From e3c06eb93bbc14f66801db539c59a32e0781c2da Mon Sep 17 00:00:00 2001
From: natsoni <natsoni@protonmail.com>
Date: Fri, 23 Aug 2024 15:46:30 +0200
Subject: [PATCH] Add V2 API endpoint for decimal recommended fees

---
 backend/src/api/bitcoin/bitcoin.routes.ts | 13 +++++++++++++
 backend/src/api/fee-api.ts                | 22 +++++++++++++++-------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/backend/src/api/bitcoin/bitcoin.routes.ts b/backend/src/api/bitcoin/bitcoin.routes.ts
index 6225a9c1d..c4a98010b 100644
--- a/backend/src/api/bitcoin/bitcoin.routes.ts
+++ b/backend/src/api/bitcoin/bitcoin.routes.ts
@@ -47,6 +47,9 @@ class BitcoinRoutes {
       .post(config.MEMPOOL.API_URL_PREFIX + 'psbt/addparents', this.postPsbtCompletion)
       .get(config.MEMPOOL.API_URL_PREFIX + 'blocks-bulk/:from', this.getBlocksByBulk.bind(this))
       .get(config.MEMPOOL.API_URL_PREFIX + 'blocks-bulk/:from/:to', this.getBlocksByBulk.bind(this))
+
+      // V2 API
+      .get(config.MEMPOOL.API_V2_URL_PREFIX + 'fees/recommended', this.getRecommendedFeesDecimal)
       ;
 
       if (config.MEMPOOL.BACKEND !== 'esplora') {
@@ -100,6 +103,16 @@ class BitcoinRoutes {
     res.json(result);
   }
 
+  private getRecommendedFeesDecimal(req: Request, res: Response) {
+    if (!mempool.isInSync()) {
+      res.statusCode = 503;
+      res.send('Service Unavailable');
+      return;
+    }
+    const result = feeApi.getRecommendedFee(true);
+    res.json(result);
+  }
+
   private getMempoolBlocks(req: Request, res: Response) {
     try {
       const result = mempoolBlocks.getMempoolBlocks();
diff --git a/backend/src/api/fee-api.ts b/backend/src/api/fee-api.ts
index 24fd25a4b..be42b2fa5 100644
--- a/backend/src/api/fee-api.ts
+++ b/backend/src/api/fee-api.ts
@@ -19,10 +19,12 @@ class FeeApi {
   defaultFee = isLiquid ? 0.1 : 1;
   minimumIncrement = isLiquid ? 0.1 : 1;
 
-  public getRecommendedFee(): RecommendedFees {
+  public getRecommendedFee(decimal: boolean = false): RecommendedFees {
     const pBlocks = projectedBlocks.getMempoolBlocks();
     const mPool = mempool.getMempoolInfo();
-    const minimumFee = this.roundUpToNearest(mPool.mempoolminfee * 100000, this.minimumIncrement);
+    const minimumFee = decimal ? 
+      this.roundUpToNearestDecimal(mPool.mempoolminfee * 100000) :
+      this.roundUpToNearest(mPool.mempoolminfee * 100000, this.minimumIncrement);
     const defaultMinFee = Math.max(minimumFee, this.defaultFee);
 
     if (!pBlocks.length) {
@@ -35,9 +37,9 @@ class FeeApi {
       };
     }
 
-    const firstMedianFee = this.optimizeMedianFee(pBlocks[0], pBlocks[1]);
-    const secondMedianFee = pBlocks[1] ? this.optimizeMedianFee(pBlocks[1], pBlocks[2], firstMedianFee) : this.defaultFee;
-    const thirdMedianFee = pBlocks[2] ? this.optimizeMedianFee(pBlocks[2], pBlocks[3], secondMedianFee) : this.defaultFee;
+    const firstMedianFee = this.optimizeMedianFee(pBlocks[0], pBlocks[1], undefined, decimal);
+    const secondMedianFee = pBlocks[1] ? this.optimizeMedianFee(pBlocks[1], pBlocks[2], firstMedianFee, decimal) : this.defaultFee;
+    const thirdMedianFee = pBlocks[2] ? this.optimizeMedianFee(pBlocks[2], pBlocks[3], secondMedianFee, decimal) : this.defaultFee;
 
     let fastestFee = Math.max(minimumFee, firstMedianFee);
     let halfHourFee = Math.max(minimumFee, secondMedianFee);
@@ -62,7 +64,7 @@ class FeeApi {
     };
   }
 
-  private optimizeMedianFee(pBlock: MempoolBlock, nextBlock: MempoolBlock | undefined, previousFee?: number): number {
+  private optimizeMedianFee(pBlock: MempoolBlock, nextBlock: MempoolBlock | undefined, previousFee?: number, decimal: boolean = false): number {
     const useFee = previousFee ? (pBlock.medianFee + previousFee) / 2 : pBlock.medianFee;
     if (pBlock.blockVSize <= 500000) {
       return this.defaultFee;
@@ -71,12 +73,18 @@ class FeeApi {
       const multiplier = (pBlock.blockVSize - 500000) / 500000;
       return Math.max(Math.round(useFee * multiplier), this.defaultFee);
     }
-    return this.roundUpToNearest(useFee, this.minimumIncrement);
+    return decimal ?
+      this.roundUpToNearestDecimal(useFee) :
+      this.roundUpToNearest(useFee, this.minimumIncrement);
   }
 
   private roundUpToNearest(value: number, nearest: number): number {
     return Math.ceil(value / nearest) * nearest;
   }
+
+  private roundUpToNearestDecimal(value: number): number {
+    return Number(this.roundUpToNearest(value, 0.1).toFixed(1)); // avoid floating point errors
+  }
 }
 
 export default new FeeApi();