aiken-auction

A naïve implementation of simple forward auction for Cardano blockchain in Aiken programming language. This is an education project for Emurgo Academy "Cardano Developer Professional" program.

This is a rewrite in Aiken of an educational project by Plutus Pioneer Program.

The original code is here: EnglishAuction.hs.

Protocol

Clients to this service want to sell their NFTs (sellers). They deposit their tokens to the script address, specifying time in the future when the auction should be closed. Other clients that are interested in that NFT (bidders) make bids by locking ADA values in the contract address. When the time period specified by seller is over, he can close the auction. When the seller closes auction, if there were bids then it receives the locked ADA and sends the lot to the last bidder, if not, he receives the lot back.

Let's call any eUTxO on the address of the smart contract lot.

Listing

To participate in the auction, seller issues a transaction with eUTxO to the contract address. This eUTxO should have exactly one token as its value and data of type LotDatum.

type Bid {
  bidOwner: VerificationKeyHash,
  value: Int,
}

type LotDatum {
  seller:     PubKeyHash,
  deadline:   PosixTime,
  minBid:     Int,
  currency:   PolicyId,
  token:      AssetName,
  highestBid: Option<Bid>,
}

The seller fileld should be the seller's public key hash. deadline is the time after which the auction should be losed minBid is minimal bid, currency and token specify the NFT locked by seller, highestBid is the last bid.

Bidding

When Bidder wants to make a bid, it issues a transaction that has the lot as an input, to the auction script address as an output. MakeBid constructor of type AuctionRedeemer should be specified as a redeemer. If is is not the first bid, the transaction should also return the locked value to the previous bidder.

type AuctionRedeemer {
  MakeBid(Bid)
  Close
}

Closing the auction

When the aution timeframe is over and no bids were made, seller should get its NFT back. If there were bids, he should send the locked NFT to the last bidder and receive the ADA locked by the last bidder.

Development

I don't like how aiken fmt works. So I disable formatting in vscode (.config/VSCodium/User/settings.json):

    "[aiken]": {
        "editor.formatOnSave": false,
        "editor.formatOnType": false
    }

flake.nix expects .secrets file in the flakes's directory. It should be a bash script exporting these variables:

• BLOCKFROST_PROJECT_ID: The project ID from Blockfrost.
• STATE_NODE_DIR: The directory where the state-node-preview directory located. cardano-node-preview script uses that directory to create the database and socket in it.
• WALLETS_DIR: The directory where wallets located. A wallet is a directory which name is the name of the wallet, see cli/functions.sh

To run cardano node on the preview net enter the nix development environment and start cardano-node-preview script in directory $STATE_NODE_DIR:

nix develop
cd "$STATE_NODE_DIR"
exec cardano-node-preview

Or you can run the script run-preview-node.sh provided by the flake.

UTXOs on the contract's addres can be inspected here: aiken-auction.deno.dev