Allow cycling between streams with shift+{A,D}

Closes trac #2273.

(imported from commit 858ffd47aa6dbb372d426fe94b860dfe1c1cce34)

static/js/hotkey.js

@@ -67,8 +67,12 @@ function get_event_name(e) {
         return 'search';
     case 63: // '?': Show keyboard shortcuts page
         return 'show_shortcuts';
+    case 65: // 'A'
+        return 'stream_cycle_backward';
     case 67: // 'C'
         return 'compose_private_message';
+    case 68: // 'D'
+        return 'stream_cycle_forward';
     case 74: // 'J'
         return 'page_down';
     case 75: // 'K'
@@ -271,6 +275,12 @@ function process_hotkey(e) {
         case 'show_shortcuts': // Show keyboard shortcuts page
             $('#keyboard-shortcuts').modal('show');
             return true;
+        case 'stream_cycle_backward':
+            navigate.cycle_stream('backward');
+            return true;
+        case 'stream_cycle_forward':
+            navigate.cycle_stream('forward');
+            return true;
     }
 
     if (current_msg_list.empty()) {

static/js/navigate.js

@@ -70,5 +70,37 @@ exports.page_down = function () {
     }
 };
 
+exports.cycle_stream = function (direction) {
+    var currentStream, nextStream;
+    if (narrow.stream() !== undefined) {
+        currentStream = stream_list.get_stream_li(narrow.stream());
+    }
+    switch (direction) {
+        case 'forward':
+            if (narrow.stream() === undefined) {
+                nextStream = $("#stream_filters").children().first();
+            } else {
+                nextStream = currentStream.next();
+                if (nextStream.length === 0) {
+                    nextStream = $("#stream_filters").children().first();
+                }
+            }
+            break;
+        case 'backward':
+            if (narrow.stream() === undefined) {
+                nextStream = $("#stream_filters").children().last();
+            } else {
+                nextStream = currentStream.prev();
+                if (nextStream.length === 0) {
+                    nextStream = $("#stream_filters").children().last();
+                }
+            }
+            break;
+        default:
+            blueslip.error("Invalid parameter to cycle_stream", {value: direction});
+    }
+    narrow.by('stream', nextStream.data('name'));
+};
+
 return exports;
 }());

templates/zerver/keyboard_shortcuts.html

@@ -94,6 +94,10 @@
           <td class="hotkey">v</td>
           <td class="definition">Narrow to all private messages</td>
         </tr>
+        <tr>
+          <td class="hotkey">A or D</td>
+          <td class="definition">Cycle between stream narrows</td>
+        </tr>
         <tr>
           <td class="hotkey">Esc</td>
           <td class="definition">Return to home view</td>