# Quickstart Guide: Google Drive HTTP Proxy Adapter

**Feature**: 001-drive-proxy-adapter  
**Date**: 2026-03-07  
**Version**: 1.0.0

---

## Overview

The Google Drive HTTP Proxy Adapter is a Node.js application that generates XML sitemaps of Google Drive documents. It provides a single HTTP endpoint (`/sitemap.xml`) that queries the Google Drive API and returns a sitemap listing all accessible documents with links in RESTful format.

**Key Features**:
- Service Account authentication (JWT-based, no user interaction)
- Sitemap protocol compliant (50,000 URL limit enforced)
- FIFO request queuing (sequential processing)
- Configurable Drive API filters
- Plain text logging to stdout/stderr

---

## Prerequisites

1. **Node.js**: v18.0.0 or later (LTS version recommended)
2. **Google Cloud Project**: With Drive API enabled
3. **Service Account**: JSON key file with Drive API access
4. **Network Access**: Connectivity to googleapis.com

---

## Installation

### 1. Clone Repository

```bash
git clone <repository-url>
cd google-drive-content-adapter
```

### 2. Install Dependencies

```bash
npm install
```

**Dependencies**:
- `googleapis@^140.0.0` - Official Google API client for Node.js

---

## Configuration

### 1. Service Account Setup

**Create Service Account** (Google Cloud Console):
1. Navigate to [IAM & Admin > Service Accounts](https://console.cloud.google.com/iam-admin/serviceaccounts)
2. Click "Create Service Account"
3. Name: `drive-sitemap-adapter` (or your choice)
4. Grant role: None required if accessing service account's own Drive
5. Click "Create Key" → Choose JSON format → Download key file

**Enable Drive API**:
1. Navigate to [APIs & Services > Library](https://console.cloud.google.com/apis/library)
2. Search for "Google Drive API"
3. Click "Enable"

**Grant Access** (if accessing user drives):
- Share Drive folders/files with Service Account email (`xxx@project.iam.gserviceaccount.com`)
- OR configure domain-wide delegation (for G Suite organizations)

---

### 2. Environment Variables

Create `.env` file in project root (or set environment variables):

```bash
# REQUIRED: Service Account credentials (inline JSON)
GOOGLE_SERVICE_ACCOUNT_KEY='{"type":"service_account","project_id":"your-project","private_key_id":"...","private_key":"-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----\n","client_email":"xxx@project.iam.gserviceaccount.com","client_id":"...","auth_uri":"https://accounts.google.com/o/oauth2/auth","token_uri":"https://oauth2.googleapis.com/token","auth_provider_x509_cert_url":"https://www.googleapis.com/oauth2/v1/certs","client_x509_cert_url":"..."}'

# OPTIONAL: Server configuration
PORT=3000                                    # Default: 3000
BASE_URL=http://localhost:3000               # Default: http://localhost:3000

# OPTIONAL: Drive API query filter
DRIVE_QUERY="trashed = false"                # Default: "trashed = false"
```

**Important Notes**:
- `GOOGLE_SERVICE_ACCOUNT_KEY` must be a single-line JSON string (escape newlines in private_key)
- `BASE_URL` should match your production domain for sitemap URLs
- `DRIVE_QUERY` supports Drive API query syntax ([docs](https://developers.google.com/drive/api/guides/search-files))

---

### 3. Configuration Files

**config/config.js**: Server settings (auto-generated from env vars)
```javascript
export default {
  server: {
    port: process.env.PORT || 3000,
    baseUrl: process.env.BASE_URL || 'http://localhost:3000'
  }
};
```

**config/settings.js**: Drive API configuration
```javascript
export default {
  drive: {
    query: process.env.DRIVE_QUERY || "trashed = false",
    fields: 'files(id, name, mimeType, modifiedTime)',
    pageSize: 1000,
    scope: 'https://www.googleapis.com/auth/drive.readonly'
  }
};
```

**To customize Drive API filter**, edit `config/settings.js` or set `DRIVE_QUERY` env var.

---

## Usage

### Start Server (Development)

```bash
npm run dev
```

**Output**:
```
[2026-03-07T10:00:00.000Z] [INFO] Server configuration loaded: port=3000, baseUrl=http://localhost:3000
[2026-03-07T10:00:00.100Z] [INFO] Service Account authenticated: xxx***@project.iam.gserviceaccount.com
[2026-03-07T10:00:00.200Z] [INFO] HTTP server listening on port 3000
```

