//
// "$Id: sudoku.cxx 7903 2010-11-28 21:06:39Z matt $"
//
// Sudoku game using the Fast Light Tool Kit (FLTK).
//
// Copyright 2005-2010 by Michael Sweet.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA.
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//

#include <FL/Fl.H>
#include <FL/Enumerations.H>
#include <FL/Fl_Double_Window.H>
#include <FL/Fl_Button.H>
#include <FL/Fl_Group.H>
#include <FL/fl_ask.H>
#include <FL/fl_draw.H>
#include <FL/Fl_Help_Dialog.H>
#include <FL/Fl_Preferences.H>
#include <FL/Fl_Sys_Menu_Bar.H>
#include <FL/x.H>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <FL/math.h>

#ifdef WIN32
#  include "sudokurc.h"
#elif !defined(__APPLE__)
#  include "pixmaps/sudoku.xbm"
#endif // WIN32

// Audio headers...
#include <config.h>

#ifndef WIN32
#  include <unistd.h>
#endif // !WIN32

#ifdef HAVE_ALSA_ASOUNDLIB_H
#  define ALSA_PCM_NEW_HW_PARAMS_API
#  include <alsa/asoundlib.h>
#endif // HAVE_ALSA_ASOUNDLIB_H
#ifdef __APPLE__
#  include <CoreAudio/AudioHardware.h>
#endif // __APPLE__
#ifdef WIN32
#  include <mmsystem.h>
#endif // WIN32


//
// Default sizes...
//

#define GROUP_SIZE	160
#define CELL_SIZE	50
#define CELL_OFFSET	5
#ifdef __APPLE__
#  define MENU_OFFSET	0
#else
#  define MENU_OFFSET	25
#endif // __APPLE__

// Sound class for Sudoku...
//
// There are MANY ways to implement sound in a FLTK application.
// The approach we are using here is to conditionally compile OS-
// specific code into the application - CoreAudio for MacOS X, the
// standard Win32 API stuff for Windows, ALSA or X11 for Linux, and
// X11 for all others.  We have to support ALSA on Linux because the
// current Xorg releases no longer support XBell() or the PC speaker.
//
// There are several good cross-platform audio libraries we could also
// use, such as OpenAL, PortAudio, and SDL, however they were not chosen
// for this application because of our limited use of sound.
//
// Many thanks to Ian MacArthur who provided sample code that led to
// the CoreAudio implementation you see here!
class SudokuSound {
  // Private, OS-specific data...
#ifdef __APPLE__
  AudioDeviceID device;
#  if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5
  AudioDeviceIOProcID audio_proc_id;
#  endif
  AudioStreamBasicDescription format;
  short *data;
  int remaining;

  static OSStatus audio_cb(AudioDeviceID device,
			   const AudioTimeStamp *current_time,
			   const AudioBufferList *data_in,
			   const AudioTimeStamp *time_in,
			   AudioBufferList *data_out,
			   const AudioTimeStamp *time_out,
			   void *client_data);
#elif defined(WIN32)
  HWAVEOUT	device;
  HGLOBAL	header_handle;
  LPWAVEHDR	header_ptr;
  HGLOBAL	data_handle;
  LPSTR		data_ptr;

#else
#  ifdef HAVE_ALSA_ASOUNDLIB_H
  snd_pcm_t *handle;
#  endif // HAVE_ALSA_ASOUNDLIB_H
#endif // __APPLE__

  // Common data...
  static int frequencies[9];
  static short *sample_data[9];
  static int sample_size;

  public:

  SudokuSound();
  ~SudokuSound();

  void	play(char note);
};


// Sudoku cell class...
class SudokuCell : public Fl_Widget {
  bool		readonly_;
  int		value_;
  int		test_value_[9];

  public:

		SudokuCell(int X, int Y, int W, int H);
  void		draw();
  int		handle(int event);
  void		readonly(bool r) { readonly_ = r; redraw(); }
  bool		readonly() const { return readonly_; }
  void		test_value(int v, int n) { test_value_[n] = v; redraw(); }
  int		test_value(int n) const { return test_value_[n]; }
  void		value(int v) {
		  value_ = v;
		  for (int i = 0; i < 8; i ++) test_value_[i] = 0;
		  redraw();
		}
  int		value() const { return value_; }
};


// Sudoku window class...
class Sudoku : public Fl_Double_Window {
  Fl_Sys_Menu_Bar *menubar_;
  Fl_Group	*grid_;
  time_t	seed_;
  char		grid_values_[9][9];
  SudokuCell	*grid_cells_[9][9];
  Fl_Group	*grid_groups_[3][3];
  int		difficulty_;
  SudokuSound	*sound_;

  static void	check_cb(Fl_Widget *widget, void *);
  static void	close_cb(Fl_Widget *widget, void *);
  static void	diff_cb(Fl_Widget *widget, void *d);
  static void	update_helpers_cb(Fl_Widget *, void *);
  static void	help_cb(Fl_Widget *, void *);
  static void	mute_cb(Fl_Widget *widget, void *);
  static void	new_cb(Fl_Widget *widget, void *);
  static void	reset_cb(Fl_Widget *widget, void *);
  static void	restart_cb(Fl_Widget *widget, void *);
  void		set_title();
  static void	solve_cb(Fl_Widget *widget, void *);

  static Fl_Help_Dialog *help_dialog_;
  static Fl_Preferences	prefs_;
  public:

