import greenfoot.*;

public class Hanoi extends World
{
    private int[] cts = new int[3]; // track the number of rings on each of the 3 pegs
    private static int ringCount = 8; // holds the total number of rings in the puzzle
    private Ring[] order = new Ring[ringCount]; // lists order of rings by size
    private Ring[][] rings = new Ring[3][ringCount]; // tracks the arrangement of rings on each of the 3 pegs
    Counter counter; // to track and display move count
    
    public Hanoi()
    {
        super(800, 400, 1);
        prepareBackground();
        addActors();
    }
    
    private void addActors()
    {
        // the rings (added to arrays as needed)
        for (int i=0; i<ringCount; i++)
        {
            rings[0][i] = new Ring(ringCount-1-i);
            addObject(rings[0][i], 200, 300-30*i);
            addRing(0, rings[0][i]);
            order[ringCount-1-i] = rings[0][i];
        }
        // the move counter
        counter = new Counter("Moves: ");
        addObject(counter, 80, 25);
    }
    
    private void prepareBackground()
    {
        GreenfootImage bg = getBackground();
        // the board with pegs
        bg.setColor(new java.awt.Color(128, 50, 50));
        bg.fillRect(50, 316, 700, 30);
        bg.fillRect(195, 51, 10, 265);
        bg.fillRect(395, 51, 10, 265);
        bg.fillRect(595, 51, 10, 265);
        // the instructions and ring count text
        GreenfootImage text = new GreenfootImage("Use 'space' to execute a move", 24, java.awt.Color.black, null);
        bg.drawImage(text, 100, 360);
        text = new GreenfootImage("Use '3' through '8' to adjust ring count", 24, java.awt.Color.black, null);
        bg.drawImage(text, 400, 360);
        text = new GreenfootImage("Rings: "+ringCount, 24, java.awt.Color.black, null);
        bg.drawImage(text, 700, 15);
    }
    
    /**
     * removes the top ring from the array that tracks the arrangement of the rings on the pegs
     * and returns the ring removed from the array
     */
    private Ring removeRing(int pegNum)
    {
        Ring ring = rings[pegNum][cts[pegNum]-1];
        cts[pegNum]--;
        return ring;
    }
    
    /**
     * adds a ring to a peg in the array that tracks the arrangement of the rings on the pegs
     */
    private void addRing(int pegNum, Ring ring)
    {
        rings[pegNum][cts[pegNum]] = ring;
        cts[pegNum]++;
    }
    
    /**
     * checks for keystrokes for move execution and setting ring count
     */
    public void act()
    {
        String key = Greenfoot.getKey();
        if ("space".equals(key)) executeMove();
        if (key != null && "345678".indexOf(key) >= 0)
        {
            ringCount = "345678".indexOf(key)+3;
            Greenfoot.setWorld(new Hanoi());
        }
    }
    
    /**
     * executes the next move in solving the puzzle if not solved yet
     */
    private void executeMove()
    {
        // check if all moves have been executed
        if (counter.getValue() == (int)Math.pow(2, ringCount)-1) return;  // puzzle completed
        int moves = counter.increment(); // get incremented move count
        // determine 'from' peg
        int bit = ringCount-1;
        while (moves%(int)Math.pow(2, bit) != 0) bit--;
        int from = (order[bit].getX()-200)/200;
        // remove ring from 'from' peg
        Ring ring = removeRing(from);
        // determine 'to' peg
        int to = from;
        // first possible 'to' peg with rings
        if (cts[(from+1)%3] != 0 && // rings on 'to' peg
             ring.getIndex() < rings[(from+1)%3][cts[(from+1)%3]-1].getIndex() && // top ring on 'to' peg is larger
            (rings[(from+1)%3][cts[(from+1)%3]-1].getIndex()+ring.getIndex())%2 == 1) // top ring on 'to' peg is legal
        {
            to = (from+1)%3;
        }
        // other possible 'to' peg with rings
        else if (cts[(from+2)%3] != 0 && // rings on 'to' peg
            ring.getIndex() < rings[(from+2)%3][cts[(from+2)%3]-1].getIndex() && // top ring on 'to' peg is larger
            (rings[(from+2)%3][cts[(from+2)%3]-1].getIndex()+ring.getIndex())%2 == 1) // top ring on 'to' peg is legal
        {
            to = (from+2)%3;
        }
        // empty 'to' pegs
        else if (cts[(from+1)%3] == 0) to = (from+1)%3; else to = (from+2)%3; // 'to' peg is empty
        moveRing(ring, from, to);
        addRing(to, ring);
    }
    
    /**
     * animates the movement of a ring from one peg to another
     */
    private void moveRing(Ring ring, int from, int to)
    {
        while (ring.getY() != 30)
        {
            ring.setLocation(ring.getX(), ring.getY()-10);
            Greenfoot.delay(1);
        }
        int dir = (int)Math.signum(to-from);
        while (ring.getX() != 200+200*to)
        {
            ring.setLocation(ring.getX()+dir*10, ring.getY());
            Greenfoot.delay(1);
        }
        int targetY = 300-30*(cts[to]);
        while (ring.getY() != targetY)
        {
            ring.setLocation(ring.getX(), ring.getY()+10);
            Greenfoot.delay(1);
        }
    }
}