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];
15 add_connection(connection) {
16 /* Don't add a duplicate connection if this player already has it. */
17 for (let c of this.connections) {
22 this.connections.push(connection);
25 /* Returns the number of remaining connections after this one is removed. */
26 remove_connection(connection) {
27 this.connections = this.connections.filter(c => c !== connection);
28 return this.connections.length;
31 /* Send a string to all connections for this player. */
33 this.connections.forEach(connection => connection.write(data));
37 return JSON.stringify({
46 /* This replacer function allows for JSON.stringify to give results
47 * for objects of various types that are used in game state.
49 function stringify_replacer(key, value) {
50 if (typeof value === 'object' && value instanceof Set) {
56 /* Base class providing common code for game engine implementations. */
61 this.players_by_session = {};
62 this.active_players = 0;
63 this.next_player_id = 1;
68 this.first_move = true;
70 /* Send a comment to every connected client every 15 seconds. */
71 setInterval(() => {this.broadcast_string(":");}, 15000);
74 /* Suport for game meta-data.
76 * What we want here is an effectively static field that is
77 * accessible through either the class name (SomeGame.meta) or an
78 * instance (some_game.meta). To pull this off we do keep two copies
79 * of the data. But the game classes can just set SomeGame.meta once
80 * and then reference it either way.
82 static set meta(data) {
83 /* This allows class access (SomeGame.meta) via the get method below. */
86 /* While this allows access via an instance (some_game.meta). */
87 this.prototype.meta = data;
94 /* Just performs some checks for whether a move is definitely not
95 * legal (such as not the player's turn). A child class is expected
96 * to override this (and call super.add_move early!) to implement
97 * the actual logic for a move. */
98 add_move(player, move) {
100 /* The checks here don't apply on the first move. */
101 if (! this.first_move) {
103 /* Discard any move asserting to be the first move if it's no
104 * longer the first move. This resolves the race condition if
105 * multiple players attempt to make the first move. */
106 if (move.assert_first_move) {
107 return { legal: false,
108 message: "Your opponent beat you to the first move" };
111 /* Cannot move if you are not on a team. */
112 if (player.team === no_team)
114 return { legal: false,
115 message: "You must be on a team to take a turn" };
118 /* Cannot move if it's not this player's team's turn. */
119 if (player.team !== this.state.team_to_play)
121 return { legal: false,
122 message: "It's not your turn to move" };
126 return { legal: true };
129 /* Assign team only if player is unassigned.
130 * Return true if assignment made, false otherwise. */
131 assign_player_to_team_perhaps(player, team)
133 if (player.team !== no_team)
137 this.broadcast_event("player-update", player.info_json());
142 /* This function is called after the child add_move has returned
143 * 'result' so that any generic processing can happen.
145 * In particular, we assign teams for a two-player game where a
146 * player assumed a team by making the first move. */
147 post_move(player, result)
149 if (this.first_move && result.legal) {
150 this.first_move = false;
152 this.assign_player_to_team_perhaps(player, this.teams[0]);
154 /* Yes, start at 1 to skip teams[0] which we just assigned. */
155 for (let i = 1; i < this.teams.length; i++) {
156 const other = this.players.find(p => (p !== player) && (p.team === no_team));
159 this.assign_player_to_team_perhaps(other, this.teams[i]);
164 add_player(session, connection) {
165 /* First see if we already have a player object for this session. */
166 const existing = this.players_by_session[session.id];
168 existing.add_connection(connection);
172 /* No existing player. Add a new one. */
173 const id = this.next_player_id;
174 let nickname = session.nickname;
177 const nickname_orig = nickname;
179 /* Ensure we don't have a name collision with a previous player. */
180 let unique_suffix = 1;
181 while (this.players.find(player => player.name === nickname))
183 nickname = `${nickname_orig}${unique_suffix.toString().padStart(2, '0')}`;
187 const player = new Player(id, session.id, nickname, connection);
189 /* Broadcast before adding player to list (to avoid announcing the
190 * new player to itself). */
191 const player_data = JSON.stringify({ id: player.id, name: player.name });
192 this.broadcast_event("player-enter", player_data);
194 this.players.push(player);
195 this.players_by_session[session.id] = player;
196 this.active_players++;
197 this.next_player_id++;
199 /* After adding the player to the list, and if we are already past
200 * the first move, assign this player to the first team that
201 * doesn't already have a player assigned (if any). */
202 if (! this.first_move) {
203 const have_players = Array(this.teams.length).fill(false);
204 this.players.forEach(p => {
205 if (p.team.id !== undefined)
206 have_players[p.team.id] = true;
208 const first_empty = have_players.findIndex(i => i === false);
209 this.assign_player_to_team_perhaps(player, this.teams[first_empty]);
215 /* Drop a connection object from a player, and if it's the last one,
216 * then drop that player from the game's list of players. */
217 remove_player_connection(player, connection) {
218 const remaining = player.remove_connection(connection);
219 if (remaining === 0) {
220 player.active = false;
221 this.active_players--;
222 const player_data = JSON.stringify({ id: player.id });
223 this.broadcast_event("player-exit", player_data);
227 /* Send a string to all players */
228 broadcast_string(str) {
229 this.players.forEach(player => player.send(str + '\n'));
232 /* Send an event to all players.
234 * An event has both a declared type and a separate data block.
235 * It also ends with two newlines (to mark the end of the event).
237 broadcast_event(type, data) {
238 this.broadcast_string(`event: ${type}\ndata: ${data}\n`);
241 broadcast_event_object(type, obj) {
242 this.broadcast_event(type, JSON.stringify(obj));
245 handle_events(request, response) {
246 /* These headers will keep the connection open so we can stream events. */
248 "Content-type": "text/event-stream",
249 "Connection": "keep-alive",
250 "Cache-Control": "no-cache"
252 response.writeHead(200, headers);
254 /* Add this new player. */
255 const player = this.add_player(request.session, response);
257 /* And queue up cleanup to be triggered on client close. */
258 request.on('close', () => {
259 this.remove_player_connection(player, response);
262 /* Give the client the game-info event. */
263 const game_info_json = JSON.stringify({
265 url: `${request.protocol}://${request.hostname}/${this.id}`
267 response.write(`event: game-info\ndata: ${game_info_json}\n\n`);
269 /* And the player-info event. */
270 response.write(`event: player-info\ndata: ${player.info_json()}\n\n`);
272 /* As well as player-enter events for all existing, active players. */
273 this.players.filter(p => p !== player && p.active).forEach(p => {
274 response.write(`event: player-enter\ndata: ${p.info_json()}\n\n`);
277 /* Finally, if this game class has a "state" property, stream that
278 * current state to the client. */
280 const state_json = JSON.stringify(this.state, stringify_replacer);
281 response.write(`event: game-state\ndata: ${state_json}\n\n`);
285 handle_player(request, response) {
286 const player = this.players_by_session[request.session.id];
287 const name = request.body.name;
288 const team_name = request.body.team;
291 response.sendStatus(404);
295 if (name && (player.name !== name)) {
298 /* In addition to setting the name within this game's player
299 * object, also set the name in the session. */
300 request.session.nickname = name;
301 request.session.save();
306 if (team_name !== null && (player.team.name !== team_name))
308 if (team_name === "") {
309 player.team = no_team;
312 const index = this.teams.findIndex(t => t.name === team_name);
314 player.team = this.teams[index];
321 this.broadcast_event("player-update", player.info_json());
326 broadcast_move(move) {
327 this.broadcast_event("move", JSON.stringify(move));
332 module.exports = Game;