	      	Sudoku();
		~Sudoku();

  void		check_game(bool highlight = true);
  void		load_game();
  void		new_game(time_t seed);
  int		next_value(SudokuCell *c);
  void		resize(int X, int Y, int W, int H);
  void		save_game();
  void		solve_game();
  void	        update_helpers();
};


// Sound class globals...
int SudokuSound::frequencies[9] = {
  880,	// A(5)
  988,	// B(5)
  1046,	// C(5)
  1174,	// D(5)
  1318,	// E(5)
  1396,	// F(5)
  1568,	// G(5)
  1760,	// H (A6)
  1976	// I (B6)
};
short *SudokuSound::sample_data[9] = { 0 };
int SudokuSound::sample_size = 0;


// Initialize the SudokuSound class
SudokuSound::SudokuSound() {
  sample_size = 0;

#ifdef __APPLE__
  remaining = 0;

  UInt32 size = sizeof(device);

  if (AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice,
			       &size, (void *)&device) != noErr) return;

  size = sizeof(format);
  if (AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat,
			     &size, &format) != noErr) return;

  // Set up a format we like...
  format.mSampleRate       = 44100.0;	// 44.1kHz
  format.mChannelsPerFrame = 2;		// stereo

  if (AudioDeviceSetProperty(device, NULL, 0, false,
                             kAudioDevicePropertyStreamFormat,
	                     sizeof(format), &format) != noErr) return;

  // Check we got linear pcm - what to do if we did not ???
  if (format.mFormatID != kAudioFormatLinearPCM) return;

  // Attach the callback and start the device
#  if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5
  if (AudioDeviceCreateIOProcID(device, audio_cb, (void *)this, &audio_proc_id) != noErr) return;
  AudioDeviceStart(device, audio_proc_id);
#  else
  if (AudioDeviceAddIOProc(device, audio_cb, (void *)this) != noErr) return;
  AudioDeviceStart(device, audio_cb);
#  endif
  
  sample_size = (int)format.mSampleRate / 20;

#elif defined(WIN32)
  WAVEFORMATEX	format;

  memset(&format, 0, sizeof(format));
  format.cbSize          = sizeof(format);
  format.wFormatTag      = WAVE_FORMAT_PCM;
  format.nChannels       = 2;
  format.nSamplesPerSec  = 44100;
  format.nAvgBytesPerSec = 44100 * 4;
  format.nBlockAlign     = 4;
  format.wBitsPerSample  = 16;

  data_handle = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE, format.nSamplesPerSec / 5);
  if (!data_handle) return;

  data_ptr = (LPSTR)GlobalLock(data_handle);

  header_handle = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE, sizeof(WAVEHDR));
  if (!header_handle) return;

  header_ptr = (WAVEHDR *)GlobalLock(header_handle);

  header_ptr->lpData         = data_ptr;
  header_ptr->dwBufferLength = format.nSamplesPerSec / 5;
  header_ptr->dwFlags        = 0;
  header_ptr->dwLoops        = 0;

  if (waveOutOpen(&device, WAVE_MAPPER, &format, 0, 0, WAVE_ALLOWSYNC)
          != MMSYSERR_NOERROR) return;

  waveOutPrepareHeader(device, header_ptr, sizeof(WAVEHDR));

  sample_size = 44100 / 20;

#else
#  ifdef HAVE_ALSA_ASOUNDLIB_H
  handle = NULL;

  if (snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0) >= 0) {
    // Initialize PCM sound stuff...
    snd_pcm_hw_params_t *params;

    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(handle, params);
    snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16);
    snd_pcm_hw_params_set_channels(handle, params, 2);
    unsigned rate = 44100;
    int dir;
    snd_pcm_hw_params_set_rate_near(handle, params, &rate, &dir);
    snd_pcm_uframes_t period = (int)rate / 4;
    snd_pcm_hw_params_set_period_size_near(handle, params, &period, &dir);

    sample_size = rate / 20;

    if (snd_pcm_hw_params(handle, params) < 0) {
      sample_size = 0;
      snd_pcm_close(handle);
      handle = NULL;
    }
  }
#  endif // HAVE_ALSA_ASOUNDLIB_H
#endif // __APPLE__

  if (sample_size) {
    // Make each of the notes using a combination of sine and sawtooth waves
    int attack = sample_size / 10;
    int decay = 4 * sample_size / 5;

    for (int i = 0; i < 9; i ++) {
      sample_data[i] = new short[2 * sample_size];

      short *sample_ptr = sample_data[i];

