Add environment variables configuration file

Add string caster to parse environment variables

config/dotenv.js

+/**
+ * File: dotenv.js
+ * Author: Markus Grigull <mgrigull@eonerc.rwth-aachen.de>
+ * Date: 10.05.2018
+ *
+ * This file is part of VILLASweb-backend.
+ *
+ * VILLASweb-backend is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * VILLASweb-backend is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with VILLASweb-backend. If not, see <http://www.gnu.org/licenses/>.
+ ******************************************************************************/
+
+'use strict';
+
+const stringCaster = require('../utils/stringcaster');
+
+module.exports = {
+    port: stringCaster.toNumber(process.env.PORT),
+    databaseName: process.env.DATABASE_NAME,
+    databaseURL: process.env.DATABASE_URL,
+    secret: process.env.SECRET,
+    amqpEndpoint: process.env.AMQP_ENDPOINT,
+    amqpUpdateRate: stringCaster.toNumber(process.env.AMQP_UPDATE_RATE),
+    logLevel: process.env.LOG_LEVEL,
+    logFile: process.env.LOG_FILE,
+    publicDir: process.env.PUBLIC_DIR,
+    defaultAdmin: stringCaster.toBoolean(process.env.DEFAULT_ADMIN)
+};

utils/stringcaster.js

+/**
+ * File: stringcaster.js
+ * Author: Markus Grigull <mgrigull@eonerc.rwth-aachen.de>
+ * Date: 10.05.2018
+ *
+ * This file is part of VILLASweb-backend.
+ *
+ * VILLASweb-backend is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * VILLASweb-backend is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with VILLASweb-backend. If not, see <http://www.gnu.org/licenses/>.
+ ******************************************************************************/
+
+'use strict';
+
+class StringCaster {
+    toBoolean(value) {
+        return value ? value.toLowerCase().trim() === 'true' : undefined;
+    }
+
+    toNumber(value) {
+        const number = parseInt(value);
+        
+        return isNaN(number) ? undefined : number;
+    }
+}
+
+module.exports = new StringCaster();