Fix : TxAnalyzer RBF calculations

packages/caravan-fees/src/tests/transactionAnalyzer.fixtures.ts

@@ -42,7 +42,7 @@ export const transactionAnalyzerFixtures = {
         fee: "327",
         feeRate: "2.61",
         recommendedStrategy: FeeBumpStrategy.NONE,
-        estimatedRBFFee: 454, // 327  + 1*125.25
+        estimatedRBFFee: 453, // 327  + 1*125.25
         estimatedCPFPFee: 73,
         inputSequences: [4294967293],
         outputValues: [37114, 0],
@@ -85,7 +85,7 @@ export const transactionAnalyzerFixtures = {
         fee: "482",
         feeRate: "3.43",
         recommendedStrategy: FeeBumpStrategy.CPFP,
-        estimatedRBFFee: 702.5, // 562 + 1*140.5 = 576.5(minimum RBF for bumping , 1 sats/vbyte incremental fee) , here 5(user defined) * 140.5 = 702.5 ... note our txAnalyzer gives 705 for this because of vsize rounding from bitcoin-js lib
+        estimatedRBFFee: 623, // 482 + 1*140.5 = 622.5(minimum RBF for bumping , 1 sats/vbyte incremental fee)
         estimatedCPFPFee: 2303,
         inputSequences: [4294967295],
         outputValues: [16741, 525461],
@@ -130,7 +130,7 @@ export const transactionAnalyzerFixtures = {
         fee: "2289",
         feeRate: "7.02",
         recommendedStrategy: FeeBumpStrategy.RBF,
-        estimatedRBFFee: 4894, // 15(target Rate) * 326.25
+        estimatedRBFFee: 2616, // 2289 + 1 * 326.25
         estimatedCPFPFee: 14692,
         inputSequences: [4294967293],
         outputValues: [

packages/caravan-fees/src/transactionAnalyzer.ts

@@ -265,23 +265,6 @@ export class TransactionAnalyzer {
     return this._targetFeeRate;
   }
 
-  /**
-   * Get the estimated fee rate for Replace-by-Fee (RBF).
-   *
-   * This method calculates the effective fee rate for the RBF transaction
-   * based on the minimum RBF fee and the transaction's virtual size.
-   *
-   * It's important to note that this rate might be higher than the original
-   * user-specified target fee rate, as it needs to satisfy both BIP 125 rules
-   * and current network conditions for effective replacement.
-   *
-   * @returns {string} The estimated RBF fee rate in satoshis per vbyte.
-   * @see https://bitcoinops.org/en/topics/replace-by-fee/
-   */
-  get rbfFeeRate(): string {
-    return new BigNumber(this.minimumRBFFee).dividedBy(this.vsize).toString();
-  }
-
   /**
    * Calculates and returns the fee rate required for a successful CPFP.
    * @returns {string} The CPFP fee rate in satoshis per vbyte
@@ -301,24 +284,21 @@ export class TransactionAnalyzer {
   /**
    * Calculates the minimum total fee required for a valid RBF (Replace-By-Fee) replacement transaction.
    *
-   * This method implements the current RBF rules as defined in BIP 125, while also
-   * considering the fee rate importance. It balances:
-   * 1. BIP 125 requirements (anti-DDoS measures)
-   * 2. Current miner preferences for fee rates over absolute fees
-   * 3. User-specified target fee rate
+   * This method determines the minimum fee needed to replace the current transaction
+   * using the RBF protocol, as defined in BIP 125. It considers two key factors:
+   * 1. The current transaction fee
+   * 2. The minimum required fee increase (incremental relay fee * transaction size)
    *
    * Key considerations:
    * - BIP 125 Rule 4: Replacement must pay for its own bandwidth at minimum relay fee
    *   This rule doesn't explicitly consider fee rates, focusing on anti-DDoS protection.
    * - Modern mining preferences favor higher fee rates over absolute fees.
    *
-   * Approach Taken:
-   * 1. Calculate minimum fee based on BIP 125 rules
-   * 2. Calculate fee based on user-specified target fee rate
-   * 3. Use the higher of these two to ensure compliance and desired confirmation speed
+   * The calculation ensures that the new transaction meets the minimum fee increase
+   * required by the RBF rules, which is:
+   * minimum_fee = original_fee + (incremental_relay_fee * transaction_size)
+   *
    *
-   * This method allows for effective fee bumping while adhering to current network rules,
-   * even if the user-specified target fee rate is lower than necessary to unstick the transaction.
    *
    * References:
    * - BIP 125 (RBF): https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki
@@ -327,25 +307,14 @@ export class TransactionAnalyzer {
    * - One-Shot Replace-By-Fee-Rate proposal: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2024-January/022298.html
    *
    * @returns {Satoshis} The minimum total fee required for the replacement transaction in satoshis.
-   *                     This is always at least the current fee plus the minimum required increase,
-   *                     but may be higher if the user-specified target fee rate demands it.
+   *                     This is always at least the current fee plus the minimum required increase.
+   * @note This getter does not consider the user's target fee rate. It's the responsibility
+   *       of the RBF function to ensure that the new transaction's fee is the maximum of
+   *       this minimum fee and the fee calculated using the user's target fee rate.
    */
   get minimumRBFFee(): Satoshis {
-    // Calculate the minimum fee increase required by BIP 125 Rule 4
-    // This includes the original fee rate plus the incremental relay fee rate
-    const minReplacementFee = new BigNumber(this.feeRate)
-      .plus(this._incrementalRelayFeeRate)
-      .multipliedBy(this.vsize);
-
-    // Calculate the fee based on the user-specified target fee rate
-    // This addresses modern miner preferences for higher fee rates
-    const targetFeeBasedOnUserRate = new BigNumber(
-      this.targetFeeRate,
-    ).multipliedBy(this.vsize);
-
-    // Return the maximum of the two calculations
-    // This ensures we meet both RBF rules and user's desired fee rate
-    return BigNumber.max(minReplacementFee, targetFeeBasedOnUserRate)
+    return new BigNumber(this.fee)
+      .plus(this._incrementalRelayFeeRate.multipliedBy(this.vsize))
       .integerValue(BigNumber.ROUND_CEIL)
       .toString();
   }