Refactored database connection system to use a shared pool per-request

lib/Subject.js

@@ -1,7 +1,5 @@
 'use strict';
 
-const DatabaseConnectionPool = require('./DatabaseConnectionPool');
-
 class Subject {
 	/**
 	 * The id of the subject
@@ -15,10 +13,14 @@ class Subject {
 	 */
 	name;
 
+	#conn;
+
 	/**
 	 * @param {number} subjectID - The id of the subject to fetch
 	 */
-	constructor(subjectId) {
+	constructor(conn, subjectId) {
+		this.#conn = conn;
+
 		const sql = `
 			select
 				subjectId as id,
@@ -30,13 +32,10 @@ class Subject {
 		`;
 
 		return (async () => {
-			const conn = await new DatabaseConnectionPool();
-			const record = await conn.runQuery(sql, [
+			const record = await this.#conn.runQuery(sql, [
 				subjectId,
 			]);
 
-			conn.close();
-
 			if (!record.length)
 				throw new Error('No subject found');
 
@@ -47,7 +46,7 @@ class Subject {
 		})();
 	}
 
-	static async getAllSubjects() {
+	static async getAllSubjects(conn) {
 		const sql = `
 			select
 				subjectId as id
@@ -55,14 +54,12 @@ class Subject {
 				subject;
 		`;
 
-		const conn = await new DatabaseConnectionPool();
 		const records = await conn.runQuery(sql);
-		conn.close();
 
 		const objectPromises = [];
 
 		records.forEach(record => {
-			objectPromises.push(new Subject(record.id));
+			objectPromises.push(new Subject(conn, record.id));
 		});
 
 		const objects = await Promise.all(objectPromises);