Partial work - need to load config from somewhere

Author: megoth

lib/utils.js

@@ -5,6 +5,7 @@ module.exports.pathBasename = pathBasename
 module.exports.getFullUri = getFullUri
 module.exports.hasSuffix = hasSuffix
 module.exports.parse = parse
+module.exports.processHandlebarFile = processHandlebarFile
 module.exports.serialize = serialize
 module.exports.translate = translate
 module.exports.stringToStream = stringToStream
@@ -19,6 +20,8 @@ const path = require('path')
 const $rdf = require('rdflib')
 const from = require('from2')
 const url = require('url')
+const Handlebars = require('handlebars')
+const debug = require('./debug').errors
 
 /**
  * Returns a fully qualified URL from an Express.js Request object.
@@ -147,6 +150,54 @@ function parse (data, baseUri, contentType, callback) {
   }
 }
 
+/**
+ * Reads a file, processes it (performing template substitution), and saves
+ * back the processed result.
+ *
+ * @param filePath {string}
+ * @param substitutions {Object}
+ *
+ * @return {Promise}
+ */
+async function processHandlebarFile (filePath, substitutions) {
+  return new Promise((resolve, reject) => {
+    fs.readFile(filePath, 'utf8', (error, rawSource) => {
+      if (error) {
+        return reject(error)
+      }
+
+      const output = processHandlebarTemplate(rawSource, substitutions)
+
+      fs.writeFile(filePath, output, (error) => {
+        if (error) {
+          return reject(error)
+        }
+        resolve()
+      })
+    })
+  })
+}
+
+/**
+ * Performs a Handlebars string template substitution, and returns the
+ * resulting string.
+ *
+ * @see https://www.npmjs.com/package/handlebars
+ *
+ * @param source {string} e.g. 'Hello, {{name}}'
+ *
+ * @return {string} Result, e.g. 'Hello, Alice'
+ */
+function processHandlebarTemplate (source, substitutions) {
+  try {
+    const template = Handlebars.compile(source)
+    return template(substitutions)
+  } catch (error) {
+    debug(`Error processing template: ${error}`)
+    return source
+  }
+}
+
 function serialize (graph, baseUri, contentType, callback) {
   try {
     // target, kb, base, contentType, callback