/*
 _
(_
 _)UDOKU 

Authored by abakh <abakh@tuta.io>
To the extent possible under law, the author(s) have dedicated all copyright and related and neighboring rights to this software to the public domain worldwide. This software is distributed without any warranty.

You should have received a copy of the CC0 Public Domain Dedication along with this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.


NOTE: This program is only made for entertainment porpuses. The puzzles are generated by randomly clearing tiles on the table and are guaranteed to have a solution , but are not guaranteed to have only one unique solution.
*/
#include <curses.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>  //to seed random
#include <limits.h>
#include <signal.h>
#include <math.h>
#include "config.h"
typedef signed char byte;

byte _wait=0, waitcycles=0;//apparently 'wait' conflicts with a variable in a library macOS includes by default
byte py,px;
byte diff;
unsigned int filled;
chtype colors[6]={0};


#if defined Plan9 //the Plan9 compiler can not handle VLAs  
#define size 3
#define s 9
// I hope this is approximately right 
int round(float x)
{
    int y;
    if(x > 0)
        y = (int)(x + 0.5); //int will round down, so if the decimal of x is .5 or higher this will round up.
    else if(x < 0)
        y = (int)(x - 0.5); // the same but opposite
    return y;
}   
#else
byte size,s;//s=size*size
#endif
void cross(byte sy,byte sx,chtype start,chtype middle,chtype end){ //to simplify drawing tables. doesn't draw a cross (why did I choose that name?)
		mvaddch(sy,sx,start);
		byte f = 2*size;
		for(char n=1;n<size;++n){
			mvaddch(sy,sx+f,middle);
			f+=2*size;
		}
		mvaddch(sy,sx+f,end);
}

void table(byte sy,byte sx){ //empty table
		byte l;//line
		for(l=0;l<=size;++l){
			for(byte y=0;y<=s+size;++y)
				mvaddch(sy+y,sx+l*size*2,ACS_VLINE);
			for(byte x=0;x<=s*2;++x)
				mvaddch(sy+(size+1)*l,sx+x,ACS_HLINE);
		}
		cross(sy,sx,ACS_ULCORNER,ACS_TTEE,ACS_URCORNER);
		for(l=1;l<size;++l)
			cross(sy+l*size+l,sx,ACS_LTEE,ACS_PLUS,ACS_RTEE);
		cross(sy+l*size+l,sx,ACS_LLCORNER,ACS_BTEE,ACS_LRCORNER);
}

byte sgn2int(char sgn){
	if('0'<sgn && sgn <='9')
		return sgn-'0';
	if('a'<=sgn && sgn <='z')
		return sgn-'a'+10;
	if('A'<=sgn && sgn <= 'Z')
		return sgn-'A'+36;
	return 0;
}

char int2sgn(byte num){// convert integer to representing sign
	if(0< num && num <= 9)
		return num+'0';
	else if(10<=num && num <=35)
		return num-10+'a';
	else if(36<=num && num <=51)
		return num-36+'A';
	return 0;
}

bool isvalid(byte ty,byte tx,char board[s][s]){ //is it allowed to place that char there?
	char t= board[ty][tx];
	if(!t)
		return 0;
	byte y,x;
	for(y=0;y<s;++y){
		if(board[y][tx] == t && y!=ty)
			return 0;
	}
	for(x=0;x<s;++x){
		if(board[ty][x] == t && x!= tx)
			return 0;
	}
	byte sy=size*(ty/size);//square
	byte sx=size*(tx/size);
	for(y=0;y<size;++y){
		for(x=0;x<size;++x){
			if(board[sy+y][sx+x]==t && sy+y != ty && sx+x != tx)
				return 0;
		}
	}				
	return 1;
}

