buidler-fest-2024-workshop

A Cardano blockchain indexer and reward system that monitors transactions and automatically sends rewards based on configurable criteria.

Environment Variables

The application uses environment variables to configure its behavior. You can set these variables in your environment or create a .env file in the project root.

General

• NETWORK: Cardano network to use (default: preprod)

Indexer

Use one of the following:

• INDEXER_TCP_ADDRESS: TCP address and port of the remote Cardano Node for the indexer
• INDEXER_SOCKET_PATH: Socket path of the local Cardano Node for the indexer

Reward

• MIN_LOVELACE: Minimum Lovelace required to trigger a reward (default: 50_000_000)
• REWARD_ADDRESS: Address to send rewards to
• REWARD_AMOUNT: Amount of Lovelace to send as a reward (default: 5_000_000)
• SOURCE_ADDRESS: Source address to filter transactions

Submit

Use one of the following:

• SUBMIT_TCP_ADDRESS: TCP address and port of the remote Cardano Node for transaction submission
• SUBMIT_SOCKET_PATH: Socket path of the local Cardano Node for transaction submission
• SUBMIT_URL: API URL for transaction submission

TxBuilder

Use one of the following:

• BLOCKFROST_API_KEY: Blockfrost API key for UTxO queries
• KUPO_URL: Kupo URL for UTxO queries

Wallet

• MNEMONIC: Wallet mnemonic (if not set, will use or generate seed.txt)

Application Workflow

1. Startup (cmd/workshop/main.go)

• The main entry point is the main() function
• Loads configuration from environment variables and .env file
• Sets up logging
• Initializes the wallet (loads or generates mnemonic)
• Starts the indexer

2. Wallet Setup (internal/wallet/wallet.go)

• Loads mnemonic from config or seed.txt
• If not present, generates a new mnemonic and writes it to seed.txt
• Initializes the wallet for use

3. Indexer (internal/indexer/indexer.go)

• Creates a pipeline to listen for transaction events on the configured network and addresses
• Filters events for relevant addresses (wallet and reward)
• On transaction events, triggers the transaction builder

4. Transaction Builder (internal/txbuilder/txbuilder.go)

• Handles transaction events
• Checks if the transaction meets reward criteria (source address, minimum Lovelace, etc.)
• Builds a reward transaction if criteria are met
• Signs the transaction with the wallet keys

5. Transaction Submission (internal/txsubmit/txsubmit.go)

• Submits the built transaction to the network via TCP, socket, or API, depending on config

Building and Running

To build the application:

make build

To run the application:

./workshop

The application will run continuously, monitoring the blockchain for transactions and automatically sending rewards when criteria are met.