From 45cea188f3a6dc0cddc0d1336428cfde0be12cbe Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 13:47:24 +0200
Subject: [PATCH 01/11] fix: existing tests with latest API versions

---
 sdk/test/esplora.test.ts     | 2 +-
 sdk/test/ordinal-api.test.ts | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sdk/test/esplora.test.ts b/sdk/test/esplora.test.ts
index 54347601..40d4d6b1 100644
--- a/sdk/test/esplora.test.ts
+++ b/sdk/test/esplora.test.ts
@@ -132,7 +132,7 @@ describe('Esplora Tests', () => {
     it('should get fee rate', async () => {
         const client = new EsploraClient('testnet');
         const feeRate = await client.getFeeEstimate(1);
-        assert.isAtLeast(feeRate, 1);
+        assert(feeRate > 0);
     });
 
     it('should get balance', async () => {
diff --git a/sdk/test/ordinal-api.test.ts b/sdk/test/ordinal-api.test.ts
index 52830321..67184f27 100644
--- a/sdk/test/ordinal-api.test.ts
+++ b/sdk/test/ordinal-api.test.ts
@@ -72,7 +72,7 @@ describe('Ordinal API Tests', () => {
         const expectedOutputJson: OutputJson = {
             value: 10737,
             script_pubkey:
-                'OP_PUSHNUM_1 OP_PUSHBYTES_32 e18a5367c5d11ee31d10bf4c53e743a7479c70e3336e70dbdea1fd927305c022',
+                '5120e18a5367c5d11ee31d10bf4c53e743a7479c70e3336e70dbdea1fd927305c022',
             address: 'bc1pux99xe796y0wx8gshax98e6r5arecu8rxdh8pk77587eyuc9cq3q2e3nng',
             transaction: 'dfe942a58b7e29a3952d8d1ed6608086c66475d20bc7bdbc3d784d616f9a6a7a',
             sat_ranges: null,

From 8027475946d181c84cb2cfc98b8f2c52a8b3b768 Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 13:47:47 +0200
Subject: [PATCH 02/11] chore: typo and formatting

---
 sdk/README.md | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sdk/README.md b/sdk/README.md
index adba5bba..ad3a8021 100644
--- a/sdk/README.md
+++ b/sdk/README.md
@@ -24,16 +24,19 @@ or
 npm i @gobob/bob-sdk
 ```
 
-## Building BOB sdk
+## Building BOB SDK
 
 ### Clone the repository
+
 Clone the repository and change to the `sdk` subfolder.
+
 ```shell
 git clone git@github.com:bob-collective/bob.git
 cd bob/sdk
 ```
 
 ### Install dependencies
+
 We use `pnpm` in the examples below. But the steps below should also work when using `yarn` or `npm` instead.
 
 ```shell

From 49796e17cd15b62026f3e4faa81d012564b1ebad Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 14:09:32 +0200
Subject: [PATCH 03/11] chore: use mainnet

---
 sdk/test/esplora.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/test/esplora.test.ts b/sdk/test/esplora.test.ts
index 40d4d6b1..58cc813f 100644
--- a/sdk/test/esplora.test.ts
+++ b/sdk/test/esplora.test.ts
@@ -130,7 +130,7 @@ describe('Esplora Tests', () => {
     });
 
     it('should get fee rate', async () => {
-        const client = new EsploraClient('testnet');
+        const client = new EsploraClient('mainnet');
         const feeRate = await client.getFeeEstimate(1);
         assert(feeRate > 0);
     });

From b13d56d184ed7358c464943b1c610a526e6f8094 Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 14:09:56 +0200
Subject: [PATCH 04/11] feat: add better fee estimation

---
 sdk/src/wallet/utxo.ts | 133 +++++++++++++++++++++++++++++++++++++++--
 sdk/test/utxo.test.ts  |  41 ++++++++++++-
 2 files changed, 167 insertions(+), 7 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index 7a882465..f2c8225d 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -39,6 +39,7 @@ export interface Input {
  * @param publicKey Optional public key needed if using P2SH-P2WPKH.
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
+ * @param utxoSelectionStrategy The strategy to use for selecting UTXOs. See https://github.com/paulmillr/scure-btc-signer/tree/main#utxo-selection for options.
  * @returns {Promise<string>} The Base64 encoded PSBT.
  */
 export async function createBitcoinPsbt(
@@ -47,11 +48,12 @@ export async function createBitcoinPsbt(
     amount: number,
     publicKey?: string,
     opReturnData?: string,
-    confirmationTarget: number = 3
+    confirmationTarget: number = 3,
+    utxoSelectionStrategy: string = 'default'
 ): Promise<string> {
     const addressInfo = getAddressInfo(fromAddress);
-    const network = addressInfo.network;
-    if (network === 'regtest') {
+
+    if (addressInfo.network === 'regtest') {
         throw new Error('Bitcoin regtest not supported');
     }
 
@@ -80,7 +82,7 @@ export async function createBitcoinPsbt(
         confirmedUtxos.map(async (utxo) => {
             const hex = await esploraClient.getTransactionHex(utxo.txid);
             const transaction = Transaction.fromRaw(Buffer.from(hex, 'hex'), { allowUnknownOutputs: true });
-            const input = getInputFromUtxoAndTx(network, utxo, transaction, addressInfo.type, publicKey);
+            const input = getInputFromUtxoAndTx(addressInfo.network, utxo, transaction, addressInfo.type, publicKey);
             possibleInputs.push(input);
         })
     );
@@ -108,12 +110,12 @@ export async function createBitcoinPsbt(
     // https://github.com/paulmillr/scure-btc-signer?tab=readme-ov-file#utxo-selection
     // default = exactBiggest/accumBiggest creates tx with smallest fees, but it breaks
     // big outputs to small ones, which in the end will create a lot of outputs close to dust.
-    const transaction = selectUTXO(possibleInputs, outputs, 'default', {
+    const transaction = selectUTXO(possibleInputs, outputs, utxoSelectionStrategy, {
         changeAddress: fromAddress, // Refund surplus to the payment address
         feePerByte: BigInt(Math.ceil(feeRate)), // round up to the nearest integer
         bip69: true, // Sort inputs and outputs according to BIP69
         createTx: true, // Create the transaction
-        network: getBtcNetwork(network),
+        network: getBtcNetwork(addressInfo.network),
         allowUnknownOutputs: true, // Required for OP_RETURN
         allowLegacyWitnessUtxo: true, // Required for P2SH-P2WPKH
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -179,3 +181,122 @@ export function getInputFromUtxoAndTx(
 
