Migrate app to TypeScript (#1637)

* Initial setup and migrated src/common

* WIP

* WIP

* WIP

* Main module basically finished

* Renderer process migrated

* Added CI step and some fixes

* Fixed remainder of issues and added proper ESLint config

* Fixed a couple issues

* Progress!

* Some more fixes

* Fixed a test

* Fix build step

* PR feedback

src/main/AppVersionManager.ts

@@ -0,0 +1,48 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+// Copyright (c) 2015-2016 Yuya Ochiai
+
+import {AppState} from 'types/appState';
+
+import JsonFileManager from '../common/JsonFileManager';
+
+import * as Validator from './Validator';
+
+export default class AppVersionManager extends JsonFileManager<AppState> {
+    constructor(file: string) {
+        super(file);
+
+        // ensure data loaded from file is valid
+        const validatedJSON = Validator.validateAppState(this.json);
+        if (!validatedJSON) {
+            this.setJson({});
+        }
+    }
+    set lastAppVersion(version) {
+        this.setValue('lastAppVersion', version);
+    }
+
+    get lastAppVersion() {
+        return this.getValue('lastAppVersion');
+    }
+
+    set skippedVersion(version) {
+        this.setValue('skippedVersion', version);
+    }
+
+    get skippedVersion() {
+        return this.getValue('skippedVersion');
+    }
+
+    set updateCheckedDate(date) {
+        this.setValue('updateCheckedDate', date?.toISOString());
+    }
+
+    get updateCheckedDate() {
+        const date = this.getValue('updateCheckedDate');
+        if (date) {
+            return new Date(date);
+        }
+        return null;
+    }
+}