---

### Start Server (Production)

```bash
npm start
```

---

### Request Sitemap

**Using curl**:
```bash
curl http://localhost:3000/sitemap.xml
```

**Expected Response** (200 OK):
```xml
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>http://localhost:3000/documents/1A2B3C4D5E6F7G8H</loc>
    <lastmod>2026-03-07</lastmod>
  </url>
  <url>
    <loc>http://localhost:3000/documents/9I0J1K2L3M4N5O6P</loc>
    <lastmod>2026-03-05</lastmod>
  </url>
</urlset>
```

---

## Testing

### Run All Tests

```bash
npm test
```

**Test Suites**:
- `tests/unit/` - Unit tests for Drive client, auth, sitemap generator, queue
- `tests/integration/` - End-to-end endpoint tests for /sitemap.xml
- `tests/contract/` - XML sitemap schema validation tests

---

### Run Specific Test Suite

```bash
npm run test:unit          # Unit tests only
npm run test:integration   # Integration tests only
npm run test:contract      # Contract tests only
```

---

## API Reference

### Endpoint: `GET /sitemap.xml`

**Description**: Generate XML sitemap of all accessible Google Drive documents.

**Request**:
```http
GET /sitemap.xml HTTP/1.1
Host: example.com
```

**Success Response** (200 OK):
```http
HTTP/1.1 200 OK
Content-Type: application/xml; charset=utf-8
Content-Length: {size}

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <!-- up to 50,000 URL entries -->
</urlset>
```

**Error Responses**:
- `404 Not Found` - Invalid endpoint (only /sitemap.xml supported)
- `413 Payload Too Large` - More than 50,000 documents in Drive
- `429 Too Many Requests` - Rate limit exceeded (includes `Retry-After` header)
- `401 Unauthorized` - Authentication failed
- `503 Service Unavailable` - Drive API unavailable
- `500 Internal Server Error` - Unexpected error

**Note**: All error responses have **empty body** (status code only).

See [contracts/sitemap-xml-schema.md](./contracts/sitemap-xml-schema.md) for full API contract.

---

## Architecture

### Project Structure

```
google-drive-content-adapter/
├── src/
│   ├── server.js        # HTTP server entry point
│   ├── proxy.js         # Monolithic route handler (sitemap logic)
│   ├── logger.js        # Logging module (console.js alias)
│   ├── auth.js          # Service Account JWT authentication
│   └── xml-utils.js     # XML generation utilities
├── config/
│   ├── config.js        # Server configuration (port, baseUrl)
│   └── settings.js      # Drive API filter configuration
├── tests/
│   ├── unit/            # Unit tests
│   ├── integration/     # Integration tests
│   └── contract/        # Contract tests
├── specs/               # Feature specifications and planning docs
│   └── 001-drive-proxy-adapter/
│       ├── spec.md
│       ├── plan.md
│       ├── research.md
│       ├── data-model.md
│       ├── quickstart.md (this file)
│       └── contracts/
│           └── sitemap-xml-schema.md
├── package.json
└── README.md
```

---

### Request Flow

```
1. Client → GET /sitemap.xml
2. Server → Create RequestContext (ID, timestamp)
3. Server → Enqueue request (FIFO queue)
4. Queue → Process request (sequential, one at a time)
5. Proxy → Authenticate with Service Account JWT
6. Proxy → Query Drive API files.list() (paginate if >1000 docs)
7. Proxy → Check count ≤ 50,000
8. Proxy → Transform Documents to SitemapEntries
9. Proxy → Generate XML sitemap
10. Server → Return 200 + XML (or error status)
11. Queue → Process next request
```

---

## Troubleshooting

### 1. Fatal Error: Invalid Service Account Credentials

**Error**:
```
[2026-03-07T10:00:00.000Z] [ERROR] FATAL: Invalid client_email in Service Account credentials
```

**Solution**:
- Check `GOOGLE_SERVICE_ACCOUNT_KEY` env var is valid JSON
- Ensure `client_email` field ends with `.gserviceaccount.com`
- Ensure `private_key` field starts with `-----BEGIN PRIVATE KEY-----`
- Verify no extra escaping/quotes in JSON string

---

### 2. Fatal Error: Port Already in Use

**Error**:
```
[2026-03-07T10:00:00.000Z] [ERROR] FATAL: Unable to bind to port 3000 (EADDRINUSE)
```

**Solution**:
- Change `PORT` env var to different port (e.g., 8080)
- OR stop other process using port 3000: `lsof -ti:3000 | xargs kill`

---

### 3. 401 Unauthorized Response

**Cause**: Service Account token refresh failed

**Solution**:
- Verify Service Account has Drive API access (share folders with service account email)
- Check Drive API is enabled in Google Cloud Console
- Ensure scope is correct: `https://www.googleapis.com/auth/drive.readonly`