void genocide(char board[s][s],char victim){
	for(byte y=0;y<s;++y)
		for(byte x=0;x<s;++x)
			if(board[y][x]==victim)
				board[y][x]=0;
}
bool fill_with(char board[s][s],char fillwith){//returns 1 on failure
	byte firstx,x,tries=0;
	Again:
	++tries;
	if (tries>s)
		return 1;
	for(byte y=0;y<s;++y){//there should be only one occurence of a number in a row, and this function makes use of this fact to improve generation speed
		firstx=x=rand()%s;
		while(1){
			if(!board[y][x]){
				board[y][x]=fillwith;
				if(isvalid(y,x,board)){
					break;
				}
				else{
					board[y][x]=0;
					goto Next;
				}
			}
			else{
				Next:
				++x;
				if(x==s)
					x=0;
				if(x==firstx){
					genocide(board,fillwith);
					goto Again;
				}
			}
		}
	}
	refresh();
	return 0;
}
void fill(char board[s][s]){
	for(byte num=1;num<=s;++num){//it fills random places in the board with 1s, then random places in the remaining space with 2s and so on...
		if(num==4){//something that randomly happens
			_wait=(_wait+1)%60;
			if(!_wait && waitcycles<3)
				++waitcycles;
		}
		if ( fill_with(board,int2sgn(num) ) ){
			memset(board,0,s*s);
			num=0;
			mvaddstr(0,0,"My algorithm sucks, so you need to wait a bit                    ");//with animated dots to entertain the waiter
			if(waitcycles==3)
				mvaddstr(2,0,"(You can set SUDOKU_FASTGEN if you just want to see if it works)");
			move(0,45);
			for(byte b=0;b<_wait;b+=10)
				addch('.');
		}
	}
}
void swap(char board[s][s],char A,char B){
	byte y,x;
	for(y=0;y<s;++y){
		for(x=0;x<s;++x){
			if(board[y][x]==A)
				board[y][x]=B;
			else if(board[y][x]==B)
				board[y][x]=A;
		}
	}
}
void justfill(char board[s][s]){//sometimes fill() gets too much , and you just want a 49x49 sudoku puzzle of any quality
	byte y,x,k;//k is here to minimize calls to isvalid()
	for(y=0;y<s;++y){//fill with 1,2,3,4...
		k=1;
		for(x=0;x<s;++x){
			board[y][x]=int2sgn(k);
			while(!isvalid(y,x,board)){
				board[y][x]=int2sgn(k=k+1);
				if(k>s)
					board[y][x]=int2sgn(k=1);
			}
			++k;
			if(k>s)
				k=1;
		}
	}
	for(byte n=0;n<s*2;++n)//randomize
		swap(board,int2sgn(1+(rand()%s)),int2sgn(1+(rand()%s)) );
}
void mkpuzzle(char board[s][s],char empty[s][s],char game[s][s]){//makes a puzzle to solve
	byte y,x;
	for(y=0;y<s;++y){
		for(x=0;x<s;++x){
			if( !(rand()%diff) ){
				empty[y][x]=board[y][x];
				game[y][x]=board[y][x];
			}
		}
	}
}

void header(byte sy,byte sx){
	mvaddch(sy, sx+1, '_');
	mvprintw(sy+1,sx,"(_       Solved:%d/%d",filled,s*s);
	mvprintw(sy+2,sx," _)UDOKU Left  :%d/%d",s*s-filled,s*s);
}
	
void draw(byte sy,byte sx,char empty[s][s],char game[s][s]){
	chtype attr;
	table(sy,sx);
	filled=0;
	for(byte y=0;y<s;++y){
		for(byte x=0;x<s;++x){
			attr=A_NORMAL;
			if(x==px && y==py)
				attr |= A_STANDOUT;
			if(empty[y][x])
				attr |= A_BOLD;
			if(game[y][x]){
				if(!isvalid(y,x,game))
					attr |= colors[5];
				else{
					attr |= colors[game[y][x]%5];
					++filled;
				}
				mvaddch(sy+y+y/size+1,sx+x*2+1,attr|game[y][x]);
			}
			else
				mvaddch(sy+y+y/size+1,sx+x*2+1,attr|' ');
		}
	}
}

