1 const no_team = { name: "" };
3 /* A single player can have multiple connections, (think, multiple
4 * browser windows with a common session cookie). */
6 constructor(id, session_id, name, connection) {
8 this.session_id = session_id;
10 this.connections = [connection];
14 add_connection(connection) {
15 /* Don't add a duplicate connection if this player already has it. */
16 for (let c of this.connections) {
21 this.connections.push(connection);
24 /* Returns the number of remaining connections after this one is removed. */
25 remove_connection(connection) {
26 this.connections.filter(c => c !== connection);
27 return this.connections.length;
30 /* Send a string to all connections for this player. */
32 this.connections.forEach(connection => connection.write(data));
36 return JSON.stringify({
45 /* This replacer function allows for JSON.stringify to give results
46 * for objects of various types that are used in game state.
48 function stringify_replacer(key, value) {
49 if (typeof value === 'object' && value instanceof Set) {
55 /* Base class providing common code for game engine implementations. */
60 this.players_by_session = {};
61 this.next_player_id = 1;
66 this.first_move = true;
68 /* Send a comment to every connected client every 15 seconds. */
69 setInterval(() => {this.broadcast_string(":");}, 15000);
72 /* Suport for game meta-data.
74 * What we want here is an effectively static field that is
75 * accessible through either the class name (SomeGame.meta) or an
76 * instance (some_game.meta). To pull this off we do keep two copies
77 * of the data. But the game classes can just set SomeGame.meta once
78 * and then reference it either way.
80 static set meta(data) {
81 /* This allows class access (SomeGame.meta) via the get method below. */
84 /* While this allows access via an instance (some_game.meta). */
85 this.prototype.meta = data;
92 /* Just performs some checks for whether a move is definitely not
93 * legal (such as not the player's turn). A child class is expected
94 * to override this (and call super.add_move early!) to implement
95 * the actual logic for a move. */
96 add_move(player, move) {
98 /* The checks here don't apply on the first move. */
99 if (! this.first_move) {
101 /* Discard any move asserting to be the first move if it's no
102 * longer the first move. This resolves the race condition if
103 * multiple players attempt to make the first move. */
104 if (move.assert_first_move) {
105 return { legal: false,
106 message: "Your opponent beat you to the first move" };
109 /* Cannot move if you are not on a team. */
110 if (player.team === no_team)
112 return { legal: false,
113 message: "You must be on a team to take a turn" };
116 /* Cannot move if it's not this player's team's turn. */
117 if (player.team !== this.state.team_to_play)
119 return { legal: false,
120 message: "It's not your turn to move" };
124 return { legal: true };
127 /* Assign team only if player is unassigned.
128 * Return true if assignment made, false otherwise. */
129 assign_player_to_team_perhaps(player, team)
131 if (player.team !== no_team)
135 this.broadcast_event("player-update", player.info_json());
140 /* This function is called after the child add_move has returned
141 * 'result' so that any generic processing can happen.