     return input;
 }
+
+
+/**
+ * Estimate the tx inclusion fee for a given address or public key with an optional OP_RETURN output.
+ *
+ * @param fromAddress The Bitcoin address which is sending to the `toAddress`.
+ * @param amount The amount of BTC (as satoshis) to send. If no amount is specified, the fee is estimated for all UTXOs, i.e., the max amount.
+ * @param publicKey Optional public key needed if using P2SH-P2WPKH.
+ * @param opReturnData Optional OP_RETURN data to include in an output.
+ * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
+ * @param utxoSelectionStrategy The strategy to use for selecting UTXOs. See https://github.com/paulmillr/scure-btc-signer/tree/main#utxo-selection for options.
+ * @returns {Promise<number>} The fee amount for estiamted transaction inclusion in satoshis.
+ * 
+ * @dev Wtih no amount set, we estimate the fee for all UTXOs by trying to spend all inputs using strategy 'all'. If an amount is set, we use the 'default
+ * strategy to select the UTXOs.
+ */
+export async function estimateTxFee(
+    fromAddress: string,
+    amount?: number,
+    publicKey?: string,
+    opReturnData?: string,
+    confirmationTarget: number = 3,
+    utxoSelectionStrategy: string = 'default'
+): Promise<number> {
+    const addressInfo = getAddressInfo(fromAddress);
+
+    if (addressInfo.network === 'regtest') {
+        throw new Error('Bitcoin regtest not supported');
+    }
+
+    // We need the public key to generate the redeem and witness script to spend the scripts
+    if (addressInfo.type === (AddressType.p2sh || AddressType.p2wsh)) {
+        if (!publicKey) {
+            throw new Error('Public key is required to spend from the selected address type');
+        }
+    }
+
+    // Use the from address as the toAddress for the fee estimate
+    const toAddress = fromAddress;
+
+    // TODO: allow submitting the UTXOs, fee estimate and confirmed transactions
+    const esploraClient = new EsploraClient(addressInfo.network);
+
+    const [confirmedUtxos, feeRate] = await Promise.all([
+        esploraClient.getAddressUtxos(fromAddress),
+        esploraClient.getFeeEstimate(confirmationTarget),
+    ]);
+
+    if (confirmedUtxos.length === 0) {
+        throw new Error('No confirmed UTXOs');
+    }
+
+    // To construct the spending transaction and estimate the fee, we need the transactions for the UTXOs
+    const possibleInputs: Input[] = [];
+
+    await Promise.all(
+        confirmedUtxos.map(async (utxo) => {
+            const hex = await esploraClient.getTransactionHex(utxo.txid);
+            const transaction = Transaction.fromRaw(Buffer.from(hex, 'hex'), { allowUnknownOutputs: true });
+            const input = getInputFromUtxoAndTx(addressInfo.network, utxo, transaction, addressInfo.type, publicKey);
+            possibleInputs.push(input);
+        })
+    );
+
+    // Create transaction without outputs
+    const targetOutputs: Output[] = [
+        {
+            address: toAddress,
+            amount: BigInt(amount? amount : 0),
+        },
+    ];
+
+    if (opReturnData) {
+        // Strip 0x prefix from opReturn
+        if (opReturnData.startsWith('0x')) {
+            opReturnData = opReturnData.slice(2);
+        }
+        targetOutputs.push({
+            // OP_RETURN https://github.com/paulmillr/scure-btc-signer/issues/26
+            script: Script.encode(['RETURN', hex.decode(opReturnData)]),
+            amount: BigInt(0),
+        });
+    }
+
+    let outputs: Output[] = [];
+    if (amount === undefined) {
+        // Select all UTXOs if no amount is specified
+        // Add outputs to the transaction after all UTXOs are selected to prevent tx creation failures
+        utxoSelectionStrategy = 'all';
+    } else {
+        // Add the target outputs to the transaction
+        // Tx creation might fail if the requested amount is more than the available balance plus fees
+        outputs = targetOutputs;
+    }
+
+    // Outsource UTXO selection to btc-signer
+    // https://github.com/paulmillr/scure-btc-signer?tab=readme-ov-file#utxo-selection
+    // default = exactBiggest/accumBiggest creates tx with smallest fees, but it breaks
+    // big outputs to small ones, which in the end will create a lot of outputs close to dust.
+    const transaction = selectUTXO(possibleInputs, outputs, utxoSelectionStrategy, {
+        changeAddress: fromAddress, // Refund surplus to the payment address
+        feePerByte: BigInt(Math.ceil(feeRate)), // round up to the nearest integer
+        bip69: true, // Sort inputs and outputs according to BIP69
+        createTx: true, // Create the transaction
+        network: getBtcNetwork(addressInfo.network),
+        allowUnknownOutputs: true, // Required for OP_RETURN
+        allowLegacyWitnessUtxo: true, // Required for P2SH-P2WPKH
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        dust: BigInt(546) as any, // TODO: update scure-btc-signer
+    });
+    
+    // Add the target outputs after the fact
+    if (amount === undefined) {
+        transaction.tx.addOutput(targetOutputs[0]);
+        transaction.tx.addOutput(targetOutputs[1]);
+    }
+
+    return transaction.fee;
+}
\ No newline at end of file
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index 95b1e6f4..0ff94c9b 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -2,7 +2,7 @@ import { describe, it, assert } from 'vitest';
 import { AddressType, getAddressInfo, Network } from 'bitcoin-address-validation';
 import { Address, NETWORK, OutScript, Script, Transaction, p2sh, p2wpkh, selectUTXO } from '@scure/btc-signer';
 import { hex, base64 } from '@scure/base';
-import { createBitcoinPsbt, getInputFromUtxoAndTx } from '../src/wallet/utxo';
+import { createBitcoinPsbt, getInputFromUtxoAndTx, estimateTxFee } from '../src/wallet/utxo';
 import { TransactionOutput } from '@scure/btc-signer/psbt';
 
 // TODO: Add more tests using https://github.com/paulmillr/scure-btc-signer/tree/5ead71ea9a873d8ba1882a9cd6aa561ad410d0d1/test/bitcoinjs-test/fixtures/bitcoinjs
@@ -49,6 +49,8 @@ describe('UTXO Tests', () => {
                             // Use a random public key for P2SH-P2WPKH
                             pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
                         }
+                        // Note: it is possible that the above addresses have spent all of their funds
+                        // and the transaction will fail.
                         const psbtBase64 = await createBitcoinPsbt(paymentAddress, toAddress, amount, pubkey, opReturn);
                         const transaction = Transaction.fromPSBT(base64.decode(psbtBase64));
 