void sigint_handler(int x){
	endwin();
	puts("Quit.");
	exit(x);
}
void mouseinput(int sy, int sx){
#ifndef NO_MOUSE
	MEVENT m;
	#ifdef PDCURSES
	nc_getmouse(&m);
	#else
	getmouse(&m);
	#endif
	if( m.y < (3+1+size+s)-sy && m.x<(2*s+1)-sx ){//it's a shame to include math.h only for round() but it was the only moral way to make gcc shut up
		py= round( (float)(size*(m.y-4-sy))/(size+1) );//these are derived from the formulas in draw() by simple algebra
		px=(m.x-1-sx)/2;
	}
	else
		return;
	if(m.bstate & BUTTON1_CLICKED)
		ungetch('\n');
	if(m.bstate & (BUTTON2_CLICKED|BUTTON3_CLICKED) )
		ungetch(' ');
#endif //NO_MOUSE
}
void help(void){
	erase();
	header(0,0);
	attron(A_BOLD);
	mvprintw(3,0,"  **** THE CONTROLS ****");
	mvprintw(13,0,"YOU CAN ALSO USE THE MOUSE!");
	attroff(A_BOLD);
	mvprintw(4,0,"1 - %c : Enter number/character",int2sgn(s));
	mvprintw(5,0,"SPACE : Clear tile");
	mvprintw(6,0,"ARROW KEYS : Move cursor");
	mvprintw(7,0,"q : Quit");
	mvprintw(8,0,"n : New board");
	mvprintw(9,0,"r : Restart");
	if(size>4)
		printw(" (some of these alphabet controls maybe overridden in certain sizes)");
	mvprintw(10,0,"? : Hint (not like in other games)");
	mvprintw(11,0,"F1 & F2: Help on controls & gameplay");
	mvprintw(12,0,"PgDn,PgUp,<,> : Scroll");
	mvprintw(15,0,"Press a key to continue");
	refresh();
	getch();
	erase();
}
void gameplay(void){
	erase();
	header(0,0);
	attron(A_BOLD);
	mvprintw(3,0,"  **** THE GAMEPLAY ****");
	attroff(A_BOLD);
	move(4,0);
	printw("Fill the table with digits");
	if(size>3)
		printw(" (and characters)  \n");
	else
		addch('\n');

	printw("so that all the rows, columns and smaller subregions \n");
	printw("contain all of the digits from 1 to ");
	if(size<=3){
		addch(int2sgn(s));
		addch('.');
	}
	if(size>3){
		addch('9');
		printw(" and all\nthe alphabet letters from 'a' to '%c'.",int2sgn(s));
	}
	printw("\n\nPress a key to continue.");
	refresh();
	getch();
	erase();
}
int main(int argc,char** argv){
	signal(SIGINT,sigint_handler);
#ifndef Plan9
	if(argc>4 || (argc==2 && !strcmp("help",argv[1])) ){
		printf("Usage: %s [size [ difficulty]] \n",argv[0]);
		return EXIT_FAILURE;
	}
	if(argc>1 ){
		if(strlen(argv[1])>1 || argv[1][0]-'0'>7 || argv[1][0]-'0'< 2){ 
			printf("2 <= size <= 7\n");
			return EXIT_FAILURE;
		}
		else
			size = *argv[1]-'0';
	}	
	else
		size=3;
	if(argc>2){ 
		if (strlen(argv[2])>1 || argv[2][0]-'0'>4 || argv[2][0]-'0'<= 0 ){
			printf("1 <= diff <=4\n");
			return EXIT_FAILURE;
		}
		else
			diff = *argv[2]-'0'+1;
	}
	else
		diff=2;
#else //Plan9 doesn't take size
	if(argc>2 || (argc==2 && !strcmp("help",argv[1])) ){
		printf("Usage: %s  [difficulty]\n",argv[0]);
		return EXIT_FAILURE;
	}
	if(argc>1){ 
		if (strlen(argv[2])>1 || argv[2][0]-'0'>4 || argv[2][0]-'0'<= 0 ){
			printf("1 <= diff <=4\n");
			return EXIT_FAILURE;
		}
		else
			diff = *argv[2]-'0'+1;
	}
	else
		diff=2;
#endif
	bool fastgen= !(!getenv("SUDOKU_FASTGEN"));
	initscr();
#ifndef NO_MOUSE
	mousemask(ALL_MOUSE_EVENTS,NULL);
#endif //NO_MOUSE
	noecho();
	cbreak();
	keypad(stdscr,1);
	srand(time(NULL)%UINT_MAX);
	if( has_colors() ){
		start_color();
		use_default_colors();
		init_pair(1,COLOR_YELLOW,-1);
		init_pair(2,COLOR_GREEN,-1);
		init_pair(3,COLOR_BLUE,-1);
		init_pair(4,COLOR_CYAN,-1);
		init_pair(5,COLOR_MAGENTA,-1);
		init_pair(6,COLOR_RED,-1);
		for(byte b=0;b<6;++b){
			colors[b]=COLOR_PAIR(b+1);
		}
	}
#ifndef Plan9
	s= size*size;
#endif
	char board[s][s];
	char empty[s][s];
	char game[s][s];
	int input=0;
	int sy,sx;
	Start:
	sy=sx=0;
	erase();
	curs_set(0);
	filled =0;
	memset(board,0,s*s);
	memset(empty,0,s*s);
	memset(game,0,s*s);
	if(fastgen)
		justfill(board);
	else
		fill(board);
	mkpuzzle(board,empty,game);
	py=px=0;

