 36x36 units, so the half size is 18 units

	// Map containing data for all scanned robots.
	// The key to the map is a robot name and the value is an object containing robot data.
	final Map<String, RobotData> enemyMap;

	// Scanning direction, where the radar turns to the right with positive values, and turns
	// to the left with negative values.
	double scanDir = 1;

	// Oldest scanned robot. Can be null.
	RobotData oldestScanned;

	// Target robot for the gun. Can be null meaning that there is currently no target robot.
	RobotData target;

	// Last time when the robot shifted its direction
	long lastDirectionShift;

	// Current direction, where 1 means ahead (forward) and -1 means back
	int direction = 1;

	/**
	 * Constructs this robot.
	 */
	public BorderGuard() {
		// We initialize a specialized HashMap that uses a linked list for the access order.
		// This means that the last accessed robot entry is listed first, when we iterate over its
		// values. This robot always sweep the radar towards the oldest scanned robot.
		enemyMap = new LinkedHashMap<String, RobotData>(5, 2, true);
	}

	/**
	 * Main method that is called by the game when the robot engage in the next round of a battle.
	 */
	@Override
	public void run() {
		// Do initialization stuff here before the loop
		initialize();

		// Loop forever. If the robot does not take action, the game will disable our robot!
		while (true) {
			// Handle a single turn...

			// Handle the radar that scans enemy robots
			handleRadar();
			// Handle the gun by turning it and fire at our target
			handleGun();
			// Move the robot around on the battlefield
			moveRobot();

			// Scan for other robots. Note that this method will execute all pending commands for
			// the next turn. Hence, scan() ends the turn for our robot.
			scan();
		}
	}

	/**
	 * This method is called by the game when your robot sees another robot, i.e. when the robot's
	 * radar scan "hits" another robot.
	 * 
	 * @param scannedRobotEvent
	 *            is a ScannedRobotEvent event.
	 */
	@Override
	public void onScannedRobot(ScannedRobotEvent scannedRobotEvent) {
		// Check that the scanned robot is not a sentry robot
		if (!scannedRobotEvent.isSentryRobot()) {
			// The scanned robot is not a sentry robot...

			// Update the enemy map
			updateEnemyMap(scannedRobotEvent);

			// Update the scan direction
			updateScanDirection(scannedRobotEvent);

			// Update enemy target positions
			updateEnemyTargetPositions();
		}
	}

	/**
	 * This method is called by the game when another robot dies.
	 * 
	 * @param robotDeathEvent
	 *            is the RobotDeathEvent that occurs, when another robot dies, which contains data
	 *            for the robot that died.
	 */
	@Override
	public void onRobotDeath(RobotDeathEvent robotDeathEvent) {
		// Gets the name of the robot that died
		final String deadRobotName = robotDeathEvent.getName();

		// Remove the robot data for the robot that died from the enemy map
		enemyMap.remove(deadRobotName);

		// Remove the data entry for the oldest scanned robot, if we have such an entry
		if (oldestScanned != null && oldestScanned.name.equals(deadRobotName)) {
			oldestScanned = null;
		}
		if (target != null && target.name.equals(deadRobotName)) {
			target = null;
		}
	}

	/**
	 * This method is called by the every time the robot is painted. In order to see the painting,
	 * make sure to enable the Paint button on the robot console for this robot.
	 * 
	 * @param g
	 *            is the {@link Graphics2D} object, which is the graphics context used for painting
	 *            various shapes like rectangles, circles, lines etc. on top of the battlefield for
	 *            debugging graphics.
	 */
	@Override
	public void onPaint(Graphics2D g) {
		// Set the line width to 2 pixels
		g.setStroke(new BasicStroke(2f));

		// Prepare colors for painting the scanned coordinate and target coordinate
		Color color1 = new Color(0x00, 0xFF, 0x00, 0x40); // Green with 25% alpha blending
		Color color2 = new Color(0xFF, 0xFF, 0x00, 0x40); // Yellow with 25% alhpa blending

