X-Git-Url: https://git.cworth.org/git?a=blobdiff_plain;f=game.js;h=f1f764fa1968425d597e4e2ab47e4b8d916650a8;hb=f27cdf8b57b41a91dd7ab67be407d803dcaad1a3;hp=028c0393f9be02ac027922fa6b9244d70380608e;hpb=de78893aec1d5a4a0ae84610f2f01f78e9455f18;p=empires-server

diff --git a/game.js b/game.js
index 028c039..f1f764f 100644
--- a/game.js
+++ b/game.js
@@ -1,8 +1,87 @@
 /* Base class providing common code for game engine implementations. */
 class Game {
-  constructor(name) {
-    this.name = name;
+  constructor(id) {
+    this.id = id;
+    this.clients = [];
+    this.next_client_id = 1;
   }
+
+  /* Suport for game meta-data.
+   *
+   * What we want here is an effectively static field that is
+   * accessible through either the class name (SomeGame.meta) or an
+   * instance (some_game.meta). To pull this off we do keep two copies
+   * of the data. But the game classes can just set SomeGame.meta once
+   * and then reference it either way.
+   */
+  static set meta(data) {
+    /* This allows class access (SomeGame.meta) via the get method below. */
+    this._meta = data;
+
+    /* While this allows access via an instance (some_game.meta). */
+    this.prototype.meta = data;
+  }
+
+  static get meta() {
+    return this._meta;
+  }
+
+  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`);
+  }
+
+  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);
+
+    /* Add this new client to our list of clients. */
+    const id = this.add_client(response);
+
+    /* And queue up cleanup to be triggered on client close. */
+    request.on('close', () => {
+      this.remove_client(id);
+    });
+
+    /* Finally, if this game class has a "state" property, stream that
+     * current state to the client. */
+    if (this.state) {
+      const state_json = JSON.stringify(this.state);
+      response.write(`event: game-state\ndata: ${state_json}\n\n`);
+    }
+  }
+
+  broadcast_move(move) {
+    this.broadcast_event("move", move);
+  }
+
 }
 
 module.exports = Game;