	while(1){
		erase();
		draw(sy+3,sx+0,empty,game);
		header(sy+0,sx+0);
		refresh();
		if(filled == s*s)
			break;
		input = getch();
		if( input==KEY_PPAGE && LINES< s+size+3){//the board starts in 3
			sy+=10;
			if(sy>0)
				sy=0;
		}
		if( input==KEY_NPAGE && LINES< s+size+3){
			sy-=10;
			if(sy< -(s+size+3) )
				sy=-(s+size+3);
		}
		if( input=='<' && COLS< s*2){
			sx+=10;
			if(sx>0)
				sx=0;
		}
		if( input=='>' && COLS< s*2){
			sx-=10;
			if(sx< -(s*2))
				sx=-(s*2);
		}
		if(input == KEY_F(1))
			help();
		if(input == KEY_F(2))
			gameplay();
		if(input == KEY_MOUSE)
			mouseinput(sy,sx);
		if(input == KEY_UP && py)
			--py;
		if(input == KEY_DOWN && py<s-1)
			++py;
		if(input == KEY_LEFT && px)
			--px;
		if(input == KEY_RIGHT && px<s-1)
			++px;
		if(!empty[py][px]){
			if(input == ' ' )
				game[py][px]=0;
			else if(input<=CHAR_MAX && sgn2int(input) && sgn2int(input)<=s )
				game[py][px]=input;
		}
		if( (input=='q' && size<= 5) || input=='Q')
			sigint_handler(EXIT_SUCCESS);
		if(input=='n'&& size <= 4)
			goto Start;
		if(input=='r'&& size <= 5){
			byte y,x;
			for(y=0;y<s;++y)
				for(x=0;x<s;++x)
					game[y][x]=empty[y][x];
		}
				
		if(input=='?')
			game[py][px]=board[py][px];
		if(input == 'X' && getch()=='Y' && getch()=='Z' && getch()=='Z' && getch()=='Y'){
			byte y,x;
			for(y=0;y<s;++y)
				for(x=0;x<s;++x)
					game[y][x]=board[y][x];
		}
	}
	mvprintw(sy+s+size+4,sx+0,"Yay!! Wanna play again?(y/n)");
	curs_set(1);
	input=getch();
	if(input != 'N' && input != 'n' && input != 'q')
			goto Start;
	endwin();
	return EXIT_SUCCESS;
}