Refactor Navigation Include to use ESI

Merging since adobe/project-helix#184 has been merged.

src/default.htl

@@ -12,7 +12,7 @@
         </div>
         <div class="main">
             <div class="nav">
-                <div data-sly-test="${it.nav}" data-sly-list="${it.nav}">${item}</div>
+                <esi:include src="/${it.contextPath}/SUMMARY.html" />
             </div>
             <div class="content">
                 <div class="content-body">

src/default.pre.js

@@ -1,6 +1,5 @@
 const moment = require('moment');
 const request = require('request-promise');
-const md2json = require('md2json');
 
 /**
  * Appends the context path to the resource based on the strain
@@ -50,32 +49,6 @@ function collectMetadata(ctx) {
     });
 };
 
-/**
- * Collects the nav and append it to the resource
- * @param {RequestContext} ctx Context
- */
-function collectNav(ctx) {
-    const params = {
-        org: ctx.strainConfig.urls.content.owner,
-        repo: ctx.strainConfig.urls.content.repo,
-        tree: ctx.strainConfig.urls.content.ref,
-        path: 'SUMMARY.md'
-    };
-
-    return md2json.main(params).then(info => {
-        let nav = info.body.children;
-        // remove first title
-        delete nav[0];
-
-        // link re-writing
-        // TODO: move into md2json + parameters
-        ctx.resource.nav = nav.map(element => {
-            return element.replace(new RegExp('href="', 'g'), 'href="/' + ctx.strain + '/');
-        });
-        return Promise.resolve(ctx);
-    });
-};
-
 /**
  * Extracts some committers data from the list of commits and appends the list to the resource
  * @param {RequestContext} ctx Context
@@ -123,7 +96,6 @@ module.exports.main = function (ctx) {
         .then(collectMetadata)
         .then(extractCommittersFromMetadata)
         .then(extractLastModifiedFromMetadata)
-        .then(collectNav)
         .catch(error => {
             console.error('Error while executing default.pre.js', error);
         });

src/nav.htl

@@ -0,0 +1 @@
+<div data-sly-test="${it.children}" data-sly-list="${it.children}">${item}</div>

src/nav.pre.js

@@ -0,0 +1,30 @@
+const request = require('request-promise');
+
+/**
+ * Appends the context path to the resource based on the strain
+ * @param {RequestContext} ctx Context
+ */
+function setContextPath(ctx) {
+    ctx.resource.contextPath = ctx.strain;
+    return Promise.resolve(ctx);
+};
+
+/**
+ * Removes the first title from the resource children
+ * @param {RequestContext} ctx Context
+ */
+function removeFirstTitle(ctx) {
+    delete ctx.resource.children[0];
+    return Promise.resolve(ctx);
+};
+
+module.exports.main = function (ctx) {
+    ctx.resource = ctx.resource || {};
+
+    return Promise.resolve(ctx)
+        .then(setContextPath)
+        .then(removeFirstTitle)
+        .catch(error => {
+            console.error('Error while executing nav.pre.js', error);
+        });
+};