From 037d6a75eae5abf9cdbdc0835badf46db81898ad Mon Sep 17 00:00:00 2001
From: softsimon <softsimon@users.noreply.github.com>
Date: Fri, 23 Jul 2021 14:35:04 +0300
Subject: [PATCH] Adding previous difficulty retarget to the difficulty
 adjustment api. (#652)

refs #640
---
 backend/src/api/blocks.ts                         | 13 +++++++++++++
 backend/src/api/websocket-handler.ts              |  2 ++
 backend/src/routes.ts                             | 15 ++++++++-------
 .../src/app/interfaces/websocket.interface.ts     |  1 +
 4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/backend/src/api/blocks.ts b/backend/src/api/blocks.ts
index 25f92ff5c..fbfcc2828 100644
--- a/backend/src/api/blocks.ts
+++ b/backend/src/api/blocks.ts
@@ -11,7 +11,9 @@ class Blocks {
   private static INITIAL_BLOCK_AMOUNT = 8;
   private blocks: BlockExtended[] = [];
   private currentBlockHeight = 0;
+  private currentDifficulty = 0;
   private lastDifficultyAdjustmentTime = 0;
+  private previousDifficultyRetarget = 0;
   private newBlockCallbacks: ((block: BlockExtended, txIds: string[], transactions: TransactionExtended[]) => void)[] = [];
 
   constructor() { }
@@ -47,6 +49,11 @@ class Blocks {
       const blockHash = await bitcoinApi.$getBlockHash(blockHeightTip - heightDiff);
       const block = await bitcoinApi.$getBlock(blockHash);
       this.lastDifficultyAdjustmentTime = block.timestamp;
+      this.currentDifficulty = block.difficulty;
+
+      const previousPeriodBlockHash = await bitcoinApi.$getBlockHash(blockHeightTip - heightDiff - 2016);
+      const previousPeriodBlock = await bitcoinApi.$getBlock(previousPeriodBlockHash);
+      this.previousDifficultyRetarget = (block.difficulty - previousPeriodBlock.difficulty) / previousPeriodBlock.difficulty * 100;
     }
 
     while (this.currentBlockHeight < blockHeightTip) {
@@ -101,7 +108,9 @@ class Blocks {
       blockExtended.feeRange = transactions.length > 1 ? Common.getFeesInRange(transactions, 8) : [0, 0];
 
       if (block.height % 2016 === 0) {
+        this.previousDifficultyRetarget = (block.difficulty - this.currentDifficulty) / this.currentDifficulty * 100;
         this.lastDifficultyAdjustmentTime = block.timestamp;
+        this.currentDifficulty = block.difficulty;
       }
 
       this.blocks.push(blockExtended);
@@ -122,6 +131,10 @@ class Blocks {
     return this.lastDifficultyAdjustmentTime;
   }
 
+  public getPreviousDifficultyRetarget(): number {
+    return this.previousDifficultyRetarget;
+  }
+
   public getCurrentBlockHeight(): number {
     return this.currentBlockHeight;
   }
diff --git a/backend/src/api/websocket-handler.ts b/backend/src/api/websocket-handler.ts
index 135411a3d..eb2b90ccc 100644
--- a/backend/src/api/websocket-handler.ts
+++ b/backend/src/api/websocket-handler.ts
@@ -172,6 +172,7 @@ class WebsocketHandler {
       'mempoolInfo': memPool.getMempoolInfo(),
       'vBytesPerSecond': memPool.getVBytesPerSecond(),
       'lastDifficultyAdjustment': blocks.getLastDifficultyAdjustmentTime(),
+      'previousRetarget': blocks.getPreviousDifficultyRetarget(),
       'blocks': _blocks,
       'conversions': fiatConversion.getConversionRates(),
       'mempool-blocks': mempoolBlocks.getMempoolBlocks(),
@@ -384,6 +385,7 @@ class WebsocketHandler {
         'block': block,
         'mempoolInfo': memPool.getMempoolInfo(),
         'lastDifficultyAdjustment': blocks.getLastDifficultyAdjustmentTime(),
+        'previousRetarget': blocks.getPreviousDifficultyRetarget(),
       };
 
       if (mBlocks && client['want-mempool-blocks']) {
diff --git a/backend/src/routes.ts b/backend/src/routes.ts
index 3e7e487bb..bc42a9868 100644
--- a/backend/src/routes.ts
+++ b/backend/src/routes.ts
@@ -680,12 +680,12 @@ class Routes {
   public getDifficultyChange(req: Request, res: Response) {
     try {
       const now = new Date().getTime() / 1000;
-      const DATime=blocks.getLastDifficultyAdjustmentTime();
+      const DATime = blocks.getLastDifficultyAdjustmentTime();
+      const previousRetarget = blocks.getPreviousDifficultyRetarget();
       const diff = now - DATime;
-      const blockHeight=blocks.getCurrentBlockHeight();
+      const blockHeight = blocks.getCurrentBlockHeight();
       const blocksInEpoch = blockHeight % 2016;
-      const estimatedBlocks = Math.round(diff / 60 / 10);
-      const difficultyChange = (600 / (diff / blocksInEpoch ) - 1) * 100;
+      const difficultyChange = (600 / (diff / blocksInEpoch) - 1) * 100;
 
       const timeAvgDiff = difficultyChange * 0.1;
 
@@ -699,9 +699,9 @@ class Routes {
       const remainingBlocks = 2016 - blocksInEpoch;
       const timeAvgSeconds = timeAvgMins * 60;
       const remainingTime = remainingBlocks * timeAvgSeconds;
-      const estimatedRetargetDate=(remainingTime + now);
-      const totalTime=estimatedRetargetDate-DATime;
-      const progressPercent=100-((remainingTime*100)/totalTime);
+      const estimatedRetargetDate = (remainingTime + now);
+      const totalTime = estimatedRetargetDate-DATime;
+      const progressPercent = 100 - ((remainingTime * 100) / totalTime);
 
       const result={
         progressPercent,
@@ -709,6 +709,7 @@ class Routes {
         estimatedRetargetDate,
         remainingBlocks,
         remainingTime,
+        previousRetarget,
       }
       res.json(result);
 
diff --git a/frontend/src/app/interfaces/websocket.interface.ts b/frontend/src/app/interfaces/websocket.interface.ts
index 2138ad8dc..e4e31b942 100644
--- a/frontend/src/app/interfaces/websocket.interface.ts
+++ b/frontend/src/app/interfaces/websocket.interface.ts
@@ -10,6 +10,7 @@ export interface WebsocketResponse {
   mempoolInfo?: MempoolInfo;
   vBytesPerSecond?: number;
   lastDifficultyAdjustment?: number;
+  previousRetarget?: number;
   action?: string;
   data?: string[];
   tx?: Transaction;