/*  
 * Laura Toma  
 * csci 210 
 * 
 * This is a program that solves the Towers-of-Hanoi puzzle.
 */ 

import java.util.Scanner;
  
public class Hanoi { 
     
     
    private Peg peg1;  
    private Peg peg2;  
    private Peg peg3;  
    private int n;     // how many disks 
	 
 
    public Hanoi() { 
	
	// Get the number of disks  
	System.out.println("How many disks would you like? (positive number)"); 
	Scanner r = new Scanner(System.in); // for reading 
	n = r.nextInt(); 
	assert(n >= 1);  
	
	//create the 3 pegs
	peg1 = new Peg(n, "A");  
	peg2 = new Peg(n, "B"); 
	peg3 = new Peg(n, "C"); 
	
		
	// fill up the source peg with disks. A disk is just an
	// integer representing the size of the disk
	for (int i = n; i > 0; i--) 
	    peg1.addLast(i); 
    } 
    
   
	
    //start the game 
    public void solve() { 
	System.out.println("-------------------------------");
	System.out.println("GOAL: move " + n + " disks from " + 
			   peg1.getName()  + " to " + peg2.getName()); 

	System.out.println("Pegs at start:"); 
	peg1.print(); 
	peg2.print(); 
	peg3.print(); 

	System.out.println("Here is the sequence of moves:"); 
	System.out.println("-------------------------------");
	move(peg1, peg2, peg3, n); 
	
	System.out.println("\nPegs at end:"); 
	peg1.print(); 
	peg2.print(); 
	peg3.print(); 
    } 
    
    
  
    public static void main(String args[]) { 
		
	//start a new game  
	Hanoi hanoi = new Hanoi();  
	
	// solve it 
	hanoi.solve(); 
	
	//that's it  
	System.out.println("Done."); 
    } 

 


    //moves the top d disks from source to dest using tmp as
    //intermediate peg and print the sequence of moves
    public void move(Peg source, Peg dest, Peg tmp,  int d) { 
	
	
	//base case: if one disk left, move it and stop
	if (d==1) {
	    //correctness invariant: source peg must have at least one disk 
	    assert(source.getSize() >= 1); 
	    
	    //print the move
	    System.out.println("Move disk " + source.getLast() + 
			       " from " + source.getName() + 
			       " to " + dest.getName()); 
	    
	    //perform the actual move 
	    int disk = source.deleteLast(); 
	  
	    //correctness invariant: this disk must be smaller than
	    //the top disk of dest
	    assert(dest.isEmpty() || disk < dest.getLast());

	    dest.addLast(disk); 
	}
	
	//more than 1 disks: recurse
	else {
	    //move d-1 disks from source to tmp 
	    move(source, tmp, dest, d-1);
	    
	    //move bottom disk from source to dest 
	    move(source, dest, tmp, 1);

	    //move d-1 disks from tmp to dest 
	    move(tmp, dest, source, d-1);
	}
    } 
}