From d938afaedc23e9f5364fef1f0a630f07c95b8f72 Mon Sep 17 00:00:00 2001
From: Steve Howell <showell30@yahoo.com>
Date: Fri, 21 Apr 2017 14:49:33 -0700
Subject: [PATCH] Extract narrow.narrow_to_next_topic().

This borrows some code from a PR from Mahim Goyal.
---
 static/js/narrow.js | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/static/js/narrow.js b/static/js/narrow.js
index 10aad666bd..183aa2deea 100644
--- a/static/js/narrow.js
+++ b/static/js/narrow.js
@@ -400,6 +400,31 @@ exports.stream_topic = function () {
     };
 };
 
+exports.narrow_to_next_topic = function () {
+    var curr_info = exports.stream_topic();
+
+    if (!curr_info || !curr_info.stream) {
+        return;
+    }
+
+    var next_narrow = topic_generator.get_next_topic(
+        curr_info.stream,
+        curr_info.topic
+    );
+
+    if (!next_narrow) {
+        return;
+    }
+
+    var filter_expr = [
+        {operator: 'stream', operand: next_narrow.stream},
+        {operator: 'topic', operand: next_narrow.topic},
+    ];
+
+    narrow.activate(filter_expr);
+};
+
+
 // Activate narrowing with a single operator.
 // This is just for syntactic convenience.
 exports.by = function (operator, operand, opts) {