feat: add getFeeRate function, add feerate api endpoints

src/app/hooks/use-bitcoin.ts

@@ -42,6 +42,14 @@ interface UTXO {
   value: number;
 }
 
+interface FeeRates {
+  fastestFee: number;
+  halfHourFee: number;
+  hourFee: number;
+  economyFee: number;
+  minimumFee: number;
+}
+
 interface BitcoinNativeSegwitAddress {
   address: string;
   derivationPath: string;
@@ -88,7 +96,8 @@ interface UseBitcoinReturnType {
 }
 
 export function useBitcoin(): UseBitcoinReturnType {
-  const { bitcoinNetwork, bitcoinNetworkName, bitcoinBlockchainAPIURL } = useEndpoints();
+  const { bitcoinNetwork, bitcoinNetworkName, bitcoinBlockchainAPIURL, mempoolSpaceAPIFeeURL } =
+    useEndpoints();
   const { getAttestorGroupPublicKey, sendClosingTransactionToAttestors } = useAttestors();
 
   /**
@@ -132,6 +141,22 @@ export function useBitcoin(): UseBitcoinReturnType {
     }
   }
 
+  /**
+   * Fetches the fee rate from the mempool.space API.
+   *
+   * @returns A promise that resolves to the hour fee rate.
+   */
+  async function getFeeRate(): Promise<number> {
+    try {
+      const response = await fetch(mempoolSpaceAPIFeeURL);
+      const feeRates: FeeRates = await response.json();
+
+      return feeRates.hourFee;
+    } catch (error) {
+      throw new BitcoinError(`Error getting Fee Rate: ${error}`);
+    }
+  }
+
   /**
    * Fetches the UTXOs for the user's native segwit address.
 
@@ -174,6 +199,7 @@ export function useBitcoin(): UseBitcoinReturnType {
    *
    * @param userPublicKey - The user's public key.
    * @param attestorGroupPublicKey - The attestor group's public key.
+   * @param bitcoinNetwork - The bitcoin network.
    * @returns A promise that resolves to the multisig transaction.
    */
   function createMultisigTransaction(
@@ -191,23 +217,25 @@ export function useBitcoin(): UseBitcoinReturnType {
    * Creates the first PSBT, which is the funding transaction.
    * Uses the selected UTXOs to fund the transaction.
    *
-   * @param selectedUTXOs - The UTXOs selected for funding the transaction.
-   * @param multisigAddress - The multisig address.
-   * @param bitcoinAmount - The amount of bitcoin.
+   * @param multisigAddress - The multisig address created from the multisig transaction between the user and the attestor group.
+   * @param utxos - The user's UTXOs.
+   * @param feeRate - The fee rate.
+   * @param bitcoinAmount - The amount of bitcoin to be used in the transaction.
    * @param bitcoinNetwork - The bitcoin network.
    * @returns A promise that resolves to the funding PSBT.
    */ function createFundingTransaction(
     multisigAddress: string,
     userChangeAddress: string,
     utxos: any[],
+    feeRate: bigint,
     bitcoinAmount: number,
     bitcoinNetwork: BitcoinNetwork
   ): Uint8Array {
     const outputs = [{ address: multisigAddress, amount: BigInt(bitcoinAmount) }];
 
     const selected = btc.selectUTXO(utxos, outputs, 'default', {
       changeAddress: userChangeAddress,
-      feePerByte: 2n,
+      feePerByte: feeRate,
       bip69: false,
       createTx: true,
       network: bitcoinNetwork,
@@ -228,9 +256,9 @@ export function useBitcoin(): UseBitcoinReturnType {
    * The closing transaction is sent to the user's native segwit address.
    *
    * @param fundingTransactionID - The ID of the funding transaction.
-   * @param multisigTransaction - The multisig transaction.
+   * @param multisigTransaction - The multisig transaction between the user and the attestor group.
    * @param userNativeSegwitAddress - The user's native segwit address.
-   * @param bitcoinAmount - The amount of bitcoin.
+   * @param bitcoinAmount - The amount of bitcoin to be used in the transaction.
    * @param bitcoinNetwork - The bitcoin network.
    * @returns A promise that resolves to the closing PSBT.
    */
@@ -294,6 +322,10 @@ export function useBitcoin(): UseBitcoinReturnType {
         body: bytesToHex(transaction.extract()),
       });
 
+      if (!response.ok) {
+        throw new Error(`HTTP Error! Status: ${response.status}`);
+      }
+
       const transactionID = await response.text();
       return transactionID;
     } catch (error) {
@@ -330,10 +362,13 @@ export function useBitcoin(): UseBitcoinReturnType {
     const multisigAddress = multisigTransaction.address;
     if (!multisigAddress) throw new BitcoinError('Could not create multisig address');
 
