Re-architecting of the game backend interface. make_move() has been

split into two functions. The first, interpret_move(), takes all the
arguments that make_move() used to get and may have the usual side
effects of modifying the game_ui, but instead of returning a
modified game_state it instead returns a string description of the
move to be made. This string description is then passed to a second
function, execute_move(), together with an input game_state, which
is responsible for actually producing the new state. (solve_game()
also returns a string to be passed to execute_move().)

The point of this is to work towards being able to serialise the
whole of a game midend into a byte stream such as a disk file, which
will eventually support save and load functions in the desktop
puzzles, as well as restoring half-finished games after a quit and
restart in James Harvey's Palm port. Making each game supply a
convert-to-string function for its game_state format would have been
an unreliable way to do this, since those functions would not have
been used in normal play, so they'd only have been tested when you
actually tried to save and load - a recipe for latent bugs if ever I
heard one. This way, you won't even be able to _make_ a move if
execute_move() doesn't work properly, which means that if you can
play a game at all I can have pretty high confidence that
serialising it will work first time.

This is only the groundwork; there will be more checkins to come on
this theme. But the major upheaval should now be done, and as far as
I can tell everything's still working normally.

[originally from svn r6024]

samegame.c

@@ -355,8 +355,8 @@ static void free_game(game_state *state)
     sfree(state);
 }
 
-static game_state *solve_game(game_state *state, game_state *currstate,
-			      game_aux_info *aux, char **error)
+static char *solve_game(game_state *state, game_state *currstate,
+			game_aux_info *aux, char **error)
 {
     return NULL;
 }
@@ -427,20 +427,37 @@ static void game_changed_state(game_ui *ui, game_state *oldstate,
     sel_clear(ui, newstate);
 }
 
-static void sel_remove(game_ui *ui, game_state *state)
+static char *sel_movedesc(game_ui *ui, game_state *state)
 {
-    int i, nremoved = 0;
+    int i;
+    char *ret, *sep, buf[80];
+    int retlen, retsize;
 
-    state->score += npoints(&state->params, ui->nselected);
+    retsize = 256;
+    ret = snewn(retsize, char);
+    retlen = 0;
+    ret[retlen++] = 'M';
+    sep = "";
 
     for (i = 0; i < state->n; i++) {
 	if (ui->tiles[i] & TILE_SELECTED) {
-	    nremoved++;
-	    state->tiles[i] = 0;
+	    sprintf(buf, "%s%d", sep, i);
+	    sep = ",";
+	    if (retlen + strlen(buf) >= retsize) {
+		retsize = retlen + strlen(buf) + 256;
+		ret = sresize(ret, retsize, char);
+	    }
+	    strcpy(ret + retlen, buf);
+	    retlen += strlen(buf);
+
 	    ui->tiles[i] &= ~TILE_SELECTED;
 	}
     }
     ui->nselected = 0;
+
+    assert(retlen < retsize);
+    ret[retlen++] = '\0';
+    return sresize(ret, retlen, char);
 }
 
 static void sel_expand(game_ui *ui, game_state *state, int tx, int ty)
@@ -567,11 +584,13 @@ struct game_drawstate {
     int *tiles; /* contains colour and SELECTED. */
 };
 
-static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
-                             int x, int y, int button)
+static game_state *execute_move(game_state *from, char *move);
+
+static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
+			    int x, int y, int button)
 {
     int tx, ty;
-    game_state *ret = from;
+    char *ret = "";
 
     ui->displaysel = 0;
 
@@ -583,8 +602,8 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
 	ui->displaysel = 1;
 	dx = (button == CURSOR_LEFT) ? -1 : ((button == CURSOR_RIGHT) ? +1 : 0);
 	dy = (button == CURSOR_DOWN) ? +1 : ((button == CURSOR_UP)    ? -1 : 0);
-	ui->xsel = (ui->xsel + from->params.w + dx) % from->params.w;
-	ui->ysel = (ui->ysel + from->params.h + dy) % from->params.h;
+	ui->xsel = (ui->xsel + state->params.w + dx) % state->params.w;
+	ui->ysel = (ui->ysel + state->params.h + dy) % state->params.h;
 	return ret;
     } else if (button == CURSOR_SELECT || button == ' ' || button == '\r' ||
 	       button == '\n') {
@@ -594,30 +613,71 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
     } else
 	return NULL;
 
-    if (tx < 0 || tx >= from->params.w || ty < 0 || ty >= from->params.h)
+    if (tx < 0 || tx >= state->params.w || ty < 0 || ty >= state->params.h)
 	return NULL;
-    if (COL(from, tx, ty) == 0) return NULL;
+    if (COL(state, tx, ty) == 0) return NULL;
 
     if (ISSEL(ui,tx,ty)) {
 	if (button == RIGHT_BUTTON)
-	    sel_clear(ui, from);
+	    sel_clear(ui, state);
 	else {
-	    /* this is the actual move. */
-	    ret = dup_game(from);
-	    sel_remove(ui, ret);
-	    sg_snuggle(ret); /* shifts blanks down and to the left */
-	    sg_check(ret);   /* checks for completeness or impossibility */
+	    game_state *tmp;
+
+	    ret = sel_movedesc(ui, state);
+
+	    /*
+	     * Unfortunately, we must check for completeness or
+	     * impossibility now, in order to update the game_ui;
+	     * and we can't do that without constructing the new
+	     * grid. Sigh.
+	     */
+	    tmp = execute_move(state, ret);
+	    if (tmp->complete || tmp->impossible)
+		ui->displaysel = 0;
+	    free_game(tmp);
 	}
     } else {
-	sel_clear(ui, from); /* might be no-op */
-	sel_expand(ui, from, tx, ty);
+	sel_clear(ui, state); /* might be no-op */
+	sel_expand(ui, state, tx, ty);
     }
-    if (ret->complete || ret->impossible)
-	ui->displaysel = 0;
 
     return ret;
 }
 
+static game_state *execute_move(game_state *from, char *move)
+{
+    int i, n;
+    game_state *ret;
+
+    if (move[0] == 'M') {
+	ret = dup_game(from);
+
+	n = 0;
+	move++;
+
+	while (*move) {
+	    i = atoi(move);
+	    if (i < 0 || i >= ret->n) {
+		free_game(ret);
+		return NULL;
+	    }
+	    n++;
+	    ret->tiles[i] = 0;
+
+	    while (*move && isdigit((unsigned char)*move)) move++;
+	    if (*move == ',') move++;
+	}
+
+	ret->score += npoints(&ret->params, n);
+
+	sg_snuggle(ret); /* shifts blanks down and to the left */
+	sg_check(ret);   /* checks for completeness or impossibility */
+
+	return ret;
+    } else
+	return NULL;		       /* couldn't parse move string */
+}
+
 /* ----------------------------------------------------------------------
  * Drawing routines.
  */
@@ -940,7 +1000,8 @@ const struct game thegame = {
     new_ui,
     free_ui,
     game_changed_state,
-    make_move,
+    interpret_move,
+    execute_move,
     game_size,
     game_colours,
     game_new_drawstate,