Add a minimal implementation of the TicTacToe game engine

[empires-server] / tictactoe.js

diff --git a/tictactoe.js b/tictactoe.js
index 18fe3428806bee30c2c533182b15e02fee36993b..82c5f7e839d770cb4b4bb33f6f040ae9f079c6aa 100644 (file)
--- a/tictactoe.js
+++ b/tictactoe.js
@@ -14,6 +14,58 @@ nunjucks.configure("templates", {
   express: app
 });
 
+class TicTacToe {
+  constructor() {
+    this.moves = [];
+    this.board = Array(9).fill(null);
+    this.clients = [];
+    this.next_client_id = 1;
+  }
+
+  /* Returns Boolean indicating whether move was legal and added. */
+  add_move(square) {
+    /* Cannot move to an occupied square. */
+    if (this.board[square])
+      return false;
+
+    this.board[square] = 'X';
+    this.moves.push(square);
+
+    return true;
+  }
+
+  add_client(response) {
+    const id = this.next_client_id;
+    this.clients.push({id: id,
+                       response: response});
+    this.next_client_id++;
+
+    return id;
+  }
+
+  remove_client(id) {
+    this.clients = this.clients.filter(client => client.id !== id);
+  }
+
+  /* Send a string to all clients */
+  broadcast_string(str) {
+    this.clients.forEach(client => client.response.write(str + '\n'));
+  }
+
+  /* Send an event to all clients.
+   *
+   * An event has both a declared type and a separate data block.
+   * It also ends with two newlines (to mark the end of the event).
+   */
+  broadcast_event(type, data) {
+    this.broadcast_string(`event: ${type}\ndata: ${data}\n`);
+  }
+
+  broadcast_move(square) {
+    this.broadcast_event("move", square);
+  }
+}
+
 app.get('/', (request, response) => {
   const game = request.game;
 
@@ -23,4 +75,42 @@ app.get('/', (request, response) => {
     response.render('tictactoe-game.html');
 });
 
+app.post('/move', (request, response) => {
+  const game = request.game;
+  const square = request.body.square;
+
+  const legal = game.add_move(square);
+
+  /* Inform this client whether the move was legal. */
+  response.send(JSON.stringify(legal));
+
+  /* And only if legal, inform all clients. */
+  if (! legal)
+    return;
+
+  game.broadcast_move(square);
+});
+
+app.get('/events', (request, response) => {
+  const game = request.game;
+
+  /* These headers will keep the connection open so we can stream events. */
+  const headers = {
+    "Content-type": "text/event-stream",
+    "Connection": "keep-alive",
+    "Cache-Control": "no-cache"
+  };
+  response.writeHead(200, headers);
+
+  /* Add this new client to our list of clients. */
+  const id = game.add_client(response);
+
+  /* And queue up cleanup to be triggered on client close. */
+  request.on('close', () => {
+    game.remove_client(id);
+  });
+});
+
 exports.app = app;
+exports.name = "tictactoe";
+exports.Game = TicTacToe;