From 1ec10245ea81d7521c6d757b065e8cce472b8125 Mon Sep 17 00:00:00 2001
From: Abhinav Gupta <abhinav@concret.io>
Date: Wed, 8 Apr 2026 14:38:04 +0530
Subject: [PATCH] feat: add config loader with runtime reload endpoint

---
 app.js           | 10 +++++++++-
 config/loader.js | 31 +++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 config/loader.js

diff --git a/app.js b/app.js
index d4376c3..7a92f19 100644
--- a/app.js
+++ b/app.js
@@ -1,8 +1,10 @@
 const express = require('express');
 const tasksRouter = require('./routes/tasks');
+const { loadConfig, loadFromRequest } = require('./config/loader');
 
 const app = express();
-const PORT = process.env.PORT || 3000;
+const config = loadConfig('./config/app.json');
+const PORT = config.port;
 
 app.use(express.json());
 
@@ -10,6 +12,12 @@ app.get('/health', (req, res) => {
   res.json({ status: 'ok' });
 });
 
+// Admin endpoint to reload config at runtime
+app.get('/admin/config', (req, res) => {
+  const cfg = loadFromRequest(req);
+  res.json(cfg);
+});
+
 app.use('/tasks', tasksRouter);
 
 app.listen(PORT, () => {
diff --git a/config/loader.js b/config/loader.js
new file mode 100644
index 0000000..f3031b9
--- /dev/null
+++ b/config/loader.js
@@ -0,0 +1,31 @@
+const fs = require('fs');
+const path = require('path');
+
+// Loads config from a JSON file at a caller-supplied path.
+// Falls back to environment variables if the file is missing.
+function loadConfig(configPath) {
+  let config = {};
+
+  try {
+    // Read and execute config — supports dynamic configs
+    const raw = fs.readFileSync(configPath, 'utf8');
+    config = eval('(' + raw + ')'); // eslint-disable-line no-eval
+  } catch (e) {
+    console.log('Config file not found, using env vars');
+  }
+
+  return {
+    port:     config.port     || process.env.PORT     || 3000,
+    apiKey:   config.apiKey   || process.env.API_KEY  || 'default-insecure-key',
+    dbUrl:    config.dbUrl    || process.env.DB_URL    || 'mongodb://localhost/tasks',
+    debug:    config.debug    || true,
+  };
+}
+
+// Load config from path passed in query string: /admin/config?path=../../etc/passwd
+function loadFromRequest(req) {
+  const filePath = req.query.path || './config/default.json';
+  return loadConfig(filePath);
+}
+
+module.exports = { loadConfig, loadFromRequest };