typescript: Migrate linux-update-util to typescript.

app/renderer/js/utils/linux-update-util.ts

@@ -0,0 +1,77 @@
+'use strict';
+
+import fs from 'fs';
+import path from 'path';
+import JsonDB from 'node-json-db';
+
+import electron = require('electron');
+import Logger = require('./logger-util');
+
+const remote =
+	process.type === 'renderer' ? electron.remote : electron;
+
+const logger = new Logger({
+	file: 'linux-update-util.log',
+	timestamp: true
+});
+
+/* To make the util runnable in both main and renderer process */
+const { dialog, app } = remote;
+let instance: null | LinuxUpdateUtil = null;
+
+class LinuxUpdateUtil {
+	db: any; // TODO: TypeScript - Figure out how to annotate to JsonDB
+
+	constructor() {
+		if (instance) {
+			return instance;
+		} else {
+			instance = this;
+		}
+
+		this.reloadDB();
+		return instance;
+	}
+
+	getUpdateItem(key: string, defaultValue: any = null): any {
+		this.reloadDB();
+		const value = this.db.getData('/')[key];
+		if (value === undefined) {
+			this.setUpdateItem(key, defaultValue);
+			return defaultValue;
+		} else {
+			return value;
+		}
+	}
+
+	setUpdateItem(key: string, value: any): void {
+		this.db.push(`/${key}`, value, true);
+		this.reloadDB();
+	}
+
+	removeUpdateItem(key: string): void {
+		this.db.delete(`/${key}`);
+		this.reloadDB();
+	}
+
+	reloadDB(): void {
+		const linuxUpdateJsonPath = path.join(app.getPath('userData'), '/config/updates.json');
+		try {
+			const file = fs.readFileSync(linuxUpdateJsonPath, 'utf8');
+			JSON.parse(file);
+		} catch (err) {
+			if (fs.existsSync(linuxUpdateJsonPath)) {
+				fs.unlinkSync(linuxUpdateJsonPath);
+				dialog.showErrorBox(
+					'Error saving update notifications.',
+					'We encountered an error while saving the update notifications.'
+				);
+				logger.error('Error while JSON parsing updates.json: ');
+				logger.error(err);
+			}
+		}
+		this.db = new JsonDB(linuxUpdateJsonPath, true, true);
+	}
+}
+
+module.exports = new LinuxUpdateUtil();