rockbox/apps/plugins/sudoku.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2005 Dave Chapman
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/

/***
Sudoku by Dave Chapman

User instructions
-----------------

Use the arrow keys to move cursor, and press SELECT/ON/F2 to increment
the number under the cursor.

At any time during the game, press On to bring up the game menu with
further options:

 Save
 Reload
 Clear
 Solve

Sudoku is implemented as a "viewer" for a ".ss" file, as generated by
Simple Sudoku and other applications - http://angusj.com/sudoku/

In-progress game positions are saved in the original .ss file, with
A-I used to indicate numbers entered by the user.

Example ".ss" file, and one with a saved state:

...|...|...     ...|...|...
2..|8.4|9.1     2.C|8.4|9.1
...|1.6|32.     E..|1.6|32.
-----------     -----------
...|..5|.4.     ...|..5|.4.
8..|423|..6     8..|423|..6
.3.|9..|...     .3D|9..|A..
-----------     -----------
.63|7.9|...     .63|7.9|...
4.9|5.2|..8     4.9|5.2|.C8
...|...|...     ...|...|...

*/

#include "plugin.h"

#ifdef HAVE_LCD_BITMAP

PLUGIN_HEADER

#define STATE_FILE        PLUGIN_DIR "/sudoku.state"
#define GAMES_FILE        PLUGIN_DIR "/sudoku.levels"

/* variable button definitions */
#if CONFIG_KEYPAD == RECORDER_PAD
#define SUDOKU_BUTTON_QUIT BUTTON_OFF
#define SUDOKU_BUTTON_UP BUTTON_UP
#define SUDOKU_BUTTON_DOWN BUTTON_DOWN
#define SUDOKU_BUTTON_TOGGLE BUTTON_PLAY
#define SUDOKU_BUTTON_MENU BUTTON_F1
#define SUDOKU_BUTTON_POSSIBLE BUTTON_F2

#elif CONFIG_KEYPAD == ONDIO_PAD
#define SUDOKU_BUTTON_QUIT BUTTON_OFF
#define SUDOKU_BUTTON_UP BUTTON_UP
#define SUDOKU_BUTTON_DOWN BUTTON_DOWN
#define SUDOKU_BUTTON_ALTTOGGLE (BUTTON_MENU | BUTTON_DOWN)
#define SUDOKU_BUTTON_TOGGLE_PRE BUTTON_MENU
#define SUDOKU_BUTTON_TOGGLE (BUTTON_MENU | BUTTON_REL)
#define SUDOKU_BUTTON_MENU_PRE BUTTON_MENU
#define SUDOKU_BUTTON_MENU (BUTTON_MENU | BUTTON_REPEAT)
#define SUDOKU_BUTTON_POSSIBLE (BUTTON_MENU | BUTTON_LEFT)

#elif (CONFIG_KEYPAD == IRIVER_H100_PAD) || \
      (CONFIG_KEYPAD == IRIVER_H300_PAD)
#define SUDOKU_BUTTON_QUIT BUTTON_OFF
#define SUDOKU_BUTTON_UP BUTTON_UP
#define SUDOKU_BUTTON_DOWN BUTTON_DOWN
#define SUDOKU_BUTTON_ALTTOGGLE BUTTON_ON
#define SUDOKU_BUTTON_TOGGLE BUTTON_SELECT
#define SUDOKU_BUTTON_MENU BUTTON_MODE
#define SUDOKU_BUTTON_POSSIBLE BUTTON_REC

#elif (CONFIG_KEYPAD == IPOD_4G_PAD) || \
      (CONFIG_KEYPAD == IPOD_3G_PAD)
#define SUDOKU_BUTTON_QUIT (BUTTON_SELECT | BUTTON_MENU)
#define SUDOKU_BUTTON_UP BUTTON_SCROLL_BACK
#define SUDOKU_BUTTON_DOWN BUTTON_SCROLL_FWD
#define SUDOKU_BUTTON_TOGGLE BUTTON_SELECT
#define SUDOKU_BUTTON_MENU BUTTON_MENU
#define SUDOKU_BUTTON_POSSIBLE (BUTTON_SELECT | BUTTON_LEFT)

#elif (CONFIG_KEYPAD == IAUDIO_X5_PAD)
#define SUDOKU_BUTTON_QUIT BUTTON_POWER
#define SUDOKU_BUTTON_UP BUTTON_UP
#define SUDOKU_BUTTON_DOWN BUTTON_DOWN
#define SUDOKU_BUTTON_TOGGLE BUTTON_SELECT
#define SUDOKU_BUTTON_MENU BUTTON_PLAY
#define SUDOKU_BUTTON_POSSIBLE BUTTON_REC

