From 15bb5a966b85900088a7218d07fdd35e5f6da55e Mon Sep 17 00:00:00 2001
From: softsimon <softsimon@protonmail.com>
Date: Mon, 5 Oct 2020 11:42:54 +0700
Subject: [PATCH] Improved empty mempool as well as medium and low fee
 estimations. refs #65

---
 backend/src/api/fee-api.ts                    | 24 ++++++++++----
 .../components/fees-box/fees-box.component.ts | 32 ++++++++++++-------
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/backend/src/api/fee-api.ts b/backend/src/api/fee-api.ts
index 1fc497465..325a12ea1 100644
--- a/backend/src/api/fee-api.ts
+++ b/backend/src/api/fee-api.ts
@@ -1,4 +1,5 @@
 const config = require('../../mempool-config.json');
+import { MempoolBlock } from '../interfaces';
 import projectedBlocks from './mempool-blocks';
 
 class FeeApi {
@@ -8,6 +9,7 @@ class FeeApi {
 
   public getRecommendedFee() {
     const pBlocks = projectedBlocks.getMempoolBlocks();
+
     if (!pBlocks.length) {
       return {
         'fastestFee': this.defaultFee,
@@ -15,14 +17,10 @@ class FeeApi {
         'hourFee': this.defaultFee,
       };
     }
-    let firstMedianFee = Math.ceil(pBlocks[0].medianFee);
 
-    if (pBlocks.length === 1 && pBlocks[0].blockVSize <= 500000) {
-      firstMedianFee = this.defaultFee;
-    }
-
-    const secondMedianFee = pBlocks[1] ? Math.ceil(pBlocks[1].medianFee) : this.defaultFee;
-    const thirdMedianFee = pBlocks[2] ? Math.ceil(pBlocks[2].medianFee) : this.defaultFee;
+    const firstMedianFee = this.optimizeMedianFee(pBlocks[0]);
+    const secondMedianFee = pBlocks[1] ? this.optimizeMedianFee(pBlocks[1], firstMedianFee) : this.defaultFee;
+    const thirdMedianFee = pBlocks[2] ? this.optimizeMedianFee(pBlocks[2], secondMedianFee) : this.defaultFee;
 
     return {
       'fastestFee': firstMedianFee,
@@ -30,6 +28,18 @@ class FeeApi {
       'hourFee': thirdMedianFee,
     };
   }
+
+  private optimizeMedianFee(pBlock: MempoolBlock, previousFee?: number): number {
+    const useFee = previousFee ? (pBlock.medianFee + previousFee / 2) : pBlock.medianFee;
+    if (pBlock.blockVSize <= 500000) {
+      return this.defaultFee;
+    }
+    if (pBlock.blockVSize <= 950000) {
+      const multiplier = (pBlock.blockVSize - 500000) / 500000;
+      return Math.max(Math.round(useFee * multiplier), this.defaultFee);
+    }
+    return Math.round(useFee);
+  }
 }
 
 export default new FeeApi();
diff --git a/frontend/src/app/components/fees-box/fees-box.component.ts b/frontend/src/app/components/fees-box/fees-box.component.ts
index 9e7a53136..71e0519ef 100644
--- a/frontend/src/app/components/fees-box/fees-box.component.ts
+++ b/frontend/src/app/components/fees-box/fees-box.component.ts
@@ -2,6 +2,7 @@ import { Component, OnInit, ChangeDetectionStrategy } from '@angular/core';
 import { StateService } from 'src/app/services/state.service';
 import { map, filter } from 'rxjs/operators';
 import { merge, Observable } from 'rxjs';
+import { MempoolBlock } from 'src/app/interfaces/websocket.interface';
 
 interface FeeEstimations {
   fastestFee: number;
@@ -18,13 +19,14 @@ interface FeeEstimations {
 export class FeesBoxComponent implements OnInit {
   feeEstimations$: Observable<FeeEstimations>;
   isLoadingWebSocket$: Observable<boolean>;
+  defaultFee: number;
 
   constructor(
     private stateService: StateService,
   ) { }
 
   ngOnInit(): void {
-    const defaultFee = this.stateService.network === 'liquid' ? 0.1 : 1;
+    this.defaultFee = this.stateService.network === 'liquid' ? 0.1 : 1;
 
     this.isLoadingWebSocket$ = this.stateService.isLoadingWebSocket$;
     this.feeEstimations$ = this.stateService.mempoolBlocks$
@@ -32,19 +34,15 @@ export class FeesBoxComponent implements OnInit {
         map((pBlocks) => {
           if (!pBlocks.length) {
             return {
-              'fastestFee': defaultFee,
-              'halfHourFee': defaultFee,
-              'hourFee': defaultFee,
+              'fastestFee': this.defaultFee,
+              'halfHourFee': this.defaultFee,
+              'hourFee': this.defaultFee,
             };
           }
-          let firstMedianFee = Math.ceil(pBlocks[0].medianFee);
 
-          if (pBlocks.length === 1 && pBlocks[0].blockVSize <= 500000) {
-            firstMedianFee = defaultFee;
-          }
-
-          const secondMedianFee = pBlocks[1] ? Math.ceil(pBlocks[1].medianFee) : defaultFee;
-          const thirdMedianFee = pBlocks[2] ? Math.ceil(pBlocks[2].medianFee) : defaultFee;
+          const firstMedianFee = this.optimizeMedianFee(pBlocks[0]);
+          const secondMedianFee = pBlocks[1] ? this.optimizeMedianFee(pBlocks[1], firstMedianFee) : this.defaultFee;
+          const thirdMedianFee = pBlocks[2] ? this.optimizeMedianFee(pBlocks[2], secondMedianFee) : this.defaultFee;
 
           return {
             'fastestFee': firstMedianFee,
@@ -55,4 +53,16 @@ export class FeesBoxComponent implements OnInit {
       );
   }
 
+  optimizeMedianFee(pBlock: MempoolBlock, previousFee?: number): number {
+    const useFee = previousFee ? (pBlock.medianFee + previousFee / 2) : pBlock.medianFee;
+    if (pBlock.blockVSize <= 500000) {
+      return this.defaultFee;
+    }
+    if (pBlock.blockVSize <= 950000) {
+      const multiplier = (pBlock.blockVSize - 500000) / 500000;
+      return Math.max(Math.round(useFee * multiplier), this.defaultFee);
+    }
+    return Math.round(useFee);
+  }
+
 }