@@ -258,4 +260,41 @@ describe('UTXO Tests', () => {
 
         assert.isDefined(transaction);
     });
+
+    it('should estimate the fee for a transaction', async () => {
+        // Addresses where randomly picked from blockstream.info
+        const paymentAddresses = [
+            // P2WPKH: https://blockstream.info/address/bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq
+            'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq',
+            // P2SH-P2WPKH: https://blockstream.info/address/3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr
+            '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
+            // P2PKH: https://blockstream.info/address/1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g
+            '1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g',
+        ];
+
+        const amounts = [undefined, 2000, 3000];
+
+        // EVM address for OP return
+        let opReturn = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2';
+
+        // Refactor to execute in parallel
+        await Promise.all(
+            amounts.map(async (amount) => Promise.all(
+                paymentAddresses.map(async (paymentAddress) => {
+                    const paymentAddressType = getAddressInfo(paymentAddress).type;
+
+                    let pubkey: string | undefined;
+
+                    if (paymentAddressType === AddressType.p2sh) {
+                        // Use a random public key for P2SH-P2WPKH
+                        pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
+                    }
+
+                    // If the amount is undefined, the fee should be estimated
+                    const fee = await estimateTxFee(paymentAddress, undefined, pubkey, opReturn);
+                    assert(fee > 0, 'Fee should be greater than 0');
+                }
+            )
+        )))
+    });
 });

From a4540ca689a033d4bd40dd77e5fa44464e1c883b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rui=20Sim=C3=A3o?= <rui.daniel.simao@gmail.com>
Date: Mon, 14 Oct 2024 13:28:47 +0100
Subject: [PATCH 05/11] fix(sdk): types

---
 sdk/src/wallet/utxo.ts       | 34 +++++++++++++++++++++++-----------
 sdk/test/ordinal-api.test.ts |  3 +--
 sdk/test/utxo.test.ts        | 32 +++++++++++++++++---------------
 3 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index f2c8225d..81288470 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -2,6 +2,7 @@ import { Transaction, Script, selectUTXO, TEST_NETWORK, NETWORK, p2wpkh, p2sh }
 import { hex, base64 } from '@scure/base';
 import { AddressType, getAddressInfo, Network } from 'bitcoin-address-validation';
 import { EsploraClient, UTXO } from '../esplora';
+import { SelectionStrategy } from '@scure/btc-signer/lib/utxo';
 
 export type BitcoinNetworkName = Exclude<Network, 'regtest'>;
 
@@ -49,7 +50,7 @@ export async function createBitcoinPsbt(
     publicKey?: string,
     opReturnData?: string,
     confirmationTarget: number = 3,
-    utxoSelectionStrategy: string = 'default'
+    utxoSelectionStrategy: SelectionStrategy = 'default'
 ): Promise<string> {
     const addressInfo = getAddressInfo(fromAddress);
 
@@ -82,7 +83,13 @@ export async function createBitcoinPsbt(
         confirmedUtxos.map(async (utxo) => {
             const hex = await esploraClient.getTransactionHex(utxo.txid);
             const transaction = Transaction.fromRaw(Buffer.from(hex, 'hex'), { allowUnknownOutputs: true });
-            const input = getInputFromUtxoAndTx(addressInfo.network, utxo, transaction, addressInfo.type, publicKey);
+            const input = getInputFromUtxoAndTx(
+                addressInfo.network as BitcoinNetworkName,
+                utxo,
+                transaction,
+                addressInfo.type,
+                publicKey
+            );
             possibleInputs.push(input);
         })
     );
@@ -182,7 +189,6 @@ export function getInputFromUtxoAndTx(
     return input;
 }
 
-
 /**
  * Estimate the tx inclusion fee for a given address or public key with an optional OP_RETURN output.
  *
@@ -192,8 +198,8 @@ export function getInputFromUtxoAndTx(
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
  * @param utxoSelectionStrategy The strategy to use for selecting UTXOs. See https://github.com/paulmillr/scure-btc-signer/tree/main#utxo-selection for options.
- * @returns {Promise<number>} The fee amount for estiamted transaction inclusion in satoshis.
- * 
+ * @returns {Promise<bigint>} The fee amount for estiamted transaction inclusion in satoshis.
+ *
  * @dev Wtih no amount set, we estimate the fee for all UTXOs by trying to spend all inputs using strategy 'all'. If an amount is set, we use the 'default
  * strategy to select the UTXOs.
  */
@@ -203,8 +209,8 @@ export async function estimateTxFee(
     publicKey?: string,
     opReturnData?: string,
     confirmationTarget: number = 3,
-    utxoSelectionStrategy: string = 'default'
-): Promise<number> {
+    utxoSelectionStrategy: SelectionStrategy = 'default'
+): Promise<bigint> {
     const addressInfo = getAddressInfo(fromAddress);
 
     if (addressInfo.network === 'regtest') {
@@ -240,7 +246,13 @@ export async function estimateTxFee(
         confirmedUtxos.map(async (utxo) => {
             const hex = await esploraClient.getTransactionHex(utxo.txid);
             const transaction = Transaction.fromRaw(Buffer.from(hex, 'hex'), { allowUnknownOutputs: true });
-            const input = getInputFromUtxoAndTx(addressInfo.network, utxo, transaction, addressInfo.type, publicKey);
+            const input = getInputFromUtxoAndTx(
+                addressInfo.network as BitcoinNetworkName,
+                utxo,
+                transaction,
+                addressInfo.type,
+                publicKey
+            );
             possibleInputs.push(input);
         })
     );
@@ -249,7 +261,7 @@ export async function estimateTxFee(
     const targetOutputs: Output[] = [
         {
             address: toAddress,
-            amount: BigInt(amount? amount : 0),
+            amount: BigInt(amount ? amount : 0),
         },
     ];
 