#elif (CONFIG_KEYPAD == GIGABEAT_PAD)
#define SUDOKU_BUTTON_QUIT BUTTON_A
#define SUDOKU_BUTTON_UP BUTTON_UP
#define SUDOKU_BUTTON_DOWN BUTTON_DOWN
#define SUDOKU_BUTTON_TOGGLE BUTTON_SELECT
#define SUDOKU_BUTTON_MENU BUTTON_MENU
#define SUDOKU_BUTTON_POSSIBLE BUTTON_POWER

#elif
  #error SUDOKU: Unsupported keypad
#endif

/* The bitmaps */
extern const fb_data sudoku_normal[];
extern const fb_data sudoku_start[];
extern const fb_data sudoku_inverse[];

#if (LCD_HEIGHT==128) && (LCD_WIDTH==160)
/* For iriver H1x0 - 160x128, 9 cells @ 12x12 with 14 border lines*/

/* Internal dimensions of a cell */
#define CELL_WIDTH 12
#define CELL_HEIGHT 12

#define BOARD_WIDTH (CELL_WIDTH*9+10+4)
#define BOARD_HEIGHT (CELL_HEIGHT*9+10+4)

#define XOFS (((LCD_WIDTH-BOARD_WIDTH)/2)+10)
#define YOFS ((LCD_HEIGHT-BOARD_HEIGHT)/2)

#define XOFSSCRATCHPAD 3

/* Locations of each cell */
static unsigned char cellxpos[9]={ 2, 15, 28, 42, 55, 68, 82, 95, 108 };
static unsigned char cellypos[9]={ 2, 15, 28, 42, 55, 68, 82, 95, 108 };

/* The height of one cell in the bitmap */
#define BITMAP_HEIGHT 12
#define BITMAP_STRIDE 12

#elif (LCD_HEIGHT==64) && (LCD_WIDTH==112)
/* For Archos Recorder, FM and Ondio (112x64):
   9 cells @ 8x6 with 10 border lines
*/

/* Internal dimensions of a cell */
#define CELL_WIDTH 8
#define CELL_HEIGHT 6

#define BOARD_WIDTH (CELL_WIDTH*9+10)
#define BOARD_HEIGHT (CELL_HEIGHT*9+10)

#define XOFS (((LCD_WIDTH-BOARD_WIDTH)/2)+7)
#define YOFS ((LCD_HEIGHT-BOARD_HEIGHT)/2)

#define XOFSSCRATCHPAD 2

/* Locations of each cell */
static unsigned char cellxpos[9]={ 1, 10, 19, 28, 37, 46, 55, 64, 73 };
static unsigned char cellypos[9]={ 1,  8, 15, 22, 29, 36, 43, 50, 57 }; 

/* The height of one cell in the bitmap */
#define BITMAP_HEIGHT 8
#define BITMAP_STRIDE 8

#elif (LCD_HEIGHT>=176) && (LCD_WIDTH>=220)
/* iriver h300 */

/* Internal dimensions of a cell */
#define CELL_WIDTH 16
#define CELL_HEIGHT 16

#define BOARD_WIDTH (CELL_WIDTH*9+10+4)
#define BOARD_HEIGHT (CELL_HEIGHT*9+10+4)

#define XOFS (((LCD_WIDTH-BOARD_WIDTH)/2)+15)
#define YOFS ((LCD_HEIGHT-BOARD_HEIGHT)/2)

#define XOFSSCRATCHPAD 10

/* Locations of each cell */
static unsigned char cellxpos[9]={ 2, 19, 36, 54, 71, 88, 106, 123, 140 };
static unsigned char cellypos[9]={ 2, 19, 36, 54, 71, 88, 106, 123, 140 };

/* The height of one cell in the bitmap */
#define BITMAP_HEIGHT 16
#define BITMAP_STRIDE  16

#else
  #error SUDOKU: Unsupported LCD size
#endif

/* here is a global api struct pointer. while not strictly necessary,
   it's nice not to have to pass the api pointer in all function calls
   in the plugin */
static struct plugin_api* rb;

struct sudoku_state_t {
  char filename[MAX_PATH];  /* Filename */
  char startboard[9][9];    /* The initial state of the game */
  char currentboard[9][9];  /* The current state of the game */
  char savedboard[9][9];    /* Cached copy of saved state */
  int x,y;                  /* Cursor position */
  int editmode;             /* We are editing the start board */
#ifdef SUDOKU_BUTTON_POSSIBLE 
  short possiblevals[9][9];  /* possible values a cell could be, user sets them */
#endif
};

/****** Solver routine by Tom Shackell <shackell@cs.york.ac.uk>

Downloaded from:

http://www-users.cs.york.ac.uk/~shackell/sudoku/Sudoku.html

Released under GPLv2

*/

typedef unsigned int  Bitset;

