Add preliminary implementation of local backup service

frontend/src/app/Models/backup.model.ts

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2014-2020 Bjoern Kimminich.
+ * SPDX-License-Identifier: MIT
+ */
+
+export interface Backup {
+  continueCode?: string
+  language?: string
+  banners?: { welcomeBannerStatus?: string; cookieConsentStatus?: string }
+  scoreBoard?: { showOnlyTutorialChallenges?: string; displayedChallengeCategories?: string; displayedDifficulties?: string; showDisabledChallenges?: string; showSolvedChallenges?: string }
+}

frontend/src/app/Services/local-backup.service.spec.ts

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+import { inject, TestBed } from '@angular/core/testing'
+
+import { LocalBackupService } from './local-backup.service'
+import { CookieService } from 'ngx-cookie-service'
+
+describe('LocalBackupService', () => {
+  let service: LocalBackupService
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      providers: [CookieService]
+    })
+    service = TestBed.inject(LocalBackupService)
+  })
+
+  it('should be created', inject([CookieService], (service: LocalBackupService) => {
+    expect(service).toBeTruthy()
+  }))
+})

frontend/src/app/Services/local-backup.service.ts

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+import { Injectable } from '@angular/core'
+import { Backup } from '../Models/backup.model'
+import { CookieService } from 'ngx-cookie-service'
+
+@Injectable({
+  providedIn: 'root'
+})
+export class LocalBackupService {
+
+  constructor (private cookieService: CookieService) { }
+
+  save () {
+    const backup: Backup = { }
+
+    backup.scoreBoard = {
+      displayedDifficulties: localStorage.getItem('displayedDifficulties'),
+      showSolvedChallenges: localStorage.getItem('showSolvedChallenges'),
+      showDisabledChallenges: localStorage.getItem('showDisabledChallenges'),
+      showOnlyTutorialChallenges: localStorage.getItem('showOnlyTutorialChallenges'),
+      displayedChallengeCategories: localStorage.getItem('displayedChallengeCategories')
+    }
+    backup.banners = {
+      welcomeBannerStatus: this.cookieService.get('welcomebanner_status'),
+      cookieConsentStatus: this.cookieService.get('cookieconsent_status')
+    }
+    backup.language = this.cookieService.get('language')
+    backup.continueCode = this.cookieService.get('continueCode')
+
+    return JSON.stringify(backup)
+  }
+
+  restore (backupData: string) {
+    const backup: Backup = JSON.parse(backupData)
+
+    localStorage.setItem('displayedDifficulties', JSON.stringify(backup.scoreBoard.displayedDifficulties))
+    localStorage.setItem('showSolvedChallenges', JSON.stringify(backup.scoreBoard.showSolvedChallenges))
+    localStorage.setItem('showDisabledChallenges', JSON.stringify(backup.scoreBoard.showDisabledChallenges))
+    localStorage.setItem('showOnlyTutorialChallenges', JSON.stringify(backup.scoreBoard.showOnlyTutorialChallenges))
+    localStorage.setItem('displayedChallengeCategories', JSON.stringify(backup.scoreBoard.displayedChallengeCategories))
+    let expires = new Date()
+    expires.setFullYear(expires.getFullYear() + 1)
+    this.cookieService.set('welcomebanner_status', JSON.stringify(backup.banners.welcomeBannerStatus), expires, '/')
+    this.cookieService.set('cookieconsent_status', JSON.stringify(backup.banners.cookieConsentStatus), expires, '/')
+    this.cookieService.set('language', JSON.stringify(backup.language), expires, '/')
+    this.cookieService.set('continueCode', JSON.stringify(backup.continueCode), expires, '/')
+  }
+}