@@ -291,7 +303,7 @@ export async function estimateTxFee(
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         dust: BigInt(546) as any, // TODO: update scure-btc-signer
     });
-    
+
     // Add the target outputs after the fact
     if (amount === undefined) {
         transaction.tx.addOutput(targetOutputs[0]);
@@ -299,4 +311,4 @@ export async function estimateTxFee(
     }
 
     return transaction.fee;
-}
\ No newline at end of file
+}
diff --git a/sdk/test/ordinal-api.test.ts b/sdk/test/ordinal-api.test.ts
index 67184f27..b9726174 100644
--- a/sdk/test/ordinal-api.test.ts
+++ b/sdk/test/ordinal-api.test.ts
@@ -71,8 +71,7 @@ describe('Ordinal API Tests', () => {
         });
         const expectedOutputJson: OutputJson = {
             value: 10737,
-            script_pubkey:
-                '5120e18a5367c5d11ee31d10bf4c53e743a7479c70e3336e70dbdea1fd927305c022',
+            script_pubkey: '5120e18a5367c5d11ee31d10bf4c53e743a7479c70e3336e70dbdea1fd927305c022',
             address: 'bc1pux99xe796y0wx8gshax98e6r5arecu8rxdh8pk77587eyuc9cq3q2e3nng',
             transaction: 'dfe942a58b7e29a3952d8d1ed6608086c66475d20bc7bdbc3d784d616f9a6a7a',
             sat_ranges: null,
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index 0ff94c9b..ab8b278b 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -62,7 +62,7 @@ describe('UTXO Tests', () => {
                         // Get all outputs and add them to array
                         const outputs: TransactionOutput[] = [];
 
-                        for (var i = 0; i < transaction.outputsLength; i++) {
+                        for (let i = 0; i < transaction.outputsLength; i++) {
                             const output = transaction.getOutput(i);
 
                             outputs.push(output);
@@ -275,26 +275,28 @@ describe('UTXO Tests', () => {
         const amounts = [undefined, 2000, 3000];
 
         // EVM address for OP return
-        let opReturn = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2';
+        const opReturn = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2';
 
         // Refactor to execute in parallel
         await Promise.all(
-            amounts.map(async (amount) => Promise.all(
-                paymentAddresses.map(async (paymentAddress) => {
-                    const paymentAddressType = getAddressInfo(paymentAddress).type;
+            amounts.map(async () =>
+                Promise.all(
+                    paymentAddresses.map(async (paymentAddress) => {
+                        const paymentAddressType = getAddressInfo(paymentAddress).type;
 
-                    let pubkey: string | undefined;
+                        let pubkey: string | undefined;
 
-                    if (paymentAddressType === AddressType.p2sh) {
-                        // Use a random public key for P2SH-P2WPKH
-                        pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
-                    }
+                        if (paymentAddressType === AddressType.p2sh) {
+                            // Use a random public key for P2SH-P2WPKH
+                            pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
+                        }
 
-                    // If the amount is undefined, the fee should be estimated
-                    const fee = await estimateTxFee(paymentAddress, undefined, pubkey, opReturn);
-                    assert(fee > 0, 'Fee should be greater than 0');
-                }
+                        // If the amount is undefined, the fee should be estimated
+                        const fee = await estimateTxFee(paymentAddress, undefined, pubkey, opReturn);
+                        assert(fee > 0, 'Fee should be greater than 0');
+                    })
+                )
             )
-        )))
+        );
     });
 });

From bcc5711391db7310695f4dc919f7524350bf6e28 Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 15:05:52 +0200
Subject: [PATCH 06/11] refactor: remove the utxo selection strategy argument

---
 sdk/src/wallet/utxo.ts | 19 ++++++++++++-------
 sdk/test/utxo.test.ts  |  4 +++-
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index 81288470..16440dda 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -50,10 +50,12 @@ export async function createBitcoinPsbt(
     publicKey?: string,
     opReturnData?: string,
     confirmationTarget: number = 3,
-    utxoSelectionStrategy: SelectionStrategy = 'default'
 ): Promise<string> {
     const addressInfo = getAddressInfo(fromAddress);
 
+    // TODO: possibly, allow other strategies to be passed to this function
+    const utxoSelectionStrategy: SelectionStrategy = 'default';
+
     if (addressInfo.network === 'regtest') {
         throw new Error('Bitcoin regtest not supported');
     }
@@ -130,6 +132,8 @@ export async function createBitcoinPsbt(
     });
 
     if (!transaction || !transaction.tx) {
+        console.debug(`fromAddress: ${fromAddress}, toAddress: ${toAddress}, amount: ${amount}`);
+        console.debug(`publicKey: ${publicKey}, opReturnData: ${opReturnData}`);
         throw new Error('Failed to create transaction. Do you have enough funds?');
     }
 
@@ -209,7 +213,6 @@ export async function estimateTxFee(
     publicKey?: string,
     opReturnData?: string,
     confirmationTarget: number = 3,
-    utxoSelectionStrategy: SelectionStrategy = 'default'
 ): Promise<bigint> {
     const addressInfo = getAddressInfo(fromAddress);
 
@@ -228,6 +231,7 @@ export async function estimateTxFee(
     const toAddress = fromAddress;
 
     // TODO: allow submitting the UTXOs, fee estimate and confirmed transactions
+    // to avoid fetching them again.
     const esploraClient = new EsploraClient(addressInfo.network);
 
     const [confirmedUtxos, feeRate] = await Promise.all([
@@ -278,13 +282,14 @@ export async function estimateTxFee(
     }
 
     let outputs: Output[] = [];
-    if (amount === undefined) {
-        // Select all UTXOs if no amount is specified
-        // Add outputs to the transaction after all UTXOs are selected to prevent tx creation failures
-        utxoSelectionStrategy = 'all';
-    } else {
+    // Select all UTXOs if no amount is specified
+    // Add outputs to the transaction after all UTXOs are selected to prevent tx creation failures
+    let utxoSelectionStrategy: SelectionStrategy = 'all';
+    if (amount) {
         // Add the target outputs to the transaction
         // Tx creation might fail if the requested amount is more than the available balance plus fees
+        // TODO: allow passing other UTXO selection strategies for fee etimates
+        utxoSelectionStrategy = 'default';
         outputs = targetOutputs;
     }
 
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index ab8b278b..af7ec53d 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -14,7 +14,9 @@ describe('UTXO Tests', () => {
             // P2WPKH: https://blockstream.info/address/bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq
             'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq',
             // P2SH-P2WPKH: https://blockstream.info/address/3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr
-            '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
+            // TODO: Use a real P2SH-P2WPKH address
+            // TODO: Add the pubkey to allow spending from the outputs 
+            // '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
             // P2PKH: https://blockstream.info/address/1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g
             '1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g',
         ];

