track lastPresenceTs

lib/models/user.js

@@ -30,7 +30,12 @@ limitations under the License.
  * @prop {string} displayName The 'displayname' of the user if known.
  * @prop {string} avatarUrl The 'avatar_url' of the user if known.
  * @prop {string} presence The presence enum if known.
- * @prop {Number} lastActiveAgo The last time the user performed some action in ms.
+ * @prop {Number} lastActiveAgo The time elapsed in ms since the user interacted
+ *                proactively with the server, or we saw a message from the user
+ * @prop {Number} lastPresenceTs Timestamp (ms since the epoch) for when we last
+ *                received presence data for this user.  We can subtract
+ *                lastActiveAgo from this to approximate an absolute value for
+ *                when a user was last active.
  * @prop {Boolean} currentlyActive Whether we should consider lastActiveAgo to be
  *               an approximation and that the user should be seen as active 'now'
  * @prop {Object} events The events describing this user.
@@ -42,6 +47,7 @@ function User(userId) {
     this.displayName = userId;
     this.avatarUrl = null;
     this.lastActiveAgo = 0;
+    this.lastPresenceTs = 0;
     this.currentlyActive = false;
     this.events = {
         presence: null,
@@ -82,6 +88,7 @@ User.prototype.setPresenceEvent = function(event) {
     this.displayName = event.getContent().displayname;
     this.avatarUrl = event.getContent().avatar_url;
     this.lastActiveAgo = event.getContent().last_active_ago;
+    this.lastPresenceTs = Date.now();
     this.currentlyActive = event.getContent().currently_active;
 
     if (eventsToFire.length > 0) {