+    const feeRate = BigInt(await getFeeRate());
+
     const fundingTransaction = createFundingTransaction(
       multisigAddress,
       userNativeSegwitAddress,
       userUTXOs,
+      feeRate,
       bitcoinAmount,
       bitcoinNetwork
     );

src/app/hooks/use-endpoints.ts

@@ -11,6 +11,7 @@ interface NetworkEndpoints {
   ethereumAttestorChainID: string;
   bitcoinExplorerAPIURL: string;
   bitcoinBlockchainAPIURL: string;
+  mempoolSpaceAPIFeeURL: string;
   bitcoinNetwork: BitcoinNetwork;
   bitcoinNetworkName: string;
 }
@@ -23,6 +24,8 @@ export function useEndpoints(): NetworkEndpoints {
   const [ethereumAttestorChainID, setEthereumAttestorChainID] = useState<string>('');
   const [bitcoinExplorerAPIURL, setBitcoinExplorerAPIURL] = useState<string>('');
   const [bitcoinBlockchainAPIURL, setBitcoinBlockchainAPIURL] = useState<string>('');
+  const [mempoolSpaceAPIFeeURL, setMempoolSpaceAPIFeeURL] = useState<string>('');
+
   const [bitcoinNetwork, setBitcoinNetwork] = useState<BitcoinNetwork>(regtest);
   const [bitcoinNetworkName, setBitcoinNetworkName] = useState<string>('');
 
@@ -35,6 +38,7 @@ export function useEndpoints(): NetworkEndpoints {
       ethereumAttestorChainID,
       bitcoinExplorerAPIURL,
       bitcoinBlockchainAPIURL,
+      mempoolSpaceAPIFeeURL,
       bitcoinNetwork,
       bitcoinNetworkName,
     } = getEndpoints();
@@ -44,6 +48,7 @@ export function useEndpoints(): NetworkEndpoints {
     setEthereumAttestorChainID(ethereumAttestorChainID);
     setBitcoinExplorerAPIURL(bitcoinExplorerAPIURL);
     setBitcoinBlockchainAPIURL(bitcoinBlockchainAPIURL);
+    setMempoolSpaceAPIFeeURL(mempoolSpaceAPIFeeURL);
     setBitcoinNetwork(bitcoinNetwork);
     setBitcoinNetworkName(bitcoinNetworkName);
     // eslint-disable-next-line react-hooks/exhaustive-deps
@@ -55,17 +60,22 @@ export function useEndpoints(): NetworkEndpoints {
     const bitcoinNetworkName = import.meta.env.VITE_BITCOIN_NETWORK;
     const bitcoinBlockchainAPIURL = import.meta.env.VITE_BITCOIN_BLOCKCHAIN_API_URL;
     const bitcoinExplorerAPIURL = import.meta.env.VITE_BITCOIN_EXPLORER_API_URL;
-    let bitcoinNetwork;
+
+    let bitcoinNetwork: BitcoinNetwork;
+    let mempoolSpaceAPIFeeURL: string;
 
     switch (bitcoinNetworkName) {
       case 'mainnet':
         bitcoinNetwork = bitcoin;
+        mempoolSpaceAPIFeeURL = 'https://mempool.space/api/v1/fees/recommended';
         break;
       case 'testnet':
         bitcoinNetwork = testnet;
+        mempoolSpaceAPIFeeURL = 'https://mempool.space/testnet/api/v1/fees/recommended';
         break;
       default:
         bitcoinNetwork = regtest;
+        mempoolSpaceAPIFeeURL = 'https://mempool.space/testnet/api/v1/fees/recommended';
     }
 
     switch (network?.id) {
@@ -76,6 +86,7 @@ export function useEndpoints(): NetworkEndpoints {
           ethereumAttestorChainID: 'evm-sepolia',
           bitcoinExplorerAPIURL,
           bitcoinBlockchainAPIURL,
+          mempoolSpaceAPIFeeURL,
           bitcoinNetwork,
           bitcoinNetworkName,
         };
@@ -86,6 +97,7 @@ export function useEndpoints(): NetworkEndpoints {
           ethereumAttestorChainID: 'evm-goerli',
           bitcoinExplorerAPIURL,
           bitcoinBlockchainAPIURL,
+          mempoolSpaceAPIFeeURL,
           bitcoinNetwork,
           bitcoinNetworkName,
         };
@@ -96,6 +108,7 @@ export function useEndpoints(): NetworkEndpoints {
           ethereumAttestorChainID: 'evm-x1-test',
           bitcoinExplorerAPIURL,
           bitcoinBlockchainAPIURL,
+          mempoolSpaceAPIFeeURL,
           bitcoinNetwork,
           bitcoinNetworkName,
         };
@@ -109,6 +122,7 @@ export function useEndpoints(): NetworkEndpoints {
     ethereumAttestorChainID,
     bitcoinExplorerAPIURL,
     bitcoinBlockchainAPIURL,
+    mempoolSpaceAPIFeeURL,
     bitcoinNetwork,
     bitcoinNetworkName,
   };