Search streams from left sidebar (resolves #565).

Assigns hotkey 'w' to search streams.
Only show search box when active. Activate with hotkey or by clicking
STREAMS.
Filter matches at the beginning of words in stream name.
Behaviour is otherwise almost identical to user search.
Casper tests.

static/js/stream_list.js

@@ -19,12 +19,40 @@ function active_stream_name() {
     return false;
 }
 
+function filter_streams_by_search(streams) {
+    var search_box = $(".stream-list-filter");
+
+    var search_term = search_box.expectOne().val().trim();
+
+    if (search_term === '') {
+        return streams;
+    }
+
+    var search_terms = search_term.toLowerCase().split(",");
+    search_terms = _.map(search_terms, function (s) {
+        return s.trim();
+    });
+
+    var filtered_streams = _.filter(streams, function (stream) {
+        return _.any(search_terms, function (search_term) {
+            var lower_stream_name = stream.toLowerCase().split(" ");
+            return _.any(lower_stream_name, function (name) {
+                return name.indexOf(search_term) === 0;
+            });
+        });
+    });
+
+    return filtered_streams;
+}
+
 exports.build_stream_list = function () {
     var streams = stream_data.subscribed_streams();
     if (streams.length === 0) {
         return;
     }
 
+    streams = filter_streams_by_search(streams);
+
     var sort_recent = (streams.length > 40);
 
     streams.sort(function (a, b) {
@@ -643,6 +671,89 @@ $(function () {
 
 });
 
+function actually_update_streams_for_search() {
+    exports.update_streams_sidebar();
+    resize.resize_page_components();
+}
+
+var update_streams_for_search = _.throttle(actually_update_streams_for_search, 50);
+
+exports.searching = function () {
+    return $('.stream-list-filter').expectOne().is(':focus');
+};
+
+exports.escape_search = function () {
+    var filter = $('.stream-list-filter').expectOne();
+    if (filter.val() === '') {
+        exports.clear_and_hide_search();
+        return;
+    }
+    filter.val('');
+    update_streams_for_search();
+};
+
+exports.initiate_search = function () {
+    var filter = $('.stream-list-filter').expectOne();
+    filter.removeClass('notdisplayed');
+    filter.focus();
+};
+
+exports.clear_and_hide_search = function () {
+    var filter = $('.stream-list-filter');
+    if (filter.val() !== '') {
+        filter.val('');
+        update_streams_for_search();
+    }
+    filter.blur();
+    filter.addClass('notdisplayed');
+};
+
+function focus_stream_filter (e) {
+    e.stopPropagation();
+}
+
+function maybe_select_stream (e) {
+    if (e.keyCode === 13) {
+        // Enter key was pressed
+
+        var topStream = $('#stream_filters li.narrow-filter').first().data('name');
+        if (topStream !== undefined) {
+            // undefined if there are no results
+            if (ui.home_tab_obscured()) {
+                ui.change_tab_to('#home');
+            }
+            exports.clear_and_hide_search();
+            narrow.by('stream', topStream, {select_first_unread: true, trigger: 'sidebar enter key'});
+            e.preventDefault();
+            e.stopPropagation();
+        }
+    }
+}
+
+function toggle_filter_displayed(e) {
+    if (e.target.id === 'streams_inline_cog') {
+        return;
+    }
+    if (0 === $('.stream-list-filter.notdisplayed').length) {
+        exports.clear_and_hide_search();
+    } else {
+        exports.initiate_search();
+    }
+    e.preventDefault();
+}
+
+$(function () {
+    $(".stream-list-filter").expectOne()
+        .on('click', focus_stream_filter)
+        .on('input', update_streams_for_search)
+        .on('keydown', maybe_select_stream);
+});
+
+$(function () {
+    $("#streams_header").expectOne()
+        .on('click', toggle_filter_displayed);
+});
+
 return exports;
 }());
 if (typeof module !== 'undefined') {