		// Paint a two circles for each robot in the enemy map. One circle where the robot was
		// scanned the last time, and another circle where our robot must point the gun in order to
		// hit it (target coordinate). In addition, a line is drawn between these circles.
		for (RobotData robot : enemyMap.values()) {
			// Paint the two circles and a line
			fillCircle(g, robot.scannedX, robot.scannedY, color1); // scanned coordinate
			fillCircle(g, robot.targetX, robot.targetY, color2); // target coordinate
			g.setColor(color1);
			g.drawLine((int) robot.scannedX, (int) robot.scannedY, (int) robot.targetX, (int) robot.targetY);
		}

		// Paint a two circles for the target robot. One circle where the robot was
		// scanned the last time, and another circle where our robot must point the gun in order to
		// hit it (target coordinate). In addition, a line is drawn between these circles.
		if (target != null) {
			// Prepare colors for painting the scanned coordinate and target coordinate
			color1 = new Color(0xFF, 0x7F, 0x00, 0x40); // Orange with 25% alpha blending
			color2 = new Color(0xFF, 0x00, 0x00, 0x80); // Red with 50% alpha blending

			// Paint the two circles and a line
			fillCircle(g, target.scannedX, target.scannedY, color1); // scanned coordinate
			fillCircle(g, target.targetX, target.targetY, color2); // target coordinate
			g.setColor(color1);
			g.drawLine((int) target.scannedX, (int) target.scannedY, (int) target.targetX, (int) target.targetY);
		}
	}

	/**
	 * Initializes this robot before a new round in a battle.
	 */
	private void initialize() {
		// Let the robot body, gun, and radar turn independently of each other
		setAdjustRadarForGunTurn(true);
		setAdjustGunForRobotTurn(true);

		// Set robot colors
		setBodyColor(new Color(0x5C, 0x33, 0x17)); // Chocolate Brown
		setGunColor(new Color(0x45, 0x8B, 0x74)); // Aqua Marine
		setRadarColor(new Color(0xD2, 0x69, 0x1E)); // Orange Chocolate
		setBulletColor(new Color(0xFF, 0xD3, 0x9B)); // Burly wood
		setScanColor(new Color(0xCA, 0xFF, 0x70)); // Olive Green
	}

	/**
	 * This method handles the radar that scans for enemy robots.
	 */
	private void handleRadar() {
		// Set the radar to turn infinitely to the right if the scan direction is positive;
		// otherwise the radar is moved to the left, if the scan direction is negative.
		// Notice that onScannedRobot(ScannedRobotEvent) is responsible for determining the scan
		// direction.
		setTurnRadarRightRadians(scanDir * Double.POSITIVE_INFINITY);
	}

	/**
	 * Method that handles the gun be turning it and fire at a target.
	 */
	private void handleGun() {
		// Update our target robot to fire at
		updateTarget();
		// Update the gun direction
		updateGunDirection();
		// Fires the gun, when it is ready
		fireGunWhenReady();
	}

	/**
	 * Method that moves our robot around the battlefield.
	 */
	private void moveRobot() {

		// The movement strategy is to move as close to our target robot as possible.
		// Our robot should move along the borders all the time, vertically or horizontally.
		// When we get close to our target, or have no where to go, our robot should shift its
		// direction from side to side so it does not stand still at any time.
		// If the robot stands still, it will be an easy target for enemy robots.

		int newDirection = direction;

		// Get closer to our target if we have a target robot
		if (target != null) {
			// Calculate the range from the walls/borders, our robot should keep within
			int borderRange = getSentryBorderSize() - 20;

			// The horizontal and vertical flags are used for determining, if our robot should
			// move horizontal or vertical.
			boolean horizontal = false;
			boolean vertical = false;

			// Initialize the new heading of the robot to the current heading of the robot
			double newHeading = getHeadingRadians();

			// Check if our robot is at the upper or lower border and hence should move horizontally
			if (getY() < borderRange || getY() > getBattleFieldHeight() - borderRange) {
				horizontal = true;
			}
			// Check if our robot is at the left or right border and hence should move vertically
			if (getX() < borderRange || getX() > getBattleFieldWidth() - borderRange) {
				vertical = true;
			}

