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({
44 /* Base class providing common code for game engine implementations. */
49 this.players_by_session = {};
50 this.next_player_id = 1;
55 this.first_move = true;
57 /* Send a comment to every connected client every 15 seconds. */
58 setInterval(() => {this.broadcast_string(":");}, 15000);
61 /* Suport for game meta-data.
63 * What we want here is an effectively static field that is
64 * accessible through either the class name (SomeGame.meta) or an
65 * instance (some_game.meta). To pull this off we do keep two copies
66 * of the data. But the game classes can just set SomeGame.meta once
67 * and then reference it either way.
69 static set meta(data) {
70 /* This allows class access (SomeGame.meta) via the get method below. */
73 /* While this allows access via an instance (some_game.meta). */
74 this.prototype.meta = data;
81 /* Just performs some checks for whether a move is definitely not
82 * legal (such as not the player's turn). A child class is expected
83 * to override this (and call super.add_move early!) to implement
84 * the actual logic for a move. */
85 add_move(player, move) {
87 /* The checks here don't apply on the first move. */
88 if (! this.first_move) {
90 /* Discard any move asserting to be the first move if it's no
91 * longer the first move. This resolves the race condition if
92 * multiple players attempt to make the first move. */
93 if (move.assert_first_move) {
94 return { legal: false,
95 message: "Your opponent beat you to the first move" };
98 /* Cannot move if you are not on a team. */
99 if (player.team === no_team)
101 return { legal: false,
102 message: "You must be on a team to take a turn" };
105 /* Cannot move if it's not this player's team's turn. */
106 if (player.team !== this.state.team_to_play)
108 return { legal: false,
109 message: "It's not your turn to move" };
113 return { legal: true };
116 /* Assign team only if player is unassigned.
117 * Return true if assignment made, false otherwise. */
118 assign_player_to_team_perhaps(player, team)
120 if (player.team !== no_team)
124 this.broadcast_event("player-update", player.info_json());
129 /* This function is called after the child add_move has returned
130 * 'result' so that any generic processing can happen.
132 * In particular, we assign teams for a two-player game where a
133 * player assumed a team by making the first move. */
134 post_move(player, result)
136 if (this.first_move && result.legal) {
137 this.first_move = false;
139 this.assign_player_to_team_perhaps(player, this.teams[0]);
141 /* Yes, start at 1 to skip teams[0] which we just assigned. */
142 for (let i = 1; i < this.teams.length; i++) {
143 const other = this.players.find(p => (p !== player) && (p.team === no_team));
146 this.assign_player_to_team_perhaps(other, this.teams[i]);
151 add_player(session, connection) {
152 /* First see if we already have a player object for this session. */
153 const existing = this.players_by_session[session.id];
155 existing.add_connection(connection);
159 /* No existing player. Add a new one. */
160 const id = this.next_player_id;
161 const player = new Player(id, session.id, session.nickname, connection);
163 /* Broadcast before adding player to list (to avoid announcing the
164 * new player to itself). */
165 const player_data = JSON.stringify({ id: player.id, name: player.name });
166 this.broadcast_event("player-enter", player_data);
168 this.players.push(player);
169 this.players_by_session[session.id] = player;
170 this.next_player_id++;
172 /* After adding the player to the list, and if we are already past
173 * the first move, assign this player to the first team that
174 * doesn't already have a player aissgned (if any). */
175 if (! this.first_move) {
176 const have_players = Array(this.teams.length).fill(false);
177 this.players.forEach(p => {
178 if (p.team.id !== undefined)
179 have_players[p.team.id] = true;
181 const first_empty = have_players.findIndex(i => i === false);
182 this.assign_player_to_team_perhaps(player, this.teams[first_empty]);
188 /* Drop a connection object from a player, and if it's the last one,
189 * then drop that player from the game's list of players. */
190 remove_player_connection(player, connection) {
191 const remaining = player.remove_connection(connection);
192 if (remaining === 0) {
193 const player_data = JSON.stringify({ id: player.id });
194 this.players.filter(p => p !== player);
195 delete this.players_by_session[player.session_id];
196 this.broadcast_event("player-exit", player_data);
200 /* Send a string to all players */
201 broadcast_string(str) {
202 this.players.forEach(player => player.send(str + '\n'));
205 /* Send an event to all players.
207 * An event has both a declared type and a separate data block.
208 * It also ends with two newlines (to mark the end of the event).
210 broadcast_event(type, data) {
211 this.broadcast_string(`event: ${type}\ndata: ${data}\n`);
214 handle_events(request, response) {
215 /* These headers will keep the connection open so we can stream events. */
217 "Content-type": "text/event-stream",
218 "Connection": "keep-alive",
219 "Cache-Control": "no-cache"
221 response.writeHead(200, headers);
223 /* Add this new player. */
224 const player = this.add_player(request.session, response);
226 /* And queue up cleanup to be triggered on client close. */
227 request.on('close', () => {
228 this.remove_player_connection(player, response);
231 /* Give the client the game-info event. */
232 const game_info_json = JSON.stringify({
234 url: `${request.protocol}://${request.hostname}/${this.id}`
236 response.write(`event: game-info\ndata: ${game_info_json}\n\n`);
238 /* And the player-info event. */
239 response.write(`event: player-info\ndata: ${player.info_json()}\n\n`);
241 /* As well as player-enter events for all existing players. */
242 this.players.filter(p => p !== player).forEach(p => {
243 response.write(`event: player-enter\ndata: ${p.info_json()}\n\n`);
246 /* Finally, if this game class has a "state" property, stream that
247 * current state to the client. */
249 const state_json = JSON.stringify(this.state);
250 response.write(`event: game-state\ndata: ${state_json}\n\n`);
254 handle_player(request, response) {
255 const player = this.players_by_session[request.session.id];
256 const name = request.body.name;
257 const team_name = request.body.team;
260 response.sendStatus(404);
264 if (name && (player.name !== name)) {
267 /* In addition to setting the name within this game's player
268 * object, also set the name in the session. */
269 request.session.nickname = name;
270 request.session.save();
275 if (team_name !== null && (player.team.name !== team_name))
277 if (team_name === "") {
278 player.team = no_team;
281 const index = this.teams.findIndex(t => t.name === team_name);
283 player.team = this.teams[index];
290 this.broadcast_event("player-update", player.info_json());
295 broadcast_move(move) {
296 this.broadcast_event("move", move);
301 module.exports = Game;