      for (int j = 0; j < sample_size; j ++, sample_ptr += 2) {
        double theta = 0.05 * frequencies[i] * j / sample_size;
        double val = 0.5 * sin(2.0 * M_PI * theta) + theta - (int)theta - 0.5;

        if (j < attack) {
	  *sample_ptr = (int)(32767 * val * j / attack);
	} else if (j > decay) {
	  *sample_ptr = (int)(32767 * val * (sample_size - j + decay) /
	                      sample_size);
	} else *sample_ptr = (int)(32767 * val);

        sample_ptr[1] = *sample_ptr;
      }
    }
  }
}


// Cleanup the SudokuSound class
SudokuSound::~SudokuSound() {
#ifdef __APPLE__
  if (sample_size) {
#  if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5
    AudioDeviceStop(device, audio_proc_id);
    AudioDeviceDestroyIOProcID(device, audio_proc_id);
#  else
    AudioDeviceStop(device, audio_cb);
    AudioDeviceRemoveIOProc(device, audio_cb);
#  endif
  }

#elif defined(WIN32)
  if (sample_size) {
    waveOutClose(device);

    GlobalUnlock(header_handle);
    GlobalFree(header_handle);

    GlobalUnlock(data_handle);
    GlobalFree(data_handle);
  }

#else
#  ifdef HAVE_ALSA_ASOUNDLIB_H
  if (handle) {
    snd_pcm_drain(handle);
    snd_pcm_close(handle);
  }
#  endif // HAVE_ALSA_ASOUNDLIB_H
#endif // __APPLE__

  if (sample_size) {
    for (int i = 0; i < 9; i ++) {
      delete[] sample_data[i];
    }
  }
}


#ifdef __APPLE__
// Callback function for writing audio data...
OSStatus
SudokuSound::audio_cb(AudioDeviceID device,
		      const AudioTimeStamp *current_time,
		      const AudioBufferList *data_in,
		      const AudioTimeStamp *time_in,
		      AudioBufferList *data_out,
		      const AudioTimeStamp *time_out,
		      void *client_data) {
  SudokuSound *ss = (SudokuSound *)client_data;
  int count;
  float *buffer;

  if (!ss->remaining) return noErr;

  for (count = data_out->mBuffers[0].mDataByteSize / sizeof(float),
          buffer = (float*) data_out->mBuffers[0].mData;
       ss->remaining > 0 && count > 0;
       count --, ss->data ++, ss->remaining --) {
    *buffer++ = *(ss->data) / 32767.0;
  }

  while (count > 0) {
    *buffer++ = 0.0;
    count --;
  }

  return noErr;
}
#endif // __APPLE__


// Play a note for 250ms...
void SudokuSound::play(char note) {
  Fl::check();

#ifdef __APPLE__
  // Point to the next note...
  data      = sample_data[note - 'A'];
  remaining = sample_size * 2;

  // Wait for the sound to complete...
  usleep(50000);

#elif defined(WIN32)
  if (sample_size) {
    memcpy(data_ptr, sample_data[note - 'A'], sample_size * 4);

    waveOutWrite(device, header_ptr, sizeof(WAVEHDR));

    Sleep(50);
  } else Beep(frequencies[note - 'A'], 50);

#else
#  ifdef HAVE_ALSA_ASOUNDLIB_H
  if (handle) {
    // Use ALSA to play the sound...
    if (snd_pcm_writei(handle, sample_data[note - 'A'], sample_size) < 0) {
      snd_pcm_prepare(handle);
      snd_pcm_writei(handle, sample_data[note - 'A'], sample_size);
    }
    usleep(50000);
    return;
  }
#  endif // HAVE_ALSA_ASOUNDLIB_H

  // Just use standard X11 stuff...
  XKeyboardState	state;
  XKeyboardControl	control;

  // Get original pitch and duration...
  XGetKeyboardControl(fl_display, &state);

  // Sound a tone for the given note...
  control.bell_percent  = 100;
  control.bell_pitch    = frequencies[note - 'A'];
  control.bell_duration = 50;

  XChangeKeyboardControl(fl_display,
                         KBBellPercent | KBBellPitch | KBBellDuration,
			 &control);
  XBell(fl_display, 100);
  XFlush(fl_display);

  // Restore original pitch and duration...
  control.bell_percent  = state.bell_percent;
  control.bell_pitch    = state.bell_pitch;
  control.bell_duration = state.bell_duration;

  XChangeKeyboardControl(fl_display,
                         KBBellPercent | KBBellPitch | KBBellDuration,
			 &control);
#endif // __APPLE__
}


// Create a cell widget
SudokuCell::SudokuCell(int X, int Y, int W, int H)
  : Fl_Widget(X, Y, W, H, 0) {
  value(0);
}


// Draw cell
void
SudokuCell::draw() {
  static Fl_Align align[8] = {
    FL_ALIGN_TOP_LEFT,
    FL_ALIGN_TOP,
    FL_ALIGN_TOP_RIGHT,
    FL_ALIGN_RIGHT,
    FL_ALIGN_BOTTOM_RIGHT,
    FL_ALIGN_BOTTOM,
    FL_ALIGN_BOTTOM_LEFT,
    FL_ALIGN_LEFT
  };