143 * In particular, we assign teams for a two-player game where a
144 * player assumed a team by making the first move. */
145 post_move(player, result)
147 if (this.first_move && result.legal) {
148 this.first_move = false;
150 this.assign_player_to_team_perhaps(player, this.teams[0]);
152 /* Yes, start at 1 to skip teams[0] which we just assigned. */
153 for (let i = 1; i < this.teams.length; i++) {
154 const other = this.players.find(p => (p !== player) && (p.team === no_team));
157 this.assign_player_to_team_perhaps(other, this.teams[i]);
162 add_player(session, connection) {
163 /* First see if we already have a player object for this session. */
164 const existing = this.players_by_session[session.id];
166 existing.add_connection(connection);
170 /* No existing player. Add a new one. */
171 const id = this.next_player_id;
172 let nickname = session.nickname;
175 const nickname_orig = nickname;
177 /* Ensure we don't have a name collision with a previous player. */
178 let unique_suffix = 1;
179 while (this.players.find(player => player.name === nickname))
181 nickname = `${nickname_orig}${unique_suffix.toString().padStart(2, '0')}`;
185 const player = new Player(id, session.id, nickname, connection);
187 /* Broadcast before adding player to list (to avoid announcing the
188 * new player to itself). */
189 const player_data = JSON.stringify({ id: player.id, name: player.name });
190 this.broadcast_event("player-enter", player_data);
192 this.players.push(player);
193 this.players_by_session[session.id] = player;
194 this.next_player_id++;
196 /* After adding the player to the list, and if we are already past
197 * the first move, assign this player to the first team that
198 * doesn't already have a player assigned (if any). */
199 if (! this.first_move) {
200 const have_players = Array(this.teams.length).fill(false);
201 this.players.forEach(p => {
202 if (p.team.id !== undefined)
203 have_players[p.team.id] = true;
205 const first_empty = have_players.findIndex(i => i === false);
206 this.assign_player_to_team_perhaps(player, this.teams[first_empty]);
212 /* Drop a connection object from a player, and if it's the last one,
213 * then drop that player from the game's list of players. */
214 remove_player_connection(player, connection) {
215 const remaining = player.remove_connection(connection);
216 if (remaining === 0) {
217 const player_data = JSON.stringify({ id: player.id });
218 this.players.filter(p => p !== player);
219 delete this.players_by_session[player.session_id];
220 this.broadcast_event("player-exit", player_data);
224 /* Send a string to all players */
225 broadcast_string(str) {
226 this.players.forEach(player => player.send(str + '\n'));
229 /* Send an event to all players.
231 * An event has both a declared type and a separate data block.
232 * It also ends with two newlines (to mark the end of the event).
234 broadcast_event(type, data) {
235 this.broadcast_string(`event: ${type}\ndata: ${data}\n`);
238 broadcast_event_object(type, obj) {
239 this.broadcast_event(type, JSON.stringify(obj));
242 handle_events(request, response) {
243 /* These headers will keep the connection open so we can stream events. */
245 "Content-type": "text/event-stream",
246 "Connection": "keep-alive",
247 "Cache-Control": "no-cache"
249 response.writeHead(200, headers);
251 /* Add this new player. */
252 const player = this.add_player(request.session, response);
254 /* And queue up cleanup to be triggered on client close. */
255 request.on('close', () => {
256 this.remove_player_connection(player, response);
259 /* Give the client the game-info event. */
260 const game_info_json = JSON.stringify({
262 url: `${request.protocol}://${request.hostname}/${this.id}`
264 response.write(`event: game-info\ndata: ${game_info_json}\n\n`);
266 /* And the player-info event. */
267 response.write(`event: player-info\ndata: ${player.info_json()}\n\n`);
269 /* As well as player-enter events for all existing players. */
270 this.players.filter(p => p !== player).forEach(p => {
271 response.write(`event: player-enter\ndata: ${p.info_json()}\n\n`);
274 /* Finally, if this game class has a "state" property, stream that
275 * current state to the client. */
277 const state_json = JSON.stringify(this.state, stringify_replacer);
278 response.write(`event: game-state\ndata: ${state_json}\n\n`);
282 handle_player(request, response) {
283 const player = this.players_by_session[request.session.id];
284 const name = request.body.name;
285 const team_name = request.body.team;
288 response.sendStatus(404);
292 if (name && (player.name !== name)) {
295 /* In addition to setting the name within this game's player
296 * object, also set the name in the session. */
297 request.session.nickname = name;
298 request.session.save();
303 if (team_name !== null && (player.team.name !== team_name))
305 if (team_name === "") {
306 player.team = no_team;
309 const index = this.teams.findIndex(t => t.name === team_name);
311 player.team = this.teams[index];
318 this.broadcast_event("player-update", player.info_json());
323 broadcast_move(move) {
324 this.broadcast_event("move", JSON.stringify(move));
329 module.exports = Game;