Fix previous/next chapter navigation

1 files changed, 12 insertions, 7 deletions

diff --git a/lib/parse/navigation.js b/lib/parse/navigation.js
index 8d39a4e..52f3028 100644
--- a/lib/parse/navigation.js
+++ b/lib/parse/navigation.js
@@ -3,7 +3,7 @@ var _ = require('lodash');
 // Cleans up an article/chapter object
 // remove 'articles' and '_path' attributes
 function clean(obj) {
-    return _.omit(obj, ['articles', '_path']);
+    return obj && _.omit(obj, ['articles', '_path']);
 }
 
 // Returns a map of
@@ -26,13 +26,18 @@ function navigation(summary, files) {
     // Walk the chapter/article tree and create navigation entires
     _.each(summary.chapters, function(chapter, idx, chapters) {
         var currentChapter = clean(chapter);
-        var prevChapter = (idx-1 < 0) ? null : clean(chapters[idx-1]);
-        var nextChapter = (idx+1 >= chapters.length) ? null : clean(chapters[idx+1]);
+        var prevChapter = (idx-1 < 0) ? null : chapters[idx-1];
+        var nextChapter = (idx+1 >= chapters.length) ? null : chapters[idx+1];
+
+        var prev = (!prevChapter || _.isEmpty(prevChapter.articles)) ?
+            prevChapter : _.last(prevChapter.articles);
+        var next = (!chapter || _.isEmpty(chapter.articles)) ?
+            nextChapter : _.first(chapter.articles);
 
         // Add chapter mapping
         mapping[chapter.path] = {
-            prev: prevChapter,
-            next: nextChapter,
+            prev: clean(prev),
+            next: clean(next),
         };
 
         // Check a chapter's articles
@@ -42,8 +47,8 @@ function navigation(summary, files) {
             var next = (_idx+1 >= articles.length) ? nextChapter : clean(articles[_idx+1]);
 
             mapping[article.path] = {
-                prev: prev,
-                next: next,
+                prev: clean(prev),
+                next: clean(next),
             };
         });
     });