implement random precaching of unread feeds on timer

FeedTree.js

@@ -297,6 +297,38 @@ dojo.declare("fox.FeedTree", dijit.Tree, {
 
 		});
 	},
+	getVisibleUnreadFeeds: function() {
+		var items = this.model.store._arrayOfAllItems;
+		var rv = [];
+
+		for (var i = 0; i < items.length; i++) {
+			var id = String(items[i].id);
+			var box = this._itemNodesMap[id];
+
+			if (box) {
+				var row = box[0].rowNode;
+				var cat = false;
+
+				try {
+					cat = box[0].rowNode.parentNode.parentNode;
+				} catch (e) { }
+
+				if (row) {
+					if (Element.visible(row) && (!cat || Element.visible(cat))) {
+						var feed_id = String(items[i].bare_id);
+						var is_cat = !id.match('FEED:');
+						var unread = this.model.getFeedUnread(feed_id, is_cat);
+
+						if (unread > 0)
+							rv.push([feed_id, is_cat]);
+
+					}
+				}
+			}
+		}
+
+		return rv;
+	},
 	getNextFeed: function (feed, is_cat) {
 		if (is_cat) {
 			treeItem = this.model.store._itemsByIdentity['CAT:' + feed];

feedlist.js

@@ -202,6 +202,7 @@ function feedlist_init() {
 		hideOrShowFeeds(getInitParam("hide_read_feeds") == 1);
 
 		setTimeout("timeout()", 5000);
+		setTimeout("precache_headlines_idle()", 3000);
 
 	} catch (e) {
 		exception_error("feedlist/init", e);

viewfeed.js

@@ -10,6 +10,7 @@ var last_requested_article = false;
 var catchup_id_batch = [];
 var catchup_timeout_id = false;
 var feed_precache_timeout_id = false;
+var precache_idle_timeout_id = false;
 
 var cids_requested = [];
 
@@ -2108,6 +2109,29 @@ function render_local_headlines(feed, is_cat, obj) {
 	}
 }
 
+function precache_headlines_idle() {
+	try {
+		if (!feed_precache_timeout_id) {
+			var feeds = dijit.byId("feedTree").getVisibleUnreadFeeds();
+			var uncached = [];
+
+			feeds.each(function(item) {
+				if (parseInt(item[0]) > 0 && !cache_get("feed:" + item[0] + ":" + item[1]))
+					uncached.push(item);
+			});
+
+			if (uncached.length > 0) {
+				var rf = uncached[Math.floor(Math.random()*uncached.length)];
+				viewfeed(rf[0], '', rf[1], 0, true);
+			}
+		}
+		precache_idle_timeout_id = setTimeout("precache_headlines_idle()", 5000);
+
+	} catch (e) {
+		exception_error("precache_headlines_idle", e);
+	}
+}
+
 function precache_headlines() {
 	try {