---

### 4. 413 Payload Too Large Response

**Cause**: Google Drive contains more than 50,000 documents

**Solution**:
- Adjust `DRIVE_QUERY` to filter documents (e.g., by folder, date, file type)
- Example: `DRIVE_QUERY="'folder-id' in parents and trashed = false"`

---

### 5. 429 Too Many Requests Response

**Cause**: Drive API rate limit exceeded

**Solution**:
- Wait for time specified in `Retry-After` response header (seconds)
- Reduce request frequency
- Consider Drive API quota limits ([docs](https://developers.google.com/drive/api/guides/limits))

---

### 6. 503 Service Unavailable Response

**Cause**: Google Drive API is temporarily unavailable

**Solution**:
- Wait and retry manually (no automatic retries per spec)
- Check [Google Workspace Status Dashboard](https://www.google.com/appsstatus)

---

## Performance Tips

### 1. Optimize Drive Query Filter

**Default** (all files):
```javascript
DRIVE_QUERY="trashed = false"
```

**Filter by folder**:
```javascript
DRIVE_QUERY="'folder-id' in parents and trashed = false"
```

**Filter by date**:
```javascript
DRIVE_QUERY="modifiedTime > '2026-01-01T00:00:00' and trashed = false"
```

**Filter by MIME type**:
```javascript
DRIVE_QUERY="mimeType = 'application/pdf' and trashed = false"
```

See [Drive API search query syntax](https://developers.google.com/drive/api/guides/search-files) for more options.

---

### 2. Adjust BASE_URL for Production

**Development**:
```
BASE_URL=http://localhost:3000
```

**Production**:
```
BASE_URL=https://your-domain.com
```

This ensures sitemap URLs point to the correct domain.

---

### 3. Monitor Memory Usage

**Check memory usage** (production):
```bash
node --inspect src/server.js
# Open chrome://inspect in Chrome DevTools
```

**Expected**: <256MB under normal load (<10 concurrent requests)

---

## Security Best Practices

1. **Never commit** Service Account JSON key file to version control
2. **Use environment variables** for all sensitive configuration
3. **Restrict Service Account permissions** to minimum required (readonly scope)
4. **Monitor logs** for unauthorized access attempts
5. **Use HTTPS** in production (configure reverse proxy like nginx)
6. **Filter credentials from logs** (private_key field never logged)

---

## Deployment

### Docker (Recommended)

**Dockerfile**:
```dockerfile
FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
EXPOSE 3000
CMD ["npm", "start"]
```

**Build and run**:
```bash
docker build -t drive-sitemap-adapter .
docker run -p 3000:3000 \
  -e GOOGLE_SERVICE_ACCOUNT_KEY='{"type":"service_account",...}' \
  -e BASE_URL=https://your-domain.com \
  drive-sitemap-adapter
```

---

### Cloud Platforms

**Google Cloud Run**:
```bash
gcloud run deploy drive-sitemap-adapter \
  --source . \
  --set-env-vars BASE_URL=https://your-domain.com \
  --set-secrets GOOGLE_SERVICE_ACCOUNT_KEY=service-account-key:latest
```

**AWS ECS / Fargate**: Use environment variables in task definition

**Heroku**: Set environment variables via Heroku CLI or dashboard

---

## Additional Resources

- **Feature Specification**: [specs/001-drive-proxy-adapter/spec.md](./spec.md)
- **Implementation Plan**: [specs/001-drive-proxy-adapter/plan.md](./plan.md)
- **Research Document**: [specs/001-drive-proxy-adapter/research.md](./research.md)
- **Data Model**: [specs/001-drive-proxy-adapter/data-model.md](./data-model.md)
- **API Contract**: [specs/001-drive-proxy-adapter/contracts/sitemap-xml-schema.md](./contracts/sitemap-xml-schema.md)
- **Google Drive API Docs**: [https://developers.google.com/drive/api/v3/reference](https://developers.google.com/drive/api/v3/reference)
- **Sitemap Protocol**: [https://www.sitemaps.org/protocol.html](https://www.sitemaps.org/protocol.html)

---

## Support

For issues or questions, refer to:
1. This quickstart guide
2. Feature specification (spec.md) for requirements
3. Research document (research.md) for technical decisions
4. Contract documentation (contracts/) for API details

---

## Version History

| Version | Date | Changes |
|---------|------|---------|
| 1.0.0 | 2026-03-07 | Initial quickstart guide |