add support for live call control

lib/session/session-tracker.js

@@ -0,0 +1,42 @@
+const Emitter = require('events');
+const assert = require('assert');
+
+class SessionTracker extends Emitter {
+  constructor() {
+    super();
+
+    this.sessions = new Map();
+  }
+
+  get logger() {
+    if (!this._logger) {
+      const {logger} = require('../../app');
+      this._logger = logger;
+    }
+    return this._logger;
+  }
+
+  add(callSid, callSession) {
+    assert(callSid);
+    this.sessions.set(callSid, callSession);
+    this.logger.info(`SessionTracker:add callSid ${callSid}, we have ${this.sessions.size} session being tracked`);
+  }
+
+  remove(callSid) {
+    assert(callSid);
+    this.sessions.delete(callSid);
+    this.logger.info(`SessionTracker:remove callSid ${callSid}, we have ${this.sessions.size} being tracked`);
+  }
+
+  has(callSid) {
+    return this.sessions.has(callSid);
+  }
+
+  get(callSid) {
+    return this.sessions.get(callSid);
+  }
+}
+
+const singleton = new SessionTracker();
+
+module.exports = singleton;