  // Draw the cell box...
  if (readonly()) fl_draw_box(FL_UP_BOX, x(), y(), w(), h(), color());
  else fl_draw_box(FL_DOWN_BOX, x(), y(), w(), h(), color());

  // Draw the cell background...
  if (Fl::focus() == this) {
    Fl_Color c = fl_color_average(FL_SELECTION_COLOR, color(), 0.5f);
    fl_color(c);
    fl_rectf(x() + 4, y() + 4, w() - 8, h() - 8);
    fl_color(fl_contrast(labelcolor(), c));
  } else fl_color(labelcolor());

  // Draw the cell value...
  char s[2];

  s[1] = '\0';

  if (value_) {
    s[0] = value_ + '0';

    fl_font(FL_HELVETICA_BOLD, h() - 10);
    fl_draw(s, x(), y(), w(), h(), FL_ALIGN_CENTER);
  }

  fl_font(FL_HELVETICA_BOLD, h() / 5);

  for (int i = 0; i < 8; i ++) {
    if (test_value_[i]) {
      s[0] = test_value_[i] + '0';
      fl_draw(s, x() + 5, y() + 5, w() - 10, h() - 10, align[i]);
    }
  }
}


// Handle events in cell
int
SudokuCell::handle(int event) {
  switch (event) {
    case FL_FOCUS :
      Fl::focus(this);
      redraw();
      return 1;

    case FL_UNFOCUS :
      redraw();
      return 1;

    case FL_PUSH :
      if (!readonly() && Fl::event_inside(this)) {
        if (Fl::event_clicks()) {
	  // 2+ clicks increments/sets value
	  if (value()) {
	    if (value() < 9) value(value() + 1);
	    else value(1);
	  } else value(((Sudoku *)window())->next_value(this));
	}

        Fl::focus(this);
	redraw();
	return 1;
      }
      break;

    case FL_KEYDOWN :
      if (Fl::event_state() & FL_CTRL) break;
      int key = Fl::event_key() - '0';
      if (key < 0 || key > 9) key = Fl::event_key() - FL_KP - '0';
      if (key > 0 && key <= 9) {
        if (readonly()) {
          fl_beep(FL_BEEP_ERROR);
          return 1;
        }

        if (Fl::event_state() & (FL_SHIFT | FL_CAPS_LOCK)) {
	  int i;

	  for (i = 0; i < 8; i ++)
	    if (test_value_[i] == key) {
	      test_value_[i] = 0;
	      break;
	    }

          if (i >= 8) {
	    for (i = 0; i < 8; i ++)
	      if (!test_value_[i]) {
		test_value_[i] = key;
		break;
	      }
	  }

	  if (i >= 8) {
	    for (i = 0; i < 7; i ++) test_value_[i] = test_value_[i + 1];
	    test_value_[i] = key;
	  }

	  redraw();
	} else {
	  value(key);
	  do_callback();
	}
	return 1;
      } else if (key == 0 || Fl::event_key() == FL_BackSpace ||
                 Fl::event_key() == FL_Delete) {
        if (readonly()) {
          fl_beep(FL_BEEP_ERROR);
          return 1;
        }

        value(0);
	do_callback();
	return 1;
      }
      break;
  }

  return Fl_Widget::handle(event);
}


// Sudoku class globals...
Fl_Help_Dialog	*Sudoku::help_dialog_ = (Fl_Help_Dialog *)0;
Fl_Preferences	Sudoku::prefs_(Fl_Preferences::USER, "fltk.org", "sudoku");


// Create a Sudoku game window...
Sudoku::Sudoku()
  : Fl_Double_Window(GROUP_SIZE * 3, GROUP_SIZE * 3 + MENU_OFFSET, "Sudoku")
{
  int j, k;
  Fl_Group *g;
  SudokuCell *cell;
  static Fl_Menu_Item	items[] = {
    { "&Game", 0, 0, 0, FL_SUBMENU },
    { "&New Game", FL_COMMAND | 'n', new_cb, 0, FL_MENU_DIVIDER },
    { "&Check Game", FL_COMMAND | 'c', check_cb, 0, 0 },
    { "&Restart Game", FL_COMMAND | 'r', restart_cb, 0, 0 },
    { "&Solve Game", FL_COMMAND | 's', solve_cb, 0, FL_MENU_DIVIDER },
    { "&Update Helpers", 0, update_helpers_cb, 0, 0 },
    { "&Mute Sound", FL_COMMAND | 'm', mute_cb, 0, FL_MENU_TOGGLE | FL_MENU_DIVIDER },
    { "&Quit", FL_COMMAND | 'q', close_cb, 0, 0 },
    { 0 },
    { "&Difficulty", 0, 0, 0, FL_SUBMENU },
    { "&Easy", 0, diff_cb, (void *)"0", FL_MENU_RADIO },
    { "&Medium", 0, diff_cb, (void *)"1", FL_MENU_RADIO },
    { "&Hard", 0, diff_cb, (void *)"2", FL_MENU_RADIO },
    { "&Impossible", 0, diff_cb, (void *)"3", FL_MENU_RADIO },
    { 0 },
    { "&Help", 0, 0, 0, FL_SUBMENU },
    { "&About Sudoku", FL_F + 1, help_cb, 0, 0 },
    { 0 },
    { 0 }
  };


