polar-file-sharing

File Sharing Service with Polar

A WeTransfer-style file sharing service with authentication and tiered subscriptions using Polar and BetterAuth.

Build from scratch with a tutorial

If you prefer, check out the full tutorial to learn how to build this application from scratch.

Features

Authentication:

• Email/password signup and login
• Secure session management with BetterAuth
• Protected API endpoints

Free Tier:

• Upload files up to 100MB
• Files stored for 7 days
• Generate shareable download links

Premium Tier ($10/month):

• Upload files up to 5GB
• Files stored for 30 days

Architecture

• Auth Service - User authentication with BetterAuth
• Files Service - File upload/download with object storage
• Payments Service - Polar subscription management and webhooks
• Frontend Service - Static HTML/JS frontend

Prerequisites

Install Encore:

• macOS: brew install encoredev/tap/encore
• Linux: curl -L https://encore.dev/install.sh | bash
• Windows: iwr https://encore.dev/install.ps1 | iex

Docker:

• Install Docker
• Start Docker

Running locally

1. Install dependencies:

npm install

2. Set required secrets:

# BetterAuth secret
encore secret set --dev BetterAuthSecret
# When prompted, enter a random string (e.g., output of: openssl rand -base64 32)

# Polar API token (get from https://sandbox.polar.sh/settings)
encore secret set --dev PolarAccessToken
# Paste your Polar sandbox access token

3. Start the backend (make sure Docker is running):

encore run

4. Open the frontend at http://localhost:4000

Note: The example uses Polar's sandbox environment for testing without real payments.

Local Testing

1. Create an account

1. Open http://localhost:4000
2. Click "Don't have an account? Sign up"
3. Enter your details and create an account
4. You'll be automatically signed in

2. Upload a free file

1. Select a file under 100MB
2. Click "Upload File"
3. You'll see the download link and expiration date (7 days)

3. Test the premium upgrade flow

1. Click "Upgrade Now" button
2. You'll be redirected to Polar's sandbox checkout
3. Complete the checkout (use test card info)
4. Important: After checkout, webhooks won't work locally

Local limitation: Polar webhooks can't reach localhost, so your subscription won't activate automatically. See "Deployment" below for full webhook testing.

Local Development Dashboard

Open http://localhost:9400 to access Encore's local development dashboard with:

• API Explorer with interactive documentation
• Service architecture diagram
• Distributed tracing for all requests
• Database explorer

Deployment

Self-hosting

See the self-hosting instructions for how to use encore build docker to create a Docker image and configure it.

Encore Cloud Platform

Deploy your application to a free staging environment in Encore's development cloud using git push encore:

git add -A .
git commit -m 'Commit message'
git push encore

Set your production secrets:

encore secret set --prod BetterAuthSecret
# For production Polar, also set:
# encore secret set --prod PolarAccessToken

You can also open your app in the Cloud Dashboard to integrate with GitHub, or connect your AWS/GCP account, enabling Encore to automatically handle cloud deployments for you.

Configure Polar Webhooks

To enable automatic subscription activation:

1. Go to https://sandbox.polar.sh/dashboard → Settings → Webhooks
2. Add webhook URL: https://[your-app].encr.app/webhooks/polar
3. Select events: subscription.created, subscription.updated, customer.created

API Endpoints

Authentication

• POST /auth/signup - Create new account
• POST /auth/signin - Sign in
• POST /auth/signout - Sign out

Files

• POST /upload - Upload file (requires auth)
• GET /download/:fileId - Download file

Payments

• GET /subscriptions/me - Check subscription status (requires auth)
• POST /checkout - Create Polar checkout session (requires auth)
• POST /webhooks/polar - Polar webhook handler

Tech Stack

• Encore.ts - Backend framework with Infrastructure from Code
• BetterAuth - TypeScript authentication framework
• Polar - Merchant of record for subscriptions
• Drizzle ORM - Type-safe database queries
• PostgreSQL - Database (automatically provisioned by Encore)
• Object Storage - File storage (S3/GCS, automatically provisioned by Encore)

Project Structure

├── auth/                  # Authentication service
│   ├── auth.ts           # Signup/signin/signout endpoints
│   ├── handler.ts        # Auth handler for protected endpoints
│   ├── better-auth.ts    # BetterAuth configuration
│   └── migrations/       # Database schema for auth tables
├── files/                # File management service
│   ├── upload.ts        # File upload endpoint
│   ├── download.ts      # File download endpoint
│   └── bucket.ts        # Object storage bucket
├── payments/            # Payments service
│   ├── checkout.ts     # Create Polar checkout sessions
│   ├── webhooks.ts     # Handle Polar webhooks
│   └── subscriptions.ts # Check subscription status
└── frontend/           # Static frontend
    └── assets/
        └── index.html  # Single-page app

Learn More

• Encore.ts Documentation
• BetterAuth Documentation
• Polar Documentation
• Tutorial Article - Full step-by-step guide

License

MIT