--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/board.c	Sat Mar 15 18:41:03 2014 +0100
@@ -0,0 +1,269 @@
+/*
+ * Copyright (C) 2014 Guido Berhoerster <guido+rantaiwarna@berhoerster.name>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#define	_XOPEN_SOURCE	600
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <curses.h>	/* for OK, ERR */
+
+#include "board.h"
+#include "compat.h"
+#include "util.h"
+
+struct stack_element {
+	struct stack_element	*next;
+	int	x;
+	int	y;
+};
+
+struct board_ctx *
+board_create(int height, int width, short colors)
+{
+	struct board_ctx *board;
+
+	board = rantaiwarna_malloc(sizeof (struct board_ctx));
+	board->elements = rantaiwarna_calloc((size_t)(width * height),
+	    sizeof (short));
+	board->seed = (uint32_t)getpid();
+	board->height = height;
+	board->width = width;
+	board->colors = colors;
+	board->status = GAME_OVER;
+	board->score = 0;
+	if (board_generate(board) == ERR) {
+		board_free(board);
+		return (NULL);
+	}
+
+	return (board);
+}
+
+void
+board_free(struct board_ctx *board)
+{
+	free(board->elements);
+	free(board);
+}
+
+int
+board_check_status(struct board_ctx *board)
+{
+	int	status = GAME_OVER | GAME_OVER_CLEARED;
+	int	y;
+	int	x;
+
+	for (y = board->height - 1; y >= 0; y--) {
+		for (x = 0; x < board->width; x++) {
+			if (board->elements[y * board->width + x] != 0) {
+				status &= ~GAME_OVER_CLEARED;
+				if (((y - 1 >= 0) &&
+				    (board->elements[y * board->width + x] ==
+				    board->elements[(y - 1) * board->width +
+				    x])) ||
+				    ((x + 1 < board->width) &&
+				    (board->elements[y * board->width + x] ==
+				    (board->elements[y * board->width + x +
+				    1])))) {
+					status &= ~GAME_OVER;
+					goto out;
+				}
+			}
+		}
+	}
+
+out:
+	board->status = status;
+	return (status);
+}
+
+int
+board_generate(struct board_ctx *board)
+{
+	int	i;
+	int	j;
+
+	/* make up to 1000 attempts to create a board that is playable */
+	for (i = 0; i < 1000; i++) {
+		for (j = 0; j < board->width * board->height; j++) {
+			board->elements[j] =
+			    (short)(rantaiwarna_rand(&board->seed) %
+			    board->colors) + 1;
+		}
+		if (board_check_status(board) & GAME_OVER) {
+			return (ERR);
+		}
+	}
+
+	board->score = 0;
+
+	return (OK);
+}
+
+int
+board_compact(struct board_ctx *board)
+{
+	int	changes = 0;
+	int	x;
+	int	y;
+	int	top;
+	int	left;
+
+	/* close vertical gaps iby moving elements down */
+	for (x = 0; x < board->width; x++) {
+		for (y = top = board->height - 1; y >= 0; y--) {
+			if (board->elements[y * board->width + x] != 0) {
+				board->elements[top * board->width + x] =
+				    board->elements[y * board->width + x];
+				top--;
+				changes++;
+			}
+		}
+		for (y = top; y >= 0; y--) {
+			board->elements[y * board->width + x] = 0;
+		}
+	}
+
+	/* close column gaps by moving columns to the left */
+	for (x = left = 0; x < board->width; x++) {
+		if (board->elements[(board->height - 1) * board->width + x] !=
+		    0) {
+			if (x > left) {
+				for (y = 0; y < board->height; y++) {
+					board->elements[y * board->width +
+					    left] = board->elements[y *
+					    board->width + x];
+				}
+				changes++;
+			}
+			left++;
+		}
+	}
+	for (x = left; x < board->width; x++) {
+		for (y = 0; y < board->height; y++) {
+			board->elements[y * board->width + x] = 0;
+		}
+	}
+
+	return (changes);
+}
+
+int
+board_remove_elements(struct board_ctx *board, int start_y, int start_x)
+{
+	int	removed = 0;
+	int	color;
+	int	x;
+	int	y;
+	int	west;
+	int	east;
+	int	n = 0;
+	int	i;
+	int	save_x;
+	int	save_y;
+	struct stack_element *stack_start;
+	struct stack_element *stack_tmp;
+	struct stack_element *stack_new;
+
+	color = board->elements[start_y * board->width + start_x];
+	if (color == 0) {
+		return (0);
+	}
+
+	stack_new = rantaiwarna_malloc(sizeof (struct stack_element));
+	stack_new->next = NULL;
+	stack_new->y = start_y;
+	stack_new->x = start_x;
+	stack_start = stack_new;
+
+	while (stack_start != NULL) {
+		x = stack_start->x;
+		y = stack_start->y;
+		stack_tmp = stack_start;
+		stack_start = stack_start->next;
+		free(stack_tmp);
+
+		if (board->elements[y * board->width + x] != color) {
+			continue;
+		}
+
+		for (west = x; (west - 1 >= 0) &&
+		    (board->elements[y * board->width + west - 1] == color);
+		    west--);
+		for (east = x; (east + 1 < board->width) &&
+		    (board->elements[y * board->width + east + 1] == color);
+		    east++);
+		for (i = west; i <= east; i++) {
+			/*
+			 * only really start removing elements if there are
+			 * more than two adjacent elements of the same color
+			 */
+			n++;
+			if (n < 2) {
+				save_x = i;
+				save_y = y;
+			} else {
+				if (n == 2) {
+					board->elements[save_y * board->width +
+					    save_x] = 0;
+					removed++;
+				}
+				board->elements[y * board->width + i] = 0;
+				removed++;
+			}
+
+			if ((y - 1 >= 0) &&
+			    (board->elements[(y - 1) * board->width + i] ==
+			    color)) {
+				stack_new = rantaiwarna_malloc(
+				    sizeof (struct stack_element));
+				stack_new->next = stack_start;
+				stack_new->y = y - 1;
+				stack_new->x = i;
+				stack_start = stack_new;
+			}
+			if ((y + 1 < board->height) &&
+			    (board->elements[(y + 1) * board->width + i] ==
+			    color)) {
+				stack_new = rantaiwarna_malloc(
+				    sizeof (struct stack_element));
+				stack_new->next = stack_start;
+				stack_new->y = y + 1;
+				stack_new->x = i;
+				stack_start = stack_new;
+			}
+		}
+	}
+	if (removed > 0) {
+		board_compact(board);
+		board->score += (removed - 1) * (removed - 1);
+		board_check_status(board);
+		if (board->status & GAME_OVER) {
+			if (board->status & GAME_OVER_CLEARED) {
+				board->score += 1000;
+			}
+		}
+	}
+
+	return (removed);
+}