  // Setup sound output...
  prefs_.get("mute_sound", j, 0);
  if (j) {
    // Mute sound?
    sound_ = NULL;
    items[6].flags |= FL_MENU_VALUE;
  } else sound_ = new SudokuSound();

  // Menubar...
  prefs_.get("difficulty", difficulty_, 0);
  if (difficulty_ < 0 || difficulty_ > 3) difficulty_ = 0;

  items[10 + difficulty_].flags |= FL_MENU_VALUE;

  menubar_ = new Fl_Sys_Menu_Bar(0, 0, 3 * GROUP_SIZE, 25);
  menubar_->menu(items);

  // Create the grids...
  grid_ = new Fl_Group(0, MENU_OFFSET, 3 * GROUP_SIZE, 3 * GROUP_SIZE);

  for (j = 0; j < 3; j ++)
    for (k = 0; k < 3; k ++) {
      g = new Fl_Group(k * GROUP_SIZE, j * GROUP_SIZE + MENU_OFFSET,
		       GROUP_SIZE, GROUP_SIZE);
      g->box(FL_BORDER_BOX);
      if ((int)(j == 1) ^ (int)(k == 1)) g->color(FL_DARK3);
      else g->color(FL_DARK2);
      g->end();

      grid_groups_[j][k] = g;
    }

  for (j = 0; j < 9; j ++)
    for (k = 0; k < 9; k ++) {
      cell = new SudokuCell(k * CELL_SIZE + CELL_OFFSET +
                                (k / 3) * (GROUP_SIZE - 3 * CELL_SIZE),
	                    j * CELL_SIZE + CELL_OFFSET + MENU_OFFSET +
			        (j / 3) * (GROUP_SIZE - 3 * CELL_SIZE),
			    CELL_SIZE, CELL_SIZE);
      cell->callback(reset_cb);
      grid_cells_[j][k] = cell;
    }

  // Set icon for window (MacOS uses app bundle for icon...)
#ifdef WIN32
  icon((char *)LoadIcon(fl_display, MAKEINTRESOURCE(IDI_ICON)));
#elif !defined(__APPLE__)
  fl_open_display();
  icon((char *)XCreateBitmapFromData(fl_display, DefaultRootWindow(fl_display),
                                     (char *)sudoku_bits, sudoku_width,
				     sudoku_height));
#endif // WIN32

  // Catch window close events...
  callback(close_cb);

  // Make the window resizable...
  resizable(grid_);
  size_range(3 * GROUP_SIZE, 3 * GROUP_SIZE + MENU_OFFSET, 0, 0, 5, 5, 1);

  // Restore the previous window dimensions...
  int X, Y, W, H;

  if (prefs_.get("x", X, -1)) {
    prefs_.get("y", Y, -1);
    prefs_.get("width", W, 3 * GROUP_SIZE);
    prefs_.get("height", H, 3 * GROUP_SIZE + MENU_OFFSET);

    resize(X, Y, W, H);
  }

  set_title();
}


// Destroy the sudoku window...
Sudoku::~Sudoku() {
  if (sound_) delete sound_;
}


// Check for a solution to the game...
void
Sudoku::check_cb(Fl_Widget *widget, void *) {
  ((Sudoku *)(widget->window()))->check_game();
}


// Check if the user has correctly solved the game...
void
Sudoku::check_game(bool highlight) {
  bool empty = false;
  bool correct = true;
  int j, k, m;

  // Check the game for right/wrong answers...
  for (j = 0; j < 9; j ++)
    for (k = 0; k < 9; k ++) {
      SudokuCell *cell = grid_cells_[j][k];
      int val = cell->value();

      if (cell->readonly()) continue;

      if (!val) empty = true;
      else {
        for (m = 0; m < 9; m ++)
          if ((j != m && grid_cells_[m][k]->value() == val) ||
	      (k != m && grid_cells_[j][m]->value() == val)) break;

        if (m < 9) {
          if (highlight) {
	    cell->color(FL_YELLOW);
	    cell->redraw();
	  }

	  correct = false;
	} else if (highlight) {
	  cell->color(FL_LIGHT3);
	  cell->redraw();
	}
      }
    }

