Handle specfic errors at the controller level

Author: vilasmaciel

src/Contexts/Mooc/Courses/domain/CourseAlreadyExists.ts

@@ -0,0 +1,5 @@
+export default class CourseAlreadyExists extends Error {
+  constructor(courseId: string) {
+    super(`Course ${courseId} already exists`);
+  }
+}

src/apps/mooc_backend/controllers/CoursePutController.ts

@@ -2,6 +2,7 @@ import { Request, Response } from 'express';
 import CreateCourse from '../../../Contexts/Mooc/Courses/application/CreateCourse';
 import httpStatus from 'http-status';
 import Controller from './Controller';
+import CourseAlreadyExists from '../../../Contexts/Mooc/Courses/domain/CourseAlreadyExists';
 
 export default class CoursePutController implements Controller {
   constructor(private createCourse: CreateCourse) {}
@@ -14,7 +15,13 @@ export default class CoursePutController implements Controller {
     try {
       await this.createCourse.run(id, name, duration);
     } catch (e) {
-      res.status(httpStatus.INTERNAL_SERVER_ERROR).json(e);
+
+      if (e instanceof CourseAlreadyExists) {
+        res.status(httpStatus.BAD_REQUEST).send(e.message);
+      } else {
+        res.status(httpStatus.INTERNAL_SERVER_ERROR).json(e);
+      }
+
     }
 
     res.status(httpStatus.CREATED).send();