Clean up startup code for streams.

The startup code in subs.js used to intermingle data
stuff and UI stuff in a loop inside a called function,
which made the code hard to reason about.

Now there is a clear separation of concerns, with these methods
being called in succession:

    stream_data.initialize_from_page_params();
    stream_list.create_initial_sidebar_rows();

The first method was mostly extracted from subs.js, but I simplified
some things, like not needing to make a copy of the hashes
we were passed in, plus I now garbage collect email_dict.  Also,
the code path that initialize_from_page_params() mostly replaces
used to call create_sub(), which fired a trigger, but now it
just does data stuff.

Once the data structure is built up, it's a very simple matter
to build the initial sidebar rows, and that's what the second
method does.

static/js/stream_data.js

@@ -263,6 +263,34 @@ exports.get_streams_for_settings_page = function (public_streams) {
     return sub_rows;
 };
 
+exports.initialize_from_page_params = function () {
+    function populate_subscriptions(subs, subscribed) {
+        subs.forEach(function (sub) {
+            var stream_name = sub.name;
+            sub.subscribed = subscribed;
+
+            // When we get subscriber lists from the back end,
+            // they are sent as user ids to save bandwidth,
+            // but the legacy JS code wants emails.
+            if (sub.subscribers) {
+                sub.subscribers = _.map(sub.subscribers, function (subscription) {
+                    return page_params.email_dict[subscription];
+                });
+            }
+            exports.create_sub_from_server_data(stream_name, sub);
+        });
+    }
+
+    populate_subscriptions(page_params.subbed_info, true);
+    populate_subscriptions(page_params.unsubbed_info, false);
+
+    // Garbage collect data structures that were only used for initialization.
+    delete page_params.subbed_info;
+    delete page_params.unsubbed_info;
+    delete page_params.email_dict;
+};
+
+
 return exports;
 
 }());

static/js/stream_list.js

@@ -46,7 +46,22 @@ function filter_streams_by_search(streams) {
     return filtered_streams;
 }
 
+exports.create_initial_sidebar_rows = function () {
+    // This code is slightly opaque, but it ends up building
+    // up list items and attaching them to the "sub" data
+    // structures that are kept in stream_data.js.
+    var subs = stream_data.subscribed_subs();
+
+    _.each(subs, function (sub) {
+        exports.create_sidebar_row(sub);
+    });
+};
+
 exports.build_stream_list = function () {
+    // This function assumes we have already created the individual
+    // sidebar rows.  Our job here is to build the bigger widget,
+    // which largely is a matter of arranging the individual rows in
+    // the right order.
     var streams = stream_data.subscribed_streams();
     if (streams.length === 0) {
         return;

static/js/subs.js

@@ -373,29 +373,6 @@ exports.pin_or_unpin_stream = function (stream_name) {
     }
 };
 
-function populate_subscriptions(subs, subscribed) {
-    var sub_rows = [];
-    subs.sort(function (a, b) {
-        return util.strcmp(a.name, b.name);
-    });
-    subs.forEach(function (elem) {
-        var stream_name = elem.name;
-        var sub = create_sub(stream_name, {color: elem.color, in_home_view: elem.in_home_view,
-                                           invite_only: elem.invite_only,
-                                           desktop_notifications: elem.desktop_notifications,
-                                           audible_notifications: elem.audible_notifications,
-                                           pin_to_top: elem.pin_to_top,
-                                           subscribed: subscribed,
-                                           email_address: elem.email_address,
-                                           stream_id: elem.stream_id,
-                                           subscribers: elem.subscribers,
-                                           description: elem.description});
-        sub_rows.push(sub);
-    });
-
-    return sub_rows;
-}
-
 exports.filter_table = function (query) {
     var sub_name_elements = $('#subscriptions_table .subscription_name');
 
@@ -663,31 +640,11 @@ exports.remove_user_from_stream = function (user_email, stream_name, success, fa
     });
 };
 
-function inline_emails_into_subscriber_list(subs, email_dict) {
-    // When we get subscriber lists from the back end, they are sent as user ids to
-    // save bandwidth, but the legacy JS code wants emails.
-    _.each(subs, function (sub) {
-        if (sub.subscribers) {
-            sub.subscribers = _.map(sub.subscribers, function (subscription) {
-                return email_dict[subscription];
-            });
-        }
-    });
-}
-
 $(function () {
     var i;
 
-    inline_emails_into_subscriber_list(page_params.subbed_info, page_params.email_dict);
+    stream_data.initialize_from_page_params();
-    inline_emails_into_subscriber_list(page_params.unsubbed_info, page_params.email_dict);
+    stream_list.create_initial_sidebar_rows();
-
-    // Populate stream_info with data handed over to client-side template.
-    populate_subscriptions(page_params.subbed_info, true);
-    populate_subscriptions(page_params.unsubbed_info, false);
-
-    // Garbage collect data structures that were only used for initialization.
-    delete page_params.subbed_info;
-    delete page_params.unsubbed_info;
 
     // We build the stream_list now.  It may get re-built again very shortly
     // when new messages come in, but it's fairly quick.