/*
 * Expands a layout by 2x in each dimension.
 * H. S. Teoh
 * --------------------------------------------------------------------------
 * $Id: expand2x.C,v 1.7 2008/04/14 22:41:17 root Exp $
 *
 * ALGORITHM
 *
 * ... (TBW)
 */

#include "global.h"
#include "random_map.h"
#include "rproto.h"

/* Copy the old tile X into the new one at location (i*2, j*2) and
 * fill up the rest of the 2x2 result with \0:
 *	X  --->	X  \0
 *		\0 \0
 */
static void
expand_misc (Maze newlayout, int i, int j, Maze layout)
{
  newlayout[i * 2][j * 2] = layout[i][j];
  /* (Note: no need to reset rest of 2x2 area to \0 because calloc does that
   * for us.) */
}

/* Returns a bitmap that represents which squares on the right and bottom
 * edges of a square (i,j) match the given character:
 *	1	match on (i+1, j)
 *	2	match on (i, j+1)
 *	4	match on (i+1, j+1)
 * and the possible combinations thereof.
 */
static int
calc_pattern (char ch, Maze layout, int i, int j)
{
  int pattern = 0;

  if (i + 1 < layout->w && layout[i + 1][j] == ch)
    pattern |= 1;

  if (j + 1 < layout->h)
    {
      if (layout[i][j + 1] == ch)
        pattern |= 2;
      if (i + 1 < layout->w && layout[i + 1][j + 1] == ch)
        pattern |= 4;
    }

  return pattern;
}

/* Expand a wall. This function will try to sensibly connect the resulting
 * wall to adjacent wall squares, so that the result won't have disconnected
 * walls.
 */
static void
expand_wall (Maze newlayout, int i, int j, Maze layout)
{
  int wall_pattern = calc_pattern ('#', layout, i, j);
  int door_pattern = calc_pattern ('D', layout, i, j);
  int both_pattern = wall_pattern | door_pattern;

  newlayout[i * 2][j * 2] = '#';

  if (i + 1 < layout->w)
    {
      if (both_pattern & 1)
        {                       /* join walls/doors to the right */
/*      newlayout[i*2+1][j*2] = '#'; */
          newlayout[i * 2 + 1][j * 2] = layout[i + 1][j];
        }
    }

  if (j + 1 < layout->h)
    {
      if (both_pattern & 2)
        {                       /* join walls/doors to the bottom */
/*      newlayout[i*2][j*2+1] = '#'; */
          newlayout[i * 2][j * 2 + 1] = layout[i][j + 1];
        }

      if (wall_pattern == 7)
        {                       /* if orig layout is a 2x2 wall block,
                                 * we fill the result with walls. */
          newlayout[i * 2 + 1][j * 2 + 1] = '#';
        }
    }
}

/* This function will try to sensibly connect doors so that they meet up with
 * adjacent walls. Note that it will also presumptuously delete (ignore) doors
 * that it doesn't know how to correctly expand.
 */
static void
expand_door (Maze newlayout, int i, int j, Maze layout)
{
  int wall_pattern = calc_pattern ('#', layout, i, j);
  int door_pattern = calc_pattern ('D', layout, i, j);
  int join_pattern;

  /* Doors "like" to connect to walls more than other doors. If there is
   * a wall and another door, this door will connect to the wall and
   * disconnect from the other door. */
  if (wall_pattern & 3)
    join_pattern = wall_pattern;
  else
    join_pattern = door_pattern;

  newlayout[i * 2][j * 2] = 'D';

  if (i + 1 < layout->w)
    if (join_pattern & 1)
      /* there is a door/wall to the right */
      newlayout[i * 2 + 1][j * 2] = 'D';

  if (j + 1 < layout->h)
    if (join_pattern & 2)
      /* there is a door/wall below */
      newlayout[i * 2][j * 2 + 1] = 'D';
}

void
expand2x (Maze layout)
{
  Maze newlayout (layout->w * 2 - 1, layout->h * 2 - 1);
  newlayout->clear ();

  for (int i = 0; i < layout->w; i++)
    for (int j = 0; j < layout->h; j++)
      switch (layout[i][j])
        {
          case '#': expand_wall (newlayout, i, j, layout); break; 
          case 'D': expand_door (newlayout, i, j, layout); break; 
          default:  expand_misc (newlayout, i, j, layout); break;
        }

  layout.swap (newlayout);
}