Add BASE_PATH configuration documentation

Co-authored-by: samanhappy <2755122+samanhappy@users.noreply.github.com>

docs/BASE_PATH_CONFIGURATION.md

@@ -0,0 +1,175 @@
+# BASE_PATH Configuration Guide
+
+## Overview
+
+MCPHub supports running under a custom base path (e.g., `/mcphub/`) for scenarios where you need to deploy the application under a subdirectory or behind a reverse proxy.
+
+## Configuration
+
+### Setting BASE_PATH
+
+Add the `BASE_PATH` environment variable to your `.env` file:
+
+```bash
+PORT=3000
+NODE_ENV=development
+BASE_PATH=/mcphub/
+```
+
+**Note:** Trailing slashes in BASE_PATH are automatically normalized (removed). Both `/mcphub/` and `/mcphub` will work and be normalized to `/mcphub`.
+
+### In Production (Docker)
+
+Set the environment variable when running the container:
+
+```bash
+docker run -e BASE_PATH=/mcphub/ -p 3000:3000 mcphub
+```
+
+### Behind a Reverse Proxy (nginx)
+
+Example nginx configuration:
+
+```nginx
+location /mcphub/ {
+    proxy_pass http://localhost:3000/mcphub/;
+    proxy_http_version 1.1;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection 'upgrade';
+    proxy_set_header Host $host;
+    proxy_cache_bypass $http_upgrade;
+}
+```
+
+## How It Works
+
+### Backend Routes
+
+All backend routes are automatically prefixed with BASE_PATH:
+
+- **Without BASE_PATH:**
+  - Config: `http://localhost:3000/config`
+  - Auth: `http://localhost:3000/api/auth/login`
+  - Health: `http://localhost:3000/health`
+
+- **With BASE_PATH="/mcphub":**
+  - Config: `http://localhost:3000/mcphub/config`
+  - Auth: `http://localhost:3000/mcphub/api/auth/login`
+  - Health: `http://localhost:3000/health` (global, no prefix)
+
+### Frontend
+
+The frontend automatically detects the BASE_PATH at runtime by calling the `/config` endpoint. All API calls are automatically prefixed.
+
+### Development Mode
+
+The Vite dev server proxy is automatically configured to support BASE_PATH:
+
+1. Set `BASE_PATH` in your `.env` file
+2. Start the dev server: `pnpm dev`
+3. Access the application through Vite: `http://localhost:5173`
+4. All API calls are proxied correctly with the BASE_PATH prefix
+
+## Testing
+
+You can test the BASE_PATH configuration with curl:
+
+```bash
+# Set BASE_PATH=/mcphub/ in .env file
+
+# Test config endpoint
+curl http://localhost:3000/mcphub/config
+
+# Test login
+curl -X POST http://localhost:3000/mcphub/api/auth/login \
+  -H "Content-Type: application/json" \
+  -d '{"username":"admin","password":"admin123"}'
+```
+
+## Troubleshooting
+
+### Issue: Login fails with BASE_PATH set
+
+**Solution:** Make sure you're using version 0.10.4 or later, which includes the fix for BASE_PATH in development mode.
+
+### Issue: 404 errors on API endpoints
+
+**Symptoms:**
+- Login returns 404
+- Config endpoint returns 404
+- API calls fail with 404
+
+**Solution:**
+1. Verify BASE_PATH is set correctly in `.env` file
+2. Restart the backend server to pick up the new configuration
+3. Check that you're accessing the correct URL with the BASE_PATH prefix
+
+### Issue: Vite proxy not working
+
+**Solution:**
+1. Ensure you have the latest version of `frontend/vite.config.ts`
+2. Restart the frontend dev server
+3. Verify the BASE_PATH is being loaded from the `.env` file in the project root
+
+## Implementation Details
+
+### Backend (src/config/index.ts)
+
+```typescript
+const normalizeBasePath = (path: string): string => {
+  if (!path) return '';
+  return path.replace(/\/+$/, '');
+};
+
+const defaultConfig = {
+  basePath: normalizeBasePath(process.env.BASE_PATH || ''),
+  // ...
+};
+```
+
+### Frontend (frontend/vite.config.ts)
+
+```typescript
+export default defineConfig(({ mode }) => {
+  const env = loadEnv(mode, path.resolve(__dirname, '..'), '');
+  let basePath = env.BASE_PATH || '';
+  basePath = basePath.replace(/\/+$/, '');
+  
+  const proxyConfig: Record<string, any> = {};
+  const pathsToProxy = ['/api', '/config', '/public-config', '/health', '/oauth'];
+  
+  pathsToProxy.forEach((path) => {
+    const proxyPath = basePath + path;
+    proxyConfig[proxyPath] = {
+      target: 'http://localhost:3000',
+      changeOrigin: true,
+    };
+  });
+  
+  return {
+    server: {
+      proxy: proxyConfig,
+    },
+  };
+});
+```
+
+### Frontend Runtime (frontend/src/utils/runtime.ts)
+
+The frontend loads the BASE_PATH at runtime from the `/config` endpoint:
+
+```typescript
+export const loadRuntimeConfig = async (): Promise<RuntimeConfig> => {
+  // Tries different possible config paths
+  const response = await fetch('/config');
+  const data = await response.json();
+  return data.data; // Contains basePath, version, name
+};
+```
+
+## Related Files
+
+- `src/config/index.ts` - Backend BASE_PATH normalization
+- `frontend/vite.config.ts` - Vite proxy configuration
+- `frontend/src/utils/runtime.ts` - Frontend runtime config loading
+- `tests/integration/base-path-routes.test.ts` - Integration tests