From 4681435ee9a21352ba617882114153e011de1159 Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 15:10:32 +0200
Subject: [PATCH 07/11] docs: add examples

---
 sdk/src/wallet/utxo.ts | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index 16440dda..decfa863 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -40,8 +40,22 @@ export interface Input {
  * @param publicKey Optional public key needed if using P2SH-P2WPKH.
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
- * @param utxoSelectionStrategy The strategy to use for selecting UTXOs. See https://github.com/paulmillr/scure-btc-signer/tree/main#utxo-selection for options.
  * @returns {Promise<string>} The Base64 encoded PSBT.
+ * 
+ * @example
+ * ```typescript
+ * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
+ * const toAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
+ * const amount = 100000;
+ * const publicKey = '02d4...`; // only for P2SH
+ * const opReturnData = 'Hello, World!'; // optional
+ * const confirmationTarget = 3; // optional
+ * 
+ * const psbt = await createBitcoinPsbt(fromAddress, toAddress, amount, publicKey, opReturnData, confirmationTarget);
+ * console.log(psbt);
+ * 
+ * // The PSBT can then be signed with the private key using sats-wagmi, sats-connect, ...
+ * ```
  */
 export async function createBitcoinPsbt(
     fromAddress: string,
@@ -201,8 +215,29 @@ export function getInputFromUtxoAndTx(
  * @param publicKey Optional public key needed if using P2SH-P2WPKH.
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
- * @param utxoSelectionStrategy The strategy to use for selecting UTXOs. See https://github.com/paulmillr/scure-btc-signer/tree/main#utxo-selection for options.
  * @returns {Promise<bigint>} The fee amount for estiamted transaction inclusion in satoshis.
+ * 
+ * @example
+ * ```typescript
+ * // Using a target amount (call might fail if amount is larger than balance plus fees)
+ * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
+ * const amount = 100000;
+ * const publicKey = '02d4...`; // only for P2SH
+ * const opReturnData = 'Hello, World!'; // optional
+ * const confirmationTarget = 3; // optional
+ * 
+ * const fee = await estimateTxFee(fromAddress, amount, publicKey, opReturnData, confirmationTarget);
+ * console.log(fee);
+ * 
+ * // Using all UTXOs without a target amount (max fee for spending all UTXOs)
+ * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
+ * const publicKey = '02d4...`; // only for P2SH
+ * const opReturnData = 'Hello, World!'; // optional
+ * const confirmationTarget = 3; // optional
+ * 
+ * const fee = await estimateTxFee(fromAddress, undefined, publicKey, opReturnData, confirmationTarget);
+ * console.log(fee);
+ * ```
  *
  * @dev Wtih no amount set, we estimate the fee for all UTXOs by trying to spend all inputs using strategy 'all'. If an amount is set, we use the 'default
  * strategy to select the UTXOs.

From 3ef5ec3a9ac936d4440e9e501e15649e15bfaa3c Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 15:11:44 +0200
Subject: [PATCH 08/11] chore: linting

---
 sdk/src/wallet/utxo.ts | 18 +++++++++---------
 sdk/test/utxo.test.ts  |  2 +-
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index decfa863..8d289635 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -41,7 +41,7 @@ export interface Input {
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
  * @returns {Promise<string>} The Base64 encoded PSBT.
- * 
+ *
  * @example
  * ```typescript
  * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
@@ -50,10 +50,10 @@ export interface Input {
  * const publicKey = '02d4...`; // only for P2SH
  * const opReturnData = 'Hello, World!'; // optional
  * const confirmationTarget = 3; // optional
- * 
+ *
  * const psbt = await createBitcoinPsbt(fromAddress, toAddress, amount, publicKey, opReturnData, confirmationTarget);
  * console.log(psbt);
- * 
+ *
  * // The PSBT can then be signed with the private key using sats-wagmi, sats-connect, ...
  * ```
  */
@@ -63,7 +63,7 @@ export async function createBitcoinPsbt(
     amount: number,
     publicKey?: string,
     opReturnData?: string,
-    confirmationTarget: number = 3,
+    confirmationTarget: number = 3
 ): Promise<string> {
     const addressInfo = getAddressInfo(fromAddress);
 
@@ -216,7 +216,7 @@ export function getInputFromUtxoAndTx(
  * @param opReturnData Optional OP_RETURN data to include in an output.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
  * @returns {Promise<bigint>} The fee amount for estiamted transaction inclusion in satoshis.
- * 
+ *
  * @example
  * ```typescript
  * // Using a target amount (call might fail if amount is larger than balance plus fees)
@@ -225,16 +225,16 @@ export function getInputFromUtxoAndTx(
  * const publicKey = '02d4...`; // only for P2SH
  * const opReturnData = 'Hello, World!'; // optional
  * const confirmationTarget = 3; // optional
- * 
+ *
  * const fee = await estimateTxFee(fromAddress, amount, publicKey, opReturnData, confirmationTarget);
  * console.log(fee);
- * 
+ *
  * // Using all UTXOs without a target amount (max fee for spending all UTXOs)
  * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
  * const publicKey = '02d4...`; // only for P2SH
  * const opReturnData = 'Hello, World!'; // optional
  * const confirmationTarget = 3; // optional
- * 
+ *
  * const fee = await estimateTxFee(fromAddress, undefined, publicKey, opReturnData, confirmationTarget);
  * console.log(fee);
  * ```
@@ -247,7 +247,7 @@ export async function estimateTxFee(
     amount?: number,
     publicKey?: string,
     opReturnData?: string,
-    confirmationTarget: number = 3,
+    confirmationTarget: number = 3
 ): Promise<bigint> {
     const addressInfo = getAddressInfo(fromAddress);
 
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index af7ec53d..799e0e3a 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -15,7 +15,7 @@ describe('UTXO Tests', () => {
             'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq',
             // P2SH-P2WPKH: https://blockstream.info/address/3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr
             // TODO: Use a real P2SH-P2WPKH address
-            // TODO: Add the pubkey to allow spending from the outputs 
+            // TODO: Add the pubkey to allow spending from the outputs
             // '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
             // P2PKH: https://blockstream.info/address/1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g
             '1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g',

From 6c4008408a7f6cd9019c3717f7a26f74f81b1dee Mon Sep 17 00:00:00 2001
From: Dominik Harz <dominik.harz@gmail.com>
Date: Mon, 14 Oct 2024 15:27:57 +0200
Subject: [PATCH 09/11] feat: allow passing the fee per byte as a parameter

