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 /* Base class providing common code for game engine implementations. */
50 this.players_by_session = {};
51 this.next_player_id = 1;
56 this.first_move = true;
58 /* Send a comment to every connected client every 15 seconds. */
59 setInterval(() => {this.broadcast_string(":");}, 15000);
62 /* Suport for game meta-data.
64 * What we want here is an effectively static field that is
65 * accessible through either the class name (SomeGame.meta) or an
66 * instance (some_game.meta). To pull this off we do keep two copies
67 * of the data. But the game classes can just set SomeGame.meta once
68 * and then reference it either way.
70 static set meta(data) {
71 /* This allows class access (SomeGame.meta) via the get method below. */
74 /* While this allows access via an instance (some_game.meta). */
75 this.prototype.meta = data;
82 /* Just performs some checks for whether a move is definitely not
83 * legal (such as not the player's turn). A child class is expected
84 * to override this (and call super.add_move early!) to implement
85 * the actual logic for a move. */
86 add_move(player, move) {
88 /* The checks here don't apply on the first move. */
89 if (! this.first_move) {
91 /* Discard any move asserting to be the first move if it's no
92 * longer the first move. This resolves the race condition if
93 * multiple players attempt to make the first move. */
94 if (move.assert_first_move) {
95 return { legal: false,
96 message: "Your opponent beat you to the first move" };
99 /* Cannot move if you are not on a team. */
100 if (player.team === no_team)
102 return { legal: false,
103 message: "You must be on a team to take a turn" };
106 /* Cannot move if it's not this player's team's turn. */
107 if (player.team !== this.state.team_to_play)
109 return { legal: false,
110 message: "It's not your turn to move" };
114 return { legal: true };
117 /* Assign team only if player is unassigned.
118 * Return true if assignment made, false otherwise. */
119 assign_player_to_team_perhaps(player, team)
121 if (player.team !== no_team)
125 this.broadcast_event("player-update", player.info_json());
130 /* This function is called after the child add_move has returned
131 * 'result' so that any generic processing can happen.
133 * In particular, we assign teams for a two-player game where a
134 * player assumed a team by making the first move. */
135 post_move(player, result)
137 if (this.first_move && result.legal) {
138 this.first_move = false;
140 this.assign_player_to_team_perhaps(player, this.teams[0]);
142 /* Yes, start at 1 to skip teams[0] which we just assigned. */
143 for (let i = 1; i < this.teams.length; i++) {
144 const other = this.players.find(p => (p !== player) && (p.team === no_team));
147 this.assign_player_to_team_perhaps(other, this.teams[i]);
152 add_player(session, connection) {
153 /* First see if we already have a player object for this session. */
154 const existing = this.players_by_session[session.id];
156 existing.add_connection(connection);
160 /* No existing player. Add a new one. */
161 const id = this.next_player_id;
162 let nickname = session.nickname;
165 const nickname_orig = nickname;
167 /* Ensure we don't have a name collision with a previous player. */
168 let unique_suffix = 1;
169 while (this.players.find(player => player.name === nickname))
171 nickname = `${nickname_orig}${unique_suffix.toString().padStart(2, '0')}`;
175 const player = new Player(id, session.id, nickname, connection);
177 /* Broadcast before adding player to list (to avoid announcing the
178 * new player to itself). */
179 const player_data = JSON.stringify({ id: player.id, name: player.name });
180 this.broadcast_event("player-enter", player_data);
182 this.players.push(player);
183 this.players_by_session[session.id] = player;
184 this.next_player_id++;
186 /* After adding the player to the list, and if we are already past
187 * the first move, assign this player to the first team that
188 * doesn't already have a player assigned (if any). */
189 if (! this.first_move) {
190 const have_players = Array(this.teams.length).fill(false);
191 this.players.forEach(p => {
192 if (p.team.id !== undefined)
193 have_players[p.team.id] = true;
195 const first_empty = have_players.findIndex(i => i === false);
196 this.assign_player_to_team_perhaps(player, this.teams[first_empty]);
202 /* Drop a connection object from a player, and if it's the last one,
203 * then drop that player from the game's list of players. */
204 remove_player_connection(player, connection) {
205 const remaining = player.remove_connection(connection);
206 if (remaining === 0) {
207 const player_data = JSON.stringify({ id: player.id });
208 this.players.filter(p => p !== player);
209 delete this.players_by_session[player.session_id];
210 this.broadcast_event("player-exit", player_data);
214 /* Send a string to all players */
215 broadcast_string(str) {
216 this.players.forEach(player => player.send(str + '\n'));
219 /* Send an event to all players.
221 * An event has both a declared type and a separate data block.
222 * It also ends with two newlines (to mark the end of the event).
224 broadcast_event(type, data) {
225 this.broadcast_string(`event: ${type}\ndata: ${data}\n`);
228 broadcast_event_object(type, obj) {
229 this.broadcast_event(type, JSON.stringify(obj));
232 handle_events(request, response) {
233 /* These headers will keep the connection open so we can stream events. */
235 "Content-type": "text/event-stream",
236 "Connection": "keep-alive",
237 "Cache-Control": "no-cache"
239 response.writeHead(200, headers);
241 /* Add this new player. */
242 const player = this.add_player(request.session, response);
244 /* And queue up cleanup to be triggered on client close. */
245 request.on('close', () => {
246 this.remove_player_connection(player, response);
249 /* Give the client the game-info event. */
250 const game_info_json = JSON.stringify({
252 url: `${request.protocol}://${request.hostname}/${this.id}`
254 response.write(`event: game-info\ndata: ${game_info_json}\n\n`);
256 /* And the player-info event. */
257 response.write(`event: player-info\ndata: ${player.info_json()}\n\n`);
259 /* As well as player-enter events for all existing players. */
260 this.players.filter(p => p !== player).forEach(p => {
261 response.write(`event: player-enter\ndata: ${p.info_json()}\n\n`);
264 /* Finally, if this game class has a "state" property, stream that
265 * current state to the client. */
267 const state_json = JSON.stringify(this.state);
268 response.write(`event: game-state\ndata: ${state_json}\n\n`);
272 handle_player(request, response) {
273 const player = this.players_by_session[request.session.id];
274 const name = request.body.name;
275 const team_name = request.body.team;
278 response.sendStatus(404);
282 if (name && (player.name !== name)) {
285 /* In addition to setting the name within this game's player
286 * object, also set the name in the session. */
287 request.session.nickname = name;
288 request.session.save();
293 if (team_name !== null && (player.team.name !== team_name))
295 if (team_name === "") {
296 player.team = no_team;
299 const index = this.teams.findIndex(t => t.name === team_name);
301 player.team = this.teams[index];
308 this.broadcast_event("player-update", player.info_json());
313 broadcast_move(move) {
314 this.broadcast_event("move", JSON.stringify(move));
319 module.exports = Game;