Implemented session.getExpiry, session.hasExpired.

Documentation/Books/Users/FoxxBundledApps/Sessions.mdpp

@@ -6,7 +6,7 @@ The sessions app provides a session storage JavaScript API that can be used in o
 
 This app has the following configuration options:
 
-* *timeToLive* (optional): number of milliseconds until the session expires. Default: *604800000* (one week).
+* *timeToLive* (optional): number of milliseconds until the session expires or *0* to disable session expiry. Default: *604800000* (one week).
 * *ttlType* (optional): attribute against which the *timeToLive* is enforced. Valid options: *lastAccess*, *lastUpdate*, *created*. Default: *"created"*.
 * *sidTimestamp* (optional): whether to append a timestamp to the random part of generated session IDs. Default: *false*.
 * *sidLength* (optional): number of random characters to use for new session IDs. Default *20*.
@@ -222,6 +222,22 @@ assertEqual(session.get('uid'), user.get('_key'));
 assertEqual(session.get('userData'), user.get('userData'));
 ```
 
+!SUBSECTION Determine whether a session has expired
+
+Get a session's expiry state.
+
+`session.hasExpired()`
+
+Returns *true* if the session's expiry time lies in the past, *false* otherwise.
+
+!SUBSECTION Determine when a session will expire
+
+Get a session's expiry time.
+
+`session.getExpiry()`
+
+Returns an integer representing the time at which the session will expire, or *Number.MAX_VALUE* (indicating the session will never expire) if session expiry is disabled.
+
 !SUBSECTION Add a session cookie to a response
 
 Add a session cookie to a Foxx response.

js/apps/system/sessions/storage.js

@@ -127,17 +127,22 @@
 
   _.extend(Session.prototype, {
     enforceTimeout: function () {
-      if (!cfg.timeToLive) {
-        return;
+      if (this.hasExpired()) {
+        throw new errors.SessionExpired(this.get('_key'));
       }
-      var now = Number(new Date()),
-        prop = cfg.ttlType;
+    },
+    hasExpired: function () {
+      return Date.now() > this.getExpiry();
+    },
+    getExpiry: function () {
+      if (!cfg.timeToLive) {
+        return Number.MAX_VALUE;
+      }
+      var prop = cfg.ttlType;
       if (!prop || !this.get(prop)) {
         prop = 'created';
       }
-      if (cfg.timeToLive < (now - this.get(prop))) {
-        throw new errors.SessionExpired(this.get('_key'));
-      }
+      return this.get(prop) + cfg.timeToLive;
     },
     addCookie: function (res, cookieName, secret) {
       var value = this.get('_key'),