2803. Online Judge - Frontend with Angular
Angular


Setup frontend UI for Online Judge app with Angular.

1. Project Structure

1.1 Client Files

All source files for client is under ‘./src’ folder.

1.2 Angular Project

This app is created by ‘ng new’ command with Angular CLI.

2. Main Components

Separate app functions to different components as follows.

Component Path Description
component ’./src/app/component’ UI components
interceptor ’./src/app/interceptor’ HTTP interceptor
model ’./src/app/models’ Model class
service ’./src/app/services’ HTTP services to communicate with backend RESTful services
util ’./src/app/util’ Helper class

2.1 UI Components

The app page contains 5 components. In ‘./src/app/components/pages/app.component.html’, setup the app page as follows.

<div class="mainpage">
  <app-widget-progress-bar></app-widget-progress-bar>
  <app-header></app-header>
  <app-alert></app-alert>
  <router-outlet></router-outlet>
  <app-footer></app-footer>
</div>

Details are explained in the table.

selector Description
app-widget-progress-bar Progress bar displays whenever Http request happens
app-header Top menus
app-alert Common alert dialog, eg. Save, Submit
router-outlet Angular Routing, navigate to sub component
app-footer Footage of the app

2.2 Http Interceptor

Use HttpInterceptor to intercept and modify HTTP requests globally.

File Name Class Name Description
cookie.interceptor.ts CookieHttpInterceptor Manipulate Cookies settings on request
error.interceptor.ts ErrorHttpInterceptor Handle http request error globally
jwt.interceptor.ts JwtHttpInterceptor Add token to each http request
timeout.interceptor.ts TimeoutHttpInterceptor Set timeout before sending http request

2.3 Model

Model class for user, question, submission, etc.

2.4 Service

Services are collections of common methods. Most of the services are used to send HTTP requests to call RESTful API.

File Name Class Name Description
alert.service.ts AlertService Display Alert message from anywhere. The Alert will be shown at the top of the page.
auth-guard.service.ts AuthGuardService Guard access right. If user hasn’t logged in, he/she will be navigated to login page if he/she tries to access some pages only available for registered users.
authentication.service.ts AuthenticationService Http requests for register, login, etc.
database.service.ts DatabaseService Http requests for data import and export.
question.service.ts QuestionService Http requests for question management.
submission.service.ts SubmissionService Http requests for solution submission.
user.service.ts UserService Http requests for user management.

2.5 Util

Some helper methods, string manipulation, cookie manipulation, etc.

3. Angular Routing

Define all the routings in file ‘src/app/app.route.ts’. Notice, some components are guarded by ‘AuthGuardService’. These components are accessible only when user has logged in.

import { RouterModule, Routes } from "@angular/router";

// components
import {
  AlertComponent,
  AppComponent,
  HeaderComponent,
  FooterComponent,
  HomepageComponent,
  SignupComponent,
  LoginComponent,
  ResetpwdComponent,
  ProfileComponent,
  DatabaseComponent,
  QuestionsComponent,
  QuestionComponent,
  EditorComponent,
  UsersComponent,
  UserComponent,
  WysiwygComponent,
  AlgorithmQuestionComponent,
  AlgorithmQuestionsComponent,
  SubmissionComponent
} from "./components/";

// services
import { AuthGuardService } from "./services/";

export const appRoutes: Routes = [
  { path: "", component: HomepageComponent },
  { path: "homepage", component: HomepageComponent },
  { path: "questions", component: AlgorithmQuestionsComponent },
  { path: "question/:uniquename", component: AlgorithmQuestionComponent },
  { path: "submission/:id", component: SubmissionComponent },
  {
    path: "admin/database",
    component: DatabaseComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/users",
    component: UsersComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/user",
    component: UserComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/user/:_id",
    component: UserComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/questions",
    component: QuestionsComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/question",
    component: QuestionComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "admin/question/:_id",
    component: QuestionComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "editor",
    component: EditorComponent
  },
  {
    path: "wysiwyg",
    component: WysiwygComponent
  },
  { path: "signup", component: SignupComponent },
  { path: "login", component: LoginComponent },
  {
    path: "resetpwd",
    component: ResetpwdComponent,
    canActivate: [AuthGuardService]
  },
  {
    path: "profile",
    component: ProfileComponent,
    canActivate: [AuthGuardService]
  },
  // otherwise redirect to home
  { path: "**", redirectTo: "" }
];