Rename broadcast() to broadcast_event() supported by broadcast_string()

[lmno-server] / server.js

diff --git a/server.js b/server.js
index 64694d83610c109ae71302b5ece8f6013ffc6d4c..deb0b9c58a44bf17fd3307f46831c8a3009c6d06 100644 (file)
--- a/server.js
+++ b/server.js
@@ -1,28 +1,38 @@
-const express = require("express")
-const cors = require("cors")
+const express = require("express");
+const cors = require("cors");
 const body_parser = require("body-parser");
 
 const app = express();
-app.use(cors())
+app.use(cors());
 
 class Game {
   constructor() {
     this._players = [];
     this.next_player_id = 1;
+    this.clients = [];
+    this.next_client_id = 1;
   }
 
   add_player(name, character) {
-    this._players.push({id: this.next_player_id,
+    const new_player = {id: this.next_player_id,
                        name: name,
                        character: character,
                        captures: [],
-                      })
+                       };
+    this._players.push(new_player);
     this.next_player_id++;
+    /* The syntax here is using an anonymous function to create a new
+      object from new_player with just the subset of fields that we
+      want. */
+    const player_string = JSON.stringify((({id, name}) => ({id, name}))(new_player));
+    this.broadcast_event("player-register", player_string);
   }
 
   remove_player(id) {
     const index = this._players.findIndex(player => player.id === id);
     this._players.splice(index, 1);
+
+    this.broadcast_event("player-deregister", `{"id": ${id}}`);
   }
 
   remove_all_players() {
@@ -36,6 +46,8 @@ class Game {
      * the API specification which we want here. */
     let captor = this._players.find(player => player.id === captor_id);
     captor.captures.push(captee_id);
+
+    this.broadcast_event("capture", `{"captor": ${captor_id}, "captee": ${captee_id}}`);
   }
 
   liberate(captee_id) {
@@ -60,13 +72,66 @@ class Game {
   get players() {
     return this._players.map(player => ({id: player.id, name: player.name }));
   }
+
+  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`);
+  }
 }
 
-game = new Game();
+const game = new Game();
 
 app.use(body_parser.urlencoded({ extended: false }));
 app.use(body_parser.json());
 
+function handle_events(request, response) {
+  /* 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);
+
+  /* Now that a client has connected, first we need to stream all of
+   * the existing players (if any). */
+  if (game._players.length > 0) {
+    const players_json = JSON.stringify(game.players);
+    const players_data = `event: players\ndata: ${players_json}\n\n`;
+    response.write(players_data);
+  }
+
+  /* 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);
+  });
+}
+
 app.get('/', (request, response) => {
   response.send('Hello World!');
 });
@@ -113,6 +178,8 @@ app.get('/players', (request, response) => {
   response.send(game.players);
 });
 
+app.get('/events', handle_events);
+
 app.listen(3000, function () {
   console.log('Example app listening on port 3000!');
 });