src/ch/epfl/maze/physical/ProbabilisticAnimal.java


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package ch.epfl.maze.physical;

import ch.epfl.maze.util.Direction;
import ch.epfl.maze.util.Vector2D;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import java.util.stream.Collectors;

/**
 * A probabilistic animal that use a random component in its decision making process.
 *
 * @author Pacien TRAN-GIRARD
 */
abstract public class ProbabilisticAnimal extends Animal {

    private final Random randomSource;
    private Direction currentDirection;

    /**
     * Constructs a probabilistic animal with a starting position
     *
     * @param position Starting position of the probabilistic animal in the labyrinth
     */
    public ProbabilisticAnimal(Vector2D position) {
        super(position); // no pun intended
        this.randomSource = new Random();
        this.currentDirection = Direction.NONE;
    }

    /**
     * Excludes the origin direction for choices.
     *
     * @param choices An array of choices
     * @return An array of smart choices
     */
    protected Direction[] excludeOrigin(Direction[] choices) {
        return (new ArrayList<>(Arrays.asList(choices)))
                .stream()
                .filter(dir -> !dir.isOpposite(this.currentDirection))
                .collect(Collectors.toList())
                .toArray(new Direction[0]);
    }

    /**
     * Returns a random Direction from the given choices.
     *
     * @param choices An array of Direction
     * @return A random Direction taken from the given choices
     */
    protected Direction getRandomDirection(Direction[] choices) {
        return choices[randomSource.nextInt(choices.length)];
    }

    /**
     * Moves according to an improved version of a <i>random walk</i> : the
     * probabilistic animal does not directly retrace its steps if not forced.
     */
    @Override
    public Direction move(Direction[] choices) {
        if (choices.length == 0) return Direction.NONE;

        Direction[] smartChoices = choices.length > 1 ? this.excludeOrigin(choices) : choices;
        this.currentDirection = this.getRandomDirection(smartChoices);
        return this.currentDirection;
    }

}