Abstract Chain

Contents

• Description
• Add New Chain
• Add New Network
• Chain Class Document
  • AbstractChain
  • AbstractUtxoChain
• Network Class Document
  • AbstractChainNetwork
  • AbstractUtxoChainNetwork

Description

Every blockchain supported by the guard-service in the bridge has some requirements that are defined in abstract classes and structures in this project.

AbstractChain is an abstract class containing all actions required by guard-service to support a blockchain in rosen-bridge. Each chain requires some actions to communicate with the blockchain APIs to get/send data from/to the blockchain. These actions are defined in AbstractChainNetwork and a single object of it will be initiated in AbstractChain constructor.

Since UTxO-based blockchains require some additional and common actions such as getting boxes (UTxOs), AbstractUtxoChain and AbstractUtxoChainNetwork class are provided too.

Add New Chain

Adding a new chain to the guard-service is being done in two steps and is independent of implementing a required network package.

The first step is to define an abstract network class inheriting AbstractChain (or AbstractUtxoChain if the blockchain is UTxO-based). Based on the implementation of chain class, some network functions may be added to this network class.

// Ergo is an UTxO-based blockchain, so class inherits `AbstractUtxoChainNetwork`
// Abstract<chain_name>Network
class AbstractErgoNetwork extends AbstractUtxoChainNetwork {
  ...
}

After defining network class, a chain class should be implemented, inheriting AbstractChain (or AbstractUtxoChain if the blockchain is UTxO-based) which implements all required functions. The functions will be explained in the Chain Class Document section. Any required actions found in this step which relates directly to the blockchain network should be added to the network class. Also network variable type should be declared as the network class type.

// Ergo is an UTxO-based blockchain, so class inherits `AbstractUtxoChain`
// <chain_name>Chain
class ErgoChain extends AbstractUtxoChain {
  declare network: ErgoNetwork;

  ...
}

Note that implementing chain class is independent of implementing its network class and only its definition is required.

Add New Network

Implementing a network class for a chain can proceed after an abstract network class is defined for that chain. In order to implement a new network, a class inheriting the chain's network class should be implemented. The functions will be explained in the Network Class Document section. Class name should contain both name of the chain and source of data. For example, in case of Ergo chain and adding a network class to communicate with Explorer, the class will be as follows:

// <chain_name><data_source>Network
class ErgoExplorerNetwork extends ErgoNetwork {
  ...
}

Note that network class should be developed in a separate package, independent of the chain package.

Chain Class Document

AbstractChain

Required functions are as follows:

• generatePaymentTransaction
  • generates unsigned PaymentTransaction for payment order
  • @param eventId the event id
  • @param txType transaction type
  • @param order the payment order (list of single payments)
  • @param unsignedTransactions ongoing unsigned PaymentTransactions which will be used to prevent double spending (gathered from database and guard TxAgreement process)
  • @param serializedSignedTransactions the serialized string of ongoing signed transactions which will be used for chaining transactions (gathered from database and mempool)
  • @returns the generated PaymentTransaction
• getTransactionAssets
  • gets input and output assets of a PaymentTransaction
  • @param transaction the PaymentTransaction
  • @returns an object containing the amount of input and output assets
• extractTransactionOrder
  • extracts payment order of a PaymentTransaction
  • @param transaction the PaymentTransaction
  • @returns the transaction payment order (list of single payments)
• verifyTransactionFee
  • verifies transaction fee for a PaymentTransaction
  • @param transaction the PaymentTransaction
  • @returns true if the transaction fee is verified
• verifyNoTokenBurned
  • verifies no token burned in a PaymentTransaction
  • @param transaction the PaymentTransaction
  • @returns true if no token burned
• verifyTransactionExtraConditions
  • verifies additional conditions for a PaymentTransaction
  • @param transaction the PaymentTransaction
  • @returns true if the transaction is verified
  • NOTE: This function is implemented in AbstractChain and will return true. In any chain that requires extra check to verify the transaction, this function should be overridden.
• verifyEvent
  • verifies an event data with its corresponding lock transaction
  • @param event the event trigger model
  • @param eventSerializedBox the serialized string of the event trigger box
  • @param feeConfig minimum fee and rsn ratio config for the event
  • @returns true if the event is verified
• isTxValid
  • checks if a transaction is still valid and can be sent to the network
  • @param transaction the transaction
  • @returns true if the transaction is still valid
• signTransaction
  • requests the corresponding signer service to sign the transaction
  • @param transaction the transaction
  • @param requiredSign the required number of sign
  • @returns the signed transaction
• getTxConfirmationStatus
  • extracts confirmation status for a transaction
  • @param transactionId the transaction id
  • @param transactionType type of the transaction
  • @returns the transaction confirmation status
• submitTransaction
  • submits a transaction to the blockchain
  • @param transaction the transaction
• isTxInMempool
  • checks if a transaction is in mempool (returns false if the chain has no mempool)
  • @param transactionId the transaction id
  • @returns true if the transaction is in mempool
• getMinimumNativeToken
  • gets the minimum amount of native token for transferring asset
  • @returns the minimum amount
• getRWTToken
  • gets the RWT token id
  • @returns the RWT token id
• PaymentTransactionFromJson
  • converts json representation of the payment transaction to PaymentTransaction
  • @param jsonString the json representation of the payment transaction
  • @returns PaymentTransaction object

AbstractUtxoChain

Required functions which only are needed in UTxO-based chains are as follows:

• getMempoolBoxMapping
  • generates mapping from input box id to serialized string of output box (filtered by address, containing the token)
  • @param address the address
  • @param tokenId the token id
  • @returns a Map from input box id to serialized string of output box
• getBoxInfo
  • extracts box id and assets of a box
  • @param serializedBox the serialized string of the box
  • @returns an object containing the box id and assets

Network Class Document

AbstractChainNetwork

Required functions are as follows:

• getHeight
  • gets the blockchain height
  • @returns the blockchain height
• getTxConfirmation
  • gets confirmation for a transaction or -1 if tx is not in the blockchain
  • @param transactionId the transaction id
  • @returns the transaction confirmation
• getAddressAssets
  • gets the amount of each asset in an address
  • @param address the address
  • @returns an object containing the amount of each asset
• getBlockTransactionIds
  • gets id of all transactions in the given block
  • @param blockId the block id
  • @returns list of the transaction ids in the block
• getBlockInfo
  • gets info of the given block
  • @param blockId the block id
  • @returns an object containing block info (hash, parent hash and height of the block)
• getTransaction
  • gets a transaction
  • @param transactionId the transaction id
  • @param blockId the block id
  • @returns the serialized string of the transaction
• submitTransaction
  • submits a transaction
  • @param transaction the transaction
• getMempoolTransactions
  • gets all transactions in mempool (returns empty list if the chain has no mempool)
  • @returns list of serialized string of the transactions in mempool

AbstractUtxoChainNetwork

Required functions that are only needed in UTxO-based chains are as follows:

• getAddressBoxes
  • gets confirmed and unspent boxes of an address
  • @param address the address
  • @param offset
  • @param limit
  • @returns list of serialized string of the boxes
• isBoxUnspentAndValid
  • checks if a box is still unspent and valid
  • @param boxId the box id
  • @returns true if the box is unspent and valid