#define BLOCK        3
#define SIZE         (BLOCK*BLOCK)

#define true  1
#define false 0

typedef struct _Sudoku {
    Bitset          table[SIZE][SIZE];
}Sudoku;

typedef struct _Stats {
    int             numTries;
    int             backTracks;
    int             numEmpty;
    bool            solutionFound;
}Stats;

typedef struct _Options {
    bool            allSolutions;
    bool            uniquenessCheck;
}Options;

void sudoku_init(Sudoku* sud);
void sudoku_set(Sudoku* sud, int x, int y, int num, bool original);
int  sudoku_get(Sudoku* sud, int x, int y, bool* original);

#define BIT(n)          ((Bitset)(1<<(n)))
#define BIT_TEST(v,n)   ((((Bitset)v) & BIT(n)) != 0)
#define BIT_CLEAR(v,n)  (v) &= ~BIT(n)
#define MARK_BIT        BIT(0)
#define ORIGINAL_BIT    BIT(SIZE+1)

#define ALL_BITS        (BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5) | BIT(6) | BIT(7) | BIT(8) | BIT(9))

/* initialize a sudoku problem, should be called before using set or get */
void sudoku_init(Sudoku* sud)
{
    int y, x;
    for (y = 0; y < SIZE; y++){
        for (x = 0; x < SIZE; x++){
            sud->table[x][y] = ALL_BITS;
        }
    }
}

/* set the number at a particular x and y column */
void sudoku_set(Sudoku* sud, int x, int y, int num, bool original)
{
    int i, j;
    int bx, by;
    Bitset orig;

    /* clear the row and columns  */
    for (i = 0; i < SIZE; i++){
        BIT_CLEAR(sud->table[i][y], num);
        BIT_CLEAR(sud->table[x][i], num);
    }
    /* clear the block  */
    bx = x - (x % BLOCK);
    by = y - (y % BLOCK);
    for (i = 0; i < BLOCK; i++){
        for (j = 0; j < BLOCK; j++){
            BIT_CLEAR(sud->table[bx+j][by+i], num);
        }
    }
    /* mark the table */
    orig = original ? ORIGINAL_BIT : 0;
    sud->table[x][y] = BIT(num) | MARK_BIT | orig;
}

/* get the number at a particular x and y column, if this
   is not unique return 0 */
int sudoku_get(Sudoku* sud, int x, int y, bool* original)
{
    Bitset val = sud->table[x][y];
    int result = 0;
    int i;

    if (original) {
        *original = val & ORIGINAL_BIT;
    }
    for (i = 1; i <= SIZE; i++){
        if (BIT_TEST(val, i)){
            if (result != 0){
                return 0;
            }
            result = i;
        }
    }  
    return result;
}

/* returns true if this is a valid problem, this is necessary because the input
   problem might be degenerate which breaks the solver algorithm. */
static bool is_valid(const Sudoku* sud)
{
    int x, y;
    
    for (y = 0; y < SIZE; y++){
        for (x = 0; x < SIZE; x++){
            if ((sud->table[x][y] & ALL_BITS) == 0){
                return false;
            }
        }
    }
    return true;
}

/* scan the table for the most constrained item, giving all it's options, sets
   the best x and y coordinates, the number of options and the options for
   that coordinate and returns true if the puzzle is finished */
static bool scan(const Sudoku* sud, int* rX, int* rY, int *num, int* options)
{
    int x, y, i, j;
    int bestCount = SIZE+1;
    Bitset val;
    bool allMarked = true;

    for (y = 0; y < SIZE; y++){
        for (x = 0; x < SIZE; x++){
            Bitset val = sud->table[x][y];
            int i;
            int count = 0;

            if (val & MARK_BIT) {
                /* already set  */
                continue;
            }
            allMarked = false;
            for (i = 1; i <= SIZE; i++){
                if (BIT_TEST(val, i)){
                    count++;
                }
            }
            if (count < bestCount){
                bestCount = count;
                *rX = x;
                *rY = y;
                if (count == 0){
                    /* can't possibly be beaten  */
                    *num = 0;
                    return false;
                }
            }
        }
    }
    /* now copy into options  */
    *num = bestCount;
    val = sud->table[*rX][*rY];
    for (i = 1, j = 0; i <= SIZE; i++){
        if (BIT_TEST(val, i)){
            options[j++] = i;
        }
    }
    return allMarked;
}

static bool solve(Sudoku* sud, Stats* stats, const Options* options);

/* try a particular option and return true if that gives a solution or false
   if it doesn't, restores board on backtracking */
static bool spawn_option(Sudoku* sud, Stats* stats, const Options* options,
                         int x, int y, int num)
{
    Sudoku copy;

    rb->memcpy(&copy,sud,sizeof(Sudoku));
    sudoku_set(&copy, x, y, num, false);
    stats->numTries += 1;
    if (solve(&copy, stats, options)){
        if (!options->allSolutions && stats->solutionFound){
            rb->memcpy(sud,&copy,sizeof(Sudoku));
        }
        return true;
    }else{
        stats->backTracks++;
    }
    return false;
}