---
 sdk/src/wallet/utxo.ts | 48 +++++++++++++++++++++++++++++++-----------
 sdk/test/utxo.test.ts  | 38 +++++++++++++++++++--------------
 2 files changed, 58 insertions(+), 28 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index 8d289635..f14ac3ba 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -39,6 +39,7 @@ export interface Input {
  * @param amount The amount of BTC (as satoshis) to send.
  * @param publicKey Optional public key needed if using P2SH-P2WPKH.
  * @param opReturnData Optional OP_RETURN data to include in an output.
+ * @param feeRate Optional fee rate in satoshis per byte.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
  * @returns {Promise<string>} The Base64 encoded PSBT.
  *
@@ -63,6 +64,7 @@ export async function createBitcoinPsbt(
     amount: number,
     publicKey?: string,
     opReturnData?: string,
+    feeRate?: number,
     confirmationTarget: number = 3
 ): Promise<string> {
     const addressInfo = getAddressInfo(fromAddress);
@@ -83,10 +85,16 @@ export async function createBitcoinPsbt(
 
     const esploraClient = new EsploraClient(addressInfo.network);
 
-    const [confirmedUtxos, feeRate] = await Promise.all([
-        esploraClient.getAddressUtxos(fromAddress),
-        esploraClient.getFeeEstimate(confirmationTarget),
-    ]);
+    let confirmedUtxos: UTXO[] = [];
+
+    if (feeRate) {
+        confirmedUtxos = await esploraClient.getAddressUtxos(fromAddress);
+    } else {
+        [confirmedUtxos, feeRate] = await Promise.all([
+            esploraClient.getAddressUtxos(fromAddress),
+            esploraClient.getFeeEstimate(confirmationTarget),
+        ]);
+    }
 
     if (confirmedUtxos.length === 0) {
         throw new Error('No confirmed UTXOs');
@@ -148,6 +156,7 @@ export async function createBitcoinPsbt(
     if (!transaction || !transaction.tx) {
         console.debug(`fromAddress: ${fromAddress}, toAddress: ${toAddress}, amount: ${amount}`);
         console.debug(`publicKey: ${publicKey}, opReturnData: ${opReturnData}`);
+        console.debug(`feeRate: ${feeRate}, confirmationTarget: ${confirmationTarget}`);
         throw new Error('Failed to create transaction. Do you have enough funds?');
     }
 
@@ -214,8 +223,9 @@ export function getInputFromUtxoAndTx(
  * @param amount The amount of BTC (as satoshis) to send. If no amount is specified, the fee is estimated for all UTXOs, i.e., the max amount.
  * @param publicKey Optional public key needed if using P2SH-P2WPKH.
  * @param opReturnData Optional OP_RETURN data to include in an output.
+ * @param feeRate Optional fee rate in satoshis per byte.
  * @param confirmationTarget The number of blocks to include this tx (for fee estimation).
- * @returns {Promise<bigint>} The fee amount for estiamted transaction inclusion in satoshis.
+ * @returns {Promise<bigint>} The fee amount for estimated transaction inclusion in satoshis.
  *
  * @example
  * ```typescript
@@ -224,18 +234,19 @@ export function getInputFromUtxoAndTx(
  * const amount = 100000;
  * const publicKey = '02d4...`; // only for P2SH
  * const opReturnData = 'Hello, World!'; // optional
+ * const feeRate = 1; // optional
  * const confirmationTarget = 3; // optional
  *
- * const fee = await estimateTxFee(fromAddress, amount, publicKey, opReturnData, confirmationTarget);
+ * const fee = await estimateTxFee(fromAddress, amount, publicKey, opReturnData, feeRate, confirmationTarget);
  * console.log(fee);
  *
  * // Using all UTXOs without a target amount (max fee for spending all UTXOs)
  * const fromAddress = 'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq';
  * const publicKey = '02d4...`; // only for P2SH
  * const opReturnData = 'Hello, World!'; // optional
- * const confirmationTarget = 3; // optional
+ * const feeRate = 1; // optional
  *
- * const fee = await estimateTxFee(fromAddress, undefined, publicKey, opReturnData, confirmationTarget);
+ * const fee = await estimateTxFee(fromAddress, undefined, publicKey, opReturnData, feeRate);
  * console.log(fee);
  * ```
  *
@@ -247,6 +258,7 @@ export async function estimateTxFee(
     amount?: number,
     publicKey?: string,
     opReturnData?: string,
+    feeRate?: number,
     confirmationTarget: number = 3
 ): Promise<bigint> {
     const addressInfo = getAddressInfo(fromAddress);
@@ -269,10 +281,15 @@ export async function estimateTxFee(
     // to avoid fetching them again.
     const esploraClient = new EsploraClient(addressInfo.network);
 
-    const [confirmedUtxos, feeRate] = await Promise.all([
-        esploraClient.getAddressUtxos(fromAddress),
-        esploraClient.getFeeEstimate(confirmationTarget),
-    ]);
+    let confirmedUtxos: UTXO[] = [];
+    if (feeRate) {
+        confirmedUtxos = await esploraClient.getAddressUtxos(fromAddress);
+    } else {
+        [confirmedUtxos, feeRate] = await Promise.all([
+            esploraClient.getAddressUtxos(fromAddress),
+            esploraClient.getFeeEstimate(confirmationTarget),
+        ]);
+    }
 
     if (confirmedUtxos.length === 0) {
         throw new Error('No confirmed UTXOs');
@@ -344,6 +361,13 @@ export async function estimateTxFee(
         dust: BigInt(546) as any, // TODO: update scure-btc-signer
     });
 
+    if (!transaction || !transaction.tx) {
+        console.debug(`fromAddress: ${fromAddress}, amount: ${amount}`);
+        console.debug(`publicKey: ${publicKey}, opReturnData: ${opReturnData}`);
+        console.debug(`feeRate: ${feeRate}, confirmationTarget: ${confirmationTarget}`);
+        throw new Error('Failed to create transaction. Do you have enough funds?');
+    }
+
     // Add the target outputs after the fact
     if (amount === undefined) {
         transaction.tx.addOutput(targetOutputs[0]);
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index 799e0e3a..44a621b7 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -269,34 +269,40 @@ describe('UTXO Tests', () => {
             // P2WPKH: https://blockstream.info/address/bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq
             'bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq',
             // P2SH-P2WPKH: https://blockstream.info/address/3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr
-            '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
+            // TODO: As above, add a correct P2SH-P2WPKH address with its pub key
+            // '3DFVKuT9Ft4rWpysAZ1bHpg55EBy1HVPcr',
             // P2PKH: https://blockstream.info/address/1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g
             '1Kr6QSydW9bFQG1mXiPNNu6WpJGmUa9i1g',
         ];
 
         const amounts = [undefined, 2000, 3000];
+        const feeRates = [undefined, 10];
 
