fix(middlewares/errorhandler): Remove npm module and refactor for fcc use case

server/middlewares/error-handlers.js

@@ -1,11 +1,47 @@
-import errorHandler from 'errorhandler';
+import { inspect } from 'util';
+import _ from 'lodash/fp';
 import accepts from 'accepts';
 import { unwrapHandledError } from '../utils/create-handled-error.js';
 
-export default function prodErrorHandler() {
-  if (process.env.NODE_ENV === 'development') {
-    return errorHandler({ log: true });
+const isDev = process.env.NODE_ENV !== 'production';
+
+const toString = Object.prototype.toString;
+// is full error or just trace
+// _.toString(new Error('foo')) => "Error: foo
+// Object.prototype.toString.call(new Error('foo')) => "[object Error]"
+const isInspect = val => !val.stack && _.toString(val) === toString.call(val);
+const stringifyErr = val => {
+  if (val.stack) {
+    return String(val.stack);
   }
+
+  const str = String(val);
+
+  return isInspect(val) ?
+    inspect(val) :
+    str;
+};
+
+const createStackHtml = _.flow(
+  _.cond([
+    [isInspect, err => [err]],
+    // may be stack or just err.msg
+    [_.stubTrue, _.flow(stringifyErr, _.split('\n'), _.tail) ]
+  ]),
+  _.map(_.escape),
+  _.map(line => `<li>${line}</lin>`),
+  _.join('')
+);
+
+const createErrorTitle = _.cond([
+  [
+    _.negate(isInspect),
+    _.flow(stringifyErr, _.split('\n'), _.head, _.defaultTo('Error'))
+  ],
+  [_.stubTrue, _.constant('Error')]
+]);
+
+export default function prodErrorHandler() {
   // error handling in production.
   // disabling eslint due to express parity rules for error handlers
   return function(err, req, res, next) { // eslint-disable-line
@@ -27,7 +63,20 @@ export default function prodErrorHandler() {
     const redirectTo = handled.redirectTo || '/map';
     const message = handled.message ||
       'Oops! Something went wrong. Please try again later';
+
     if (type === 'html') {
+      if (isDev) {
+        return res.render(
+          'dev-error',
+          {
+            ...handled,
+            stack: createStackHtml(err),
+            errorTitle: createErrorTitle(err),
+            title: 'freeCodeCamp - Server Error',
+            status: err.statusCode
+          }
+        );
+      }
       if (typeof req.flash === 'function') {
         req.flash(
           handled.type || 'errors',