/* solve a sudoku problem, returns true if there is a solution and false
   otherwise.  stats is used to track statisticss */
static bool solve(Sudoku* sud, Stats* stats, const Options* options)
{
    while (true){
        int x, y, i, num;
        int places[SIZE];
        
        if (scan(sud, &x, &y, &num, places)){
            /* a solution was found! */
            if (options->uniquenessCheck && stats->solutionFound){
                /*printf("\n\t... But the solution is not unique!\n"); */
                return true;
            }
            stats->solutionFound = true;
            if (options->allSolutions || options->uniquenessCheck){
                /*printf("\n\tSolution after %d iterations\n", stats->numTries); */
                /*sudoku_print(sud); */
                return false;
            }
            else{
                return true;
            }
        }
        if (num == 0){
            /* can't be satisfied  */
            return false;
        }
        /* try all the places (except the last one) */
        for (i = 0; i < num-1; i++){
            if (spawn_option(sud, stats, options, x, y, places[i])){
                /* solution found! */
                if (!options->allSolutions && stats->solutionFound){
                    return true;
                }
            }
        }
        /* take the last place ourself */
        stats->numTries += 1;
        sudoku_set(sud, x, y, places[num-1], false);    
    }
}

/******** END OF IMPORTED CODE */


/* A wrapper function between the Sudoku plugin and the above solver code */
void sudoku_solve(struct sudoku_state_t* state)
{
    bool ret;
    Stats stats;
    Options options;
    Sudoku sud;
    bool original;
    int r,c;
    
    /* Initialise the parameters */
    sudoku_init(&sud);
    rb->memset(&stats,0,sizeof(stats));
    options.allSolutions=false;
    options.uniquenessCheck=false;

    /* Convert Rockbox format into format for solver */
    for (r=0;r<9;r++) {
        for (c=0;c<9;c++) {
            if (state->startboard[r][c]!='0') {
                sudoku_set(&sud, c, r, state->startboard[r][c]-'0', true);
            }
        }
    }

    /* need to check for degenerate input problems ... */
    if (is_valid(&sud)){
        ret = solve(&sud, &stats, &options);
    } else {
        ret = false;
    }
    
    if (ret) {
        /* Populate the board with the solution. */
        for (r=0;r<9;r++) {
            for (c=0;c<9;c++) {
                state->currentboard[r][c]='0'+
                    sudoku_get(&sud, c, r, &original);
            }
        }
    } else {
        rb->splash(HZ*2, true, "Solve failed");
    }

    return;
}


void clear_state(struct sudoku_state_t* state)
{
    int r,c;

    state->filename[0]=0;
    for (r=0;r<9;r++) {
        for (c=0;c<9;c++) {
            state->startboard[r][c]='0';
            state->currentboard[r][c]='0';
#ifdef SUDOKU_BUTTON_POSSIBLE 
            state->possiblevals[r][c]=0;
#endif
        }
    }

    state->x=0;
    state->y=0;
    state->editmode=0;
}

/* Load game - only ".ss" is officially supported, but any sensible
   text representation (one line per row) may load.
*/
bool load_sudoku(struct sudoku_state_t* state, char* filename)
{
    int fd;
    size_t n;
    int r = 0, c = 0;
    unsigned int i;
    int valid=0;
    char buf[300]; /* A buffer to read a sudoku board from */

    fd=rb->open(filename, O_RDONLY);
    if (fd < 0) {
        rb->splash(HZ*2, true, "Can not open");
        LOGF("Invalid sudoku file: %s\n",filename);
        return(false);
    }

    rb->strncpy(state->filename,filename,MAX_PATH);
    n=rb->read(fd,buf,300);
    if (n <= 0) {
        return(false);
    }
    rb->close(fd);

    r=0;
    c=0;
    i=0;
    while ((i < n) && (r < 9)) {
        switch (buf[i]){
            case ' ': case '\t':
                if (c > 0)
                    valid=1;
                break;
            case '|':
            case '*':
            case '-':
            case '\r':
                break;
            case '\n':
                if (valid) {
                    r++; 
                    valid=0;
                }
                c = 0;
                break;
            case '_': case '.':
                valid=1;
                if (c >= SIZE || r >= SIZE){
                    LOGF("ERROR: sudoku problem is the wrong size (%d,%d)\n",
                         c, r);
                    return(false);
                }
                c++;
                break;
            default:
                if (((buf[i]>='A') && (buf[i]<='I')) ||
                    ((buf[i]>='0') && (buf[i]<='9'))) {
                    valid=1;
                    if (r >= SIZE || c >= SIZE){
                        LOGF("ERROR: sudoku problem is the wrong size "
                             "(%d,%d)\n", c, r);
                        return(false);
                    }
                    if ((buf[i]>='0') && (buf[i]<='9')) {
                        state->startboard[r][c]=buf[i];
                        state->currentboard[r][c]=buf[i];
                    } else {
                        state->currentboard[r][c]='1'+(buf[i]-'A');
                    }
                    c++;
                }
                /* Ignore any other characters */
                break;
        }
        i++;
    }

