1 files changed, 64 insertions, 0 deletions
diff --git a/lib/api/encodeNavigation.js b/lib/api/encodeNavigation.js
new file mode 100644
index 0000000..8e329a1
--- /dev/null
+++ b/lib/api/encodeNavigation.js
@@ -0,0 +1,64 @@
+var Immutable = require('immutable');
+
+/**
+    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()
+    };
+}
+
+/**
+    this.navigation is a deprecated property from GitBook v2
+
+    @param {Output}
+    @return {Object}
+*/
+function encodeNavigation(output) {
+    var book = output.getBook();
+    var pages = output.getPages();
+    var summary = book.getSummary();
+    var articles = summary.getArticlesAsList();
+
+
+    var navigation = 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(pages, prev) : undefined,
+                    next: next? encodeArticle(pages, next) : undefined,
+                    level: article.getLevel()
+                }
+            ];
+        })
+        .filter(function(e) {
+            return Boolean(e);
+        });
+
+    return Immutable.Map(navigation).toJS();
+}
+
+module.exports = encodeNavigation;