aboutsummaryrefslogtreecommitdiffstats
path: root/bindings/samples/tic-tac-toe.c
blob: 6b7022b89932ea4ad2f40b9e109109404475fb2c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
/*
 * Copyright (C) 2016, 2017, 2018 "IoT.bzh"
 * Author José Bollo <jose.bollo@iot.bzh>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <json-c/json.h>

#define AFB_BINDING_VERSION 2
#include <afb/afb-binding.h>

/*
 * definition of waiters
 */
struct waiter
{
	struct waiter *next;
	struct afb_req req;
};

/*
 * definition of a board
 */
struct board
{
	struct board *next;
	int use_count;
	int moves;
	int history[9];
	int id;
	int level;
	char board[9];
	struct waiter *waiters;
};

/*
 * list of boards
 */
static struct board *all_boards;

/*
 * Searchs a board having the 'id'.
 * Returns it if found or NULL otherwise.
 */
static struct board *search_board(int id)
{
	struct board *board = all_boards;
	while (board != NULL && board->id != id)
		board = board->next;
	return board;
}

/*
 * Creates a new board and returns it.
 */
static struct board *get_new_board()
{
	/* allocation */
	struct board *board = calloc(1, sizeof *board);

	/* initialisation */
	memset(board->board, ' ', sizeof board->board);
	board->use_count = 1;
	board->level = 1;
	board->moves = 0;
	do {
		board->id = (rand() >> 2) % 1000;
	} while(board->id == 0 || search_board(board->id) != NULL);

	/* link */
	board->next = all_boards;
	all_boards = board;
	return board;
}

/*
 * Release a board
 */
static void release_board(struct board *board)
{
	/* decrease the reference count ... */
	if (--board->use_count == 0) {
		/* ... no more use */
		/* unlink from the list of boards */
		struct board **prv = &all_boards;
		while (*prv != NULL && *prv != board)
			prv = &(*prv)->next;
		if (*prv != NULL)
			*prv = board->next;
		/* release the used memory */
		free(board);
	}
}

/*
 * Checks who wins
 * Returns zero if there is no winner
 * Returns the char of the winner if a player won
 */
static char winner(const char b[9])
{
	int i;
	char c;

	/* check diagonals */
	c = b[4];
	if (c != ' ') {
		if (b[0] == c && b[8] == c)
			return c;
		if (b[2] == c && b[6] == c)
			return c;
	}

	/* check lines */
	for (i = 0 ; i <= 6 ; i += 3) {
		c = b[i];
		if (c != ' ' && b[i+1] == c && b[i+2] == c)
			return c;
	}

	/* check columns */
	for (i = 0 ; i <= 2 ; i++) {
		c = b[i];
		if (c != ' ' && b[i+3] == c && b[i+6] == c)
			return c;
	}

	return 0;
}

/* get the color (X or 0) of the move of index 'move' */
static char color(int move)
{
	return (move & 1) == 0 ? 'X' : '0';
}

/* adds the move to the board */
static void add_move(struct board *board, int index)
{
	int imove = board->moves++;
	board->history[imove] = index;
	board->board[index] = color(imove);
}

/* get a random possible move index from the board described by 'b' */
static int get_random_move(char b[9])
{
	int index = rand() % 9;
	while (b[index] != ' ')
		index = (index + 1) % 9;
	return index;
}

/*
 * Scores the position described by 'b'
 * for the player of color 'c' using an analysis of 'depth'.
 * Returns 1 if player 'c' will win.
 * Returns -1 if opponent of player 'c' will win.
 * returns 0 otherwise.
 */
static int score_position(char b[9], char c, int depth)
{
	int i, t, r;

	/* check if winner */
	if (winner(b) == c)
		return 1;

	/* when depth of analysis is reached return unknown case */
	if (--depth == 0)
		return 0;

	/* switch to the opponent */
	c = (char)('O' + 'X' - c);

	/* inspect opponent moves */
	r = 1;
	for (i = 0 ; i < 9 ; i++) {
		if (b[i] == ' ') {
			b[i] = c;
			t = score_position(b, c, depth);
			b[i] = ' ';
			if (t > 0)
				return -1; /* opponent will win */

			if (t == 0)
				r = 0; /* something not clear */
		}
	}
	return r;
}

/* get one move: return the computed index of the move */
static int get_move(struct board *board)
{
	int index, depth, t, f;
	char c;
	char b[9];