    /* Save a copy of the saved state - so we can reload without using the
       disk */
    rb->memcpy(state->savedboard,state->currentboard,81);
    return(true);
}

bool save_sudoku(struct sudoku_state_t* state)
{
    int fd;
    int r,c;
    int i;
    char line[16];
    char sep[16];

    rb->memcpy(line,"...|...|...\r\n",13);
    rb->memcpy(sep,"-----------\r\n",13);

    if (state->filename[0]==0) {
        return false;
    }

    fd=rb->open(state->filename, O_WRONLY|O_CREAT);
    if (fd >= 0) {
        for (r=0;r<9;r++) {
            i=0;
            for (c=0;c<9;c++) {
                if (state->startboard[r][c]!='0') {
                    line[i]=state->startboard[r][c];
                } else if (state->currentboard[r][c]!='0') {
                    line[i]='A'+(state->currentboard[r][c]-'1');
                } else {
                    line[i]='.';
                }
                i++;
                if ((c==2) || (c==5)) {
                    i++;
                }
            }
            rb->write(fd,line,sizeof(line)-1);
            if ((r==2) || (r==5)) {
                rb->write(fd,sep,sizeof(sep)-1);
            }
        }
        /* Add a blank line at end */
        rb->write(fd,"\r\n",2);
        rb->close(fd);
        /* Save a copy of the saved state - so we can reload without
           using the disk */
        rb->memcpy(state->savedboard,state->currentboard,81);
        return true;
    } else {
        return false;
    }
}

void restore_state(struct sudoku_state_t* state)
{
    rb->memcpy(state->currentboard,state->savedboard,81);
}

void clear_board(struct sudoku_state_t* state)
{
    int r,c;

    for (r=0;r<9;r++) {
        for (c=0;c<9;c++) {
            state->currentboard[r][c]=state->startboard[r][c];
        }
    }
    state->x=0;
    state->y=0;
}

void update_cell(struct sudoku_state_t* state, int r, int c) 
{
    /* We have four types of cell:
       1) User-entered number
       2) Starting number
       3) Cursor in cell
    */

    if ((r==state->y) && (c==state->x)) {
        rb->lcd_bitmap_part(sudoku_inverse,0,
                            BITMAP_HEIGHT*(state->currentboard[r][c]-'0'),
                            BITMAP_STRIDE,
                            XOFS+cellxpos[c],YOFS+cellypos[r],CELL_WIDTH,
                            CELL_HEIGHT);
    } else {
        if (state->startboard[r][c]!='0') {
            rb->lcd_bitmap_part(sudoku_start,0,
                                BITMAP_HEIGHT*(state->startboard[r][c]-'0'),
                                BITMAP_STRIDE,
                                XOFS+cellxpos[c],YOFS+cellypos[r],
                                CELL_WIDTH,CELL_HEIGHT);
        } else {
            rb->lcd_bitmap_part(sudoku_normal,0,
                                BITMAP_HEIGHT*(state->currentboard[r][c]-'0'),
                                BITMAP_STRIDE,
                                XOFS+cellxpos[c],YOFS+cellypos[r],
                                CELL_WIDTH,CELL_HEIGHT);
        }
    }

    rb->lcd_update_rect(cellxpos[c],cellypos[r],CELL_WIDTH,CELL_HEIGHT);
}


void display_board(struct sudoku_state_t* state) 
{
    int r,c;

    /* Clear the display buffer */
    rb->lcd_clear_display();

