adds the tic-tac-toe example

Change-Id: I9c52b2e4f17ad3f02e0ef64fdd78864b3761e0b2
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

1 files changed, 518 insertions, 0 deletions

diff --git a/plugins/samples/tic-tac-toe.c b/plugins/samples/tic-tac-toe.c
new file mode 100644
index 00000000..81349e25
--- /dev/null
+++ b/plugins/samples/tic-tac-toe.c
@@ -0,0 +1,518 @@
+/*
+ * Copyright (C) 2016 "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>
+
+#include <afb/afb-plugin.h>
+
+/*
+ * the interface to afb-daemon
+ */
+const struct AFB_interface *afbitf;
+
+/*
+ * definition of a board
+ */
+struct board
+{
+	struct board *next;
+	int refcount;
+	int moves;
+	int history[9];
+	int id;
+	int level;
+	char board[9];
+};
+
+/*
+ * list of boards
+ */
+static struct board *all_boards;
+
+/*
+ * Search a board
+ */
+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
+ */
+static struct board *get_new_board()
+{
+	struct board *board = calloc(1, sizeof *board);
+	memset(board->board, ' ', sizeof board->board);
+	board->refcount = 1;
+	board->level = 1;
+	board->moves = 0;
+	do {
+		board->id = (rand() >> 2) % 1000;
+	} while(board->id == 0 || search_board(board->id) != NULL);
+	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->refcount == 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)
+{
+	/* TODO */
+	WARNING(afbitf, "changed is unimplmented (reason was %s)", reason);
+}
+
+/*
+ * retrieves the board of the request
+ */
+static 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);
+
+	/* 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)
+{
+	afb_req_success(req, describe(board_of_req(req)), 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);
+
+	/* retrieves the parameters of the move */
+	index = afb_req_value(req, "index");
+	i = index == NULL ? -1 : atoi(index);
+
+	/* checks validity of parameters */
+	if (i < 0 || i > 8) {
+		afb_req_fail(req, "error", "bad request");
+		return;
+	}
+
+	/* checks validity of the state */
+	if (winner(board->board) != 0) {
+		afb_req_fail(req, "error", "game terminated");
+		return;
+	}
+
+	/* checks validity of the move */
+	if (board->board[i] != ' ') {
+		afb_req_fail(req, "error", "occupied");
+		return;
+	}
+
+	/* applies the move */
+	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);
+
+	/* retrieves the parameters */
+	level = afb_req_value(req, "level");
+	l = level == NULL ? -1 : atoi(level);
+
+	/* check validity of parameters */
+	if (l < 1 || l > 10) {
+		afb_req_fail(req, "error", "bad request");
+		return;
+	}
+	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;
+	const char *id;
+
+	/* retrieves the context for the session */
+	board = board_of_req(req);
+
+	/* retrieves the parameters */
+	board = board_of_req(req);
+	id = afb_req_value(req, "boardid");
+	if (id == NULL)
+		goto bad_request;
+
+	/* check validity of parameters */
+	if (strcmp(id, "none")) {
+		board = get_new_board();
+		goto success;
+	}
+	board = search_board(atoi(id));
+	if (board == NULL)
+		goto bad_request;
+
+	board->refcount++;
+success:
+	afb_req_context_set(req, board, (void*)release_board);
+
+	/* replies */
+	afb_req_success(req, NULL, NULL);
+	return;
+
+bad_request:
+	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);
+
+	/* checks the state */
+	if (board->moves == 0) {
+		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);
+
+	/* checks validity of the state */
+	if (winner(board->board) != 0 || board->moves == 9) {
+		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");
+}
+
+/*
+ * array of the verbs exported to afb-daemon
+ */
+static const struct AFB_verb_desc_v1 verbs[] = {
+   /* VERB'S NAME     SESSION MANAGEMENT          FUNCTION TO CALL  SHORT DESCRIPTION */
+   { .name= "new",   .session= AFB_SESSION_NONE, .callback= new,   .info= "Starts a new game" },
+   { .name= "play",  .session= AFB_SESSION_NONE, .callback= play,  .info= "Tells the server to play" },
+   { .name= "move",  .session= AFB_SESSION_NONE, .callback= move,  .info= "Tells the client move" },
+   { .name= "board", .session= AFB_SESSION_NONE, .callback= board, .info= "Get the current board" },
+   { .name= "level", .session= AFB_SESSION_NONE, .callback= level, .info= "Set the server level" },
+   { .name= "join",  .session= AFB_SESSION_NONE, .callback= join,  .info= "Join a board" },
+   { .name= "undo",  .session= AFB_SESSION_NONE, .callback= undo,  .info= "Undo the last move" },
+   /* marker for end of the array */
+   { .name= NULL }
+};
+
+/*
+ * description of the plugin for afb-daemon
+ */
+static const struct AFB_plugin plugin_description =
+{
+   /* description conforms to VERSION 1 */
+   .type= AFB_PLUGIN_VERSION_1,
+   .v1= {				/* fills the v1 field of the union when AFB_PLUGIN_VERSION_1 */
+      .prefix= "tictactoe",		/* the API name (or plugin name or prefix) */
+      .info= "Sample tac-tac-toe game",	/* short description of of the plugin */
+      .verbs = verbs			/* the array describing the verbs of the API */
+   }
+};
+
+/*
+ * activation function for registering the plugin called by afb-daemon
+ */
+const struct AFB_plugin *pluginAfbV1Register(const struct AFB_interface *itf)
+{
+   afbitf = itf;         // records the interface for accessing afb-daemon
+   return &plugin_description;  // returns the description of the plugin
+}
+