	/* compute the depth */
	depth = board->level - 1;
	if (board->moves + depth > 9)
		depth = 9 - board->moves;

	/* case of null depth */
	if (depth == 0)
		return get_random_move(board->board);

	/* depth and more */
	memcpy(b, board->board, 9);
	c = color(board->moves);
	f = 0;
	for (index = 0 ; index < 9 ; index++) {
		if (board->board[index] == ' ') {
			board->board[index] = c;
			t = score_position(board->board, c, depth);
			board->board[index] = ' ';
			if (t > 0)
				return index;
			if (t < 0)
				b[index] = '+';
			else
				f = 1;
		}
	}
	return get_random_move(f ? b : board->board);
}

/*
 * get the board description
 */
static struct json_object *describe(struct board *board)
{
	int i;
	char w;
	struct json_object *resu, *arr;

	resu = json_object_new_object();

	json_object_object_add(resu, "boardid", json_object_new_int(board->id));
	json_object_object_add(resu, "level", json_object_new_int(board->level));

	arr = json_object_new_array();
	json_object_object_add(resu, "board", arr);
	for (i = 0 ; i < 9 ; i++)
		json_object_array_add(arr,
				json_object_new_string_len(&board->board[i], 1));

	arr = json_object_new_array();
	json_object_object_add(resu, "history", arr);
	for (i = 0 ; i < board->moves ; i++)
		json_object_array_add(arr, json_object_new_int(board->history[i]));

	w = winner(board->board);
	if (w)
		json_object_object_add(resu, "winner", json_object_new_string_len(&w, 1));
	else if (board->moves == 9)
		json_object_object_add(resu, "winner", json_object_new_string("none"));

	return resu;
}

/*
 * signals a change of the board
 */
static void changed(struct board *board, const char *reason)
{
	struct waiter *waiter, *next;
	struct json_object *description;

	/* get the description */
	description = describe(board);

	waiter = board->waiters;
	board->waiters = NULL;
	while (waiter != NULL) {
		next = waiter->next;
		afb_req_success(waiter->req, json_object_get(description), reason);
		afb_req_unref(waiter->req);
		free(waiter);
		waiter = next;
	}

	afb_daemon_broadcast_event(reason, description);
}

/*
 * retrieves the board of the request
 */
static inline struct board *board_of_req(struct afb_req req)
{
	return afb_req_context(req, (void*)get_new_board, (void*)release_board);
}

/*
 * start a new game
 */
static void new(struct afb_req req)
{
	struct board *board;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'new' called for boardid %d", board->id);

	/* reset the game */
	memset(board->board, ' ', sizeof board->board);
	board->moves = 0;

	/* replies */
	afb_req_success(req, NULL, NULL);

	/* signal change */
	changed(board, "new");
}

/*
 * get the board
 */
static void board(struct afb_req req)
{
	struct board *board;
	struct json_object *description;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'board' called for boardid %d", board->id);

	/* describe the board */
	description = describe(board);

	/* send the board's description */
	afb_req_success(req, description, NULL);
}

/*
 * move a piece
 */
static void move(struct afb_req req)
{
	struct board *board;
	int i;
	const char *index;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'move' called for boardid %d", board->id);

	/* retrieves the arguments of the move */
	index = afb_req_value(req, "index");
	i = index == NULL ? -1 : atoi(index);

	/* checks validity of arguments */
	if (i < 0 || i > 8) {
		AFB_WARNING("can't move to %s: %s", index?:"?", index?"wrong value":"not set");
		afb_req_fail(req, "error", "bad request");
		return;
	}

	/* checks validity of the state */
	if (winner(board->board) != 0) {
		AFB_WARNING("can't move to %s: game is terminated", index);
		afb_req_fail(req, "error", "game terminated");
		return;
	}

	/* checks validity of the move */
	if (board->board[i] != ' ') {
		AFB_WARNING("can't move to %s: room occupied", index);
		afb_req_fail(req, "error", "occupied");
		return;
	}

	/* applies the move */
	AFB_INFO("method 'move' for boardid %d, index=%s", board->id, index);
	add_move(board, i);

	/* replies */
	afb_req_success(req, NULL, NULL);