    /* Draw the gridlines - differently for different targets */

#if LCD_HEIGHT > 64
    /* Large targets - draw single/double lines */
    for (r=0;r<9;r++) {
        rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[r]-1);
        rb->lcd_vline(XOFS+cellxpos[r]-1,YOFS,YOFS+BOARD_HEIGHT-1);
        if ((r % 3)==0) { 
            rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[r]-2);
            rb->lcd_vline(XOFS+cellxpos[r]-2,YOFS,YOFS+BOARD_HEIGHT-1);
        }
    }
    rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[8]+CELL_HEIGHT);
    rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[8]+CELL_HEIGHT+1);
    rb->lcd_vline(XOFS+cellxpos[8]+CELL_WIDTH,YOFS,YOFS+BOARD_HEIGHT-1);
    rb->lcd_vline(XOFS+cellxpos[8]+CELL_WIDTH+1,YOFS,YOFS+BOARD_HEIGHT-1);
#elif (LCD_HEIGHT==64)
    /* Small targets - draw dotted/single lines */
    for (r=0;r<9;r++) {
        if ((r % 3)==0) {
            /* Solid Line */
            rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[r]-1);
            rb->lcd_vline(XOFS+cellxpos[r]-1,YOFS,YOFS+BOARD_HEIGHT-1);
        } else {
            /* Dotted line */
            for (c=XOFS;c<XOFS+BOARD_WIDTH;c+=2) {
                rb->lcd_drawpixel(c,YOFS+cellypos[r]-1);
            }
            for (c=YOFS;c<YOFS+BOARD_HEIGHT;c+=2) {
                rb->lcd_drawpixel(XOFS+cellxpos[r]-1,c);
            }
        }
    }
    rb->lcd_hline(XOFS,XOFS+BOARD_WIDTH-1,YOFS+cellypos[8]+CELL_HEIGHT);
    rb->lcd_vline(XOFS+cellxpos[8]+CELL_WIDTH,YOFS,YOFS+BOARD_HEIGHT-1);
#else
#error SUDOKU: Unsupported LCD height
#endif

#ifdef SUDOKU_BUTTON_POSSIBLE
    rb->lcd_vline(XOFSSCRATCHPAD,YOFS,YOFS+BOARD_HEIGHT-1);
    rb->lcd_vline(XOFSSCRATCHPAD+CELL_WIDTH+1,YOFS,YOFS+BOARD_HEIGHT-1);
    for (r=0;r<9;r++) {
#if LCD_HEIGHT > 64
        /* Large targets - draw single/double lines */
        rb->lcd_hline(XOFSSCRATCHPAD,XOFSSCRATCHPAD+CELL_WIDTH+1,
                      YOFS+cellypos[r]-1);
        if ((r % 3)==0)
            rb->lcd_hline(XOFSSCRATCHPAD,XOFSSCRATCHPAD+CELL_WIDTH+1,
                          YOFS+cellypos[r]-2);
#elif LCD_HEIGHT == 64
        /* Small targets - draw dotted/single lines */
        if ((r % 3)==0) {
            /* Solid Line */
            rb->lcd_hline(XOFSSCRATCHPAD,XOFSSCRATCHPAD+CELL_WIDTH+1,
                          YOFS+cellypos[r]-1);
        } else {
            /* Dotted line */
            for (c=XOFSSCRATCHPAD;c<XOFSSCRATCHPAD+CELL_WIDTH+1;c+=2) {
                rb->lcd_drawpixel(c,YOFS+cellypos[r]-1);
            }
        }
#endif
        if ((r>0) && state->possiblevals[state->y][state->x]&(1<<(r)))
            rb->lcd_bitmap_part(sudoku_normal,0,BITMAP_HEIGHT*r,BITMAP_STRIDE,
                                XOFSSCRATCHPAD+1,YOFS+cellypos[r-1],
                                CELL_WIDTH,CELL_HEIGHT);
    }
    rb->lcd_hline(XOFSSCRATCHPAD,XOFSSCRATCHPAD+CELL_WIDTH+1,
                  YOFS+cellypos[8]+CELL_HEIGHT);
#if LCD_HEIGHT > 64
    rb->lcd_hline(XOFSSCRATCHPAD,XOFSSCRATCHPAD+CELL_WIDTH+1,
                  YOFS+cellypos[8]+CELL_HEIGHT+1);
#endif
    if (state->possiblevals[state->y][state->x]&(1<<(r)))
        rb->lcd_bitmap_part(sudoku_normal,0,BITMAP_HEIGHT*r,BITMAP_STRIDE,
                            XOFSSCRATCHPAD+1,YOFS+cellypos[8],
                            CELL_WIDTH,CELL_HEIGHT);
#endif

    /* Draw the numbers */
    for (r=0;r<9;r++) {
        for (c=0;c<9;c++) {
            /* We have four types of cell:
               1) User-entered number
               2) Starting number
               3) Cursor in cell
            */
            
            if ((r==state->y) && (c==state->x)) {
                rb->lcd_bitmap_part(sudoku_inverse,0,
                                    BITMAP_HEIGHT*(state->currentboard[r][c]-
                                                   '0'),
                                    BITMAP_STRIDE,
                                    XOFS+cellxpos[c],YOFS+cellypos[r],
                                    CELL_WIDTH,CELL_HEIGHT);
            } else {
                if (state->startboard[r][c]!='0') {
                    rb->lcd_bitmap_part(sudoku_start,0,
                                        BITMAP_HEIGHT*(state->startboard[r][c]-
                                                       '0'),
                                        BITMAP_STRIDE,
                                        XOFS+cellxpos[c],YOFS+cellypos[r],
                                        CELL_WIDTH,CELL_HEIGHT);
                } else {
                    rb->lcd_bitmap_part(sudoku_normal,0,
                                        BITMAP_HEIGHT*
                                        (state->currentboard[r][c]-'0'),
                                        BITMAP_STRIDE,
                                        XOFS+cellxpos[c],YOFS+cellypos[r],
                                        CELL_WIDTH,CELL_HEIGHT);
                }
            }
        }
    }