			// If we are in one of the corners of the battlefield, we could move both horizontally
			// or vertically.
			// In this situation, we need to choose one of the two directions.
			if (horizontal && vertical) {
				// If the horizontal distance to our target is lesser than the vertical distance,
				// then we choose to move vertically, and hence we clear the horizontal flag.
				if (Math.abs(target.targetX - getX()) <= Math.abs(target.targetY - getY())) {
					horizontal = false; // Do not move horizontally => move vertically
				}
			}
			// Adjust the heading of our robot with 90 degrees, if it must move horizontally.
			// Otherwise the calculated heading is towards moving vertically.
			if (horizontal) {
				newHeading -= Math.PI / 2;
			}
			// Set the robot to turn left the amount of radians we have just calculated
			setTurnLeftRadians(Utils.normalRelativeAngle(newHeading));

			// Check if our robot has finished turning, i.e. has less than 1 degrees left to turn
			if (Math.abs(getTurnRemaining()) < 1 || Math.abs(getVelocity()) < 0.01) {
				// If we should move horizontally, the set the robot to move ahead with the
				// horizontal distance to the target robot. Otherwise, use the vertical distance.
				double delta; // delta is the delta distance to move
				if (horizontal) {
					delta = target.targetX - getX();
				} else {
					delta = target.targetY - getY();
				}
				setAhead(delta);

				// Set the new direction of our robot to 1 (meaning move forward) if the delta
				// distance is positive; otherwise it is set to -1 (meaning move backward).
				newDirection = delta > 0 ? 1 : -1;

				// Check if more than 10 turns have past since we changed the direction the last
				// time
				if (getTime() - lastDirectionShift > 10) {
					// If so, set the new direction to be the reverse direction if the velocity < 1
					if (Math.abs(getVelocity()) < 1) {
						newDirection = direction * -1;
					}
					// Check if the direction really changed
					if (newDirection != direction) {
						// If the new direction != current direction, then set the current direction
						// to be the new direction and save the current time so we know when we
						// changed the direction the last time.
						direction = newDirection;
						lastDirectionShift = getTime();
					}
				}
			}
		}
		// Set ahead 100 units forward or backward depending on the direction
		setAhead(100 * direction);
	}

	/**
	 * Method the updates the enemy map based on new scan data for a scanned robot.
	 * 
	 * @param scannedRobotEvent
	 *            is a ScannedRobotEvent event containing data about a scanned robot.
	 */
	private void updateEnemyMap(ScannedRobotEvent scannedRobotEvent) {
		// Gets the name of the scanned robot
		final String scannedRobotName = scannedRobotEvent.getName();

		// Get robot data for the scanned robot, if we have an entry in the enemy map
		RobotData scannedRobot = enemyMap.get(scannedRobotName);

		// Check if data entry exists for the scanned robot
		if (scannedRobot == null) {
			// No data entry exists => Create a new data entry for the scanned robot
			scannedRobot = new RobotData(scannedRobotEvent);
			// Put the new data entry into the enemy map
			enemyMap.put(scannedRobotName, scannedRobot);
		} else {
			// Data entry exists => Update the current entry with new scanned data
			scannedRobot.update(scannedRobotEvent);
		}
	}

	/**
	 * Method that updates the direction of the radar based on new scan data for a scanned robot.
	 * 
	 * @param scannedRobotEvent
	 *            is a ScannedRobotEvent event containing data about a scanned robot.
	 */
	private void updateScanDirection(ScannedRobotEvent scannedRobotEvent) {
		// Gets the name of the scanned robot
		final String scannedRobotName = scannedRobotEvent.getName();

		// Change the scanning direction if and only if we have no record for the oldest scanned
		// robot or the scanned robot IS the oldest scanned robot (based on the name) AND the enemy
		// map contains scanned data entries for ALL robots (the size of the enemy map is equal to
		// the number of opponent robots found by calling the getOthers() method).
		if ((oldestScanned == null || scannedRobotName.equals(oldestScanned.name)) && enemyMap.size() == getOthers()) {

			// Get the oldest scanned robot data from our LinkedHashMap, where the first value
			// contains the oldest accessed entry, which is the robot we need to get.
			RobotData oldestScannedRobot = enemyMap.values().iterator().next();

