feat: Persist config file alongside sourceDir by default

Save backup-config.json in the same directory as sourceDir when
configPath is not explicitly specified. This simplifies configuration
for cloud deployments (Fly.io, Railway, etc.) where a single persistent
volume can be mounted at sourceDir to persist both data and config.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ciro-maciel

README.md

@@ -41,7 +41,6 @@ const app = new Elysia()
     .use(
         r2Backup({
             sourceDir: './data',
-            configPath: './backup-config.json',
         })
     )
     .listen(3000)
@@ -60,10 +59,10 @@ On first run, you'll be guided through an onboarding wizard to configure:
 
 ### Plugin Options
 
-| Option       | Type   | Required | Description                                                   |
-| ------------ | ------ | -------- | ------------------------------------------------------------- |
-| `sourceDir`  | string | ✅       | Local directory to backup                                     |
-| `configPath` | string | ❌       | Path to save runtime config (default: `./backup-config.json`) |
+| Option       | Type   | Required | Description                                                         |
+| ------------ | ------ | -------- | ------------------------------------------------------------------- |
+| `sourceDir`  | string | ✅       | Local directory to backup                                           |
+| `configPath` | string | ❌       | Path to save runtime config (default: same directory as `sourceDir`) |
 
 ### Runtime Configuration (via UI or backup-config.json)
 
@@ -119,6 +118,27 @@ The plugin adds the following routes under `/backup`:
 | POST   | `/backup/api/totp/verify`   | Verify and enable 2FA         |
 | POST   | `/backup/api/totp/disable`  | Disable 2FA                   |
 
+## ☁️ Cloud Deployment (Fly.io, Railway, etc.)
+
+For cloud platforms with ephemeral file systems, mount a persistent volume at your `sourceDir` path. The configuration file will be automatically saved alongside your data:
+
+```javascript
+import { Elysia } from 'elysia'
+import { r2Backup } from '@riligar/elysia-backup'
+
+const app = new Elysia()
+    .use(
+        r2Backup({
+            // Mount your persistent volume here
+            // Config will be saved at /data/backup-config.json
+            sourceDir: '/data',
+        })
+    )
+    .listen(3000)
+```
+
+This ensures both your backup data and configuration persist across deployments and restarts.
+
 ## 🔐 Security Features
 
 ### Session-Based Authentication

src/core/config.js

@@ -1,5 +1,6 @@
 import { readFileSync, existsSync } from 'node:fs'
 import { writeFile } from 'node:fs/promises'
+import { dirname, join } from 'node:path'
 
 /**
  * Load configuration from a JSON file
@@ -43,7 +44,8 @@ export const saveConfig = async (configPath, config) => {
  * @returns {Object} Configuration manager with get/set/save methods
  */
 export const createConfigManager = initialConfig => {
-    const configPath = initialConfig.configPath || './backup-config.json'
+    // If configPath not specified, save config alongside sourceDir for cloud deployments
+    const configPath = initialConfig.configPath || join(dirname(initialConfig.sourceDir), 'backup-config.json')
     const savedConfig = loadConfig(configPath)
 
     let config = { ...initialConfig, ...savedConfig }

src/index.js

@@ -5,6 +5,7 @@ import { authenticator } from 'otplib'
 import QRCode from 'qrcode'
 import { writeFile } from 'node:fs/promises'
 import { readFileSync, existsSync } from 'node:fs'
+import { dirname, join } from 'node:path'
 // Helper to return HTML responses with proper Content-Type
 const htmlResponse = content =>
     new Response(content, {
@@ -36,11 +37,12 @@ const sessionManager = createSessionManager()
  * @param {string} [config.prefix] - Optional prefix for S3 keys (e.g. 'backups/')
  * @param {string} [config.cronSchedule] - Cron schedule expression
  * @param {boolean} [config.cronEnabled] - Whether the cron schedule is enabled
- * @param {string} [config.configPath] - Path to save runtime configuration (default: './backup-config.json')
+ * @param {string} [config.configPath] - Path to save runtime configuration (default: same directory as sourceDir)
  */
 export const r2Backup = initialConfig => app => {
     // State to hold runtime configuration (allows UI updates)
-    const configPath = initialConfig.configPath || './backup-config.json'
+    // If configPath not specified, save config alongside sourceDir for cloud deployments
+    const configPath = initialConfig.configPath || join(dirname(initialConfig.sourceDir), 'backup-config.json')
 
     // Load saved config if exists
     let savedConfig = {}