Taxation.ride

# This script allows to apply taxation models to assets
# Token owners can transfer it only if they pay taxes to the issuer
# The tax size is defined by token issuer in data transaction

{-# STDLIB_VERSION 2 #-}
{-# CONTENT_TYPE EXPRESSION #-}
{-# SCRIPT_TYPE ASSET #-}

match (tx) {
    # we allow only mass transfer transactions
    # first transfer in MassTransfer should always go to the issuer
    case mtt:MassTransferTransaction => {
        let firstRecipient = mtt.transfers[0].recipient
        let firstAmount = mtt.transfers[0].amount
        let assetId = extract(mtt.assetId)
        let issueTransaction = transactionById(assetId)

        # assetId equals to issue transaction id, so we can get issuer public key (and address) from the issue transaction
        match(issueTransaction) {
            case issueTx: IssueTransaction => {
                let issuerAddress = addressFromPublicKey(issueTx.senderPublicKey)
                # to set tax amount, issuer should make a data transaction with integer value by key matching assetId
                let taxSize = extract(getInteger(issuerAddress, toBase58String(assetId)))

                firstRecipient == issuerAddress # recipient for the first transfer should be the issuer address
                &&
                firstAmount >= mtt.totalAmount / 100 * taxSize # tax amount can't be less than defined in data transaction
            }
            case _ => false
        }
    }
    case _ => false
  }