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Alchemy AA + Capsule PreGen Example

This example demonstrates how to create and use Capsule's Pregenerated wallets on a server with Alchemy's AA libraries.

Overview

When a POST message is received on the root path, the example will create or retrieve a new PreGen wallet. Here's how it works:

1. A wallet is pregenerated with the Capsule client, creating a wallet share.
2. The wallet share is set on the Capsule client and must be stored for future actions.
3. A Viem Client instance is created using the Capsule Client.
4. The Viem Client is passed to Alchemy to create an Alchemy client.
5. A simple userOps array is constructed and executed on a predeployed Alchemy contract.

Important Notes

Wallet Shares

For this simple example, the userShare string is stored in a JSON file. However, best practice is to store this securely in a database.

Warning: The wallet share is sensitive content encoded in base64. We recommend encrypting it before storing, following best practices.

Custom Sign Message

In src/clients.ts, you'll find a customSignMessage function. This is a temporary fix for userOps due to the nature of DKLS signatures used by Capsule.

Note: This is not a long-term solution. Keep an eye out for patch changes to Capsule libraries for fixes to this issue.

Gas Sponsorship

Configure your Gas Manager in Alchemy's client dashboard. The policy needs to be passed into the Alchemy client when it's being created for Gas sponsorship.

Getting Started

1. Use Yarn to install dependencies:

   yarn
   

2. Start the dev server:

   yarn dev
   

3. Use the server by sending a POST request to the root path:

   curl -X POST http://localhost:3000/ -H "Content-Type: application/json" -d '{"email": "your_test_email@your_app_domain.com"}'
   

   The email is used to generate the PreGen Wallet with Capsule and will be associated with that pregenerated wallet.

Setup

1. Set all ENV variables as shown in .env.example.
2. Create an appropriate env file (e.g., .env or .env.local) with your API keys for Capsule and Alchemy.

Best Practices

• Split wallet creation and retrieval as needed by your application.
• Always retrieve and set the userShare after checking if the associated email has a PreGen wallet.
• Securely encrypt and store the userShare after creation for future use.
• You can use any Capsule client (Viem, Ethers, etc.) server-side with PreGen.
• For performance, optimize by creating clients once and not on every request to the path.

Important: DO NOT delete the user_shares.json file or its content without backing it up. Losing the userShares will result in loss of that account.

For more information on using PreGen with Capsule, visit our documentation.

Additional Resources

• Alchemy AA SDK UserOps Example