From 6e04535eff44c75863b547207e08edfe522af893 Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <sachkov2011@gmail.com>
Date: Wed, 29 Dec 2021 19:01:03 +0300
Subject: [PATCH 1/2] [NFC] Outline database connection into a separate file

---
 server.js    | 14 ++++----------
 server/db.js | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 10 deletions(-)
 create mode 100644 server/db.js

diff --git a/server.js b/server.js
index 4c4cb6f63..7b87ae83e 100644
--- a/server.js
+++ b/server.js
@@ -77,16 +77,10 @@ const config = require('nconf')
 	.file('environment', { file: `config/${process.env.NODE_ENV}.json` })
 	.file('defaults', { file: 'config/default.json' });
 
-//DB
-const mongoose = require('mongoose');
-mongoose.connect(config.get('mongodb_uri') || config.get('mongolab_uri') || 'mongodb://localhost/naturalcrit',
-	{ retryWrites: false });
-mongoose.connection.on('error', (err)=>{
-	console.log('Error : Could not connect to a Mongo Database.');
-	console.log('        If you are running locally, make sure mongodb.exe is running.');
-	console.log(err);
-	throw 'Can not connect to Mongo';
-});
+// DB
+const DB = require('./server/db.js');
+// FIXME: consider implementing error hanlding for a Promise returned by connect
+DB.connect(config);
 
 //Account Middleware
 app.use((req, res, next)=>{
diff --git a/server/db.js b/server/db.js
new file mode 100644
index 000000000..7adf3a58f
--- /dev/null
+++ b/server/db.js
@@ -0,0 +1,37 @@
+const Mongoose = require('mongoose');
+
+const getMongoDBURL = (config)=>{
+	return config.get('mongodb_uri') ||
+           config.get('mongolab_uri') ||
+           'mongodb://localhost/homebrewery';
+};
+
+const disconnect = ()=>{
+	return Mongoose.close();
+};
+
+const connect = (config)=>{
+	const resolver = (resolve, reject)=>{
+		Mongoose.connect(getMongoDBURL(config),
+			{ retryWrites: false },
+			(error)=>{
+				if(error) {
+					console.error('Could not connect to a Mongo Database.');
+					console.log(error);
+					console.error('If you are running locally, make sure mongodb.exe is running.');
+					// FIXME: do we need to pass 'error' to 'reject'?
+					return reject();
+				}
+
+				return resolve();
+			});
+
+	};
+
+	return new Promise(resolver);
+};
+
+module.exports = {
+	connect    : connect,
+	disconnect : disconnect
+};

From e84cd4fe8b589f687cd29746910864fe80bc57d3 Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <sachkov2011@gmail.com>
Date: Mon, 10 Jan 2022 19:25:36 +0300
Subject: [PATCH 2/2] Apply review comments

Switched from raw promises to async/await.
Outlined error handling function to reduce amount of nested code.
Added comment about the new file intent.
---
 server.js    |  1 -
 server/db.js | 40 ++++++++++++++++++++--------------------
 2 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/server.js b/server.js
index 7b87ae83e..3bdb77b92 100644
--- a/server.js
+++ b/server.js
@@ -79,7 +79,6 @@ const config = require('nconf')
 
 // DB
 const DB = require('./server/db.js');
-// FIXME: consider implementing error hanlding for a Promise returned by connect
 DB.connect(config);
 
 //Account Middleware
diff --git a/server/db.js b/server/db.js
index 7adf3a58f..030d7f61b 100644
--- a/server/db.js
+++ b/server/db.js
@@ -1,3 +1,10 @@
+// The main purpose of this file is to provide an interface for database
+// connection. Even though the code is quite simple and basically a tiny
+// wrapper around mongoose package, it works as single point where
+// database setup/config is performed and the interface provided here can be
+// reused by both the main application and all tests which require database
+// connection.
+
 const Mongoose = require('mongoose');
 
 const getMongoDBURL = (config)=>{
@@ -6,29 +13,22 @@ const getMongoDBURL = (config)=>{
            'mongodb://localhost/homebrewery';
 };
 
-const disconnect = ()=>{
-	return Mongoose.close();
+const handleConnectionError = (error)=>{
+	if(error) {
+		console.error('Could not connect to a Mongo database: \n');
+		console.error(error);
+		console.error('\nIf you are running locally, make sure mongodb.exe is running and DB URL is configured properly');
+		process.exit(1); // non-zero exit code to indicate an error
+	}
 };
 
-const connect = (config)=>{
-	const resolver = (resolve, reject)=>{
-		Mongoose.connect(getMongoDBURL(config),
-			{ retryWrites: false },
-			(error)=>{
-				if(error) {
-					console.error('Could not connect to a Mongo Database.');
-					console.log(error);
-					console.error('If you are running locally, make sure mongodb.exe is running.');
-					// FIXME: do we need to pass 'error' to 'reject'?
-					return reject();
-				}
+const disconnect = async ()=>{
+	return await Mongoose.disconnect();
+};
 
-				return resolve();
-			});
-
-	};
-
-	return new Promise(resolver);
+const connect = async (config)=>{
+	return await Mongoose.connect(getMongoDBURL(config),
+		{ retryWrites: false }, handleConnectionError);
 };
 
 module.exports = {