#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <ncurses.h>
#include <sys/ioctl.h>

enum {
	COLOR_FONT,
	COLOR_SAND
};

enum {
	ADD,
	UNDO
};

struct SAND {
	int x;
	int y;
};

WINDOW *win;
struct winsize w_size;
int px = 1, py = 1;

struct SAND *sand_array;
size_t array_index;

void clear_scr(WINDOW *win) {
	clear();
	refresh();

	if (win != NULL) {
		wclear(win);
		wrefresh(win);
	}
}

void clean_up(int sig) {
	if (sig == SIGWINCH) {
		if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &w_size) < 0)
			perror("TIOCGWINSZ");

		if (px >= w_size.ws_col)
			px = w_size.ws_col - 2;

		if (py >= w_size.ws_row)
			py = w_size.ws_row - 2;

		endwin();
		initscr();

		delwin(win);
		win = newwin(w_size.ws_row, w_size.ws_col, 0, 0);
	}

	else {
		clear_scr(win);
		delwin(win);
		endwin();
		if (sand_array != NULL)
			free(sand_array);

		exit((sig == -1) ? 1 : 0);
	}
}

int placed_on(int y, int x) {
	for (size_t i = 0; i < array_index; i++)
		if (sand_array[i].y == y && sand_array[i].x == x)
			return i;

	return -1;
}

void sand_ctl(char flag) {
	if (sand_array == NULL) {
		sand_array = malloc(sizeof(struct SAND));
		if (sand_array == NULL) {
			perror("malloc");
			clean_up(-1);
		}
	}

	if (flag == UNDO && array_index > 0) {
		array_index--;
		if (array_index == 0) {
			free(sand_array);
			sand_array = NULL;
			return;
		}
	}

	else if (flag == ADD) {
		for (size_t i = 0; i < array_index; i++)
			if (sand_array[i].x == px && sand_array[i].y == py)
				return;

		array_index++;
	}

	struct SAND *tmp = realloc(sand_array, array_index * sizeof(struct SAND));
	if (tmp == NULL) {
		perror("realloc");
		clean_up(-1);
	}

	if (flag == ADD) {
		tmp[array_index - 1].x = px;
		tmp[array_index - 1].y = py;
	}

	sand_array = tmp;
}

void move_sand(void) {
	for (size_t i = 0; i < array_index; i++) {
		if (placed_on(sand_array[i].y + 1, sand_array[i].x) == -1 && sand_array[i].y < w_size.ws_row - 2)
			sand_array[i].y++;

		else if (sand_array[i].y < w_size.ws_row - 3) {
			if (sand_array[i].x + 1 < w_size.ws_col - 1 && placed_on(sand_array[i].y + 1, sand_array[i].x + 1) == -1)
				sand_array[i].x++;

			else if (sand_array[i].x - 1 > 0 && placed_on(sand_array[i].y + 1, sand_array[i].x - 1) == -1)
				sand_array[i].x--;
		}
	}
}

void draw(void) {
	wattron(win, COLOR_PAIR(COLOR_FONT));

	for (size_t y = 1; y < w_size.ws_row - 1; y++)
		for (size_t x = 1; x < w_size.ws_col - 1; x++)
			if (!(x % 2))
				mvwprintw(win, y, x, ".");

	mvwprintw(win, py, px, "+");

	wattroff(win, COLOR_PAIR(COLOR_FONT));
	wattron(win, COLOR_PAIR(COLOR_SAND));

	for (size_t i = 0; i < array_index; i++)
		mvwprintw(win, sand_array[i].y, sand_array[i].x, "#");

	wattroff(win, COLOR_PAIR(COLOR_SAND));
	box(win, 0, 0);
	wrefresh(win);
}

int main(void) {
	signal(SIGINT, clean_up);
	signal(SIGWINCH, clean_up);

	initscr();
	noecho();
	cbreak();
	curs_set(0);
	timeout(1000);
	keypad(stdscr, TRUE);

	if (has_colors() == FALSE) {
		endwin();
		fputs("Your terminal does not support color", stderr);
		exit(1);
	}

	start_color();
	init_pair(COLOR_FONT, COLOR_RED, COLOR_BLACK);
	init_pair(COLOR_SAND, COLOR_YELLOW, COLOR_YELLOW);

	/* Init screen size */
	clean_up(SIGWINCH);
	while (1) {
		clear_scr(win);
		move_sand();
		draw();

		int k = getch();
		if (k == KEY_UP && py - 1 > 0)
			py--;

		else if (k == KEY_DOWN && py + 1 < w_size.ws_row - 1)
			py++;

		else if (k == KEY_RIGHT && px + 1 < w_size.ws_col - 1)
			px++;

		else if (k == KEY_LEFT && px - 1 > 0)
			px--;

		else if (k == ' ')
			sand_ctl(ADD);

		else if (k == 'u')
			sand_ctl(UNDO);
	}
}