import java.util.Random;  // Warn Java we want to use Random
import java.util.ArrayList;

/**
 * The Die class models a die of the sort you'd roll:  It
 * can be created with as many sides as you wish, and has
 * a roll method that returns an appropriate random result.
 * 
 * We're now updating our old friend the Die class to keep
 * track of how MANY of each possible values it has rolled.
 */
public class Die
{
    private int numSides;  // How many sides does my die have?
    private Random rng;    // Will hold our random number generator object
    
    private int[] history;  // Track how many 1's, 2's, etc. have been rolled
    
    // I wrote an ArrayList-based version of the history as well, to show
    // that it would be more difficult to take that route.
    private ArrayList<Integer> histAL = new ArrayList<Integer>();

    /**
     * Constructor for objects of class Die.  The default constructor
     * (this one, since it takes no parameters) will create a six-sided
     * die.
     */
    public Die()
    {
        numSides = 6;
        rng = new Random();
        history = new int[6];
        // If we used an ArrayList we'd have to add a bunch of zeroes
        for(int i=0; i<numSides; i=i+1) {
            histAL.add(0);
        }
    }

    /**
     * This constructor creates a Die object with the specified number
     * of sides.
     */
    public Die(int sides)
    {
        numSides = sides;
        rng = new Random();
        history = new int[sides];
        // If we used an ArrayList we'd have to add a bunch of zeroes
        for(int i=0; i<numSides; i=i+1) {
            histAL.add(0);
        }
    }

    /**
     * Simulates a roll of this Die instance.  
     */
    public int roll()
    {
        // Generate a random value in the proper range
        int value = rng.nextInt(numSides)+1;
        history[value-1] = history[value-1] + 1;
        
        // If we used an ArrayList, we'd have to do this:
        int count = histAL.remove(value-1);
        histAL.add(value-1, count+1);
        
        return value; 
    }
    
    /**
     * Print out the roll history. 
     */
    public void printHistory()
    {
        int i = 1;
        for(int count : history) {
            System.out.println("Rolled "+count+" "+i+"s");
            i = i + 1;
        }
    }
    
    /**
     * This version builds up a string containing all of the
     * counter values and returns it. 
     * @return A string containing the counts
     */
    public String toString()
    {
        String s = "This die has "+numSides+" sides and has rolled:";
        int i = 1;
        for(int count : history) {
            s = s + ("Rolled "+count+" "+i+"s\n");
            i = i + 1;
        }
        return s;
    }
}