         // EVM address for OP return
         const opReturn = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2';
 
         // Refactor to execute in parallel
         await Promise.all(
-            amounts.map(async () =>
+            feeRates.map(async (feeRate) =>
                 Promise.all(
-                    paymentAddresses.map(async (paymentAddress) => {
-                        const paymentAddressType = getAddressInfo(paymentAddress).type;
-
-                        let pubkey: string | undefined;
-
-                        if (paymentAddressType === AddressType.p2sh) {
-                            // Use a random public key for P2SH-P2WPKH
-                            pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
-                        }
-
-                        // If the amount is undefined, the fee should be estimated
-                        const fee = await estimateTxFee(paymentAddress, undefined, pubkey, opReturn);
-                        assert(fee > 0, 'Fee should be greater than 0');
-                    })
+                    amounts.map(async (amount) =>
+                        Promise.all(
+                            paymentAddresses.map(async (paymentAddress) => {
+                                const paymentAddressType = getAddressInfo(paymentAddress).type;
+
+                                let pubkey: string | undefined;
+
+                                if (paymentAddressType === AddressType.p2sh) {
+                                    // Use a random public key for P2SH-P2WPKH
+                                    pubkey = '03b366c69e8237d9be7c4f1ac2a7abc6a79932fbf3de4e2f6c04797d7ef27abfe1';
+                                }
+
+                                // If the amount is undefined, the fee should be estimated
+                                const fee = await estimateTxFee(paymentAddress, amount, pubkey, opReturn, feeRate);
+                                assert(fee > 0, 'Fee should be greater than 0');
+                            })
+                        )
+                    )
                 )
             )
         );

From 6a92bdc69ce33a11eae482de71c1831bfeda593e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rui=20Sim=C3=A3o?= <rui.daniel.simao@gmail.com>
Date: Tue, 15 Oct 2024 10:57:40 +0100
Subject: [PATCH 10/11] fix: final

---
 sdk/src/gateway/client.ts |  1 +
 sdk/src/gateway/types.ts  |  2 ++
 sdk/src/utils.ts          | 27 ---------------------------
 sdk/src/wallet/utxo.ts    |  8 ++++----
 sdk/test/utils.test.ts    |  8 ++------
 sdk/test/utxo.test.ts     |  4 ++++
 6 files changed, 13 insertions(+), 37 deletions(-)

diff --git a/sdk/src/gateway/client.ts b/sdk/src/gateway/client.ts
index 72071d4a..c03e2a46 100644
--- a/sdk/src/gateway/client.ts
+++ b/sdk/src/gateway/client.ts
@@ -203,6 +203,7 @@ export class GatewayApiClient {
                 gatewayQuote.satoshis,
                 params.fromUserPublicKey,
                 data.opReturnHash,
+                params.feeRate,
                 gatewayQuote.txProofDifficultyFactor
             );
         }
diff --git a/sdk/src/gateway/types.ts b/sdk/src/gateway/types.ts
index 19965c62..61595e35 100644
--- a/sdk/src/gateway/types.ts
+++ b/sdk/src/gateway/types.ts
@@ -60,6 +60,8 @@ export interface GatewayQuoteParams {
     /** @description The percentage of fee charged by partners in Basis Points (BPS) units. This will override the default fee rate configured via platform. 1 BPS = 0.01%. The maximum value is 1000 (which equals 10%). The minimum value is 1 (which equals 0.01%). */
     fee?: number;
 
+    feeRate?: number;
+
     // NOTE: the following are new fields added by us
     /** @description Amount of satoshis to swap for ETH */
     gasRefill?: number;
diff --git a/sdk/src/utils.ts b/sdk/src/utils.ts
index 186e17d9..2e61af6b 100644
--- a/sdk/src/utils.ts
+++ b/sdk/src/utils.ts
@@ -14,11 +14,6 @@ import { hash256 } from 'bitcoinjs-lib/src/crypto';
  * @ignore
  */
 import { Output, Transaction } from 'bitcoinjs-lib/src/transaction';
-/**
- * @ignore
- */
-import * as bitcoin from 'bitcoinjs-lib';
-
 /**
  * @ignore
  */
@@ -187,25 +182,3 @@ export function getMerkleProof(block: Block, txHash: string, forWitness?: boolea
         root: merkleAndRoot.root.toString('hex'),
     };
 }
-
-/**
- * Estimate the tx inclusion fee for N P2WPKH inputs and 3 P2WPKH outputs.
- *
- * @param feeRate - The current rate for inclusion, satoshi per byte.
- * @param numInputs - The number of inputs to estimate for.
- * @returns The estimated fee for transaction inclusion.
- */
-export function estimateTxFee(feeRate: number, numInputs: number = 1) {
-    const tx = new bitcoin.Transaction();
-    for (let i = 0; i < numInputs; i++) {
-        tx.addInput(Buffer.alloc(32, 0), 0, 0xfffffffd, Buffer.alloc(0));
-    }
-    // https://github.com/interlay/interbtc-clients/blob/6bd3e81d695b93180c5aeae4f33910ad4395ff1a/bitcoin/src/light/wallet.rs#L80
-    tx.ins.map((tx_input) => (tx_input.witness = [Buffer.alloc(33 + 32 + 7, 0), Buffer.alloc(33, 0)]));
-    tx.addOutput(Buffer.alloc(22, 0), 1000); // P2WPKH
-    tx.addOutput(Buffer.alloc(22, 0), 1000); // P2WPKH (change)
-    tx.addOutput(bitcoin.script.compile([bitcoin.opcodes.OP_RETURN, Buffer.alloc(20, 0)]), 0);
-    const vsize = tx.virtualSize();
-    const satoshis = feeRate * vsize;
-    return satoshis;
-}
diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index f14ac3ba..12082fcf 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -2,7 +2,6 @@ import { Transaction, Script, selectUTXO, TEST_NETWORK, NETWORK, p2wpkh, p2sh }
 import { hex, base64 } from '@scure/base';
 import { AddressType, getAddressInfo, Network } from 'bitcoin-address-validation';
 import { EsploraClient, UTXO } from '../esplora';
-import { SelectionStrategy } from '@scure/btc-signer/lib/utxo';
 
 export type BitcoinNetworkName = Exclude<Network, 'regtest'>;
 
