Module

Cardano.Transaction.Edit

According to the ledger spec, redeemers that are stored in a TransactionWitnessSet, contain pointers to various transaction parts. The pointers are just numbers corresponding to indices in arrays.

For example, a redeemer for spending a UTxO locked at a script address contains an index of the corresponding input of the transaction in the list of transaction body inputs.

This API is not very convenient for the developers, because of the need to keep the indices correct while modifying the transaction.

For example, if a new mint is added, all mint redeemer indices may have to be updated.

This module automates these updates by providing a better API for modifying transactions, that lets the developer abstract away from the indices.

The main functions are editTransaction and editTransactionSafe

#editTransaction 

editTransaction :: (Transaction -> Transaction) -> (Transaction -> Transaction)

Edit a transaction, ensuring proper handling of redeemers.

You can insert or delete inputs, certificates, mints or reward withdrawals: regardless of the changes, the redeemers will be re-indexed to point to the correct transaction components.

  • If you add any new redeemers and they point to the transaction components correctly, they are guaranteed to have correct indices in the output tx.

  • If some component that has a redeemer pointing to it is removed, the corresponding redeemer will be removed as well from the resulting transaction.

#editTransactionSafe 

editTransactionSafe :: (Transaction -> Transaction) -> (Transaction -> Either Redeemer Transaction)

Like editTransaction, but fails if:

  • the input transaction's redeemers have invalid index pointers
  • the resulting transaction's redeemers have invalid index pointers

The first problematic redeemer will be returned as error value.

#toEditableTransactionSafe 

toEditableTransactionSafe :: Transaction -> Either Redeemer EditableTransaction

Detach transaction redeemers. Removes redeemers from the witness set and places them alongside the transaction.

Fails if there are redeemers that do not point to anything.

#toEditableTransaction 

toEditableTransaction :: Transaction -> EditableTransaction

Detach transaction redeemers. Leaves invalid redeemers in the transaction's witness set, and places the valid ones alongside the transaction.

#fromEditableTransactionSafe 

fromEditableTransactionSafe :: EditableTransaction -> Maybe Transaction

Re-attach transaction redeemers. Fails if there are detached redeemers that are not valid (do not point to anything in the transaction).

#fromEditableTransaction 

fromEditableTransaction :: EditableTransaction -> Transaction

Re-attach transaction redeemers. Silently drops detached redeemers that are not valid.

#RedeemerPurpose 

data RedeemerPurpose

Contains a value some redeemer corresponds to.

Allows to find a redeemer index, given a transaction that contains the component the redeemer points to.

Constructors

Instances

#redeemerPurposeToRedeemerTag 

redeemerPurposeToRedeemerTag :: RedeemerPurpose -> RedeemerTag

Ignore the value that the redeemer points to and take just the tag.

#DetachedRedeemer 

type DetachedRedeemer = { datum :: RedeemerDatum, purpose :: RedeemerPurpose }

Redeemer that was detached from a transaction. Contains just enough info for it to be re-attached again, if a transaction needs a redeemer for some action.

#EditableTransaction 

type EditableTransaction = { redeemers :: Array DetachedRedeemer, transaction :: Transaction }

A transaction with redeemers detached.

#RedeemersContext 

type RedeemersContext = { certs :: Array Certificate, inputs :: Array TransactionInput, mintingPolicyHashes :: Array ScriptHash, proposals :: Array VotingProposal, rewardAddresses :: Array RewardAddress, voters :: Array Voter }

Contains parts of a transaction that are important for redeemer processing. Used to avoid re-computing.

Modules