	/* signals change */
	changed(board, "move");
}

/*
 * set the level
 */
static void level(struct afb_req req)
{
	struct board *board;
	int l;
	const char *level;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'level' called for boardid %d", board->id);

	/* retrieves the arguments */
	level = afb_req_value(req, "level");
	l = level == NULL ? -1 : atoi(level);

	/* check validity of arguments */
	if (l < 1 || l > 10) {
		AFB_WARNING("can't set level to %s: %s", level?:"?", level?"wrong value":"not set");
		afb_req_fail(req, "error", "bad request");
		return;
	}

	/* set the level */
	AFB_INFO("method 'level' for boardid %d, level=%d", board->id, l);
	board->level = l;

	/* replies */
	afb_req_success(req, NULL, NULL);

	/* signals change */
	changed(board, "level");
}

/*
 * Join a board
 */
static void join(struct afb_req req)
{
	struct board *board, *new_board;
	const char *id;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'join' called for boardid %d", board->id);

	/* retrieves the arguments */
	id = afb_req_value(req, "boardid");
	if (id == NULL)
		goto bad_request;

	/* none is a special id for joining a new session */
	if (strcmp(id, "none") == 0) {
		new_board = get_new_board();
		goto success;
	}

	/* searchs the board to join */
	new_board = search_board(atoi(id));
	if (new_board == NULL)
		goto bad_request;

	/*
	 * joining its board is stupid but possible
	 * however when called with the same stored pointer
	 * afb_req_context_set will not call the release
	 * function 'release_board'. So the use_count MUST not
	 * be incremented.
	 */
	if (new_board != board)
		new_board->use_count++;

success:
	/* set the new board (and leaves the previous one) */
	afb_req_context_set(req, new_board, (void*)release_board);

	/* replies */
	afb_req_success(req, NULL, NULL);
	return;

bad_request:
	AFB_WARNING("can't join boardid %s: %s", id ? : "?", !id ? "no boardid" : atoi(id) ? "not found" : "bad boardid");
	afb_req_fail(req, "error", "bad request");
	return;
}

/*
 * Undo the last move
 */
static void undo(struct afb_req req)
{
	struct board *board;
	int i;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'undo' called for boardid %d", board->id);

	/* checks the state */
	if (board->moves == 0) {
		AFB_WARNING("can't undo");
		afb_req_fail(req, "error", "bad request");
		return;
	}

	/* undo the last move */
	i = board->history[--board->moves];
	board->board[i] = ' ';

	/* replies */
	afb_req_success(req, NULL, NULL);

	/* signals change */
	changed(board, "undo");
}

/*
 * computer plays
 */
static void play(struct afb_req req)
{
	struct board *board;
	int index;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'play' called for boardid %d", board->id);

	/* checks validity of the state */
	if (winner(board->board) != 0 || board->moves == 9) {
		AFB_WARNING("can't play: game terminated (%s)", winner(board->board) ? "has winner" : "no room left");
		afb_req_fail(req, "error", "game terminated");
		return;
	}

	/* gets the move and plays it */
	index = get_move(board);
	add_move(board, index);

	/* replies */
	afb_req_success(req, describe(board), NULL);

	/* signals change */
	changed(board, "play");
}

static void wait(struct afb_req req)
{
	struct board *board;
	struct waiter *waiter;

	/* retrieves the context for the session */
	board = board_of_req(req);
	AFB_INFO("method 'wait' called for boardid %d", board->id);

	/* creates the waiter and enqueues it */
	waiter = calloc(1, sizeof *waiter);
	waiter->req = req;
	waiter->next = board->waiters;
	afb_req_addref(req);
	board->waiters = waiter;
}

/*
 * array of the verbs exported to afb-daemon
 */
static const struct afb_verb_v2 verbs[] = {
   { .verb="new",   .callback=new },
   { .verb="play",  .callback=play },
   { .verb="move",  .callback=move },
   { .verb="board", .callback=board },
   { .verb="level", .callback=level },
   { .verb="join",  .callback=join },
   { .verb="undo",  .callback=undo },
   { .verb="wait",  .callback=wait },
   { .verb=NULL }
};

/*
 * description of the binding for afb-daemon
 */
const afb_binding_v2 afbBindingV2 = {
	.api = "tictactoe",
	.specification = NULL,
	.verbs = verbs
};