  // Check subgrids for duplicate numbers...
  for (j = 0; j < 9; j += 3)
    for (k = 0; k < 9; k += 3)
      for (int jj = 0; jj < 3; jj ++)
        for (int kk = 0; kk < 3; kk ++) {
	  SudokuCell *cell = grid_cells_[j + jj][k + kk];
	  int val = cell->value();

	  if (cell->readonly() || !val) continue;

          int jjj;

          for (jjj = 0; jjj < 3; jjj ++) {
	    int kkk;

	    for (kkk = 0; kkk < 3; kkk ++)
              if (jj != jjj && kk != kkk &&
	          grid_cells_[j + jjj][k + kkk]->value() == val) break;

            if (kkk < 3) break;
	  }

          if (jjj < 3) {
            if (highlight) {
	      cell->color(FL_YELLOW);
	      cell->redraw();
	    }

	    correct = false;
	  }
	}

  if (!empty && correct) {
    // Success!
    for (j = 0; j < 9; j ++) {
      for (k = 0; k < 9; k ++) {
	SudokuCell *cell = grid_cells_[j][k];
	cell->color(FL_GREEN);
	cell->readonly(1);
      }

      if (sound_) sound_->play('A' + grid_cells_[j][8]->value() - 1);
    }
  }
}


// Close the window, saving the game first...
void
Sudoku::close_cb(Fl_Widget *widget, void *) {
  Sudoku *s = (Sudoku *)(widget->window() ? widget->window() : widget);

  s->save_game();
  s->hide();

  if (help_dialog_) help_dialog_->hide();
}


// Set the level of difficulty...
void
Sudoku::diff_cb(Fl_Widget *widget, void *d) {
  Sudoku *s = (Sudoku *)(widget->window() ? widget->window() : widget);
  int diff = atoi((char *)d);

  if (diff != s->difficulty_) {
    s->difficulty_ = diff;
    s->new_game(s->seed_);
    s->set_title();

    if (diff > 1)
    {
      // Display a message about the higher difficulty levels for the
      // Sudoku zealots of the world...
      int val;

      prefs_.get("difficulty_warning", val, 0);

      if (!val)
      {
        prefs_.set("difficulty_warning", 1);
	fl_alert("Note: 'Hard' and 'Impossible' puzzles may have more than "
	         "one possible solution.\n"
		 "This is not an error or bug.");
      }
    }

    prefs_.set("difficulty", s->difficulty_);
  }
}

// Update the little marker numbers in all cells
void
Sudoku::update_helpers_cb(Fl_Widget *widget, void *) {
  Sudoku *s = (Sudoku *)(widget->window() ? widget->window() : widget);
  s->update_helpers();
}

void
Sudoku::update_helpers() {
  int j, k, m;

  // First we delete any entries that the user may have made
  for (j = 0; j < 9; j ++) {
    for (k = 0; k < 9; k ++) {
      SudokuCell *cell = grid_cells_[j][k];
      for (m = 0; m < 8; m ++) {
        cell->test_value(0, m);
      }
    }
  }

  // Now go through all cells and find out, what we can not be
  for (j = 0; j < 81; j ++) {
    char taken[10] = { 0 };
    // Find our destination cell
    int row = j / 9;
    int col = j % 9;
    SudokuCell *dst_cell = grid_cells_[row][col];
    if (dst_cell->value()) continue;
    // Find all values already taken in this row
    for (k = 0; k < 9; k ++) {
      SudokuCell *cell = grid_cells_[row][k];
      int v = cell->value();
      if (v) taken[v] = 1;
    }
    // Find all values already taken in this column
    for (k = 0; k < 9; k ++) {
      SudokuCell *cell = grid_cells_[k][col];
      int v = cell->value();
      if (v) taken[v] = 1;
    }
    // Now find all values already taken in this square
    int ro = (row / 3) * 3;
    int co = (col / 3) * 3;
    for (k = 0; k < 3; k ++) {
      for (m = 0; m < 3; m ++) {
        SudokuCell *cell = grid_cells_[ro + k][co + m];
        int v = cell->value();
        if (v) taken[v] = 1;
      }
    }
    // transfer our findings to the markers
    for (m = 1, k = 0; m <= 9; m ++) {
      if (!taken[m])
        dst_cell->test_value(m, k ++);
    }
  }
}


// Show the on-line help...
void
Sudoku::help_cb(Fl_Widget *, void *) {
  if (!help_dialog_) {
    help_dialog_ = new Fl_Help_Dialog();

    help_dialog_->value(
	"<HTML>\n"
	"<HEAD>\n"
	"<TITLE>Sudoku Help</TITLE>\n"
	"</HEAD>\n"
	"<BODY BGCOLOR='#ffffff'>\n"

	"<H2>About the Game</H2>\n"

	"<P>Sudoku (pronounced soo-dough-coo with the emphasis on the\n"
        "first syllable) is a simple number-based puzzle/game played on a\n"
	"9x9 grid that is divided into 3x3 subgrids. The goal is to enter\n"
	"a number from 1 to 9 in each cell so that each number appears\n"
	"only once in each column and row. In addition, each 3x3 subgrid\n"
	"may only contain one of each number.</P>\n"

	"<P>This version of the puzzle is copyright 2005-2010 by Michael R\n"
	"Sweet.</P>\n"