			// Get the recent scanned position (x,y) of the oldest scanned robot
			double x = oldestScannedRobot.scannedX;
			double y = oldestScannedRobot.scannedY;

			// Get the heading of our robot
			double ourHeading = getRadarHeadingRadians();

			// Calculate the bearing to the oldest scanned robot.
			// The bearing is the delta angle between the heading of our robot and the other robot,
			// which can be a positive or negative angle.
			double bearing = bearingTo(ourHeading, x, y);

			// Update the scan direction based on the bearing.
			// If the bearing is positive, the radar will be moved to the right.
			// If the bearing is negative, the radar will be moved to the left.
			scanDir = bearing;
		}
	}

	/**
	 * Updates the target positions for all enemies. The target position is the position our robot
	 * must fire at in order to hit the target robot. This robot uses Linear Targeting (Exact
	 * Non-iterative Solution) as described on the RoboWiki here:
	 * http://robowiki.net/wiki/Linear_Targeting
	 */
	private void updateEnemyTargetPositions() {
		// Go thru all robots in the enemy map
		for (RobotData enemy : enemyMap.values()) {

			// Variables prefixed with e- refer to enemy and b- refer to bullet
			double bV = Rules.getBulletSpeed(FIREPOWER);
			double eX = enemy.scannedX;
			double eY = enemy.scannedY;
			double eV = enemy.scannedVelocity;
			double eH = enemy.scannedHeading;

			// These constants make calculating the quadratic coefficients below easier
			double A = (eX - getX()) / bV;
			double B = (eY - getY()) / bV;
			double C = eV / bV * Math.sin(eH);
			double D = eV / bV * Math.cos(eH);

			// Quadratic coefficients: a*(1/t)^2 + b*(1/t) + c = 0
			double a = A * A + B * B;
			double b = 2 * (A * C + B * D);
			double c = (C * C + D * D - 1);

			// If the discriminant of the quadratic formula is >= 0, we have a solution meaning that
			// at some time, t, the bullet will hit the enemy robot if we fire at it now.
			double discrim = b * b - 4 * a * c;
			if (discrim >= 0) {
				// Reciprocal of quadratic formula. Calculate the two possible solution for the
				// time, t
				double t1 = 2 * a / (-b - Math.sqrt(discrim));
				double t2 = 2 * a / (-b + Math.sqrt(discrim));

				// Choose the minimum positive time or select the one closest to 0, if the time is
				// negative
				double t = Math.min(t1, t2) >= 0 ? Math.min(t1, t2) : Math.max(t1, t2);

				// Calculate the target position (x,y) for the enemy. That is the point that our gun
				// should point at in order to hit the enemy at the time, t.
				double targetX = eX + eV * t * Math.sin(eH);
				double targetY = eY + eV * t * Math.cos(eH);

				// Assume enemy stops at walls. Hence, we limit that target position at the walls.
				double minX = HALF_ROBOT_SIZE;
				double minY = HALF_ROBOT_SIZE;
				double maxX = getBattleFieldWidth() - HALF_ROBOT_SIZE;
				double maxY = getBattleFieldHeight() - HALF_ROBOT_SIZE;

				enemy.targetX = limit(targetX, minX, maxX);
				enemy.targetY = limit(targetY, minY, maxY);
			}
		}
	}

	/**
	 * Updates which enemy robot from the enemy map that should be our current target.
	 */
	private void updateTarget() {
		// Set target to null, meaning that we have no target robot yet
		target = null;

		// Create a list over possible target robots that is a copy of robot data from the enemy map
		List<RobotData> targets = new ArrayList<RobotData>(enemyMap.values());

		// Run thru all the possible target robots and remove those that are outside the attack
		// range for this border sentry robot as our robot cannot do harm to robots outside its
		// range.
		Iterator<RobotData> it = targets.iterator();
		while (it.hasNext()) {
			RobotData robot = it.next();
			if (isOutsideAttackRange(robot.targetX, robot.targetY)) {
				it.remove();
			}
		}

