From: Nick Bowler <nbowler@draconx.ca>
Date: Sat, 5 Mar 2022 07:58:34 +0000 (-0500)
Subject: Check victory condition so the game is winnable.
X-Git-Url: http://git.draconx.ca/gitweb/rrace.git/commitdiff_plain/a3f2189bfac7e5b1acdf3640cd3b50a7a6636906

Check victory condition so the game is winnable.
---

diff --git a/src/game.c b/src/game.c
index bd1fef9..ca03830 100644
--- a/src/game.c
+++ b/src/game.c
@@ -1,8 +1,25 @@
 /*
+ * Slide puzzle core game logic
+ * Copyright © 2022 Nick Bowler
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ *
  * The RNG implementation is adapted from xoshiro256** and splitmix64
  * by David Blackman and Sebastiano Vigna, originally distributed under
  * the Creative Commons Zero public domain dedication.
  */
+
 #include <config.h>
 #include <limits.h>
 #include <string.h>
@@ -136,17 +153,17 @@ void game_reset(struct board *board)
 		uint_fast32_t position;
 
 		position = board_position(x, y);
-		if (tiles[i] == TILE_EMPTY) {
-			board->game[0] = 0x1ffffff ^ position;
-			board->x = x;
-			board->y = y;
-		} else {
+		if (tiles[i] != TILE_EMPTY) {
 			if (tiles[i] & 1)
-				board->game[1] |= position;
+				board->game[0] |= position;
 			if (tiles[i] & 2)
-				board->game[2] |= position;
+				board->game[1] |= position;
 			if (tiles[i] & 4)
-				board->game[3] |= position;
+				board->game[2] |= position;
+		} else {
+			board->game[3] = 0x1ffffff ^ position;
+			board->x = x;
+			board->y = y;
 		}
 	}
 }
@@ -179,3 +196,29 @@ int game_do_move(struct board *board, int x, int y)
 	board->y = y;
 	return 0;
 }
+
+#define GOAL_MASK 0x739c0
+
+int game_check_goal(struct board *board)
+{
+	int i, ret = 1;
+
+	for (i = 0; i < 3; i++)
+		ret &= ((board->game[i] & GOAL_MASK) >> 6) == board->goal[i];
+	return ret;
+}
+
+void game_finish(struct board *board)
+{
+	int i;
+
+	for (i = 0; i < 4; i++) {
+		board->game[i] &= GOAL_MASK;
+	}
+
+	/*
+	 * Setting both x and y hole location to a bogus value will effectively
+	 * disable the game since there will be no valid moves.
+	 */
+	board->x = board->y = -1;
+}
diff --git a/src/game.h b/src/game.h
index f4473a7..d17eb99 100644
--- a/src/game.h
+++ b/src/game.h
@@ -42,11 +42,11 @@ struct board {
 	 * corresponds to position (0,0), bit 4 is position (4,0) and bit 25
 	 * is position (4, 4).
 	 *
-	 *   game[0] - the board mask, all bits set except one indicating the
+	 *   game[0] - least significant bit of the tile's colour.
+	 *   game[1] - tile colour.
+	 *   game[2] - most significant bit of the tile's colour.
+	 *   game[3] - the board mask, all bits set except one indicating the
 	 *             absense of a tile at this position.
-	 *   game[1] - least significant bit of the tile's colour.
-	 *   game[2] - tile colour.
-	 *   game[3] - most significant bit of the tile's colour.
 	 */
 	uint_least32_t game[4];
 
@@ -119,6 +119,11 @@ static inline uint_fast32_t board_mask_v(int x, int y0, int y1)
  */
 int game_do_move(struct board *board, int x, int y);
 
+/*
+ * Returns 1 if the game is in a winning position, or 0 otherwise.
+ */
+int game_check_goal(struct board *board);
+
 /*
  * Initialize the game RNG such that the next call to game_reset will produce a
  * new board that is entirely dependent on the given seed value.
@@ -130,4 +135,9 @@ void game_reseed(unsigned long long seed);
  */
 void game_reset(struct board *board);
 
+/*
+ * Disable new moves and clear all tile bits other than the 9 goal tiles.
+ */
+void game_finish(struct board *board);
+
 #endif
diff --git a/src/motif_ui.c b/src/motif_ui.c
index 40f4632..279f550 100644
--- a/src/motif_ui.c
+++ b/src/motif_ui.c
@@ -239,6 +239,11 @@ static void game_input(Widget w, void *data, void *cb_data)
 		return;
 
 	if (game_do_move(&state->board, x, y) == 0) {
+		if (game_check_goal(&state->board)) {
+			printf("You win!\n");
+			game_finish(&state->board);
+		}
+
 		x11_redraw_game(state);
 	}
 }
diff --git a/src/x11.c b/src/x11.c
index 9ded09e..598b115 100644
--- a/src/x11.c
+++ b/src/x11.c
@@ -143,7 +143,7 @@ void x11_redraw_game(struct app_state *state)
 	w /= 5; h /= 5;
 
 	for (i = 0; i < 25; i++) {
-		uint_least32_t *gp = state->board.game+1;
+		uint_least32_t *gp = state->board.game;
 
 		redraw_tile(state, display, game,
 		            gp[0], gp[1], gp[2],