Enforce legal moves

All the checks for legal moves are now enforced, (including not
even selecting a piece if it is surrounded). Basically all that's
missing now is elimination of disconnected pieces, (and the
ability to pass when there is no available move).

diff --git a/dvonn-board.c b/dvonn-board.c
index 4d09e13be58f0ce25f2ee048bca2ea11391ee2b5..b6b36e5eac7dfefcbf1e6cce6d53901a8fcd7ff8 100644 (file)
--- a/dvonn-board.c
+++ b/dvonn-board.c
@@ -82,12 +82,50 @@ dvonn_board_init (dvonn_board_t *board)
     board->moves = 0;
 }
 
+dvonn_bool_t
+dvonn_board_cell_occupied (dvonn_board_t *board,
+                          int x, int y)
+{
+    if (x < 0 || x >= DVONN_BOARD_X_SIZE ||
+       y < 0 || y >= DVONN_BOARD_Y_SIZE)
+    {
+       return FALSE;
+    }
+
+    if (board->cells[x][y].type == DVONN_CELL_INVALID ||
+       board->cells[x][y].type == DVONN_CELL_EMPTY)
+    {
+       return FALSE;
+    }
+
+    return TRUE;
+}
+
+dvonn_bool_t
+dvonn_board_cell_surrounded (dvonn_board_t *board,
+                            int x, int y)
+{
+    int surround_count;
+
+    surround_count =
+       dvonn_board_cell_occupied (board, x - 1, y) +
+       dvonn_board_cell_occupied (board, x + 1, y) +
+       dvonn_board_cell_occupied (board, x, y - 1) +
+       dvonn_board_cell_occupied (board, x, y + 1) +
+       dvonn_board_cell_occupied (board, x + 1, y - 1) +
+       dvonn_board_cell_occupied (board, x - 1, y + 1);
+
+    return (surround_count == 6);
+}
+
 static dvonn_bool_t
 dvonn_board_move_legal (dvonn_board_t *board,
                        int x1, int y1,
                        int x2, int y2,
                        char **error)
 {
+    int distance;
+
     if (x1 < 0 || x1 >= DVONN_BOARD_X_SIZE ||
        y1 < 0 || y1 >= DVONN_BOARD_Y_SIZE ||
        x2 < 0 || x2 >= DVONN_BOARD_X_SIZE ||
@@ -97,22 +135,50 @@ dvonn_board_move_legal (dvonn_board_t *board,
        return FALSE;
     }
 
-    if (board->cells[x1][y1].type == DVONN_CELL_INVALID) {
+    if (board->cells[x1][y1].type == DVONN_CELL_INVALID ||
+       board->cells[x2][y2].type == DVONN_CELL_INVALID)
+    {
        *error = "Not a valid board space";
        return FALSE;
     }
 
     if (board->cells[x1][y1].type == DVONN_CELL_EMPTY) {
-       *error = "There is no piece there to move";
+       *error = "There are no pieces there to move";
+       return FALSE;
+    }
+
+    if (dvonn_board_cell_surrounded (board, x1, y1)) {
+       *error = "You cannot move a piece that is surrounded";
        return FALSE;
     }
 
     if (board->cells[x1][y1].type != board->player) {
-       *error = "You cannot move your opponent's piece";
+       *error = "You cannot move your opponent's stack";
        return FALSE;
     }
 
-    /* XXX: Need to code up DVONN-legal move calculation here. */
+    if (board->cells[x2][y2].type == DVONN_CELL_EMPTY) {
+       *error = "You cannot move to an empty space";
+       return FALSE;
+    }
+
+    /* Move must be in a straight line, which in our array is
+     * horizontal, vertical, or one of the diagonals. */
+    if (x2 == x1)
+       distance = abs (y2 - y1);
+    else if (y2 == y1)
+       distance = abs (x2 - x1);
+    else if ((x2 - x1) == - (y2 - y1))
+       distance = abs (x2 - x1);
+    else {
+       *error = "Move is not in a straight line";
+       return FALSE;
+    }
+
+    if (distance != board->cells[x1][y1].height) {
+       *error = "Move distance is not the same as stack height";
+       return FALSE;
+    }
 
     return TRUE;
 }

diff --git a/dvonn-board.h b/dvonn-board.h
index 2971a2738e31262c5658b8c944a74933c81d7f81..66464d8dee95d9fbd421dfc466cb70e6b3dfada9 100644 (file)
--- a/dvonn-board.h
+++ b/dvonn-board.h
@@ -88,4 +88,17 @@ dvonn_board_move (dvonn_board_t *board,
                int x2, int y2,
                char **error);
 
+/* Is the cell at (x,y) occupied by a piece. Returns FALSE for all
+ * out-of-bounds coordinates. */
+dvonn_bool_t
+dvonn_board_cell_occupied (dvonn_board_t *board,
+                          int x, int y);
+
+/* Is the cell at (x,y) surrounded by other pieces, (such that it is
+ * not legal for a piece at (x,y) to move. */
+dvonn_bool_t
+dvonn_board_cell_surrounded (dvonn_board_t *board,
+                            int x, int y);
+
+
 #endif

diff --git a/dvonn.c b/dvonn.c
index 806a8e69247c289f3a712d12293b610f54e43384..8ac72b1cdd40f4efdd97de2d968a0c40812783bd 100644 (file)
--- a/dvonn.c
+++ b/dvonn.c
@@ -157,6 +157,10 @@ on_button_press_event (GtkWidget   *widget,
     int x, y;
     char *error;
 
+    /* Ignore double and triple clicks. */
+    if (event->type >= GDK_2BUTTON_PRESS)
+       return TRUE;
+
     x = event->x;
     y = event->y;
     layout_device_to_board (layout, &x, &y);
@@ -185,12 +189,14 @@ on_button_press_event (GtkWidget  *widget,
     }
 
     if (! game->has_selected) {
-       if (game->board.cells[x][y].type == game->board.player) {
-           game->has_selected = TRUE;
-           game->selected_x = x;
-           game->selected_y = y;
-           dvonn_game_update_windows (game);
-       }
+       if (game->board.cells[x][y].type == game->board.player &&
+           ! dvonn_board_cell_surrounded (&game->board, x, y))
+           {
+                   game->has_selected = TRUE;
+                   game->selected_x = x;
+                   game->selected_y = y;
+                   dvonn_game_update_windows (game);
+           }
        return TRUE;
     }