feat: add withdrawal transaction functions

src/dlc-handlers/software-wallet-dlc-handler.ts

@@ -13,6 +13,7 @@ import {
 import {
   createClosingTransaction,
   createFundingTransaction,
+  createWithdrawalTransaction,
 } from '../functions/bitcoin/psbt-functions.js';
 import { PaymentInformation } from '../models/bitcoin-models.js';
 import { RawVault } from '../models/ethereum-models.js';
@@ -226,4 +227,41 @@ export class SoftwareWalletDLCHandler {
       throw new Error(`Error creating Closing PSBT: ${error}`);
     }
   }
+
+  async createWithdrawalPSBT(
+    vault: RawVault,
+    fundingTransactionID: string,
+    feeRateMultiplier?: number,
+    customFeeRate?: bigint
+  ): Promise<Transaction> {
+    try {
+      const { nativeSegwitPayment, taprootMultisigPayment } = this.getPayment();
+
+      if (
+        taprootMultisigPayment.address === undefined ||
+        nativeSegwitPayment.address === undefined
+      ) {
+        throw new Error('Payment Address is undefined');
+      }
+
+      const feeRate =
+        customFeeRate ??
+        BigInt(await getFeeRate(this.bitcoinBlockchainFeeRecommendationAPI, feeRateMultiplier));
+
+      const withdrawalTransaction = await createWithdrawalTransaction(
+        this.bitcoinBlockchainAPI,
+        vault.valueLocked.toBigInt(),
+        this.bitcoinNetwork,
+        fundingTransactionID,
+        taprootMultisigPayment,
+        nativeSegwitPayment.address!,
+        feeRate,
+        vault.btcFeeRecipient,
+        vault.btcRedeemFeeBasisPoints.toBigInt()
+      );
+      return Transaction.fromPSBT(withdrawalTransaction);
+    } catch (error: any) {
+      throw new Error(`Error creating Withdrawal PSBT: ${error}`);
+    }
+  }
 }

src/functions/bitcoin/psbt-functions.ts

@@ -12,6 +12,7 @@ import {
   getFeeRecipientAddressFromPublicKey,
   getUTXOs,
 } from '../bitcoin/bitcoin-functions.js';
+import { fetchBitcoinTransaction } from './bitcoin-request-functions.js';
 
 /**
  * Creates a Funding Transaction to fund the Multisig Transaction.
@@ -137,6 +138,96 @@ export function createClosingTransaction(
   return closingPSBT;
 }
 
+/**
+ * Creates the Closing Transaction.
+ * Uses the Funding Transaction's ID to create the Closing Transaction.
+ * The Closing Transaction is sent to the User's Native Segwit Address.
+ *
+ * @param bitcoinAmount - The Amount of Bitcoin to fund the Transaction with.
+ * @param bitcoinNetwork - The Bitcoin Network to use.
+ * @param fundingTransactionID - The ID of the Funding Transaction.
+ * @param multisigTransaction - The Multisig Transaction.
+ * @param userNativeSegwitAddress - The User's Native Segwit Address.
+ * @param feeRate - The Fee Rate to use for the Transaction.
+ * @param feePublicKey - The Fee Recipient's Public Key.
+ * @param feeBasisPoints - The Fee Basis Points.
+ * @returns The Closing Transaction.
+ */
+export async function createWithdrawalTransaction(
+  bitcoinBlockchainURL: string,
+  bitcoinAmount: bigint,
+  bitcoinNetwork: Network,
+  fundingTransactionID: string,
+  multisigTransaction: P2TROut,
+  userNativeSegwitAddress: string,
+  feeRate: bigint,
+  feePublicKey: string,
+  feeBasisPoints: bigint
+): Promise<Uint8Array> {
+  const multisigTransactionAddress = multisigTransaction.address;
+
+  if (!multisigTransactionAddress) {
+    throw new Error('Multisig Transaction is missing Address');
+  }
+  const fundingTransaction = await fetchBitcoinTransaction(
+    fundingTransactionID,
+    bitcoinBlockchainURL
+  );
+  const fundingTransactionOutputIndex = fundingTransaction.vout.findIndex(
+    output => output.scriptpubkey_address === multisigTransactionAddress
+  );
+
+  if (fundingTransactionOutputIndex === -1) {
+    throw new Error('Could not find Funding Transaction Output Index');
+  }
+
+  const feeAddress = getFeeRecipientAddressFromPublicKey(feePublicKey, bitcoinNetwork);
+  const feeAmount = getFeeAmount(Number(bitcoinAmount), Number(feeBasisPoints));
+
+  const inputs = [
+    {
+      txid: hexToBytes(fundingTransactionID),
+      index: fundingTransactionOutputIndex,
+      witnessUtxo: {
+        amount: bitcoinAmount,
+        script: multisigTransaction.script,
+      },
+      ...multisigTransaction,
+    },
+  ];
+
+  const outputs = [
+    {
+      address: feeAddress,
+      amount: BigInt(feeAmount),
+    },
+    {
+      address: userNativeSegwitAddress,
+      amount: BigInt(bitcoinAmount),
+    },
+  ];
+
+  const selected = selectUTXO(inputs, outputs, 'default', {
+    changeAddress: multisigTransactionAddress,
+    feePerByte: feeRate,
+    bip69: false,
+    createTx: true,
+    network: bitcoinNetwork,
+  });
+
+  const closingTX = selected?.tx;
+
+  if (!closingTX) throw new Error('Could not create Closing Transaction');
+
+  closingTX.updateInput(0, {
+    sequence: 0xfffffff0,
+  });
+
+  const closingPSBT = closingTX.toPSBT();
+
+  return closingPSBT;
+}
+
 /**
  * This function updates the PSBT with the necessary information to sign the inputs
  * that correspond to the given input signing configuration.