		// Set the target robot to be the one among all possible target robots that is closest to
		// our robot.
		double minDist = Double.POSITIVE_INFINITY;
		for (RobotData robot : targets) {
			double dist = distanceTo(robot.targetX, robot.targetY);
			if (dist < minDist) {
				minDist = dist;
				target = robot;
			}
		}

		// If we still haven't got a target robot, then take the first one from our list of target
		// robots if the list is not empty.
		if (target == null && targets.size() > 0) {
			target = targets.get(0);
		}
	}

	/**
	 * Method that updates the gun direction to point at the current target.
	 */
	private void updateGunDirection() {
		// Only update the gun direction, if we have a current target
		if (target != null) {
			// Calculate the bearing between the gun and the target, which can be positive or
			// negative
			double targetBearing = bearingTo(getGunHeadingRadians(), target.targetX, target.targetY);
			// Set the gun to turn right the amount of radians defined by the bearing to the target
			setTurnGunRightRadians(targetBearing); // positive => turn right, negative => turn left
		}
	}

	/**
	 * Method that fires a bullet when the gun is ready to fire.
	 */
	private void fireGunWhenReady() {
		// We only fire the fun, when we have a target robot
		if (target != null) {
			// Only fire when the angle of the gun is pointing at our (virtual) target robot

			// Calculate the distance between between our robot and the target robot
			double dist = distanceTo(target.targetX, target.targetY);
			// Angle that "covers" the the target robot from its center to its edge
			double angle = Math.atan(HALF_ROBOT_SIZE / dist);

			// Check if the remaining angle (turn) to move the gun is less than our calculated cover
			// angle
			if (Math.abs(getGunTurnRemaining()) < angle) {
				// If so, our gun should be pointing at our target so we can hit it => fire!!
				setFire(FIREPOWER);
			}
		}
	}

	/**
	 * Method that checks if a coordinate (x,y) is outside the Border Sentry's attack range.
	 * 
	 * @param x
	 *            is the x coordinate.
	 * @param y
	 *            is the y coordinate.
	 * @return true if the coordinate is outside the attack range; false otherwise.
	 */
	private boolean isOutsideAttackRange(double x, double y) {
		double minBorderX = getSentryBorderSize();
		double minBorderY = getSentryBorderSize();
		double maxBorderX = getBattleFieldWidth() - getSentryBorderSize();
		double maxBorderY = getBattleFieldHeight() - getSentryBorderSize();

		return (x > minBorderX) && (y > minBorderY) && (x < maxBorderX) && (y < maxBorderY);
	}

	/**
	 * Method that returns a value that is guaranteed to be within a value range defined by a
	 * minimum and maximum value based on an input value.<br>
	 * If the input value is lesser than the minimum value, the returned value will be set to the
	 * minimum value.<br>
	 * If the input value is greater than the maximum value, the returned value will be set to the
	 * maximum value.<br>
	 * Otherwise the returned value will be equal to the input value.
	 * 
	 * @param value
	 *            is the input value to limit.
	 * @param min
	 *            is the allowed minimum value.
	 * @param max
	 *            is the allowed maximum value.
	 * @return the limited input value that is guaranteed to be within the specified minimum and
	 *         maximum range.
	 */
	private double limit(double value, double min, double max) {
		return Math.min(max, Math.max(min, value));
	}

	/**
	 * Methods that returns the distance to a coordinate (x,y) from our robot.
	 * 
	 * @param x
	 *            is the x coordinate.
	 * @param y
	 *            is the y coordinate.
	 * @return the distance to the coordinate (x,y).
	 */
	private double distanceTo(double x, double y) {
		return Math.hypot(x - getX(), y - getY());
	}

	/**
	 * Method that returns the angle to a coordinate (x,y) from our robot.
	 * 
	 * @param x
	 *            is the x coordinate.
	 * @param y
	 *            is the y coordinate.
	 * @return the angle to the coordinate (x,y).
	 */
	private double angleTo(double x, double y) {
		return Math.atan2(x - getX(), y - getY());
	}