    /* update the screen */
    rb->lcd_update();
}

/* Check the status of the board, assuming a change at the cursor location */
bool check_status(struct sudoku_state_t* state)
{
    int check[9];
    int r,c;
    int r1,c1;
    int cell;

    /* First, check the column */
    for (cell=0;cell<9;cell++) {
        check[cell]=0;
    }
    for (r=0;r<9;r++) {
        cell=state->currentboard[r][state->x];
        if (cell!='0') {
            if (check[cell-'1']==1) {
                return true;
            }
            check[cell-'1']=1;
        }
    }

    /* Second, check the row */  
    for (cell=0;cell<9;cell++) {
        check[cell]=0;
    }
    for (c=0;c<9;c++) {
        cell=state->currentboard[state->y][c];
        if (cell!='0') {
            if (check[cell-'1']==1) {
                return true;
            }
            check[cell-'1']=1;
        }
    }

    /* Finally, check the 3x3 sub-grid */
    for (cell=0;cell<9;cell++) {
        check[cell]=0;
    }
    r1=(state->y/3)*3;
    c1=(state->x/3)*3;
    for (r=r1;r<r1+3;r++) {
        for (c=c1;c<c1+3;c++) {
            cell=state->currentboard[r][c];
            if (cell!='0') {
                if (check[cell-'1']==1) {
                    return true;
                }
                check[cell-'1']=1;
            }
        }
    }

    /* We passed all the checks :) */

    return false;
}

int sudoku_menu_cb(int key, int m)
{
    (void)m;
    switch(key)
    {
#ifdef MENU_ENTER2
    case MENU_ENTER2:
#endif
    case MENU_ENTER:
        key = BUTTON_NONE; /* eat the downpress, next menu reacts on release */
        break;

#ifdef MENU_ENTER2
    case MENU_ENTER2 | BUTTON_REL:
#endif
    case MENU_ENTER | BUTTON_REL:
        key = MENU_ENTER; /* fake downpress, next menu doesn't like release */
        break;
    }

    return key;
}

bool sudoku_menu(struct sudoku_state_t* state)
{
    int m;
    int result;

    static const struct menu_item items[] = {
        { "Save", NULL },
        { "Reload", NULL },
        { "Clear", NULL },
        { "Solve", NULL },
        { "New", NULL },
    };
    
    m = rb->menu_init(items, sizeof(items) / sizeof(*items),
                      sudoku_menu_cb, NULL, NULL, NULL);

    result=rb->menu_show(m);

    switch (result) {
        case 0: /* Save state */
            save_sudoku(state);
            break;

        case 1: /* Restore state */
            restore_state(state);
            break;

        case 2: /* Clear all */
            clear_board(state);
            break;

        case 3: /* Solve */
            sudoku_solve(state);
            break;

        case 4: /* Create a new game manually */
            clear_state(state);
            state->editmode=1;
            break;

        default:
            break;
    }

    rb->menu_exit(m);

    return (result==MENU_ATTACHED_USB);
}

void move_cursor(struct sudoku_state_t* state, int newx, int newy)
{
    int oldx, oldy;

    /* Check that the character at the cursor position is legal */
    if (check_status(state)) {
        rb->splash(HZ*2, true, "Illegal move!");
        /* Ignore any button presses during the splash */
        rb->button_clear_queue();
        return;
    }

    /* Move Cursor */
    oldx=state->x;
    oldy=state->y;
    state->x=newx;
    state->y=newy;

    /* Redraw current and old cells */
    update_cell(state,oldx,oldy);
    update_cell(state,newx,newy);  
}

/* plugin entry point */
enum plugin_status plugin_start(struct plugin_api* api, void* parameter)
{
    bool exit;
    int button;
    int lastbutton = BUTTON_NONE;
    long ticks;
    struct sudoku_state_t state;

    /* plugin init */
    rb = api;
    /* end of plugin init */

    clear_state(&state);

    if (parameter==NULL) {
        state.editmode=1;
    } else {
        if (!load_sudoku(&state,(char*)parameter)) {
            rb->splash(HZ*2, true, "Load error");
            return(PLUGIN_ERROR);
        }
    }

    display_board(&state);