	"<P><B>Note:</B> The 'Hard' and 'Impossible' difficulty\n"
	"levels generate Sudoku puzzles with multiple possible solutions.\n"
	"While some purists insist that these cannot be called 'Sudoku'\n"
	"puzzles, the author (me) has personally solved many such puzzles\n"
	"in published/printed Sudoku books and finds them far more\n"
	"interesting than the simple single solution variety. If you don't\n"
	"like it, don't play with the difficulty set to 'High' or\n"
	"'Impossible'.</P>\n"

	"<H2>How to Play the Game</H2>\n"

	"<P>At the start of a new game, Sudoku fills in a random selection\n"
	"of cells for you - the number of cells depends on the difficulty\n"
	"level you use. Click in any of the empty cells or use the arrow\n"
	"keys to highlight individual cells and press a number from 1 to 9\n"
	"to fill in the cell. To clear a cell, press 0, Delete, or\n"
	"Backspace. When you have successfully completed all subgrids, the\n"
	"entire puzzle is highlighted in green until you start a new\n"
	"game.</P>\n"

	"<P>As you work to complete the puzzle, you can display possible\n"
	"solutions inside each cell by holding the Shift key and pressing\n"
	"each number in turn. Repeat the process to remove individual\n"
	"numbers, or press a number without the Shift key to replace them\n"
	"with the actual number to use.</P>\n"
	"</BODY>\n"
    );
  }

  help_dialog_->show();
}


// Load the game from saved preferences...
void
Sudoku::load_game() {
  // Load the current values and state of each grid...
  memset(grid_values_, 0, sizeof(grid_values_));

  bool solved = true;

  for (int j = 0; j < 9; j ++)
    for (int k = 0; k < 9; k ++) {
      char name[255];
      int val;

      SudokuCell *cell = grid_cells_[j][k];

      sprintf(name, "value%d.%d", j, k);
      if (!prefs_.get(name, val, 0)) {
        j = 9;
	grid_values_[0][0] = 0;
	break;
      }

      grid_values_[j][k] = val;

      sprintf(name, "state%d.%d", j, k);
      prefs_.get(name, val, 0);
      cell->value(val);
 
      sprintf(name, "readonly%d.%d", j, k);
      prefs_.get(name, val, 0);
      cell->readonly(val);

      if (val) cell->color(FL_GRAY);
      else {
        cell->color(FL_LIGHT3);
	solved = false;
      }

      for (int m = 0; m < 8; m ++) {
	sprintf(name, "test%d%d.%d", m, j, k);
	prefs_.get(name, val, 0);
	cell->test_value(val, m);
      }
    }

  // If we didn't load any values or the last game was solved, then
  // create a new game automatically...
  if (solved || !grid_values_[0][0]) new_game(time(NULL));
  else check_game(false);
}


// Mute/unmute sound...
void
Sudoku::mute_cb(Fl_Widget *widget, void *) {
  Sudoku *s = (Sudoku *)(widget->window() ? widget->window() : widget);

  if (s->sound_) {
    delete s->sound_;
    s->sound_ = NULL;
    prefs_.set("mute_sound", 1);
  } else {
    s->sound_ = new SudokuSound();
    prefs_.set("mute_sound", 0);
  }
}


// Create a new game...
void
Sudoku::new_cb(Fl_Widget *widget, void *) {
  Sudoku *s = (Sudoku *)(widget->window() ? widget->window() : widget);

  if (s->grid_cells_[0][0]->color() != FL_GREEN) {
    if (!fl_choice("Are you sure you want to change the difficulty level and "
                   "discard the current game?", "Keep Current Game", "Start New Game",
                   NULL)) return;
  }

  s->new_game(time(NULL));
}


// Create a new game...
void
Sudoku::new_game(time_t seed) {
  int j, k, m, n, t, count;


  // Generate a new (valid) Sudoku grid...
  seed_ = seed;
  srand(seed);

  memset(grid_values_, 0, sizeof(grid_values_));

  for (j = 0; j < 9; j += 3) {
    for (k = 0; k < 9; k += 3) {
      for (t = 1; t <= 9; t ++) {
	for (count = 0; count < 20; count ++) {
	  m = j + (rand() % 3);
	  n = k + (rand() % 3);
	  if (!grid_values_[m][n]) {
	    int mm;

	    for (mm = 0; mm < m; mm ++)
	      if (grid_values_[mm][n] == t) break;

	    if (mm < m) continue;

	    int nn;

	    for (nn = 0; nn < n; nn ++)
	      if (grid_values_[m][nn] == t) break;

	    if (nn < n) continue;

	    grid_values_[m][n] = t;
	    break;
	  }
	}

	if (count == 20) {
	  // Unable to find a valid puzzle so far, so start over...
	  k = 9;
	  j = -3;
	  memset(grid_values_, 0, sizeof(grid_values_));
	}
      }
    }
  }

