From 14a8fd526e74211f083f08377426b77215172d2e Mon Sep 17 00:00:00 2001
From: Max Goodman <max@reddit.com>
Date: Sat, 23 Mar 2013 23:59:17 -0700
Subject: [PATCH] Add JSPreload system for including JSON data at the bottoms
 of pages.

---
 r2/r2/controllers/reddit_base.py  |  5 ++++-
 r2/r2/lib/js.py                   |  1 +
 r2/r2/lib/template_helpers.py     | 17 +++++++++++++++++
 r2/r2/public/static/js/base.js    | 14 ++++++++++++++
 r2/r2/public/static/js/preload.js | 29 +++++++++++++++++++++++++++++
 r2/r2/templates/reddit.html       |  1 +
 6 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 r2/r2/public/static/js/preload.js

diff --git a/r2/r2/controllers/reddit_base.py b/r2/r2/controllers/reddit_base.py
index e2e6b6141..59f31f5f7 100644
--- a/r2/r2/controllers/reddit_base.py
+++ b/r2/r2/controllers/reddit_base.py
@@ -57,7 +57,7 @@ from r2.lib.errors import (
 )
 from r2.lib.filters import _force_utf8
 from r2.lib.strings import strings
-from r2.lib.template_helpers import add_sr
+from r2.lib.template_helpers import add_sr, JSPreload
 from r2.lib.tracking import encrypt, decrypt
 from r2.lib.translation import set_lang
 from r2.lib.utils import (
@@ -888,6 +888,9 @@ class RedditController(MinimalController):
         if admin_bar_eligible and record_timings:
             g.stats.start_logging_timings()
 
+        # set up stuff needed in base templates at error time here.
+        c.js_preload = JSPreload()
+
         MinimalController.pre(self)
 
         set_cnameframe()
diff --git a/r2/r2/lib/js.py b/r2/r2/lib/js.py
index 94b619a34..dc344e291 100755
--- a/r2/r2/lib/js.py
+++ b/r2/r2/lib/js.py
@@ -352,6 +352,7 @@ module["reddit-init"] = Module("reddit-init.js",
     "lib/underscore-1.4.4.js",
     "lib/store.js",
     "base.js",
+    "preload.js",
     "uibase.js",
     "strings.js",
     "analytics.js",
diff --git a/r2/r2/lib/template_helpers.py b/r2/r2/lib/template_helpers.py
index c94ddfd0c..feda1ad65 100755
--- a/r2/r2/lib/template_helpers.py
+++ b/r2/r2/lib/template_helpers.py
@@ -27,6 +27,7 @@ from r2.lib.utils import vote_hash, UrlParser, timesince, is_subdomain
 from r2.lib import hooks
 from r2.lib.static import static_mtime
 from r2.lib.media import s3_direct_url
+from r2.lib import js
 
 import babel.numbers
 import simplejson
@@ -159,6 +160,22 @@ def js_config(extra_config=None):
     return config
 
 
+class JSPreload(js.DataSource):
+    def __init__(self, data=None):
+        if data is None:
+            data = {}
+        js.DataSource.__init__(self, "r.preload.set({content})", data)
+
+    def set(self, url, data):
+        self.data[url] = data
+
+    def use(self):
+        if self.data:
+            return js.DataSource.use(self)
+        else:
+            return ''
+
+
 def class_dict():
     t_cls = [Link, Comment, Message, Subreddit]
     l_cls = [Listing, OrganicListing]
diff --git a/r2/r2/public/static/js/base.js b/r2/r2/public/static/js/base.js
index 8b60ad142..d5b1d9340 100644
--- a/r2/r2/public/static/js/base.js
+++ b/r2/r2/public/static/js/base.js
@@ -17,7 +17,21 @@ r.setup = function(config) {
     r.analytics.breadcrumbs.init()
 }
 
+r.setupBackbone = function() {
+    Backbone.ajax = function(request) {
+        var preloaded = r.preload.read(request.url)
+        if (preloaded != null) {
+            request.success(preloaded)
+            return
+        }
+
+        return Backbone.$.ajax(request)
+    }
+}
+
 $(function() {
+    r.setupBackbone()
+
     r.login.ui.init()
     r.analytics.init()
     r.ui.init()
diff --git a/r2/r2/public/static/js/preload.js b/r2/r2/public/static/js/preload.js
new file mode 100644
index 000000000..837cba64c
--- /dev/null
+++ b/r2/r2/public/static/js/preload.js
@@ -0,0 +1,29 @@
+r.preload = {
+    timestamp: new Date(),
+    maxAge: 5 * 60 * 1000,
+    data: {},
+
+    isExpired: function() {
+        return new Date() - this.timestamp < this.maxAge
+    },
+
+    set: function(data) {
+        _.extend(this.data, data)
+    },
+
+    read: function(url) {
+        var data = this.data[url]
+
+        // short circuit "client side" fragment urls (which don't expire)
+        if (url[0] == '#') {
+            return data
+        }
+
+        if (this.isExpired()) {
+            return
+        }
+
+        return data
+    }
+}
+
diff --git a/r2/r2/templates/reddit.html b/r2/r2/templates/reddit.html
index dfeb8f738..13f611d79 100644
--- a/r2/r2/templates/reddit.html
+++ b/r2/r2/templates/reddit.html
@@ -118,6 +118,7 @@
 <%def name="javascript_bottom()">
   <% from r2.lib import js %>
   ${unsafe(js.use('reddit'))}
+  ${unsafe(c.js_preload.use())}
 </%def>
 
 <%def name="javascript_run()">