Solana NFT Vending Machine

This is a proof of concept of an NFT vending machine built using Solana Pay, Metaplex, Phantom Mobile, and Next.js. This was created and demoed at the 2022 Los Angeles Hacker House presented by Solana and FTX US.

Dependencies

• Node 14.x
• Yarn 1.x
• Metaboss (installed globally via cargo install metaboss or elsewhere in your $PATH)
• spl-token (installed globally via cargo install spl-token-cli or elsewhere in your $PATH)

Getting Started

Step 1: Install Dependencies

yarn install

Step 2: Set Environment Variables

This project uses Next.js' built-in environment variables support. Create a file named .env.local at the root of this repository. See .env.example for details on what to include in this file.

The environment variables are:

• NEXT_PUBLIC_RPC_URL: The RPC server to connect to.
• NEXT_PUBLIC_MERCHANT_WALLET_PUBKEY: The public key of the wallet that will receive transaction funds, mint NFTs, and be set as the update authority on the NFTs.
• MERCHANT_KEYPAIR_PATH: The path to the keypair file of the merchant wallet.
• NEXT_PUBLIC_VENDING_MODE: Set to mint to mint NFTs on-demand, set to transfer to send pre-minted NFTs from the merchant wallet.
• NFT_COLLECTION_SIZE: The quantity of random NFTs to choose from when minting.
• NFT_COLLECTION_PATH: The location of the directory that contains the on-chain JSON data files used to mint by Metaboss.
• NEXT_PUBLIC_SOLANA_PAY_TRANSACTION_AMOUNT: How much to charge for the NFTs, leave blank to allow customers to name their own price.
• NEXT_PUBLIC_SOLANA_PAY_TRANSACTION_LABEL, NEXT_PUBLIC_SOLANA_PAY_TRANSACTION_MESSAGE, and NEXT_PUBLIC_SOLANA_PAY_TRANSACTION_MEMO: Transaction metadata fields in the Solana Pay standard.

Step 3: Start the vending machine

Run yarn dev, then navigate to http://localhost:3000. Alternatively, run yarn build && yarn start if you want to run in Production mode for performance reasons.

Overview of a Transaction

The overall lifecycle of a vending machine transaction consists of the following:

1. A QR code is generated using the Solana Pay SDK that includes a reference ID based on a generated public key.
2. The vending machine polls to check for an on-chain transaction that include the reference ID.
3. Phantom Mobile is used to scan the Solana Pay QR code, which builds a transaction that is confirmed by the customer on their mobile device.
4. The vending machine detects the transaction on-chain based on the reference ID, then begins polling to determine the validity and state of the on-chain transaction.
5. Once the on-chain transaction is fully confirmed, the customer's wallet address is retrieved and is then used as the recipient when Metaboss is used to mint the NFT or when spl-token is used to transfer the NFT.
6. The vending machine displays a success (or error) message to the customer, then generates a new QR code with a new reference ID and returns to the idle state.

Project Structure

Notable portions of this codebase include:

• lib/constants.js: Copy and other content-related settings.
• styles/tokens.scss: Design tokens such as colors.
• pages/index.jsx: The React page component that contains the majority of the UI and transaction polling / confirmation logic.
• pages/api/mint.js: The API route that invokes Metaboss to mint an NFT.
• pages/api/transfer.js: The API route that invokes spl-token to transfer an NFT.
• components/: Miscellaneous UI components.
• assets/: The NFT assets including images and both on- and off-chain metadata.

To Do

1. Right now this handles the payment to the merchant and the minting of the NFT as two separate transactions. Ideally, this should be refactored to be a fully on-chain, atomic transaction that will automatically return funds to the customer in the event of a mint failure.

Additional Resources

• UI and Visual Assets have been shared via the Figma Community.