refactor: add cctp prepare transfer tx request

Author: spsjvc

packages/arb-token-bridge-ui/src/token-bridge-sdk/BridgeTransferStarter.ts

@@ -1,6 +1,7 @@
 import { Provider, TransactionRequest } from '@ethersproject/providers'
 import { BigNumber, ContractTransaction, Signer } from 'ethers'
 import { Config } from 'wagmi'
+import { SimulateContractReturnType } from '@wagmi/core'
 
 import { MergedTransaction } from '../state/app/state'
 import {
@@ -58,6 +59,13 @@ export type TransferOverrides = {
   excessFeeRefundAddress?: string
 }
 
+export type TransferPrepareTxRequestProps = {
+  amount: BigNumber
+  from: string
+  destinationAddress?: string
+  overrides?: TransferOverrides
+}
+
 export type TransferProps = {
   amount: BigNumber
   signer: Signer
@@ -169,6 +177,16 @@ export abstract class BridgeTransferStarter {
     props: ApproveTokenProps
   ): Promise<ContractTransaction | void>
 
+  // not marking this as abstract for now, as we need a dummy implementation for every class
+  // only cctp is going to override it for now, and we'll do the same for others one by one
+  // finally, once we have all implementations we'll mark it as abstract
+  public async transferPrepareTxRequest(
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    props?: TransferPrepareTxRequestProps
+  ): Promise<TransactionRequest | SimulateContractReturnType['request']> {
+    return {} as TransactionRequest | SimulateContractReturnType['request']
+  }
+
   public abstract transferEstimateGas(
     props: TransferEstimateGasProps
   ): Promise<TransferEstimateGasResult>

packages/arb-token-bridge-ui/src/token-bridge-sdk/CctpTransferStarter.ts

@@ -1,4 +1,9 @@
-import { Config, simulateContract, writeContract } from '@wagmi/core'
+import {
+  Config,
+  simulateContract,
+  SimulateContractReturnType,
+  writeContract
+} from '@wagmi/core'
 import { BigNumber, constants, utils } from 'ethers'
 import { TransactionRequest } from '@ethersproject/providers'
 import { ERC20__factory } from '@arbitrum/sdk/dist/lib/abi/factories/ERC20__factory'
@@ -8,6 +13,7 @@ import {
   ApproveTokenProps,
   BridgeTransferStarter,
   RequiresTokenApprovalProps,
+  TransferPrepareTxRequestProps,
   TransferProps,
   TransferType
 } from './BridgeTransferStarter'
@@ -85,16 +91,14 @@ export class CctpTransferStarter extends BridgeTransferStarter {
     return undefined
   }
 
-  public async transfer({
-    signer,
+  public async transferPrepareTxRequest({
+    from,
     amount,
     destinationAddress,
     wagmiConfig
-  }: TransferProps & { wagmiConfig: Config }) {
+  }: TransferPrepareTxRequestProps & { wagmiConfig: Config }) {
     const sourceChainId = await this.getSourceChainId()
 
-    const address = await getAddressFromSigner(signer)
-
     // cctp has an upper limit for transfer
     const burnLimit = await fetchPerMessageBurnLimit({
       sourceChainId,
@@ -111,10 +115,8 @@ export class CctpTransferStarter extends BridgeTransferStarter {
       )
     }
 
-    const recipient = destinationAddress ?? address
-
+    const recipient = destinationAddress ?? from
     // burn token on the selected chain to be transferred from cctp contracts to the other chain
-
     // CCTP uses 32 bytes addresses, while EVEM uses 20 bytes addresses
     const mintRecipient = utils.hexlify(utils.zeroPad(recipient, 32)) as Address
 
@@ -138,6 +140,22 @@ export class CctpTransferStarter extends BridgeTransferStarter {
       ]
     })
 
+    return request as unknown as SimulateContractReturnType['request']
+  }
+
+  async transfer({
+    signer,
+    amount,
+    destinationAddress,
+    wagmiConfig
+  }: TransferProps & { wagmiConfig: Config }) {
+    const request = await this.transferPrepareTxRequest({
+      from: await getAddressFromSigner(signer),
+      amount,
+      destinationAddress,
+      wagmiConfig
+    })
+
     const depositForBurnTx = await writeContract(wagmiConfig, request)
 
     return {