1 files changed, 47 insertions, 3 deletions
diff --git a/lib/api/encodeNavigation.js b/lib/api/encodeNavigation.js
index fa9eb16..c48ba50 100644
--- a/lib/api/encodeNavigation.js
+++ b/lib/api/encodeNavigation.js
@@ -1,14 +1,58 @@
 
+/**
+    Encode an article for next/prev
+
+    @param {Map<String:Page>}
+    @param {Article}
+    @return {Object}
+*/
+function encodeArticle(pages, article) {
+    var articlePath = article.getPath();
+
+    return {
+        path: articlePath,
+        title: article.getTitle(),
+        level: article.getLevel(),
+        exists: (articlePath && pages.has(articlePath)),
+        external: article.isExternal()
+    };
+}
 
 /**
-    page.navigation is a deprecated property from GitBook v2
+    this.navigation is a deprecated property from GitBook v2
 
     @param {Output}
     @return {Object}
 */
 function encodeNavigation(output) {
-    // todo
-    return {};
+    var book = output.getBook();
+    var summary = book.getSummary();
+    var articles = summary.getArticlesAsList();
+
+    return articles
+        .map(function(article, i) {
+            var ref = article.getRef();
+            if (ref) {
+                return undefined;
+            }
+
+            var prev = articles.get(i - 1);
+            var next = articles.get(i + 1);
+
+            return [
+                ref,
+                {
+                    index: i,
+                    title: article.getTitle(),
+                    introduction: (i === 0),
+                    prev: prev? encodeArticle(prev) : undefined,
+                    next: next? encodeArticle(next) : undefined,
+                    level: article.getLevel()
+                }
+            ];
+        })
+        .toMap()
+        .toJS();
 }
 
 module.exports = encodeNavigation;