/*
 * src/cgol.c
 * Curses Game of Life
 *
 * Copyright (C) 2011 Patrick "P. J." McDermott
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <curses.h>

void init_curses();
void init_game();
void fini_game();
void fini_curses();
void tick();
int count_live_neighbors(int i, int j);
bool get_cell(int i, int j);
void set_cell(int i, int j, bool s);
void print_cell(int i, int j, bool next);
void usage(const char *invocation);

static int width, height;
static double seedprob;
static int genrate, gens;
static bool *grid_cur, *grid_next;

int
main(int argc, char **argv)
{
	int opt, i, c;

	width = 0;
	height = 0;
	seedprob = 0.5;
	genrate = 1; /* TODO: Units. */
	gens = 0;

	while ((opt = getopt(argc, argv, "w:h:s:r:n:")) != -1) {
		switch (opt) {
			case 'w':
				width = atoi(optarg);
				break;
			case 'h':
				height = atoi(optarg);
				break;
			case 's':
				seedprob = atof(optarg);
				break;
			case 'r':
				genrate = atoi(optarg);
				break;
			case 'n':
				gens = atoi(optarg);
				break;
			default:
				usage(argv[0]);
				return 1;
		}
	}

	/* Sanity.  Let's check it. */
	if (seedprob <= 0 || seedprob > 1) {
		fprintf(stderr, "Error: Ensure 0 < SEEDPROB <= 1\n");
		return 2;
	}

	init_curses();
	init_game();

	/* TODO: Write a better main event loop with a good controller and timer. */
	timeout(1000);

	/* NB: i starts at -1 so we don't exit immediately after showing the last
	 * desired state. */
	for (i = -1; gens == 0 || i < gens; ++i) {
		c = getch();
		if (c == 'q') {
			break;
		}
		/* Calculate the next generation only if it is to be shown on the
		 * screen. */
		if (gens == 0 || i + 1 < gens) {
			tick();
		}
	}

	fini_game();
	fini_curses();

	return 0;
}

void
init_curses()
{
	int maxwidth, maxheight;

	initscr();
	noecho();
	raw();
	curs_set(0);

	/* Leave room for spaces between cells, but allow for one more cell on odd-
	 * width terminals. */
	maxwidth = (COLS - 2) / 2 + COLS % 1;
	maxheight = (LINES - 2);
	if (width == 0 || width > maxwidth) {
		width = maxwidth;
	}
	if (height == 0 || height > maxheight) {
		height = maxheight;
	}
}

void
init_game()
{
	size_t size;
	int i, j, n;
	double r;

	n = width * height;

	/* Allocate and initialize the grids. */
	size = sizeof(bool) * n;
	grid_cur = malloc(size);
	memset(grid_cur, 0, size);
	grid_next = malloc(size);
	memset(grid_next, 0, size);

	srand(time(NULL));

	/* Generate the seed pattern. */
	for (i = 0; i < n; ++i) {
		r = rand() / (double) RAND_MAX;
		if (r > seedprob) {
			/* Dead. */
			grid_cur[i] = false;
			grid_next[i] = false;
		} else {
			/* Alive. */
			grid_cur[i] = true;
			grid_next[i] = true;
		}
	}

	/* Print the grid. */
	for (i = 0; i < height; ++i) {
		for (j = 0; j < width; ++j) {
			print_cell(i, j, false);
		}
	}
}

void
fini_game()
{
	free(grid_cur);
	free(grid_next);
}

void
fini_curses()
{
	delwin(stdscr);
	endwin();
}

void
tick()
{
	int i, j, n;

	for (i = 0; i < height; ++i) {
		for (j = 0; j < width; ++j) {
			n = count_live_neighbors(i, j);
			if (get_cell(i, j) == true) {
				if (n < 2 || n > 3) {
					set_cell(i, j, false);
					print_cell(i, j, true);
				}
			} else {
				if (n == 3) {
					set_cell(i, j, true);
					print_cell(i, j, true);
				}
			}
		}
	}

	memcpy(grid_cur, grid_next, sizeof(bool) * width * height);

	refresh();
}

int
count_live_neighbors(int i, int j)
{
	return
		get_cell(i - 1, j - 1) + get_cell(i - 1, j) + get_cell(i - 1, j + 1) +
		get_cell(i,     j - 1) +                      get_cell(i,     j + 1) +
		get_cell(i + 1, j - 1) + get_cell(i + 1, j) + get_cell(i + 1, j + 1);
}

bool
get_cell(int i, int j)
{
	if (i < 0 || j < 0 || i >= height || j >= width) {
		/* This is something of a sanity check.  Anything off the finite grid
		 * is by definition dead.  With this, count_live_neighbors() can be
		 * dumb. */
		return 0;
	} else {
		return grid_cur[i * width + j];
	}
}

void
set_cell(int i, int j, bool s)
{
	grid_next[i * width + j] = s;
}

void
print_cell(int i, int j, bool next)
{
	/* TODO: Center this. */
	if (next) {
		mvprintw(1 + i, 1 + j * 2, "%c", grid_next[i * width + j] ? 'o' : ' ');
	} else {
		mvprintw(1 + i, 1 + j * 2, "%c", grid_cur[i * width + j] ? 'o' : ' ');
	}
}

void
usage(const char *invocation)
{
	fprintf(stderr, "Usage: %s [-w WIDTH] [-h HEIGHT] [-s SEEDPROB] [-r RATE] "
			"[-n GENERATIONS]\n", invocation);
}