	/**
	 * Method that returns the bearing to a coordinate (x,y) from the position and heading of our
	 * robot. The bearing is the delta angle between the heading of our robot and the angle of the
	 * specified coordinate.
	 * 
	 * @param x
	 *            is the x coordinate.
	 * @param y
	 *            is the y coordinate.
	 * @return the angle to the coordinate (x,y).
	 */
	private double bearingTo(double heading, double x, double y) {
		return Utils.normalRelativeAngle(angleTo(x, y) - heading);
	}

	/**
	 * Method that paints a filled circle at the specified coordinate (x,y) and given color. The
	 * circle will have a radius of 20 pixels (meaning that the diameter will be 40 pixels).
	 * 
	 * @param gfx
	 *            is the graphics context to draw within.
	 * @param x
	 *            is the x coordinate for the center of the circle.
	 * @param y
	 *            is the y coordinate for the center of the circle.
	 * @param color
	 *            is the color of the filled circle.
	 */
	private void fillCircle(Graphics2D gfx, double x, double y, Color color) {
		// Set the pen color
		gfx.setColor(color);
		// Paint a filled circle (oval) that has a radius of 20 pixels with a center at the input
		// coordinates.
		gfx.fillOval((int) x - 20, (int) y - 20, 40, 40);
	}

	/**
	 * This class is used for storing data about a robot that has been scanned.<br>
	 * The data is mainly a snapshot of specific scanned data like the scanned position (x,y),
	 * velocity and heading, put also the calculated predicted target position of the robot when our
	 * robot needs to fire at the scanned robot.<br>
	 * Note that this class calculates the position (x,y) of the scanned robot as our robot moves,
	 * and hence data like the angle and distance to the scanned robot will change over time. by
	 * using the position, it is easy to calculate a new angle and distance to the robot.
	 */
	class RobotData {
		final String name; // name of the scanned robot
		double scannedX; // x coordinate of the scanned robot based on the last update
		double scannedY; // y coordinate of the scanned robot based on the last update
		double scannedVelocity; // velocity of the scanned robot from the last update
		double scannedHeading; // heading of the scanned robot from the last update
		double targetX; // predicated x coordinate to aim our gun at, when firing at the robot
		double targetY; // predicated y coordinate to aim our gun at, when firing at the robot

		/**
		 * Creates a new robot data entry based on new scan data for a scanned robot.
		 * 
		 * @param event
		 *            is a ScannedRobotEvent event containing data about a scanned robot.
		 */
		RobotData(ScannedRobotEvent event) {
			// Store the name of the scanned robot
			name = event.getName();
			// Updates all scanned facts like position, velocity, and heading
			update(event);
			// Initialize the coordinates (x,y) to fire at to the updated scanned position
			targetX = scannedX;
			targetY = scannedY;
		}

		/**
		 * Updates the scanned data based on new scan data for a scanned robot.
		 * 
		 * @param event
		 *            is a ScannedRobotEvent event containing data about a scanned robot.
		 */
		void update(ScannedRobotEvent event) {
			// Get the position of the scanned robot based on the ScannedRobotEvent
			Point2D.Double pos = getPosition(event);
			// Store the scanned position (x,y)
			scannedX = pos.x;
			scannedY = pos.y;
			// Store the scanned velocity and heading
			scannedVelocity = event.getVelocity();
			scannedHeading = event.getHeadingRadians();
		}

		/**
		 * Returns the position of the scanned robot based on new scan data for a scanned robot.
		 * 
		 * @param event
		 *            is a ScannedRobotEvent event containing data about a scanned robot.
		 * @return the position (x,y) of the scanned robot.
		 */
		Point2D.Double getPosition(ScannedRobotEvent event) {
			// Gets the distance to the scanned robot
			double distance = event.getDistance();
			// Calculate the angle to the scanned robot (our robot heading + bearing to scanned
			// robot)
			double angle = getHeadingRadians() + event.getBearingRadians();

			// Calculate the coordinates (x,y) of the scanned robot
			double x = getX() + Math.sin(angle) * distance;
			double y = getY() + Math.cos(angle) * distance;

			// Return the position as a point (x,y)
			return new Point2D.Double(x, y);
		}
	}
}
