In its first version, Minswap order transactions require an embedded datum. This is quite common for Plutus v1 based AMM (Automated Market Maker) DEXes (Decentralized Exchanges).
Usually, in the context of Plutus v1, datum hashes are provided by the creator of new transaction outputs and the consumer of such output is required to provide the pre-image of the datum hash in order to spend it. But off-chain order batchers cannot know the order details since the pre-image has never been published on-chain. Hence, embedded datums offer a solution and allow output producers to include the pre-image of the datum hash as part of the transaction plutus witness set. This way, order outputs can be decoded, and inspected from on-chain data such so batchers can process them directly. DEXes that are using Plutus v2 can make use of inline datums CIP32.
The order datum type is open sourced together with the on-chain contract logic and can be found here.
data OrderDatum = OrderDatum
{ odSender :: Address,
odReceiver :: Address,
odReceiverDatumHash :: Maybe DatumHash,
odStep :: OrderStep,
odBatcherFee :: Integer,
odOutputADA :: Integer
}
deriving stock (Haskell.Show)
data OrderStep
= SwapExactIn
{ seiDesiredCoin :: AssetClass,
seiMinimumReceive :: Integer
}
| SwapExactOut
{ seoDesiredCoin :: AssetClass,
seoExpectedReceive :: Integer
}
-- other non relevant step variants
The redeemer represents an input to the plutus smart contract and often directly relates to a user's action. For Minswap, a redeemer can be of two types:
data OrderRedeemer = ApplyOrder | CancelOrder
The CancelOrder redeemer is callable by the owner of the order transaction, and ApplyOrder is used by batchers that process pending orders.