    /* The main game loop */
    exit=false;
    ticks=0;
    while(!exit) {
        button = rb->button_get(true);

        switch(button){
            /* Exit game */
            case SUDOKU_BUTTON_QUIT:
                exit=1;
                break;

      /* Increment digit */
#ifdef SUDOKU_BUTTON_ALTTOGGLE
            case SUDOKU_BUTTON_ALTTOGGLE | BUTTON_REPEAT:
#endif
            case SUDOKU_BUTTON_TOGGLE | BUTTON_REPEAT:
                /* Slow down the repeat speed to 1/3 second */
                if ((*rb->current_tick-ticks) < (HZ/3)) {
                    break;
                }

#ifdef SUDOKU_BUTTON_ALTTOGGLE
            case SUDOKU_BUTTON_ALTTOGGLE:
#endif
            case SUDOKU_BUTTON_TOGGLE:
#ifdef SUDOKU_BUTTON_TOGGLE_PRE
                if ((button == SUDOKU_BUTTON_TOGGLE)
                    && (lastbutton != SUDOKU_BUTTON_TOGGLE_PRE))
                    break;
#endif
                /* Increment digit */
                ticks=*rb->current_tick;
                if (state.editmode) {
                    if (state.startboard[state.y][state.x]=='9') { 
                        state.startboard[state.y][state.x]='0';
                        state.currentboard[state.y][state.x]='0';
                    } else {
                        state.startboard[state.y][state.x]++;
                        state.currentboard[state.y][state.x]++;
                    }
                } else {
                    if (state.startboard[state.y][state.x]=='0') {
                        if (state.currentboard[state.y][state.x]=='9') { 
                            state.currentboard[state.y][state.x]='0';
                        } else {
              state.currentboard[state.y][state.x]++;
                        }
                    }
                }
                update_cell(&state,state.y,state.x);
                break;

                /* move cursor left */
            case BUTTON_LEFT:
            case (BUTTON_LEFT | BUTTON_REPEAT):
                if (state.x==0) {
                    move_cursor(&state,8,state.y);
                } else { 
                    move_cursor(&state,state.x-1,state.y);
                }
                break;
                
                /* move cursor right */
            case BUTTON_RIGHT:
            case (BUTTON_RIGHT | BUTTON_REPEAT):
                if (state.x==8) {
                    move_cursor(&state,0,state.y);
                } else { 
                    move_cursor(&state,state.x+1,state.y);
                }
                break;

                /* move cursor up */
            case SUDOKU_BUTTON_UP:
            case (SUDOKU_BUTTON_UP | BUTTON_REPEAT):
                if (state.y==0) {
                    move_cursor(&state,state.x,8);
                } else { 
                    move_cursor(&state,state.x,state.y-1);
                }
                break;

                /* move cursor down */
            case SUDOKU_BUTTON_DOWN:
            case (SUDOKU_BUTTON_DOWN | BUTTON_REPEAT):
                if (state.y==8) {
                    move_cursor(&state,state.x,0);
                } else { 
                    move_cursor(&state,state.x,state.y+1);
                }
                break;

            case SUDOKU_BUTTON_MENU:
#ifdef SUDOKU_BUTTON_MENU_PRE
                if (lastbutton != SUDOKU_BUTTON_MENU_PRE)
                    break;
#endif
                /* Don't let the user leave a game in a bad state */
                if (check_status(&state)) {
                    rb->splash(HZ*2, true, "Illegal move!");
                    /* Ignore any button presses during the splash */
                    rb->button_clear_queue();
                } else {
                    if (state.editmode) {
                        rb->kbd_input(state.filename,MAX_PATH);
                        if (save_sudoku(&state)) {
                            state.editmode=0;
                        } else {
                            rb->splash(HZ*2, true, "Save failed");
                        }
                    } else {
                        if (sudoku_menu(&state)) {
                            return PLUGIN_USB_CONNECTED;
                        }
                    }
                }
                break;
#ifdef SUDOKU_BUTTON_POSSIBLE
            case SUDOKU_BUTTON_POSSIBLE:
                /* Toggle current number in the possiblevals structure */
                if (state.currentboard[state.y][state.x]!='0') {
                    state.possiblevals[state.y][state.x]^=
                        (1 << (state.currentboard[state.y][state.x] - '0'));
                }
                break;
#endif
            default:
                if (rb->default_event_handler(button) == SYS_USB_CONNECTED) {
                    /* Quit if USB has been connected */
                    return PLUGIN_USB_CONNECTED;
                }
                break;
        }
        if (button != BUTTON_NONE)
            lastbutton = button;

        display_board(&state);
    }

    return PLUGIN_OK;
}

#endif