Refactor navigation generation to be functional

This makes it a lot less error prone and far more robust. As well as a
lot easier to understand

1 files changed, 28 insertions, 47 deletions

diff --git a/lib/parse/navigation.js b/lib/parse/navigation.js
index bba25ce..2f8669e 100644
--- a/lib/parse/navigation.js
+++ b/lib/parse/navigation.js
@@ -6,6 +6,12 @@ function clean(obj) {
     return obj && _.omit(obj, ['articles']);
 }
 
+function flattenChapters(chapters) {
+    return _.reduce(chapters, function(accu, chapter) {
+        return accu.concat([clean(chapter)].concat(chapter.articles));
+    }, []);
+}
+
 // Returns from a summary a map of
 /*
     {
@@ -20,61 +26,36 @@ function navigation(summary, files) {
     // Support single files as well as list
     files = _.isArray(files) ? files : (_.isString(files) ? [files] : null);
 
-    // Mapping of prev/next for a give path
-    var mapping = {};
-
     // Special README nav
     var README_NAV = {
         path: 'README.md',
         title: 'Introduction',
+        level: '0',
     };
 
-    // Walk the chapter/article tree and create navigation entires
-    _.each(summary.chapters, function(chapter, idx, chapters) {
-        // Skip if no path
-        if(!chapter.path) return;
-
-        var currentChapter = clean(chapter);
-        var prevChapter = (idx-1 < 0) ? README_NAV : 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);
+    // List of all navNodes
+    var navNodes = [README_NAV].concat(flattenChapters(summary.chapters));
+    var prevNodes = [null].concat(navNodes.slice(0, -1));
+    var nextNodes = navNodes.slice(1).concat([null]);
 
-        // Add chapter mapping
-        mapping[chapter.path] = {
-            title: chapter.title,
-            prev: clean(prev),
-            next: clean(next),
-            level: (idx+1).toString(),
-        };
-
-        // Check a chapter's articles
-        _.each(chapter.articles, function(article, _idx, articles) {
-            // Skip if no path
-            if(!article.path) return;
-
-            var prev = (_idx-1 < 0) ? currentChapter : clean(articles[_idx-1]);
-            var next = (_idx+1 >= articles.length) ? nextChapter : clean(articles[_idx+1]);
-
-            mapping[article.path] = {
-                title: article.title,
-                prev: clean(prev),
-                next: clean(next),
-                level: [idx+1, _idx+1].join('.'),
-            };
-        });
-    });
+    // Mapping of prev/next for a give path
+    var mapping = _.chain(_.zip(navNodes, prevNodes, nextNodes))
+    .map(function(nodes) {
+        var current = nodes[0], prev = nodes[1], next = nodes[2];
 
-    // Hack for README.html
-    mapping['README.md'] = {
-        title: README_NAV.title,
-        prev: null,
-        next: clean(summary.chapters[0]),
-        level: '0',
-    };
+        // Skip if no path
+        if(!current.path) return null;
+
+        return [current.path, {
+            title: current.title,
+            prev: prev,
+            next: next,
+            level: current.level,
+        }];
+    })
+    .filter()
+    .object()
+    .value();
 
     // Filter for only files we want
     if(files) {