AbstractBridge

AbstractBridge is an abstract class that provides a skeleton implementation for bridging assets between Layer 1 and Layer 2. It serves as a base class that contains common functionality shared across different bridge implementations.

This class implements the core bridging functionality such as:

• Token deposits from L1 to L2
• Token withdrawals from L2 to L1
• Withdrawal finalization on L1
• ERC20 token approval management
• Transaction validation and gas estimation

Abstract Methods

Concrete bridge implementations must define the following abstract methods:

getSecondBridgeDepositCalldata

Returns the deposit calldata for the second bridge.

Inputs

protected abstract getSecondBridgeDepositCalldata(
  transaction: IDepositTransaction
): Promise<string>;

populateWithdrawTransaction

Populates the withdraw transaction for the bridge.

Inputs

protected abstract populateWithdrawTransaction(
  transaction: IWithdrawTransaction
): Promise<TransactionLike>;

finalizeL1Deposit

Finalizes the L1 deposit.

Inputs

protected abstract finalizeL1Deposit(
  bridgeAddress: Address,
  finalizeParams: FinalizeL1DepositParams,
  overrides?: Overrides
): Promise<ContractTransactionResponse>;

checkIfWithdrawalIsFinalized

Checks if a withdrawal has been finalized on L1.

Inputs

protected abstract checkIfWithdrawalIsFinalized(
  bridgeAddress: Address,
  finalizeParams: FinalizeL1DepositParams
): Promise<boolean>;

Validation Hooks

The class provides optional validation hooks that can be overridden:

validateDepositParams

Validates deposit transaction parameters. The function is expected to throw an exception if the deposit parameters are not valid.

Inputs

protected async validateDepositParams(
  transaction: IDepositTransaction
): Promise<void>;

validateWithdrawParams

Validates withdrawal transaction parameters. The function is expected to throw an exception if the withdrawal parameters are not valid.

Inputs

protected async validateWithdrawParams(
  transaction: IWithdrawTransaction
): Promise<void>;

Complete Implementation Example

For a complete implementation example, see the USDCBridge class which extends AbstractBridge and implements all required abstract methods for USDC token bridging operations.