  // Start by making all cells editable
  SudokuCell *cell;

  for (j = 0; j < 9; j ++)
    for (k = 0; k < 9; k ++) {
      cell = grid_cells_[j][k];

      cell->value(0);
      cell->readonly(0);
      cell->color(FL_LIGHT3);
    }

  // Show N cells...
  count = 11 * (5 - difficulty_);

  int numbers[9];

  for (j = 0; j < 9; j ++) numbers[j] = j + 1;

  while (count > 0) {
    for (j = 0; j < 20; j ++) {
      k          = rand() % 9;
      m          = rand() % 9;
      t          = numbers[k];
      numbers[k] = numbers[m];
      numbers[m] = t;
    }

    for (j = 0; count > 0 && j < 9; j ++) {
      t = numbers[j];

      for (k = 0; count > 0 && k < 9; k ++) {
        cell = grid_cells_[j][k];

        if (grid_values_[j][k] == t && !cell->readonly()) {
	  cell->value(grid_values_[j][k]);
	  cell->readonly(1);
	  cell->color(FL_GRAY);

	  count --;
	  break;
	}
      }
    }
  }
}


// Return the next available value for a cell...
int
Sudoku::next_value(SudokuCell *c) {
  int	j, k, m, n;


  for (j = 0; j < 9; j ++) {
    for (k = 0; k < 9; k ++)
      if (grid_cells_[j][k] == c) break;

    if (k < 9) break;
  }

  if (j == 9) return 1;

  j -= j % 3;
  k -= k % 3;

  int numbers[9];

  memset(numbers, 0, sizeof(numbers));

  for (m = 0; m < 3; m ++)
    for (n = 0; n < 3; n ++) {
      c = grid_cells_[j + m][k + n];
      if (c->value()) numbers[c->value() - 1] = 1;
    }

  for (j = 0; j < 9; j ++)
    if (!numbers[j]) return j + 1;

  return 1;
}


// Reset widget color to gray...
void
Sudoku::reset_cb(Fl_Widget *widget, void *) {
  widget->color(FL_LIGHT3);
  widget->redraw();
  
  ((Sudoku *)(widget->window()))->check_game(false);
}


// Resize the window...
void
Sudoku::resize(int X, int Y, int W, int H) {
  // Resize the window...
  Fl_Double_Window::resize(X, Y, W, H);

  // Save the new window geometry...
  prefs_.set("x", X);
  prefs_.set("y", Y);
  prefs_.set("width", W);
  prefs_.set("height", H);
}


// Restart game from beginning...
void
Sudoku::restart_cb(Fl_Widget *widget, void *) {
  Sudoku *s = (Sudoku *)(widget->window());
  bool solved = true;

  for (int j = 0; j < 9; j ++)
    for (int k = 0; k < 9; k ++) {
      SudokuCell *cell = s->grid_cells_[j][k];

      if (!cell->readonly()) {
        solved = false;
        int v = cell->value();
	cell->value(0);
	cell->color(FL_LIGHT3);
	if (v && s->sound_) s->sound_->play('A' + v - 1);
      }
    }

  if (solved) s->new_game(s->seed_);
}


// Save the current game state...
void
Sudoku::save_game() {
  // Save the current values and state of each grid...
  for (int j = 0; j < 9; j ++)
    for (int k = 0; k < 9; k ++) {
      char name[255];
      SudokuCell *cell = grid_cells_[j][k];

      sprintf(name, "value%d.%d", j, k);
      prefs_.set(name, grid_values_[j][k]);

      sprintf(name, "state%d.%d", j, k);
      prefs_.set(name, cell->value());

      sprintf(name, "readonly%d.%d", j, k);
      prefs_.set(name, cell->readonly());

      for (int m = 0; m < 8; m ++) {
	sprintf(name, "test%d%d.%d", m, j, k);
	prefs_.set(name, cell->test_value(m));
      }
    }
}


// Set title of window...
void
Sudoku::set_title() {
  static const char * const titles[] = {
    "Sudoku - Easy",
    "Sudoku - Medium",
    "Sudoku - Hard",
    "Sudoku - Impossible"
  };

  label(titles[difficulty_]);
}


// Solve the puzzle...
void
Sudoku::solve_cb(Fl_Widget *widget, void *) {
  ((Sudoku *)(widget->window()))->solve_game();
}


// Solve the puzzle...
void
Sudoku::solve_game() {
  int j, k;

  for (j = 0; j < 9; j ++) {
    for (k = 0; k < 9; k ++) {
      SudokuCell *cell = grid_cells_[j][k];

      cell->value(grid_values_[j][k]);
      cell->readonly(1);
      cell->color(FL_GRAY);
    }

    if (sound_) sound_->play('A' + grid_cells_[j][8]->value() - 1);
  }
}


// Main entry for game...
int
main(int argc, char *argv[]) {
  Sudoku s;

  // Show the game...
  s.show(argc, argv);

  // Load the previous game...
  s.load_game();

  // Run until the user quits...
  return (Fl::run());
}


//
// End of "$Id: sudoku.cxx 7903 2010-11-28 21:06:39Z matt $".
//