@@ -70,7 +69,7 @@ export async function createBitcoinPsbt(
     const addressInfo = getAddressInfo(fromAddress);
 
     // TODO: possibly, allow other strategies to be passed to this function
-    const utxoSelectionStrategy: SelectionStrategy = 'default';
+    const utxoSelectionStrategy = 'default';
 
     if (addressInfo.network === 'regtest') {
         throw new Error('Bitcoin regtest not supported');
@@ -336,7 +335,7 @@ export async function estimateTxFee(
     let outputs: Output[] = [];
     // Select all UTXOs if no amount is specified
     // Add outputs to the transaction after all UTXOs are selected to prevent tx creation failures
-    let utxoSelectionStrategy: SelectionStrategy = 'all';
+    let utxoSelectionStrategy = 'all';
     if (amount) {
         // Add the target outputs to the transaction
         // Tx creation might fail if the requested amount is more than the available balance plus fees
@@ -349,7 +348,8 @@ export async function estimateTxFee(
     // https://github.com/paulmillr/scure-btc-signer?tab=readme-ov-file#utxo-selection
     // default = exactBiggest/accumBiggest creates tx with smallest fees, but it breaks
     // big outputs to small ones, which in the end will create a lot of outputs close to dust.
-    const transaction = selectUTXO(possibleInputs, outputs, utxoSelectionStrategy, {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const transaction = selectUTXO(possibleInputs, outputs, utxoSelectionStrategy as any, {
         changeAddress: fromAddress, // Refund surplus to the payment address
         feePerByte: BigInt(Math.ceil(feeRate)), // round up to the nearest integer
         bip69: true, // Sort inputs and outputs according to BIP69
diff --git a/sdk/test/utils.test.ts b/sdk/test/utils.test.ts
index a6cb994f..18cae26d 100644
--- a/sdk/test/utils.test.ts
+++ b/sdk/test/utils.test.ts
@@ -1,7 +1,7 @@
+import { Block } from 'bitcoinjs-lib';
 import { assert, describe, it } from 'vitest';
 import { MAINNET_ESPLORA_BASE_PATH } from '../src/esplora';
-import { Block } from 'bitcoinjs-lib';
-import { estimateTxFee, getMerkleProof } from '../src/utils';
+import { getMerkleProof } from '../src/utils';
 
 describe('Utils Tests', () => {
     // NOTE: this is a bit flaky due to slow response times from electrs
@@ -19,8 +19,4 @@ describe('Utils Tests', () => {
             root: '7cee5e99c8f0fc25fb115b7d7d00befca61f59a8544adaf3980f52132baf61ae',
         });
     });
-
-    it('should estimate fee', async () => {
-        assert.equal(estimateTxFee(1), 172);
-    });
 });
diff --git a/sdk/test/utxo.test.ts b/sdk/test/utxo.test.ts
index 44a621b7..a9fc673e 100644
--- a/sdk/test/utxo.test.ts
+++ b/sdk/test/utxo.test.ts
@@ -87,17 +87,20 @@ describe('UTXO Tests', () => {
 
                                 // Check the transfer script to the toAddress
                             } else if (output.amount === BigInt(amount)) {
+                                // eslint-disable-next-line @typescript-eslint/no-explicit-any
                                 const scriptDecoded = OutScript.decode(output.script!) as any;
 
                                 // Remove "p2" from the address type as it's exluced in the OutScript type
                                 assert.equal(scriptDecoded.type, addressType.slice(2));
 
+                                // eslint-disable-next-line @typescript-eslint/no-explicit-any
                                 const address = Address(NETWORK).decode(toAddress) as any;
 
                                 assert.deepEqual(scriptDecoded.hash, address.hash);
 
                                 // Check the possible change output
                             } else {
+                                // eslint-disable-next-line @typescript-eslint/no-explicit-any
                                 const scriptDecoded = OutScript.decode(output.script!) as any;
 
                                 // Remove "p2" from the address type as it's exluced in the OutScript type
@@ -256,6 +259,7 @@ describe('UTXO Tests', () => {
                 network: NETWORK,
                 allowUnknownOutputs: true,
                 allowLegacyWitnessUtxo: true,
+                // eslint-disable-next-line @typescript-eslint/no-explicit-any
                 dust: BigInt(546) as any,
             }
         );

From 7c4edde72c9312da2a0f987e7b8a69a354b3cb98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rui=20Sim=C3=A3o?= <rui.daniel.simao@gmail.com>
Date: Tue, 15 Oct 2024 12:14:30 +0100
Subject: [PATCH 11/11] fix: code review

---
 sdk/src/wallet/utxo.ts | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/sdk/src/wallet/utxo.ts b/sdk/src/wallet/utxo.ts
index 12082fcf..573cd2f5 100644
--- a/sdk/src/wallet/utxo.ts
+++ b/sdk/src/wallet/utxo.ts
@@ -294,21 +294,18 @@ export async function estimateTxFee(
         throw new Error('No confirmed UTXOs');
     }
 
-    // To construct the spending transaction and estimate the fee, we need the transactions for the UTXOs
-    const possibleInputs: Input[] = [];
-
-    await Promise.all(
+    const possibleInputs = await Promise.all(
         confirmedUtxos.map(async (utxo) => {
             const hex = await esploraClient.getTransactionHex(utxo.txid);
             const transaction = Transaction.fromRaw(Buffer.from(hex, 'hex'), { allowUnknownOutputs: true });
-            const input = getInputFromUtxoAndTx(
+
+            return getInputFromUtxoAndTx(
                 addressInfo.network as BitcoinNetworkName,
                 utxo,
                 transaction,
                 addressInfo.type,
                 publicKey
             );
-            possibleInputs.push(input);
         })
     );
 
@@ -322,7 +319,7 @@ export async function estimateTxFee(
 
     if (opReturnData) {
         // Strip 0x prefix from opReturn
-        if (opReturnData.startsWith('0x')) {
+        if (opReturnData.toLowerCase().startsWith('0x')) {
             opReturnData = opReturnData.slice(2);
         }
         targetOutputs.push({