1 files changed, 41 insertions, 0 deletions
diff --git a/lib/models/summary.js b/lib/models/summary.js
index b04630f..3b46941 100644
--- a/lib/models/summary.js
+++ b/lib/models/summary.js
@@ -1,3 +1,4 @@
+var is = require('is');
 var Immutable = require('immutable');
 
 var error = require('../utils/error');
@@ -88,6 +89,46 @@ Summary.prototype.getFirstArticle = function() {
 };
 
 /**
+    Return next article of an article
+
+    @param {Article} current
+    @return {Article}
+*/
+Summary.prototype.getNextArticle = function(current) {
+    var level = is.string(current)? current : current.getLevel();
+    var wasPrev = false;
+
+    return this.getArticle(function(article) {
+        if (wasPrev) return true;
+
+        wasPrev = article.getLevel() == level;
+        return false;
+    });
+};
+
+/**
+    Return previous article of an article
+
+    @param {Article} current
+    @return {Article}
+*/
+Summary.prototype.getPrevArticle = function(current) {
+    var level = is.string(current)? current : current.getLevel();
+    var prev = undefined;
+
+    this.getArticle(function(article) {
+        if (article.getLevel() == level) {
+            return true;
+        }
+
+        prev = article;
+        return false;
+    });
+
+    return prev;
+};
+
+/**
     Render summary as text
 
     @return {Promise<String>}