#include <stdio.h>
#include "towers.h"

make_move(Dllist *towers, int from, int to)
{
  int piece, topofto;

  /* Error check -- is the first tower empty? */

  if (dll_empty(towers[from])) {
    printf("Illegal move of tower %d to %d\n", from, to);
    return;
  } 

  piece = jval_i(dll_val(dll_first(towers[from])));

  /* Error check -- is the piece too big to go on the destination tower? */

  if (!dll_empty(towers[to])) {
    topofto = jval_i(dll_val(dll_first(towers[to])));
    if (piece > topofto) {
      printf("Illegal move of tower %d to %d\n", from, to);
      return;
    } 
  }

  /* Move the piece from the first tower to the second */

  dll_delete_node(dll_first(towers[from]));
  dll_prepend(towers[to], new_jval_i(piece));

  /* Print that the piece has moved */

  printf("Moved piece %3d from tower %d to tower %d\n",
          piece, from, to);
}

/* Print the towers by traversing the list backwards */

print_towers(Dllist *towers)
{
  int i;
  Dllist tmp;

  for (i = 0; i < 3; i++) {
    printf("Tower %d:", i);
    dll_rtraverse(tmp, towers[i]) {
      printf("%3d", jval_i(dll_val(tmp)));
    } 
    printf("\n");
  }
}

/* Allocate the towers and put npiece disks on tower 0 */

Dllist *new_towers(int npiece)
{
  Dllist *t;
  int i;
  int piece;

  t = (Dllist *) malloc(sizeof(Dllist)*3);
  for (i = 0; i < 3; i++) {
    t[i] = new_dllist();
  }
  for (piece = 1; piece <= npiece; piece++) {
    dll_append(t[0], new_jval_i(piece));
  }
  return t;
}